Merge branch 'master' into error-format

.gitignore

@@ -47,7 +47,7 @@ perl/Makefile.config
 /src/libexpr/nix.tbl
 
 # /src/libstore/
-/src/libstore/*.gen.hh
+*.gen.*
 
 /src/nix/nix
 

Makefile.config.in

@@ -37,6 +37,7 @@ prefix = @prefix@
 sandbox_shell = @sandbox_shell@
 storedir = @storedir@
 sysconfdir = @sysconfdir@
+system = @system@
 doc_generate = @doc_generate@
 xmllint = @xmllint@
 xsltproc = @xsltproc@

doc/manual/command-ref/nix-store.xml

@@ -360,7 +360,6 @@ EOF
     <arg choice='plain'><option>--print-roots</option></arg>
     <arg choice='plain'><option>--print-live</option></arg>
     <arg choice='plain'><option>--print-dead</option></arg>
-    <arg choice='plain'><option>--delete</option></arg>
   </group>
   <arg><option>--max-freed</option> <replaceable>bytes</replaceable></arg>
 </cmdsynopsis>
@@ -407,14 +406,6 @@ the Nix store not reachable via file system references from a set of
 
   </varlistentry>
 
-  <varlistentry><term><option>--delete</option></term>
-
-    <listitem><para>This operation performs an actual garbage
-    collection.  All dead paths are removed from the
-    store.  This is the default.</para></listitem>
-
-  </varlistentry>
-
 </variablelist>
 
 <para>By default, all unreachable paths are deleted.  The following
@@ -444,10 +435,10 @@ and <link
 linkend="conf-keep-derivations"><literal>keep-derivations</literal></link>
 variables in the Nix configuration file.</para>
 
-<para>With <option>--delete</option>, the collector prints the total
+<para>By default, the collector prints the total number of freed bytes
-number of freed bytes when it finishes (or when it is interrupted).
+when it finishes (or when it is interrupted). With
-With <option>--print-dead</option>, it prints the number of bytes that
+<option>--print-dead</option>, it prints the number of bytes that would
-would be freed.</para>
+be freed.</para>
 
 </refsection>
 
@@ -1148,7 +1139,7 @@ the information that Nix considers important.  For instance,
 timestamps are elided because all files in the Nix store have their
 timestamp set to 0 anyway.  Likewise, all permissions are left out
 except for the execute bit, because all files in the Nix store have
-644 or 755 permission.</para>
+444 or 555 permission.</para>
 
 <para>Also, a NAR archive is <emphasis>canonical</emphasis>, meaning
 that “equal” paths always produce the same NAR archive.  For instance,

local.mk

@@ -6,9 +6,11 @@ dist-files += configure config.h.in perl/configure
 
 clean-files += Makefile.config
 
-GLOBAL_CXXFLAGS += -I . -I src -I src/libutil -I src/libstore -I src/libmain -I src/libexpr -I src/nix -Wno-deprecated-declarations
+GLOBAL_CXXFLAGS += -Wno-deprecated-declarations
 
 $(foreach i, config.h $(call rwildcard, src/lib*, *.hh), \
   $(eval $(call install-file-in, $(i), $(includedir)/nix, 0644)))
 
 $(GCH) $(PCH): src/libutil/util.hh config.h
+
+GCH_CXXFLAGS = -I src/libutil

mk/precompiled-headers.mk

@@ -8,14 +8,14 @@ GCH = $(buildprefix)precompiled-headers.h.gch
 $(GCH): precompiled-headers.h
 	@rm -f $@
 	@mkdir -p "$(dir $@)"
-	$(trace-gen) $(CXX) -x c++-header -o $@ $< $(GLOBAL_CXXFLAGS)
+	$(trace-gen) $(CXX) -x c++-header -o $@ $< $(GLOBAL_CXXFLAGS) $(GCH_CXXFLAGS)
 
 PCH = $(buildprefix)precompiled-headers.h.pch
 
 $(PCH): precompiled-headers.h
 	@rm -f $@
 	@mkdir -p "$(dir $@)"
-	$(trace-gen) $(CXX) -x c++-header -o $@ $< $(GLOBAL_CXXFLAGS)
+	$(trace-gen) $(CXX) -x c++-header -o $@ $< $(GLOBAL_CXXFLAGS) $(GCH_CXXFLAGS)
 
 clean-files += $(GCH) $(PCH)
 

release.nix

@@ -12,11 +12,9 @@ let
     builtins.readFile ./.version
     + (if officialRelease then "" else "pre${toString nix.revCount}_${nix.shortRev}");
 
-  jobs = rec {
-
   # Create a "vendor" directory that contains the crates listed in
   # Cargo.lock. This allows Nix to be built without network access.
-    vendoredCrates =
+  vendoredCrates' =
     let
       lockFile = builtins.fromTOML (builtins.readFile nix-rust/Cargo.lock);
 
@@ -57,6 +55,20 @@ let
         '') files)}
       '';
 
+  jobs = rec {
+
+    vendoredCrates =
+      with pkgs;
+      runCommand "vendored-crates" {}
+        ''
+          mkdir -p $out/nix-support
+          name=nix-vendored-crates-${version}
+          fn=$out/$name.tar.xz
+            tar cvfJ $fn -C ${vendoredCrates'} vendor \
+              --owner=0 --group=0 --mode=u+rw,uga+r \
+              --transform "s,vendor,$name,"
+            echo "file crates-tarball $fn" >> $out/nix-support/hydra-build-products
+        '';
 
     build = pkgs.lib.genAttrs systems (system:
 
@@ -89,7 +101,7 @@ let
               patchelf --set-rpath $out/lib:${stdenv.cc.cc.lib}/lib $out/lib/libboost_thread.so.*
             ''}
 
-            ln -sfn ${vendoredCrates}/vendor/ nix-rust/vendor
+            ln -sfn ${vendoredCrates'}/vendor/ nix-rust/vendor
 
             (cd perl; autoreconf --install --force --verbose)
           '';

scripts/install-multi-user.sh

@@ -13,12 +13,12 @@ set -o pipefail
 # however tracking which bits came from which would be impossible.
 
 readonly ESC='\033[0m'
-readonly BOLD='\033[38;1m'
+readonly BOLD='\033[1m'
-readonly BLUE='\033[38;34m'
+readonly BLUE='\033[34m'
-readonly BLUE_UL='\033[38;4;34m'
+readonly BLUE_UL='\033[4;34m'
-readonly GREEN='\033[38;32m'
+readonly GREEN='\033[32m'
-readonly GREEN_UL='\033[38;4;32m'
+readonly GREEN_UL='\033[4;32m'
-readonly RED='\033[38;31m'
+readonly RED='\033[31m'
 
 readonly NIX_USER_COUNT="32"
 readonly NIX_BUILD_GROUP_ID="30000"
@@ -567,7 +567,7 @@ install_from_extracted_nix() {
         cd "$EXTRACTED_NIX_PATH"
 
         _sudo "to copy the basic Nix files to the new store at $NIX_ROOT/store" \
-              rsync -rlpt ./store/* "$NIX_ROOT/store/"
+              rsync -rlpt --chmod=-w ./store/* "$NIX_ROOT/store/"
 
         if [ -d "$NIX_INSTALLED_NIX" ]; then
             echo "      Alright! We have our first nix at $NIX_INSTALLED_NIX"

scripts/install.in

@@ -36,6 +36,7 @@ tarball="$tmpDir/$(basename "$tmpDir/nix-@nixVersion@-$system.tar.xz")"
 
 require_util curl "download the binary tarball"
 require_util tar "unpack the binary tarball"
+require_util xz "unpack the binary tarball"
 
 echo "downloading Nix @nixVersion@ binary tarball for $system from '$url' to '$tmpDir'..."
 curl -L "$url" -o "$tarball" || oops "failed to download '$url'"

src/build-remote/build-remote.cc

@@ -17,7 +17,7 @@
 #include "store-api.hh"
 #include "derivations.hh"
 #include "local-store.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 using namespace nix;
 using std::cin;

src/libexpr/attr-path.cc

@@ -32,15 +32,13 @@ static Strings parseAttrPath(const string & s)
 }
 
 
-Value * findAlongAttrPath(EvalState & state, const string & attrPath,
+std::pair<Value *, Pos> findAlongAttrPath(EvalState & state, const string & attrPath,
     Bindings & autoArgs, Value & vIn)
 {
     Strings tokens = parseAttrPath(attrPath);
 
-    Error attrError =
-        Error(format("attribute selection path '%1%' does not match expression") % attrPath);
-
     Value * v = &vIn;
+    Pos pos = noPos;
 
     for (auto & attr : tokens) {
 
@@ -70,8 +68,9 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
 
             Bindings::iterator a = v->attrs->find(state.symbols.create(attr));
             if (a == v->attrs->end())
-                throw Error(format("attribute '%1%' in selection path '%2%' not found") % attr % attrPath);
+                throw AttrPathNotFound("attribute '%1%' in selection path '%2%' not found", attr, attrPath);
             v = &*a->value;
+            pos = *a->pos;
         }
 
         else if (apType == apIndex) {
@@ -82,14 +81,15 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
                     % attrPath % showType(*v));
 
             if (attrIndex >= v->listSize())
-                throw Error(format("list index %1% in selection path '%2%' is out of range") % attrIndex % attrPath);
+                throw AttrPathNotFound("list index %1% in selection path '%2%' is out of range", attrIndex, attrPath);
 
             v = v->listElems()[attrIndex];
+            pos = noPos;
         }
 
     }
 
-    return v;
+    return {v, pos};
 }
 
 
@@ -98,9 +98,9 @@ Pos findDerivationFilename(EvalState & state, Value & v, std::string what)
     Value * v2;
     try {
         auto dummyArgs = state.allocBindings(0);
-        v2 = findAlongAttrPath(state, "meta.position", *dummyArgs, v);
+        v2 = findAlongAttrPath(state, "meta.position", *dummyArgs, v).first;
     } catch (Error &) {
-        throw Error("package '%s' has no source location information", what);
+        throw NoPositionInfo("package '%s' has no source location information", what);
     }
 
     // FIXME: is it possible to extract the Pos object instead of doing this

src/libexpr/attr-path.hh

@@ -7,7 +7,10 @@
 
 namespace nix {
 
-Value * findAlongAttrPath(EvalState & state, const string & attrPath,
+MakeError(AttrPathNotFound, Error);
+MakeError(NoPositionInfo, Error);
+
+std::pair<Value *, Pos> findAlongAttrPath(EvalState & state, const string & attrPath,
     Bindings & autoArgs, Value & vIn);
 
 /* Heuristic to find the filename and lineno or a nix value. */

src/libexpr/attr-set.cc

@@ -43,6 +43,12 @@ Value * EvalState::allocAttr(Value & vAttrs, const Symbol & name)
 }
 
 
+Value * EvalState::allocAttr(Value & vAttrs, const std::string & name)
+{
+    return allocAttr(vAttrs, symbols.create(name));
+}
+
+
 void Bindings::sort()
 {
     std::sort(begin(), end());

src/libexpr/eval.hh

@@ -272,6 +272,7 @@ public:
     Env & allocEnv(size_t size);
 
     Value * allocAttr(Value & vAttrs, const Symbol & name);
+    Value * allocAttr(Value & vAttrs, const std::string & name);
 
     Bindings * allocBindings(size_t capacity);
 
@@ -367,7 +368,7 @@ struct EvalSettings : Config
         "Prefixes of URIs that builtin functions such as fetchurl and fetchGit are allowed to fetch."};
 
     Setting<bool> traceFunctionCalls{this, false, "trace-function-calls",
-        "Emit log messages for each function entry and exit at the 'vomit' log level (-vvvv)"};
+        "Emit log messages for each function entry and exit at the 'vomit' log level (-vvvv)."};
 };
 
 extern EvalSettings evalSettings;

src/libexpr/function-trace.cc

@@ -1,4 +1,5 @@
 #include "function-trace.hh"
+#include "logging.hh"
 
 namespace nix {
 

src/libexpr/local.mk

@@ -6,6 +6,8 @@ libexpr_DIR := $(d)
 
 libexpr_SOURCES := $(wildcard $(d)/*.cc) $(wildcard $(d)/primops/*.cc) $(d)/lexer-tab.cc $(d)/parser-tab.cc
 
+libexpr_CXXFLAGS += -I src/libutil -I src/libstore -I src/libmain -I src/libexpr
+
 libexpr_LIBS = libutil libstore libnixrust
 
 libexpr_LDFLAGS =

src/libexpr/primops/fromTOML.cc

@@ -1,7 +1,7 @@
 #include "primops.hh"
 #include "eval-inline.hh"
 
-#include "cpptoml/cpptoml.h"
+#include "../../cpptoml/cpptoml.h"
 
 namespace nix {
 

src/libmain/local.mk

@@ -6,6 +6,8 @@ libmain_DIR := $(d)
 
 libmain_SOURCES := $(wildcard $(d)/*.cc)
 
+libmain_CXXFLAGS += -I src/libutil -I src/libstore
+
 libmain_LDFLAGS = $(OPENSSL_LIBS)
 
 libmain_LIBS = libstore libutil

src/libstore/build.cc

@@ -6,6 +6,7 @@
 #include "archive.hh"
 #include "affinity.hh"
 #include "builtins.hh"
+#include "builtins/buildenv.hh"
 #include "download.hh"
 #include "finally.hh"
 #include "compression.hh"
@@ -1397,7 +1398,7 @@ void DerivationGoal::tryToBuild()
        few seconds and then retry this goal. */
     PathSet lockFiles;
     for (auto & outPath : drv->outputPaths())
-        lockFiles.insert(worker.store.toRealPath(worker.store.printStorePath(outPath)));
+        lockFiles.insert(worker.store.Store::toRealPath(outPath));
 
     if (!outputLocks.lockPaths(lockFiles, "", false)) {
         worker.waitForAWhile(shared_from_this());
@@ -1428,7 +1429,7 @@ void DerivationGoal::tryToBuild()
     for (auto & i : drv->outputs) {
         if (worker.store.isValidPath(i.second.path)) continue;
         debug("removing invalid path '%s'", worker.store.printStorePath(i.second.path));
-        deletePath(worker.store.toRealPath(worker.store.printStorePath(i.second.path)));
+        deletePath(worker.store.Store::toRealPath(i.second.path));
     }
 
     /* Don't do a remote build if the derivation has the attribute
@@ -1685,7 +1686,7 @@ void DerivationGoal::buildDone()
 
         /* Delete unused redirected outputs (when doing hash rewriting). */
         for (auto & i : redirectedOutputs)
-            deletePath(worker.store.toRealPath(worker.store.printStorePath(i.second)));
+            deletePath(worker.store.Store::toRealPath(i.second));
 
         /* Delete the chroot (if we were using one). */
         autoDelChroot.reset(); /* this runs the destructor */
@@ -1904,7 +1905,7 @@ void DerivationGoal::startBuilder()
             concatStringsSep(", ", parsedDrv->getRequiredSystemFeatures()),
             worker.store.printStorePath(drvPath),
             settings.thisSystem,
-            concatStringsSep(", ", settings.systemFeatures));
+            concatStringsSep<StringSet>(", ", settings.systemFeatures));
 
     if (drv->isBuiltin())
         preloadNSS();
@@ -2071,7 +2072,7 @@ void DerivationGoal::startBuilder()
            environment using bind-mounts.  We put it in the Nix store
            to ensure that we can create hard-links to non-directory
            inputs in the fake Nix store in the chroot (see below). */
-        chrootRootDir = worker.store.toRealPath(worker.store.printStorePath(drvPath)) + ".chroot";
+        chrootRootDir = worker.store.Store::toRealPath(drvPath) + ".chroot";
         deletePath(chrootRootDir);
 
         /* Clean up the chroot directory automatically. */
@@ -2464,7 +2465,7 @@ void DerivationGoal::initTmpDir() {
                 auto hash = hashString(htSHA256, i.first);
                 string fn = ".attr-" + hash.to_string(Base32, false);
                 Path p = tmpDir + "/" + fn;
-                writeFile(p, i.second);
+                writeFile(p, rewriteStrings(i.second, inputRewrites));
                 chownToBuilder(p);
                 env[i.first + "Path"] = tmpDirInSandbox + "/" + fn;
             }
@@ -2550,7 +2551,7 @@ static std::regex shVarName("[A-Za-z_][A-Za-z0-9_]*");
 
 void DerivationGoal::writeStructuredAttrs()
 {
-    auto & structuredAttrs = parsedDrv->getStructuredAttrs();
+    auto structuredAttrs = parsedDrv->getStructuredAttrs();
     if (!structuredAttrs) return;
 
     auto json = *structuredAttrs;
@@ -2916,7 +2917,7 @@ void DerivationGoal::addDependency(const StorePath & path)
 
         #if __linux__
 
-            Path source = worker.store.toRealPath(worker.store.printStorePath(path));
+            Path source = worker.store.Store::toRealPath(path);
             Path target = chrootRootDir + worker.store.printStorePath(path);
             debug("bind-mounting %s -> %s", target, source);
 
@@ -3578,7 +3579,7 @@ void DerivationGoal::registerOutputs()
         if (needsHashRewrite()) {
             auto r = redirectedOutputs.find(i.second.path);
             if (r != redirectedOutputs.end()) {
-                auto redirected = worker.store.toRealPath(worker.store.printStorePath(r->second));
+                auto redirected = worker.store.Store::toRealPath(r->second);
                 if (buildMode == bmRepair
                     && redirectedBadOutputs.count(i.second.path)
                     && pathExists(redirected))
@@ -3671,7 +3672,7 @@ void DerivationGoal::registerOutputs()
                     BuildError("hash mismatch in fixed-output derivation '%s':\n  wanted: %s\n  got:    %s",
                         worker.store.printStorePath(dest), h.to_string(SRI), h2.to_string(SRI)));
 
-                Path actualDest = worker.store.toRealPath(worker.store.printStorePath(dest));
+                Path actualDest = worker.store.Store::toRealPath(dest);
 
                 if (worker.store.isValidPath(dest))
                     std::rethrow_exception(delayedException);

src/libstore/builtins.hh

@@ -6,7 +6,6 @@ namespace nix {
 
 // TODO: make pluggable.
 void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData);
-void builtinBuildenv(const BasicDerivation & drv);
 void builtinUnpackChannel(const BasicDerivation & drv);
 
 }

src/libstore/builtins/buildenv.cc

@@ -1,4 +1,4 @@
-#include "builtins.hh"
+#include "buildenv.hh"
 
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -7,16 +7,14 @@
 
 namespace nix {
 
-typedef std::map<Path,int> Priorities;
+struct State
-
+{
-// FIXME: change into local variables.
+    std::map<Path, int> priorities;
-
+    unsigned long symlinks = 0;
-static Priorities priorities;
+};
-
-static unsigned long symlinks;
 
 /* For each activated package, create symlinks */
-static void createLinks(const Path & srcDir, const Path & dstDir, int priority)
+static void createLinks(State & state, const Path & srcDir, const Path & dstDir, int priority)
 {
     DirEntries srcFiles;
 
@@ -67,7 +65,7 @@ static void createLinks(const Path & srcDir, const Path & dstDir, int priority)
             auto res = lstat(dstFile.c_str(), &dstSt);
             if (res == 0) {
                 if (S_ISDIR(dstSt.st_mode)) {
-                    createLinks(srcFile, dstFile, priority);
+                    createLinks(state, srcFile, dstFile, priority);
                     continue;
                 } else if (S_ISLNK(dstSt.st_mode)) {
                     auto target = canonPath(dstFile, true);
@@ -77,8 +75,8 @@ static void createLinks(const Path & srcDir, const Path & dstDir, int priority)
                         throw SysError(format("unlinking '%1%'") % dstFile);
                     if (mkdir(dstFile.c_str(), 0755) == -1)
                         throw SysError(format("creating directory '%1%'"));
-                    createLinks(target, dstFile, priorities[dstFile]);
+                    createLinks(state, target, dstFile, state.priorities[dstFile]);
-                    createLinks(srcFile, dstFile, priority);
+                    createLinks(state, srcFile, dstFile, priority);
                     continue;
                 }
             } else if (errno != ENOENT)
@@ -90,7 +88,7 @@ static void createLinks(const Path & srcDir, const Path & dstDir, int priority)
             auto res = lstat(dstFile.c_str(), &dstSt);
             if (res == 0) {
                 if (S_ISLNK(dstSt.st_mode)) {
-                    auto prevPriority = priorities[dstFile];
+                    auto prevPriority = state.priorities[dstFile];
                     if (prevPriority == priority)
                         throw Error(
                                 "packages '%1%' and '%2%' have the same priority %3%; "
@@ -109,22 +107,20 @@ static void createLinks(const Path & srcDir, const Path & dstDir, int priority)
         }
 
         createSymlink(srcFile, dstFile);
-        priorities[dstFile] = priority;
+        state.priorities[dstFile] = priority;
-        symlinks++;
+        state.symlinks++;
     }
 }
 
-typedef std::set<Path> FileProp;
+void buildProfile(const Path & out, Packages && pkgs)
-
-static FileProp done;
-static FileProp postponed = FileProp{};
-
-static Path out;
-
-static void addPkg(const Path & pkgDir, int priority)
 {
+    State state;
+
+    std::set<Path> done, postponed;
+
+    auto addPkg = [&](const Path & pkgDir, int priority) {
         if (!done.insert(pkgDir).second) return;
-    createLinks(pkgDir, out, priority);
+        createLinks(state, pkgDir, out, priority);
 
         try {
             for (const auto & p : tokenizeString<std::vector<string>>(
@@ -134,43 +130,8 @@ static void addPkg(const Path & pkgDir, int priority)
         } catch (SysError & e) {
             if (e.errNo != ENOENT && e.errNo != ENOTDIR) throw;
         }
-}
-
-struct Package {
-    Path path;
-    bool active;
-    int priority;
-    Package(Path path, bool active, int priority) : path{path}, active{active}, priority{priority} {}
     };
 
-typedef std::vector<Package> Packages;
-
-void builtinBuildenv(const BasicDerivation & drv)
-{
-    auto getAttr = [&](const string & name) {
-        auto i = drv.env.find(name);
-        if (i == drv.env.end()) throw Error("attribute '%s' missing", name);
-        return i->second;
-    };
-
-    out = getAttr("out");
-    createDirs(out);
-
-    /* Convert the stuff we get from the environment back into a
-     * coherent data type. */
-    Packages pkgs;
-    auto derivations = tokenizeString<Strings>(getAttr("derivations"));
-    while (!derivations.empty()) {
-        /* !!! We're trusting the caller to structure derivations env var correctly */
-        auto active = derivations.front(); derivations.pop_front();
-        auto priority = stoi(derivations.front()); derivations.pop_front();
-        auto outputs = stoi(derivations.front()); derivations.pop_front();
-        for (auto n = 0; n < outputs; n++) {
-            auto path = derivations.front(); derivations.pop_front();
-            pkgs.emplace_back(path, active != "false", priority);
-        }
-    }
-
     /* Symlink to the packages that have been installed explicitly by the
      * user. Process in priority order to reduce unnecessary
      * symlink/unlink steps.
@@ -189,13 +150,42 @@ void builtinBuildenv(const BasicDerivation & drv)
      */
     auto priorityCounter = 1000;
     while (!postponed.empty()) {
-        auto pkgDirs = postponed;
+        std::set<Path> pkgDirs;
-        postponed = FileProp{};
+        postponed.swap(pkgDirs);
         for (const auto & pkgDir : pkgDirs)
             addPkg(pkgDir, priorityCounter++);
     }
 
-    printError("created %d symlinks in user environment", symlinks);
+    debug("created %d symlinks in user environment", state.symlinks);
+}
+
+void builtinBuildenv(const BasicDerivation & drv)
+{
+    auto getAttr = [&](const string & name) {
+        auto i = drv.env.find(name);
+        if (i == drv.env.end()) throw Error("attribute '%s' missing", name);
+        return i->second;
+    };
+
+    Path out = getAttr("out");
+    createDirs(out);
+
+    /* Convert the stuff we get from the environment back into a
+     * coherent data type. */
+    Packages pkgs;
+    auto derivations = tokenizeString<Strings>(getAttr("derivations"));
+    while (!derivations.empty()) {
+        /* !!! We're trusting the caller to structure derivations env var correctly */
+        auto active = derivations.front(); derivations.pop_front();
+        auto priority = stoi(derivations.front()); derivations.pop_front();
+        auto outputs = stoi(derivations.front()); derivations.pop_front();
+        for (auto n = 0; n < outputs; n++) {
+            auto path = derivations.front(); derivations.pop_front();
+            pkgs.emplace_back(path, active != "false", priority);
+        }
+    }
+
+    buildProfile(out, std::move(pkgs));
 
     createSymlink(getAttr("manifest"), out + "/manifest.nix");
 }

src/libstore/builtins/buildenv.hh

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "derivations.hh"
+#include "store-api.hh"
+
+namespace nix {
+
+struct Package {
+    Path path;
+    bool active;
+    int priority;
+    Package(Path path, bool active, int priority) : path{path}, active{active}, priority{priority} {}
+};
+
+typedef std::vector<Package> Packages;
+
+void buildProfile(const Path & out, Packages && pkgs);
+
+void builtinBuildenv(const BasicDerivation & drv);
+
+}

src/libstore/derivations.cc

@@ -65,7 +65,7 @@ bool BasicDerivation::isBuiltin() const
 
 
 StorePath writeDerivation(ref<Store> store,
-    const Derivation & drv, const string & name, RepairFlag repair)
+    const Derivation & drv, std::string_view name, RepairFlag repair)
 {
     auto references = cloneStorePathSet(drv.inputSrcs);
     for (auto & i : drv.inputDrvs)
@@ -73,8 +73,8 @@ StorePath writeDerivation(ref<Store> store,
     /* Note that the outputs of a derivation are *not* references
        (that can be missing (of course) and should not necessarily be
        held during a garbage collection). */
-    string suffix = name + drvExtension;
+    auto suffix = std::string(name) + drvExtension;
-    string contents = drv.unparse(*store, false);
+    auto contents = drv.unparse(*store, false);
     return settings.readOnlyMode
         ? store->computeStorePathForText(suffix, contents, references)
         : store->addTextToStore(suffix, contents, references, repair);

src/libstore/derivations.hh

@@ -79,7 +79,7 @@ class Store;
 
 /* Write a derivation to the Nix store, and return its path. */
 StorePath writeDerivation(ref<Store> store,
-    const Derivation & drv, const string & name, RepairFlag repair = NoRepair);
+    const Derivation & drv, std::string_view name, RepairFlag repair = NoRepair);
 
 /* Read a derivation from a file. */
 Derivation readDerivation(const Store & store, const Path & drvPath);

src/libstore/download.cc

@@ -390,6 +390,7 @@ struct CurlDownloader : public Downloader
                         case CURLE_SSL_CACERT_BADFILE:
                         case CURLE_TOO_MANY_REDIRECTS:
                         case CURLE_WRITE_ERROR:
+                        case CURLE_UNSUPPORTED_PROTOCOL:
                             err = Misc;
                             break;
                         default: // Shut up warnings

src/libstore/globals.cc

@@ -20,13 +20,6 @@ namespace nix {
    must be deleted and recreated on startup.) */
 #define DEFAULT_SOCKET_PATH "/daemon-socket/socket"
 
-/* chroot-like behavior from Apple's sandbox */
-#if __APPLE__
-    #define DEFAULT_ALLOWED_IMPURE_PREFIXES "/System/Library /usr/lib /dev /bin/sh"
-#else
-    #define DEFAULT_ALLOWED_IMPURE_PREFIXES ""
-#endif
-
 Settings settings;
 
 static GlobalConfig::Register r1(&settings);
@@ -68,7 +61,12 @@ Settings::Settings()
     sandboxPaths = tokenizeString<StringSet>("/bin/sh=" SANDBOX_SHELL);
 #endif
 
-    allowedImpureHostPrefixes = tokenizeString<StringSet>(DEFAULT_ALLOWED_IMPURE_PREFIXES);
+
+/* chroot-like behavior from Apple's sandbox */
+#if __APPLE__
+    sandboxPaths = tokenizeString<StringSet>("/System/Library/Frameworks /System/Library/PrivateFrameworks /bin/sh /bin/bash /private/tmp /private/var/tmp /usr/lib");
+    allowedImpureHostPrefixes = tokenizeString<StringSet>("/System/Library /usr/lib /dev /bin/sh");
+#endif
 }
 
 void loadConfFile()

src/libstore/globals.hh

@@ -311,12 +311,7 @@ public:
     Setting<bool> printMissing{this, true, "print-missing",
         "Whether to print what paths need to be built or downloaded."};
 
-    Setting<std::string> preBuildHook{this,
+    Setting<std::string> preBuildHook{this, "",
-#if __APPLE__
-        nixLibexecDir + "/nix/resolve-system-dependencies",
-#else
-        "",
-#endif
         "pre-build-hook",
         "A program to run just before a build to set derivation-specific build settings."};
 

src/libstore/http-binary-cache-store.cc

@@ -163,10 +163,11 @@ static RegisterStoreImplementation regStore([](
     const std::string & uri, const Store::Params & params)
     -> std::shared_ptr<Store>
 {
+    static bool forceHttp = getEnv("_NIX_FORCE_HTTP") == "1";
     if (std::string(uri, 0, 7) != "http://" &&
         std::string(uri, 0, 8) != "https://" &&
-        (getEnv("_NIX_FORCE_HTTP_BINARY_CACHE_STORE") != "1" || std::string(uri, 0, 7) != "file://")
+        (!forceHttp || std::string(uri, 0, 7) != "file://"))
-        ) return 0;
+        return 0;
     auto store = std::make_shared<HttpBinaryCacheStore>(params, uri);
     store->init();
     return store;

src/libstore/local-store.cc

@@ -298,9 +298,7 @@ void LocalStore::openDB(State & state, bool create)
     /* Open the Nix database. */
     string dbPath = dbDir + "/db.sqlite";
     auto & db(state.db);
-    if (sqlite3_open_v2(dbPath.c_str(), &db.db,
+    state.db = SQLite(dbPath, create);
-            SQLITE_OPEN_READWRITE | (create ? SQLITE_OPEN_CREATE : 0), 0) != SQLITE_OK)
-        throw Error(format("cannot open Nix database '%1%'") % dbPath);
 
 #ifdef __CYGWIN__
     /* The cygwin version of sqlite3 has a patch which calls
@@ -312,11 +310,6 @@ void LocalStore::openDB(State & state, bool create)
     SetDllDirectoryW(L"");
 #endif
 
-    if (sqlite3_busy_timeout(db, 60 * 60 * 1000) != SQLITE_OK)
-        throwSQLiteError(db, "setting timeout");
-
-    db.exec("pragma foreign_keys = 1");
-
     /* !!! check whether sqlite has been built with foreign key
        support */
 
@@ -350,7 +343,7 @@ void LocalStore::openDB(State & state, bool create)
 
     /* Initialise the database schema, if necessary. */
     if (create) {
-        const char * schema =
+        static const char schema[] =
 #include "schema.sql.gen.hh"
             ;
         db.exec(schema);
@@ -1275,7 +1268,7 @@ bool LocalStore::verifyStore(bool checkContents, RepairFlag repair)
                 else
                     hashSink = std::make_unique<HashModuloSink>(info->narHash.type, storePathToHash(printStorePath(info->path)));
 
-                dumpPath(toRealPath(printStorePath(i)), *hashSink);
+                dumpPath(Store::toRealPath(i), *hashSink);
                 auto current = hashSink->finish();
 
                 if (info->narHash != nullHash && info->narHash != current.first) {

src/libstore/local.mk

@@ -31,7 +31,8 @@ ifeq ($(HAVE_SECCOMP), 1)
 	libstore_LDFLAGS += -lseccomp
 endif
 
-libstore_CXXFLAGS = \
+libstore_CXXFLAGS += \
+ -I src/libutil -I src/libstore \
  -DNIX_PREFIX=\"$(prefix)\" \
  -DNIX_STORE_DIR=\"$(storedir)\" \
  -DNIX_DATA_DIR=\"$(datadir)\" \

src/libstore/nar-info-disk-cache.cc

@@ -78,12 +78,7 @@ public:
 
         state->db = SQLite(dbPath);
 
-        if (sqlite3_busy_timeout(state->db, 60 * 60 * 1000) != SQLITE_OK)
+        state->db.isCache();
-            throwSQLiteError(state->db, "setting timeout");
-
-        // We can always reproduce the cache.
-        state->db.exec("pragma synchronous = off");
-        state->db.exec("pragma main.journal_mode = truncate");
 
         state->db.exec(schema);
 

src/libstore/nar-info-disk-cache.hh

@@ -10,7 +10,7 @@ class NarInfoDiskCache
 public:
     typedef enum { oValid, oInvalid, oUnknown } Outcome;
 
-    virtual ~NarInfoDiskCache() { };
+    virtual ~NarInfoDiskCache() { }
 
     virtual void createCache(const std::string & uri, const Path & storeDir,
         bool wantMassQuery, int priority) = 0;

src/libstore/parsed-derivations.cc

@@ -1,5 +1,7 @@
 #include "parsed-derivations.hh"
 
+#include <nlohmann/json.hpp>
+
 namespace nix {
 
 ParsedDerivation::ParsedDerivation(StorePath && drvPath, BasicDerivation & drv)
@@ -9,13 +11,15 @@ ParsedDerivation::ParsedDerivation(StorePath && drvPath, BasicDerivation & drv)
     auto jsonAttr = drv.env.find("__json");
     if (jsonAttr != drv.env.end()) {
         try {
-            structuredAttrs = nlohmann::json::parse(jsonAttr->second);
+            structuredAttrs = std::make_unique<nlohmann::json>(nlohmann::json::parse(jsonAttr->second));
         } catch (std::exception & e) {
             throw Error("cannot process __json attribute of '%s': %s", drvPath.to_string(), e.what());
         }
     }
 }
 
+ParsedDerivation::~ParsedDerivation() { }
+
 std::optional<std::string> ParsedDerivation::getStringAttr(const std::string & name) const
 {
     if (structuredAttrs) {

src/libstore/parsed-derivations.hh

@@ -1,6 +1,6 @@
 #include "derivations.hh"
 
-#include <nlohmann/json.hpp>
+#include <nlohmann/json_fwd.hpp>
 
 namespace nix {
 
@@ -8,15 +8,17 @@ class ParsedDerivation
 {
     StorePath drvPath;
     BasicDerivation & drv;
-    std::optional<nlohmann::json> structuredAttrs;
+    std::unique_ptr<nlohmann::json> structuredAttrs;
 
 public:
 
     ParsedDerivation(StorePath && drvPath, BasicDerivation & drv);
 
-    const std::optional<nlohmann::json> & getStructuredAttrs() const
+    ~ParsedDerivation();
+
+    const nlohmann::json * getStructuredAttrs() const
     {
-        return structuredAttrs;
+        return structuredAttrs.get();
     }
 
     std::optional<std::string> getStringAttr(const std::string & name) const;

src/libstore/profiles.cc

@@ -256,4 +256,22 @@ string optimisticLockProfile(const Path & profile)
 }
 
 
+Path getDefaultProfile()
+{
+    Path profileLink = getHome() + "/.nix-profile";
+    try {
+        if (!pathExists(profileLink)) {
+            replaceSymlink(
+                getuid() == 0
+                ? settings.nixStateDir + "/profiles/default"
+                : fmt("%s/profiles/per-user/%s/profile", settings.nixStateDir, getUserName()),
+                profileLink);
+        }
+        return absPath(readLink(profileLink), dirOf(profileLink));
+    } catch (Error &) {
+        return profileLink;
+    }
+}
+
+
 }

src/libstore/profiles.hh

@@ -64,4 +64,8 @@ void lockProfile(PathLocks & lock, const Path & profile);
    rebuilt. */
 string optimisticLockProfile(const Path & profile);
 
+/* Resolve ~/.nix-profile. If ~/.nix-profile doesn't exist yet, create
+   it. */
+Path getDefaultProfile();
+
 }

src/libstore/sandbox-defaults.sb

@@ -71,6 +71,12 @@
        (literal "/dev/zero")
        (subpath "/dev/fd"))
 
+; Allow pseudo-terminals.
+(allow file*
+       (literal "/dev/ptmx")
+       (regex #"^/dev/pty[a-z]+")
+       (regex #"^/dev/ttys[0-9]+"))
+
 ; Does nothing, but reduces build noise.
 (allow file* (literal "/dev/dtracehelper"))
 
@@ -85,3 +91,7 @@
        (literal "/etc")
        (literal "/var")
        (literal "/private/var/tmp"))
+
+; This is used by /bin/sh on macOS 10.15 and later.
+(allow file*
+       (literal "/private/var/select/sh"))

src/libstore/sqlite.cc

@@ -25,11 +25,16 @@ namespace nix {
         throw SQLiteError("%s: %s (in '%s')", fs.s, sqlite3_errstr(exterr), path);
 }
 
-SQLite::SQLite(const Path & path)
+SQLite::SQLite(const Path & path, bool create)
 {
     if (sqlite3_open_v2(path.c_str(), &db,
-            SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0) != SQLITE_OK)
+            SQLITE_OPEN_READWRITE | (create ? SQLITE_OPEN_CREATE : 0), 0) != SQLITE_OK)
         throw Error(format("cannot open SQLite database '%s'") % path);
+
+    if (sqlite3_busy_timeout(db, 60 * 60 * 1000) != SQLITE_OK)
+        throwSQLiteError(db, "setting timeout");
+
+    exec("pragma foreign_keys = 1");
 }
 
 SQLite::~SQLite()
@@ -42,6 +47,12 @@ SQLite::~SQLite()
     }
 }
 
+void SQLite::isCache()
+{
+    exec("pragma synchronous = off");
+    exec("pragma main.journal_mode = truncate");
+}
+
 void SQLite::exec(const std::string & stmt)
 {
     retrySQLite<void>([&]() {
@@ -94,6 +105,16 @@ SQLiteStmt::Use & SQLiteStmt::Use::operator () (const std::string & value, bool
     return *this;
 }
 
+SQLiteStmt::Use & SQLiteStmt::Use::operator () (const unsigned char * data, size_t len, bool notNull)
+{
+    if (notNull) {
+        if (sqlite3_bind_blob(stmt, curArg++, data, len, SQLITE_TRANSIENT) != SQLITE_OK)
+            throwSQLiteError(stmt.db, "binding argument");
+    } else
+        bind();
+    return *this;
+}
+
 SQLiteStmt::Use & SQLiteStmt::Use::operator () (int64_t value, bool notNull)
 {
     if (notNull) {

src/libstore/sqlite.hh

@@ -5,8 +5,8 @@
 
 #include "types.hh"
 
-class sqlite3;
+struct sqlite3;
-class sqlite3_stmt;
+struct sqlite3_stmt;
 
 namespace nix {
 
@@ -15,13 +15,16 @@ struct SQLite
 {
     sqlite3 * db = 0;
     SQLite() { }
-    SQLite(const Path & path);
+    SQLite(const Path & path, bool create = true);
     SQLite(const SQLite & from) = delete;
     SQLite& operator = (const SQLite & from) = delete;
     SQLite& operator = (SQLite && from) { db = from.db; from.db = 0; return *this; }
     ~SQLite();
     operator sqlite3 * () { return db; }
 
+    /* Disable synchronous mode, set truncate journal mode. */
+    void isCache();
+
     void exec(const std::string & stmt);
 };
 
@@ -52,6 +55,7 @@ struct SQLiteStmt
 
         /* Bind the next parameter. */
         Use & operator () (const std::string & value, bool notNull = true);
+        Use & operator () (const unsigned char * data, size_t len, bool notNull = true);
         Use & operator () (int64_t value, bool notNull = true);
         Use & bind(); // null
 

src/libstore/store-api.cc

@@ -441,7 +441,9 @@ string Store::makeValidityRegistration(const StorePathSet & paths,
 
 
 void Store::pathInfoToJSON(JSONPlaceholder & jsonOut, const StorePathSet & storePaths,
-    bool includeImpureInfo, bool showClosureSize, AllowInvalidFlag allowInvalid)
+    bool includeImpureInfo, bool showClosureSize,
+    Base hashBase,
+    AllowInvalidFlag allowInvalid)
 {
     auto jsonList = jsonOut.list();
 
@@ -453,7 +455,7 @@ void Store::pathInfoToJSON(JSONPlaceholder & jsonOut, const StorePathSet & store
             auto info = queryPathInfo(storePath);
 
             jsonPath
-                .attr("narHash", info->narHash.to_string())
+                .attr("narHash", info->narHash.to_string(hashBase))
                 .attr("narSize", info->narSize);
 
             {
@@ -741,12 +743,7 @@ std::string Store::showPaths(const StorePathSet & paths)
 
 string showPaths(const PathSet & paths)
 {
-    string s;
+    return concatStringsSep(", ", quoteStrings(paths));
-    for (auto & i : paths) {
-        if (s.size() != 0) s += ", ";
-        s += "'" + i + "'";
-    }
-    return s;
 }
 
 

src/libstore/store-api.hh

@@ -561,6 +561,7 @@ public:
        each path is included. */
     void pathInfoToJSON(JSONPlaceholder & jsonOut, const StorePathSet & storePaths,
         bool includeImpureInfo, bool showClosureSize,
+        Base hashBase = Base32,
         AllowInvalidFlag allowInvalid = DisallowInvalid);
 
     /* Return the size of the closure of the specified path, that is,
@@ -676,6 +677,11 @@ public:
         return storePath;
     }
 
+    Path toRealPath(const StorePath & storePath)
+    {
+        return toRealPath(printStorePath(storePath));
+    }
+
     virtual void createUser(const std::string & userName, uid_t userId)
     { }
 

src/libutil/hash.hh

@@ -80,6 +80,18 @@ struct Hash
        or base-64. By default, this is prefixed by the hash type
        (e.g. "sha256:"). */
     std::string to_string(Base base = Base32, bool includeType = true) const;
+
+    std::string gitRev() const
+    {
+        assert(type == htSHA1);
+        return to_string(Base16, false);
+    }
+
+    std::string gitShortRev() const
+    {
+        assert(type == htSHA1);
+        return std::string(to_string(Base16, false), 0, 7);
+    }
 };
 
 

src/libutil/util.cc

@@ -97,10 +97,10 @@ void replaceEnv(std::map<std::string, std::string> newEnv)
 }
 
 
-Path absPath(Path path, Path dir)
+Path absPath(Path path, std::optional<Path> dir)
 {
     if (path[0] != '/') {
-        if (dir == "") {
+        if (!dir) {
 #ifdef __GNU__
             /* GNU (aka. GNU/Hurd) doesn't have any limitation on path
                lengths and doesn't define `PATH_MAX'.  */
@@ -116,7 +116,7 @@ Path absPath(Path path, Path dir)
             free(buf);
 #endif
         }
-        path = dir + "/" + path;
+        path = *dir + "/" + path;
     }
     return canonPath(path);
 }
@@ -478,6 +478,17 @@ Path createTempDir(const Path & tmpRoot, const Path & prefix,
 }
 
 
+std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix)
+{
+    Path tmpl(getEnv("TMPDIR").value_or("/tmp") + "/" + prefix + ".XXXXXX");
+    // Strictly speaking, this is UB, but who cares...
+    AutoCloseFD fd(mkstemp((char *) tmpl.c_str()));
+    if (!fd)
+        throw SysError("creating temporary file '%s'", tmpl);
+    return {std::move(fd), tmpl};
+}
+
+
 std::string getUserName()
 {
     auto pw = getpwuid(geteuid());
@@ -1205,28 +1216,6 @@ template StringSet tokenizeString(std::string_view s, const string & separators)
 template vector<string> tokenizeString(std::string_view s, const string & separators);
 
 
-string concatStringsSep(const string & sep, const Strings & ss)
-{
-    string s;
-    for (auto & i : ss) {
-        if (s.size() != 0) s += sep;
-        s += i;
-    }
-    return s;
-}
-
-
-string concatStringsSep(const string & sep, const StringSet & ss)
-{
-    string s;
-    for (auto & i : ss) {
-        if (s.size() != 0) s += sep;
-        s += i;
-    }
-    return s;
-}
-
-
 string chomp(const string & s)
 {
     size_t i = s.find_last_not_of(" \n\r\t");

src/libutil/util.hh

@@ -48,7 +48,7 @@ void clearEnv();
 /* Return an absolutized path, resolving paths relative to the
    specified directory, or the current directory otherwise.  The path
    is also canonicalised. */
-Path absPath(Path path, Path dir = "");
+Path absPath(Path path, std::optional<Path> dir = {});
 
 /* Canonicalise a path by removing all `.' or `..' components and
    double or trailing slashes.  Optionally resolves all symlink
@@ -124,10 +124,6 @@ void deletePath(const Path & path);
 
 void deletePath(const Path & path, unsigned long long & bytesFreed);
 
-/* Create a temporary directory. */
-Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
-    bool includePid = true, bool useGlobalCounter = true, mode_t mode = 0755);
-
 std::string getUserName();
 
 /* Return $HOME or the user's home directory from /etc/passwd. */
@@ -207,6 +203,14 @@ public:
 };
 
 
+/* Create a temporary directory. */
+Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
+    bool includePid = true, bool useGlobalCounter = true, mode_t mode = 0755);
+
+/* Create a temporary file, returning a file handle and its path. */
+std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix = "nix");
+
+
 class Pipe
 {
 public:
@@ -347,8 +351,26 @@ template<class C> C tokenizeString(std::string_view s, const string & separators
 
 /* Concatenate the given strings with a separator between the
    elements. */
-string concatStringsSep(const string & sep, const Strings & ss);
+template<class C>
-string concatStringsSep(const string & sep, const StringSet & ss);
+string concatStringsSep(const string & sep, const C & ss)
+{
+    string s;
+    for (auto & i : ss) {
+        if (s.size() != 0) s += sep;
+        s += i;
+    }
+    return s;
+}
+
+
+/* Add quotes around a collection of strings. */
+template<class C> Strings quoteStrings(const C & c)
+{
+    Strings res;
+    for (auto & s : c)
+        res.push_back("'" + s + "'");
+    return res;
+}
 
 
 /* Remove trailing whitespace from a string. */
@@ -426,6 +448,13 @@ void ignoreException();
 
 
 
+/* Tree formatting. */
+constexpr char treeConn[] = "├───";
+constexpr char treeLast[] = "└───";
+constexpr char treeLine[] = "│   ";
+constexpr char treeNull[] = "    ";
+
+
 /* Truncate a string to 'width' printable characters. If 'filterAll'
    is true, all ANSI escape sequences are filtered out. Otherwise,
    some escape sequences (such as colour setting) are copied but not
@@ -444,10 +473,11 @@ string base64Decode(const string & s);
 /* Get a value for the specified key from an associate container, or a
    default value if the key doesn't exist. */
 template <class T>
-std::optional<std::string> get(const T & map, const std::string & key)
+std::optional<typename T::mapped_type> get(const T & map, const typename T::key_type & key)
 {
     auto i = map.find(key);
-    return i == map.end() ? std::optional<std::string>() : i->second;
+    if (i == map.end()) return {};
+    return std::optional<typename T::mapped_type>(i->second);
 }
 
 
@@ -551,4 +581,31 @@ extern PathFilter defaultPathFilter;
 AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
 
 
+// A Rust/Python-like enumerate() iterator adapter.
+// Borrowed from http://reedbeta.com/blog/python-like-enumerate-in-cpp17.
+template <typename T,
+          typename TIter = decltype(std::begin(std::declval<T>())),
+          typename = decltype(std::end(std::declval<T>()))>
+constexpr auto enumerate(T && iterable)
+{
+    struct iterator
+    {
+        size_t i;
+        TIter iter;
+        bool operator != (const iterator & other) const { return iter != other.iter; }
+        void operator ++ () { ++i; ++iter; }
+        auto operator * () const { return std::tie(i, *iter); }
+    };
+
+    struct iterable_wrapper
+    {
+        T iterable;
+        auto begin() { return iterator{ 0, std::begin(iterable) }; }
+        auto end() { return iterator{ 0, std::end(iterable) }; }
+    };
+
+    return iterable_wrapper{ std::forward<T>(iterable) };
+}
+
+
 }

src/nix-build/nix-build.cc

@@ -16,7 +16,7 @@
 #include "get-drvs.hh"
 #include "common-eval-args.hh"
 #include "attr-path.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 using namespace nix;
 using namespace std::string_literals;
@@ -314,7 +314,7 @@ static void _main(int argc, char * * argv)
         state->eval(e, vRoot);
 
         for (auto & i : attrPaths) {
-            Value & v(*findAlongAttrPath(*state, i, *autoArgs, vRoot));
+            Value & v(*findAlongAttrPath(*state, i, *autoArgs, vRoot).first);
             state->forceValue(v);
             getDerivations(*state, v, "", *autoArgs, drvs, false);
         }

src/nix-channel/nix-channel.cc

@@ -2,7 +2,7 @@
 #include "globals.hh"
 #include "download.hh"
 #include "store-api.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 #include <fcntl.h>
 #include <regex>

src/nix-collect-garbage/nix-collect-garbage.cc

@@ -2,7 +2,7 @@
 #include "profiles.hh"
 #include "shared.hh"
 #include "globals.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 #include <iostream>
 #include <cerrno>

src/nix-copy-closure/nix-copy-closure.cc

@@ -1,6 +1,6 @@
 #include "shared.hh"
 #include "store-api.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 using namespace nix;
 

src/nix-daemon/nix-daemon.cc

@@ -6,7 +6,7 @@
 #include "globals.hh"
 #include "derivations.hh"
 #include "finally.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 #include "daemon.hh"
 
 #include <algorithm>

src/nix-env/nix-env.cc

@@ -13,7 +13,7 @@
 #include "json.hh"
 #include "value-to-json.hh"
 #include "xml-writer.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 #include <cerrno>
 #include <ctime>
@@ -178,7 +178,7 @@ static void loadDerivations(EvalState & state, Path nixExprPath,
     Value vRoot;
     loadSourceExpr(state, nixExprPath, vRoot);
 
-    Value & v(*findAlongAttrPath(state, pathPrefix, autoArgs, vRoot));
+    Value & v(*findAlongAttrPath(state, pathPrefix, autoArgs, vRoot).first);
 
     getDerivations(state, v, pathPrefix, autoArgs, elems, true);
 
@@ -408,7 +408,7 @@ static void queryInstSources(EvalState & state,
             Value vRoot;
             loadSourceExpr(state, instSource.nixExprPath, vRoot);
             for (auto & i : args) {
-                Value & v(*findAlongAttrPath(state, i, *instSource.autoArgs, vRoot));
+                Value & v(*findAlongAttrPath(state, i, *instSource.autoArgs, vRoot).first);
                 getDerivations(state, v, "", *instSource.autoArgs, elems, true);
             }
             break;
@@ -1428,21 +1428,8 @@ static int _main(int argc, char * * argv)
         if (globals.profile == "")
             globals.profile = getEnv("NIX_PROFILE").value_or("");
 
-        if (globals.profile == "") {
+        if (globals.profile == "")
-            Path profileLink = getHome() + "/.nix-profile";
+            globals.profile = getDefaultProfile();
-            try {
-                if (!pathExists(profileLink)) {
-                    replaceSymlink(
-                        getuid() == 0
-                        ? settings.nixStateDir + "/profiles/default"
-                        : fmt("%s/profiles/per-user/%s/profile", settings.nixStateDir, getUserName()),
-                        profileLink);
-                }
-                globals.profile = absPath(readLink(profileLink), dirOf(profileLink));
-            } catch (Error &) {
-                globals.profile = profileLink;
-            }
-        }
 
         op(globals, opFlags, opArgs);
 

src/nix-env/user-env.cc

@@ -15,6 +15,8 @@ namespace nix {
 DrvInfos queryInstalled(EvalState & state, const Path & userEnv)
 {
     DrvInfos elems;
+    if (pathExists(userEnv + "/manifest.json"))
+        throw Error("profile '%s' is incompatible with 'nix-env'; please use 'nix profile' instead", userEnv);
     Path manifestFile = userEnv + "/manifest.nix";
     if (pathExists(manifestFile)) {
         Value v;

src/nix-instantiate/nix-instantiate.cc

@@ -9,7 +9,7 @@
 #include "util.hh"
 #include "store-api.hh"
 #include "common-eval-args.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 #include <map>
 #include <iostream>
@@ -39,7 +39,7 @@ void processExpr(EvalState & state, const Strings & attrPaths,
     state.eval(e, vRoot);
 
     for (auto & i : attrPaths) {
-        Value & v(*findAlongAttrPath(state, i, autoArgs, vRoot));
+        Value & v(*findAlongAttrPath(state, i, autoArgs, vRoot).first);
         state.forceValue(v);
 
         PathSet context;

src/nix-prefetch-url/nix-prefetch-url.cc

@@ -6,9 +6,9 @@
 #include "eval-inline.hh"
 #include "common-eval-args.hh"
 #include "attr-path.hh"
-#include "legacy.hh"
 #include "finally.hh"
-#include "progress-bar.hh"
+#include "../nix/legacy.hh"
+#include "../nix/progress-bar.hh"
 #include "tarfile.hh"
 
 #include <iostream>
@@ -120,7 +120,7 @@ static int _main(int argc, char * * argv)
             Path path = resolveExprPath(lookupFileArg(*state, args.empty() ? "." : args[0]));
             Value vRoot;
             state->evalFile(path, vRoot);
-            Value & v(*findAlongAttrPath(*state, attrPath, autoArgs, vRoot));
+            Value & v(*findAlongAttrPath(*state, attrPath, autoArgs, vRoot).first);
             state->forceAttrs(v);
 
             /* Extract the URI. */

src/nix-store/nix-store.cc

@@ -9,7 +9,7 @@
 #include "util.hh"
 #include "worker-protocol.hh"
 #include "graphml.hh"
-#include "legacy.hh"
+#include "../nix/legacy.hh"
 
 #include <iostream>
 #include <algorithm>
@@ -229,12 +229,6 @@ static StorePathSet maybeUseOutputs(const StorePath & storePath, bool useOutput,
 /* Some code to print a tree representation of a derivation dependency
    graph.  Topological sorting is used to keep the tree relatively
    flat. */
-
-const string treeConn = "+---";
-const string treeLine = "|   ";
-const string treeNull = "    ";
-
-
 static void printTree(const StorePath & path,
     const string & firstPad, const string & tailPad, StorePathSet & done)
 {
@@ -254,10 +248,11 @@ static void printTree(const StorePath & path,
     auto sorted = store->topoSortPaths(info->references);
     reverse(sorted.begin(), sorted.end());
 
-    for (auto i = sorted.begin(); i != sorted.end(); ++i) {
+    for (const auto &[n, i] : enumerate(sorted)) {
-        auto j = i; ++j;
+        bool last = n + 1 == sorted.size();
-        printTree(*i, tailPad + treeConn,
+        printTree(i,
-            j == sorted.end() ? tailPad + treeNull : tailPad + treeLine,
+            tailPad + (last ? treeLast : treeConn),
+            tailPad + (last ? treeNull : treeLine),
             done);
     }
 }
@@ -577,7 +572,6 @@ static void opGC(Strings opFlags, Strings opArgs)
         if (*i == "--print-roots") printRoots = true;
         else if (*i == "--print-live") options.action = GCOptions::gcReturnLive;
         else if (*i == "--print-dead") options.action = GCOptions::gcReturnDead;
-        else if (*i == "--delete") options.action = GCOptions::gcDeleteDead;
         else if (*i == "--max-freed") {
             long long maxFreed = getIntArg<long long>(*i, i, opFlags.end(), true);
             options.maxFreed = maxFreed >= 0 ? maxFreed : 0;

src/nix/build.cc

@@ -5,7 +5,7 @@
 
 using namespace nix;
 
-struct CmdBuild : MixDryRun, InstallablesCommand
+struct CmdBuild : InstallablesCommand, MixDryRun, MixProfile
 {
     Path outLink = "result";
 
@@ -40,6 +40,10 @@ struct CmdBuild : MixDryRun, InstallablesCommand
                 "To build the build.x86_64-linux attribute from release.nix:",
                 "nix build -f release.nix build.x86_64-linux"
             },
+            Example{
+                "To make a profile point at GNU Hello:",
+                "nix build --profile /tmp/profile nixpkgs.hello"
+            },
         };
     }
 
@@ -49,11 +53,9 @@ struct CmdBuild : MixDryRun, InstallablesCommand
 
         if (dryRun) return;
 
+        if (outLink != "") {
             for (size_t i = 0; i < buildables.size(); ++i) {
-            auto & b(buildables[i]);
+                for (auto & output : buildables[i].outputs)
-
-            if (outLink != "")
-                for (auto & output : b.outputs)
                     if (auto store2 = store.dynamic_pointer_cast<LocalFSStore>()) {
                         std::string symlink = outLink;
                         if (i) symlink += fmt("-%d", i);
@@ -62,6 +64,9 @@ struct CmdBuild : MixDryRun, InstallablesCommand
                     }
             }
         }
+
+        updateProfile(buildables);
+    }
 };
 
 static auto r1 = registerCommand<CmdBuild>("build");

src/nix/command.cc

@@ -2,6 +2,9 @@
 #include "store-api.hh"
 #include "derivations.hh"
 #include "nixexpr.hh"
+#include "profiles.hh"
+
+extern char * * environ;
 
 namespace nix {
 
@@ -96,4 +99,95 @@ Strings editorFor(const Pos & pos)
     return args;
 }
 
+MixProfile::MixProfile()
+{
+    mkFlag()
+        .longName("profile")
+        .description("profile to update")
+        .labels({"path"})
+        .dest(&profile);
+}
+
+void MixProfile::updateProfile(const StorePath & storePath)
+{
+    if (!profile) return;
+    auto store = getStore().dynamic_pointer_cast<LocalFSStore>();
+    if (!store) throw Error("'--profile' is not supported for this Nix store");
+    auto profile2 = absPath(*profile);
+    switchLink(profile2,
+        createGeneration(
+            ref<LocalFSStore>(store),
+            profile2, store->printStorePath(storePath)));
+}
+
+void MixProfile::updateProfile(const Buildables & buildables)
+{
+    if (!profile) return;
+
+    std::optional<StorePath> result;
+
+    for (auto & buildable : buildables) {
+        for (auto & output : buildable.outputs) {
+            if (result)
+                throw Error("'--profile' requires that the arguments produce a single store path, but there are multiple");
+            result = output.second.clone();
+        }
+    }
+
+    if (!result)
+        throw Error("'--profile' requires that the arguments produce a single store path, but there are none");
+
+    updateProfile(*result);
+}
+
+MixDefaultProfile::MixDefaultProfile()
+{
+    profile = getDefaultProfile();
+}
+
+MixEnvironment::MixEnvironment() : ignoreEnvironment(false) {
+    mkFlag()
+        .longName("ignore-environment")
+        .shortName('i')
+        .description("clear the entire environment (except those specified with --keep)")
+        .set(&ignoreEnvironment, true);
+
+    mkFlag()
+        .longName("keep")
+        .shortName('k')
+        .description("keep specified environment variable")
+        .arity(1)
+        .labels({"name"})
+        .handler([&](std::vector<std::string> ss) { keep.insert(ss.front()); });
+
+    mkFlag()
+        .longName("unset")
+        .shortName('u')
+        .description("unset specified environment variable")
+        .arity(1)
+        .labels({"name"})
+        .handler([&](std::vector<std::string> ss) { unset.insert(ss.front()); });
+}
+
+void MixEnvironment::setEnviron() {
+    if (ignoreEnvironment) {
+        if (!unset.empty())
+            throw UsageError("--unset does not make sense with --ignore-environment");
+
+        for (const auto & var : keep) {
+            auto val = getenv(var.c_str());
+            if (val) stringsEnv.emplace_back(fmt("%s=%s", var.c_str(), val));
+        }
+
+        vectorEnv = stringsToCharPtrs(stringsEnv);
+        environ = vectorEnv.data();
+    } else {
+        if (!keep.empty())
+            throw UsageError("--keep does not make sense without --ignore-environment");
+
+        for (const auto & var : unset)
+            unsetenv(var.c_str());
+    }
+}
+
 }

src/nix/command.hh

@@ -1,19 +1,15 @@
 #pragma once
 
+#include "installables.hh"
 #include "args.hh"
 #include "common-eval-args.hh"
 #include "path.hh"
+#include "eval.hh"
 
 namespace nix {
 
 extern std::string programPath;
 
-struct Value;
-class Bindings;
-class EvalState;
-struct Pos;
-class Store;
-
 /* A command that requires a Nix store. */
 struct StoreCommand : virtual Command
 {
@@ -27,34 +23,7 @@ private:
     std::shared_ptr<Store> _store;
 };
 
-struct Buildable
+struct SourceExprCommand : virtual StoreCommand, MixEvalArgs
-{
-    std::optional<StorePath> drvPath;
-    std::map<std::string, StorePath> outputs;
-};
-
-typedef std::vector<Buildable> Buildables;
-
-struct Installable
-{
-    virtual ~Installable() { }
-
-    virtual std::string what() = 0;
-
-    virtual Buildables toBuildables()
-    {
-        throw Error("argument '%s' cannot be built", what());
-    }
-
-    Buildable toBuildable();
-
-    virtual Value * toValue(EvalState & state)
-    {
-        throw Error("argument '%s' cannot be evaluated", what());
-    }
-};
-
-struct SourceExprCommand : virtual Args, StoreCommand, MixEvalArgs
 {
     Path file;
 
@@ -189,4 +158,36 @@ std::set<StorePath> toDerivations(ref<Store> store,
    filename:lineno. */
 Strings editorFor(const Pos & pos);
 
+struct MixProfile : virtual StoreCommand
+{
+    std::optional<Path> profile;
+
+    MixProfile();
+
+    /* If 'profile' is set, make it point at 'storePath'. */
+    void updateProfile(const StorePath & storePath);
+
+    /* If 'profile' is set, make it point at the store path produced
+       by 'buildables'. */
+    void updateProfile(const Buildables & buildables);
+};
+
+struct MixDefaultProfile : MixProfile
+{
+    MixDefaultProfile();
+};
+
+struct MixEnvironment : virtual Args {
+
+    StringSet keep, unset;
+    Strings stringsEnv;
+    std::vector<char*> vectorEnv;
+    bool ignoreEnvironment;
+
+    MixEnvironment();
+
+    /* Modify global environ based on ignoreEnvironment, keep, and unset. It's expected that exec will be called before this class goes out of scope, otherwise environ will become invalid. */
+    void setEnviron();
+};
+
 }

src/nix/edit.cc

@@ -29,9 +29,15 @@ struct CmdEdit : InstallableCommand
     {
         auto state = getEvalState();
 
-        auto v = installable->toValue(*state);
+        auto [v, pos] = installable->toValue(*state);
 
-        Pos pos = findDerivationFilename(*state, *v, installable->what());
+        try {
+            pos = findDerivationFilename(*state, *v, installable->what());
+        } catch (NoPositionInfo &) {
+        }
+
+        if (pos == noPos)
+            throw Error("cannot find position information for '%s", installable->what());
 
         stopProgressBar();
 

src/nix/eval.cc

@@ -52,7 +52,7 @@ struct CmdEval : MixJSON, InstallableCommand
 
         auto state = getEvalState();
 
-        auto v = installable->toValue(*state);
+        auto v = installable->toValue(*state).first;
         PathSet context;
 
         stopProgressBar();

src/nix/installables.cc

@@ -109,6 +109,11 @@ struct InstallableStorePath : Installable
         bs.push_back(std::move(b));
         return bs;
     }
+
+    std::optional<StorePath> getStorePath() override
+    {
+        return storePath.clone();
+    }
 };
 
 struct InstallableValue : Installable
@@ -121,7 +126,7 @@ struct InstallableValue : Installable
     {
         auto state = cmd.getEvalState();
 
-        auto v = toValue(*state);
+        auto v = toValue(*state).first;
 
         Bindings & autoArgs = *cmd.getAutoArgs(*state);
 
@@ -169,11 +174,11 @@ struct InstallableExpr : InstallableValue
 
     std::string what() override { return text; }
 
-    Value * toValue(EvalState & state) override
+    std::pair<Value *, Pos> toValue(EvalState & state) override
     {
         auto v = state.allocValue();
         state.eval(state.parseExprFromString(text, absPath(".")), *v);
-        return v;
+        return {v, noPos};
     }
 };
 
@@ -187,16 +192,16 @@ struct InstallableAttrPath : InstallableValue
 
     std::string what() override { return attrPath; }
 
-    Value * toValue(EvalState & state) override
+    std::pair<Value *, Pos> toValue(EvalState & state) override
     {
         auto source = cmd.getSourceExpr(state);
 
         Bindings & autoArgs = *cmd.getAutoArgs(state);
 
-        Value * v = findAlongAttrPath(state, attrPath, autoArgs, *source);
+        auto v = findAlongAttrPath(state, attrPath, autoArgs, *source).first;
         state.forceValue(*v);
 
-        return v;
+        return {v, noPos};
     }
 };
 

src/nix/installables.hh

@@ -0,0 +1,45 @@
+#pragma once
+
+#include "util.hh"
+#include "path.hh"
+#include "eval.hh"
+
+#include <optional>
+
+namespace nix {
+
+struct Buildable
+{
+    std::optional<StorePath> drvPath;
+    std::map<std::string, StorePath> outputs;
+};
+
+typedef std::vector<Buildable> Buildables;
+
+struct Installable
+{
+    virtual ~Installable() { }
+
+    virtual std::string what() = 0;
+
+    virtual Buildables toBuildables()
+    {
+        throw Error("argument '%s' cannot be built", what());
+    }
+
+    Buildable toBuildable();
+
+    virtual std::pair<Value *, Pos> toValue(EvalState & state)
+    {
+        throw Error("argument '%s' cannot be evaluated", what());
+    }
+
+    /* Return a value only if this installable is a store path or a
+       symlink to it. */
+    virtual std::optional<StorePath> getStorePath()
+    {
+        return {};
+    }
+};
+
+}

src/nix/local.mk

@@ -15,6 +15,8 @@ nix_SOURCES := \
   $(wildcard src/nix-prefetch-url/*.cc) \
   $(wildcard src/nix-store/*.cc) \
 
+nix_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain
+
 nix_LIBS = libexpr libmain libstore libutil libnixrust
 
 nix_LDFLAGS = -pthread $(SODIUM_LIBS) $(EDITLINE_LIBS) $(BOOST_LDFLAGS) -lboost_context -lboost_thread -lboost_system

src/nix/main.cc

@@ -55,6 +55,7 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
 {
     bool printBuildLogs = false;
     bool useNet = true;
+    bool refresh = false;
 
     NixArgs() : MultiCommand(*RegisterCommand::commands), MixCommonArgs("nix")
     {
@@ -92,6 +93,11 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             .longName("no-net")
             .description("disable substituters and consider all previously downloaded files up-to-date")
             .handler([&]() { useNet = false; });
+
+        mkFlag()
+            .longName("refresh")
+            .description("consider all previously downloaded files out-of-date")
+            .handler([&]() { refresh = true; });
     }
 
     void printFlags(std::ostream & out) override
@@ -176,6 +182,9 @@ void mainWrapped(int argc, char * * argv)
             downloadSettings.connectTimeout = 1;
     }
 
+    if (args.refresh)
+        settings.tarballTtl = 0;
+
     args.command->prepare();
     args.command->run();
 }

src/nix/path-info.cc

@@ -89,7 +89,7 @@ struct CmdPathInfo : StorePathsCommand, MixJSON
             store->pathInfoToJSON(jsonRoot,
                 // FIXME: preserve order?
                 storePathsToSet(storePaths),
-                true, showClosureSize, AllowInvalid);
+                true, showClosureSize, SRI, AllowInvalid);
         }
 
         else {

src/nix/run.cc

@@ -8,6 +8,7 @@
 #include "fs-accessor.hh"
 #include "progress-bar.hh"
 #include "affinity.hh"
+#include "eval.hh"
 
 #if __linux__
 #include <sys/mount.h>
@@ -19,11 +20,46 @@ using namespace nix;
 
 std::string chrootHelperName = "__run_in_chroot";
 
-struct CmdRun : InstallablesCommand
+struct RunCommon : virtual Command
+{
+    void runProgram(ref<Store> store,
+        const std::string & program,
+        const Strings & args)
+    {
+        stopProgressBar();
+
+        restoreSignals();
+
+        restoreAffinity();
+
+        /* If this is a diverted store (i.e. its "logical" location
+           (typically /nix/store) differs from its "physical" location
+           (e.g. /home/eelco/nix/store), then run the command in a
+           chroot. For non-root users, this requires running it in new
+           mount and user namespaces. Unfortunately,
+           unshare(CLONE_NEWUSER) doesn't work in a multithreaded
+           program (which "nix" is), so we exec() a single-threaded
+           helper program (chrootHelper() below) to do the work. */
+        auto store2 = store.dynamic_pointer_cast<LocalStore>();
+
+        if (store2 && store->storeDir != store2->realStoreDir) {
+            Strings helperArgs = { chrootHelperName, store->storeDir, store2->realStoreDir, program };
+            for (auto & arg : args) helperArgs.push_back(arg);
+
+            execv(readLink("/proc/self/exe").c_str(), stringsToCharPtrs(helperArgs).data());
+
+            throw SysError("could not execute chroot helper");
+        }
+
+        execvp(program.c_str(), stringsToCharPtrs(args).data());
+
+        throw SysError("unable to execute '%s'", program);
+    }
+};
+
+struct CmdRun : InstallablesCommand, RunCommon, MixEnvironment
 {
     std::vector<std::string> command = { "bash" };
-    StringSet keep, unset;
-    bool ignoreEnvironment = false;
 
     CmdRun()
     {
@@ -37,28 +73,6 @@ struct CmdRun : InstallablesCommand
                 if (ss.empty()) throw UsageError("--command requires at least one argument");
                 command = ss;
             });
-
-        mkFlag()
-            .longName("ignore-environment")
-            .shortName('i')
-            .description("clear the entire environment (except those specified with --keep)")
-            .set(&ignoreEnvironment, true);
-
-        mkFlag()
-            .longName("keep")
-            .shortName('k')
-            .description("keep specified environment variable")
-            .arity(1)
-            .labels({"name"})
-            .handler([&](std::vector<std::string> ss) { keep.insert(ss.front()); });
-
-        mkFlag()
-            .longName("unset")
-            .shortName('u')
-            .description("unset specified environment variable")
-            .arity(1)
-            .labels({"name"})
-            .handler([&](std::vector<std::string> ss) { unset.insert(ss.front()); });
     }
 
     std::string description() override
@@ -94,35 +108,13 @@ struct CmdRun : InstallablesCommand
 
         auto accessor = store->getFSAccessor();
 
-        if (ignoreEnvironment) {
-
-            if (!unset.empty())
-                throw UsageError("--unset does not make sense with --ignore-environment");
-
-            std::map<std::string, std::string> kept;
-            for (auto & var : keep) {
-                auto s = getenv(var.c_str());
-                if (s) kept[var] = s;
-            }
-
-            clearEnv();
-
-            for (auto & var : kept)
-                setenv(var.first.c_str(), var.second.c_str(), 1);
-
-        } else {
-
-            if (!keep.empty())
-                throw UsageError("--keep does not make sense without --ignore-environment");
-
-            for (auto & var : unset)
-                unsetenv(var.c_str());
-        }
 
         std::unordered_set<StorePath> done;
         std::queue<StorePath> todo;
         for (auto & path : outPaths) todo.push(path.clone());
 
+        setEnviron();
+
         auto unixPath = tokenizeString<Strings>(getEnv("PATH").value_or(""), ":");
 
         while (!todo.empty()) {
@@ -142,38 +134,10 @@ struct CmdRun : InstallablesCommand
 
         setenv("PATH", concatStringsSep(":", unixPath).c_str(), 1);
 
-        std::string cmd = *command.begin();
         Strings args;
         for (auto & arg : command) args.push_back(arg);
 
-        stopProgressBar();
+        runProgram(store, *command.begin(), args);
-
-        restoreSignals();
-
-        restoreAffinity();
-
-        /* If this is a diverted store (i.e. its "logical" location
-           (typically /nix/store) differs from its "physical" location
-           (e.g. /home/eelco/nix/store), then run the command in a
-           chroot. For non-root users, this requires running it in new
-           mount and user namespaces. Unfortunately,
-           unshare(CLONE_NEWUSER) doesn't work in a multithreaded
-           program (which "nix" is), so we exec() a single-threaded
-           helper program (chrootHelper() below) to do the work. */
-        auto store2 = store.dynamic_pointer_cast<LocalStore>();
-
-        if (store2 && store->storeDir != store2->realStoreDir) {
-            Strings helperArgs = { chrootHelperName, store->storeDir, store2->realStoreDir, cmd };
-            for (auto & arg : args) helperArgs.push_back(arg);
-
-            execv(readLink("/proc/self/exe").c_str(), stringsToCharPtrs(helperArgs).data());
-
-            throw SysError("could not execute chroot helper");
-        }
-
-        execvp(cmd.c_str(), stringsToCharPtrs(args).data());
-
-        throw SysError("unable to exec '%s'", cmd);
     }
 };
 

src/nix/shell.cc

@@ -0,0 +1,319 @@
+#include "eval.hh"
+#include "command.hh"
+#include "common-args.hh"
+#include "shared.hh"
+#include "store-api.hh"
+#include "derivations.hh"
+#include "affinity.hh"
+#include "progress-bar.hh"
+
+#include <regex>
+
+using namespace nix;
+
+struct Var
+{
+    bool exported;
+    std::string value; // quoted string or array
+};
+
+struct BuildEnvironment
+{
+    std::map<std::string, Var> env;
+    std::string bashFunctions;
+};
+
+BuildEnvironment readEnvironment(const Path & path)
+{
+    BuildEnvironment res;
+
+    std::set<std::string> exported;
+
+    debug("reading environment file '%s'", path);
+
+    auto file = readFile(path);
+
+    auto pos = file.cbegin();
+
+    static std::string varNameRegex =
+        R"re((?:[a-zA-Z_][a-zA-Z0-9_]*))re";
+
+    static std::regex declareRegex(
+        "^declare -x (" + varNameRegex + ")" +
+        R"re((?:="((?:[^"\\]|\\.)*)")?\n)re");
+
+    static std::string simpleStringRegex =
+        R"re((?:[a-zA-Z0-9_/:\.\-\+=]*))re";
+
+    static std::string quotedStringRegex =
+        R"re((?:\$?'(?:[^'\\]|\\[abeEfnrtv\\'"?])*'))re";
+
+    static std::string arrayRegex =
+        R"re((?:\(( *\[[^\]]+\]="(?:[^"\\]|\\.)*")*\)))re";
+
+    static std::regex varRegex(
+        "^(" + varNameRegex + ")=(" + simpleStringRegex + "|" + quotedStringRegex + "|" + arrayRegex + ")\n");
+
+    static std::regex functionRegex(
+        "^" + varNameRegex + " \\(\\) *\n");
+
+    while (pos != file.end()) {
+
+        std::smatch match;
+
+        if (std::regex_search(pos, file.cend(), match, declareRegex)) {
+            pos = match[0].second;
+            exported.insert(match[1]);
+        }
+
+        else if (std::regex_search(pos, file.cend(), match, varRegex)) {
+            pos = match[0].second;
+            res.env.insert({match[1], Var { (bool) exported.count(match[1]), match[2] }});
+        }
+
+        else if (std::regex_search(pos, file.cend(), match, functionRegex)) {
+            res.bashFunctions = std::string(pos, file.cend());
+            break;
+        }
+
+        else throw Error("shell environment '%s' has unexpected line '%s'",
+            path, file.substr(pos - file.cbegin(), 60));
+    }
+
+    return res;
+}
+
+/* Given an existing derivation, return the shell environment as
+   initialised by stdenv's setup script. We do this by building a
+   modified derivation with the same dependencies and nearly the same
+   initial environment variables, that just writes the resulting
+   environment to a file and exits. */
+StorePath getDerivationEnvironment(ref<Store> store, Derivation drv)
+{
+    auto builder = baseNameOf(drv.builder);
+    if (builder != "bash")
+        throw Error("'nix dev-shell' only works on derivations that use 'bash' as their builder");
+
+    drv.args = {
+        "-c",
+        "set -e; "
+        "export IN_NIX_SHELL=impure; "
+        "export dontAddDisableDepTrack=1; "
+        "if [[ -n $stdenv ]]; then "
+        "  source $stdenv/setup; "
+        "fi; "
+        "export > $out; "
+        "set >> $out "};
+
+    /* Remove derivation checks. */
+    drv.env.erase("allowedReferences");
+    drv.env.erase("allowedRequisites");
+    drv.env.erase("disallowedReferences");
+    drv.env.erase("disallowedRequisites");
+
+    // FIXME: handle structured attrs
+
+    /* Rehash and write the derivation. FIXME: would be nice to use
+       'buildDerivation', but that's privileged. */
+    auto drvName = drv.env["name"] + "-env";
+    for (auto & output : drv.outputs)
+        drv.env.erase(output.first);
+    drv.env["out"] = "";
+    drv.env["outputs"] = "out";
+    Hash h = hashDerivationModulo(*store, drv, true);
+    auto shellOutPath = store->makeOutputPath("out", h, drvName);
+    drv.outputs.insert_or_assign("out", DerivationOutput(shellOutPath.clone(), "", ""));
+    drv.env["out"] = store->printStorePath(shellOutPath);
+    auto shellDrvPath2 = writeDerivation(store, drv, drvName);
+
+    /* Build the derivation. */
+    store->buildPaths({shellDrvPath2});
+
+    assert(store->isValidPath(shellOutPath));
+
+    return shellOutPath;
+}
+
+struct Common : InstallableCommand, MixProfile
+{
+    std::set<string> ignoreVars{
+        "BASHOPTS",
+        "EUID",
+        "HOME", // FIXME: don't ignore in pure mode?
+        "NIX_BUILD_TOP",
+        "NIX_ENFORCE_PURITY",
+        "NIX_LOG_FD",
+        "PPID",
+        "PWD",
+        "SHELLOPTS",
+        "SHLVL",
+        "SSL_CERT_FILE", // FIXME: only want to ignore /no-cert-file.crt
+        "TEMP",
+        "TEMPDIR",
+        "TERM",
+        "TMP",
+        "TMPDIR",
+        "TZ",
+        "UID",
+    };
+
+    void makeRcScript(const BuildEnvironment & buildEnvironment, std::ostream & out)
+    {
+        out << "nix_saved_PATH=\"$PATH\"\n";
+
+        for (auto & i : buildEnvironment.env) {
+            if (!ignoreVars.count(i.first) && !hasPrefix(i.first, "BASH_")) {
+                out << fmt("%s=%s\n", i.first, i.second.value);
+                if (i.second.exported)
+                    out << fmt("export %s\n", i.first);
+            }
+        }
+
+        out << "PATH=\"$PATH:$nix_saved_PATH\"\n";
+
+        out << buildEnvironment.bashFunctions << "\n";
+
+        // FIXME: set outputs
+
+        out << "export NIX_BUILD_TOP=\"$(mktemp -d --tmpdir nix-shell.XXXXXX)\"\n";
+        for (auto & i : {"TMP", "TMPDIR", "TEMP", "TEMPDIR"})
+            out << fmt("export %s=\"$NIX_BUILD_TOP\"\n", i);
+
+        out << "eval \"$shellHook\"\n";
+    }
+
+    StorePath getShellOutPath(ref<Store> store)
+    {
+        auto path = installable->getStorePath();
+        if (path && hasSuffix(path->to_string(), "-env"))
+            return path->clone();
+        else {
+            auto drvs = toDerivations(store, {installable});
+
+            if (drvs.size() != 1)
+                throw Error("'%s' needs to evaluate to a single derivation, but it evaluated to %d derivations",
+                    installable->what(), drvs.size());
+
+            auto & drvPath = *drvs.begin();
+
+            return getDerivationEnvironment(store, store->derivationFromPath(drvPath));
+        }
+    }
+
+    BuildEnvironment getBuildEnvironment(ref<Store> store)
+    {
+        auto shellOutPath = getShellOutPath(store);
+
+        updateProfile(shellOutPath);
+
+        return readEnvironment(store->printStorePath(shellOutPath));
+    }
+};
+
+struct CmdDevShell : Common, MixEnvironment
+{
+    std::vector<std::string> command;
+
+    CmdDevShell()
+    {
+        mkFlag()
+            .longName("command")
+            .shortName('c')
+            .description("command and arguments to be executed insted of an interactive shell")
+            .labels({"command", "args"})
+            .arity(ArityAny)
+            .handler([&](std::vector<std::string> ss) {
+                if (ss.empty()) throw UsageError("--command requires at least one argument");
+                command = ss;
+            });
+    }
+
+    std::string description() override
+    {
+        return "run a bash shell that provides the build environment of a derivation";
+    }
+
+    Examples examples() override
+    {
+        return {
+            Example{
+                "To get the build environment of GNU hello:",
+                "nix dev-shell nixpkgs.hello"
+            },
+            Example{
+                "To store the build environment in a profile:",
+                "nix dev-shell --profile /tmp/my-shell nixpkgs.hello"
+            },
+            Example{
+                "To use a build environment previously recorded in a profile:",
+                "nix dev-shell /tmp/my-shell"
+            },
+        };
+    }
+
+    void run(ref<Store> store) override
+    {
+        auto buildEnvironment = getBuildEnvironment(store);
+
+        auto [rcFileFd, rcFilePath] = createTempFile("nix-shell");
+
+        std::ostringstream ss;
+        makeRcScript(buildEnvironment, ss);
+
+        ss << fmt("rm -f '%s'\n", rcFilePath);
+
+        if (!command.empty()) {
+            std::vector<std::string> args;
+            for (auto s : command)
+                args.push_back(shellEscape(s));
+            ss << fmt("exec %s\n", concatStringsSep(" ", args));
+        }
+
+        writeFull(rcFileFd.get(), ss.str());
+
+        stopProgressBar();
+
+        auto shell = getEnv("SHELL").value_or("bash");
+
+        setEnviron();
+
+        auto args = Strings{std::string(baseNameOf(shell)), "--rcfile", rcFilePath};
+
+        restoreAffinity();
+        restoreSignals();
+
+        execvp(shell.c_str(), stringsToCharPtrs(args).data());
+
+        throw SysError("executing shell '%s'", shell);
+    }
+};
+
+struct CmdPrintDevEnv : Common
+{
+    std::string description() override
+    {
+        return "print shell code that can be sourced by bash to reproduce the build environment of a derivation";
+    }
+
+    Examples examples() override
+    {
+        return {
+            Example{
+                "To apply the build environment of GNU hello to the current shell:",
+                ". <(nix print-dev-env nixpkgs.hello)"
+            },
+        };
+    }
+
+    void run(ref<Store> store) override
+    {
+        auto buildEnvironment = getBuildEnvironment(store);
+
+        stopProgressBar();
+
+        makeRcScript(buildEnvironment, std::cout);
+    }
+};
+
+static auto r1 = registerCommand<CmdPrintDevEnv>("print-dev-env");
+static auto r2 = registerCommand<CmdDevShell>("dev-shell");

src/nix/upgrade-nix.cc

@@ -145,7 +145,7 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
         auto v = state->allocValue();
         state->eval(state->parseExprFromString(*res.data, "/no-such-path"), *v);
         Bindings & bindings(*state->allocBindings(0));
-        auto v2 = findAlongAttrPath(*state, settings.thisSystem, bindings, *v);
+        auto v2 = findAlongAttrPath(*state, settings.thisSystem, bindings, *v).first;
 
         return store->parseStorePath(state->forceString(*v2));
     }

src/nix/why-depends.cc

@@ -143,11 +143,6 @@ struct CmdWhyDepends : SourceExprCommand
            and `dependency`. */
         std::function<void(Node &, const string &, const string &)> printNode;
 
-        const string treeConn = "╠═══";
-        const string treeLast = "╚═══";
-        const string treeLine = "║   ";
-        const string treeNull = "    ";
-
         struct BailOut { };
 
         printNode = [&](Node & node, const string & firstPad, const string & tailPad) {
@@ -157,7 +152,7 @@ struct CmdWhyDepends : SourceExprCommand
             std::cout << fmt("%s%s%s%s" ANSI_NORMAL "\n",
                 firstPad,
                 node.visited ? "\e[38;5;244m" : "",
-                firstPad != "" ? "=> " : "",
+                firstPad != "" ? "→ " : "",
                 pathS);
 
             if (node.path == dependencyPath && !all

src/resolve-system-dependencies/local.mk

@@ -6,6 +6,8 @@ resolve-system-dependencies_DIR := $(d)
 
 resolve-system-dependencies_INSTALL_DIR := $(libexecdir)/nix
 
+resolve-system-dependencies_CXXFLAGS += -I src/libutil -I src/libstore -I src/libmain
+
 resolve-system-dependencies_LIBS := libstore libmain libutil libnixrust
 
 resolve-system-dependencies_SOURCES := $(d)/resolve-system-dependencies.cc

tests/binary-cache.sh

@@ -48,7 +48,7 @@ basicTests
 
 
 # Test HttpBinaryCacheStore.
-export _NIX_FORCE_HTTP_BINARY_CACHE_STORE=1
+export _NIX_FORCE_HTTP=1
 basicTests
 
 
@@ -126,7 +126,7 @@ badKey="$(cat $TEST_ROOT/pk2)"
 res=($(nix-store --generate-binary-cache-key foo.nixos.org-1 $TEST_ROOT/sk3 $TEST_ROOT/pk3))
 otherKey="$(cat $TEST_ROOT/pk3)"
 
-_NIX_FORCE_HTTP_BINARY_CACHE_STORE= nix copy --to file://$cacheDir?secret-key=$TEST_ROOT/sk1 $outPath
+_NIX_FORCE_HTTP= nix copy --to file://$cacheDir?secret-key=$TEST_ROOT/sk1 $outPath
 
 
 # Downloading should fail if we don't provide a key.

tests/config.nix.in

@@ -3,7 +3,7 @@ rec {
 
   path = "@coreutils@";
 
-  system = builtins.currentSystem;
+  system = "@system@";
 
   shared = builtins.getEnv "_NIX_TEST_SHARED";
 

tests/dependencies.sh

@@ -6,7 +6,7 @@ drvPath=$(nix-instantiate dependencies.nix)
 
 echo "derivation is $drvPath"
 
-nix-store -q --tree "$drvPath" | grep '   +---.*builder1.sh'
+nix-store -q --tree "$drvPath" | grep '───.*builder1.sh'
 
 # Test Graphviz graph generation.
 nix-store -q --graph "$drvPath" > $TEST_ROOT/graph
@@ -24,7 +24,7 @@ if test -n "$dot"; then
     $dot < $TEST_ROOT/graph
 fi
 
-nix-store -q --tree "$outPath" | grep '+---.*dependencies-input-2'
+nix-store -q --tree "$outPath" | grep '───.*dependencies-input-2'
 
 echo "output path is $outPath"
 

tests/fetchGit.sh

@@ -9,6 +9,8 @@ clearStore
 
 repo=$TEST_ROOT/git
 
+export _NIX_FORCE_HTTP=1
+
 rm -rf $repo ${repo}-tmp $TEST_HOME/.cache/nix/gitv2
 
 git init $repo

tests/plugins/local.mk

@@ -7,3 +7,5 @@ libplugintest_SOURCES := $(d)/plugintest.cc
 libplugintest_ALLOW_UNDEFINED := 1
 
 libplugintest_EXCLUDE_FROM_LIBRARY_LIST := 1
+
+libplugintest_CXXFLAGS := -I src/libutil -I src/libexpr