Move calling flakes into a Nix helper function (call-flake.nix)

corepkgs/call-flake.nix

@@ -0,0 +1,22 @@
+locks: rootSrc:
+
+let
+
+  callFlake = sourceInfo: locks:
+    let
+      flake = import (sourceInfo + "/flake.nix");
+
+      inputs = builtins.mapAttrs (n: v:
+        if v.flake or true
+        then callFlake (fetchTree v.locked) v.inputs
+        else fetchTree v.locked) locks;
+
+      outputs = flake.outputs (inputs // { self = result; });
+
+      result = outputs // sourceInfo // { inherit inputs; inherit outputs; inherit sourceInfo; };
+    in
+      assert flake.edition == 201909;
+
+      result;
+
+in callFlake rootSrc (builtins.fromJSON locks).inputs

corepkgs/local.mk

@@ -3,7 +3,8 @@ corepkgs_FILES = \
   unpack-channel.nix \
   derivation.nix \
   fetchurl.nix \
-  imported-drv-to-derivation.nix
+  imported-drv-to-derivation.nix \
+  call-flake.nix
 
 $(foreach file,config.nix $(corepkgs_FILES),$(eval $(call install-data-in,$(d)/$(file),$(datadir)/nix/corepkgs)))
 

src/libexpr/flake/flake.cc

@@ -6,10 +6,6 @@
 #include "fetchers/fetchers.hh"
 #include "finally.hh"
 
-#include <iostream>
-#include <ctime>
-#include <iomanip>
-
 namespace nix {
 
 using namespace flake;
@@ -158,7 +154,8 @@ static FlakeInput parseFlakeInput(EvalState & state,
                 if (attr.value->type == tString)
                     attrs.emplace(attr.name, attr.value->string.s);
                 else
-                    throw Error("unsupported attribute type");
+                    throw TypeError("flake input attribute '%s' is %s while a string is expected",
+                        attr.name, showType(*attr.value));
             }
         } catch (Error & e) {
             e.addPrefix(fmt("in flake attribute '%s' at '%s':\n", attr.name, *attr.pos));
@@ -621,143 +618,23 @@ LockedFlake lockFlake(
     return LockedFlake { .flake = std::move(flake), .lockFile = std::move(newLockFile) };
 }
 
-static void emitSourceInfoAttrs(
-    EvalState & state,
-    const FlakeRef & flakeRef,
-    const fetchers::Tree & sourceInfo,
-    Value & vAttrs)
-{
-    assert(state.store->isValidPath(sourceInfo.storePath));
-    auto pathS = state.store->printStorePath(sourceInfo.storePath);
-    mkString(*state.allocAttr(vAttrs, state.sOutPath), pathS, {pathS});
-
-    assert(sourceInfo.info.narHash);
-    mkString(*state.allocAttr(vAttrs, state.symbols.create("narHash")),
-        sourceInfo.info.narHash.to_string(SRI));
-
-    if (auto rev = flakeRef.input->getRev()) {
-        mkString(*state.allocAttr(vAttrs, state.symbols.create("rev")),
-            rev->gitRev());
-        mkString(*state.allocAttr(vAttrs, state.symbols.create("shortRev")),
-            rev->gitShortRev());
-    }
-
-    if (sourceInfo.info.revCount)
-        mkInt(*state.allocAttr(vAttrs, state.symbols.create("revCount")), *sourceInfo.info.revCount);
-
-    if (sourceInfo.info.lastModified)
-        mkString(*state.allocAttr(vAttrs, state.symbols.create("lastModified")),
-            fmt("%s", std::put_time(std::gmtime(&*sourceInfo.info.lastModified), "%Y%m%d%H%M%S")));
-}
-
-struct LazyInput
-{
-    bool isFlake;
-    LockedInput lockedInput;
-};
-
-/* Helper primop to make callFlake (below) fetch/call its inputs
-   lazily. Note that this primop cannot be called by user code since
-   it doesn't appear in 'builtins'. */
-static void prim_callFlake(EvalState & state, const Pos & pos, Value * * args, Value & v)
-{
-    auto lazyInput = (LazyInput *) args[0]->attrs;
-
-    if (lazyInput->isFlake) {
-        FlakeCache flakeCache;
-        auto flake = getFlake(state, lazyInput->lockedInput.lockedRef, lazyInput->lockedInput.info, false, flakeCache);
-
-        if (flake.sourceInfo->info.narHash != lazyInput->lockedInput.info.narHash)
-            throw Error("the content hash of flake '%s' (%s) doesn't match the hash recorded in the referring lock file (%s)",
-                lazyInput->lockedInput.lockedRef,
-                flake.sourceInfo->info.narHash.to_string(SRI),
-                lazyInput->lockedInput.info.narHash.to_string(SRI));
-
-        // FIXME: check all the other attributes in lockedInput.info
-        // once we've dropped support for lock file version 4.
-
-        assert(flake.sourceInfo->storePath == lazyInput->lockedInput.computeStorePath(*state.store));
-
-        callFlake(state, flake, lazyInput->lockedInput, v);
-    } else {
-        FlakeCache flakeCache;
-        auto [sourceInfo, lockedRef] = fetchOrSubstituteTree(
-            state, lazyInput->lockedInput.lockedRef, {}, false, flakeCache);
-
-        if (sourceInfo.info.narHash != lazyInput->lockedInput.info.narHash)
-            throw Error("the content hash of repository '%s' (%s) doesn't match the hash recorded in the referring lock file (%s)",
-                lazyInput->lockedInput.lockedRef,
-                sourceInfo.info.narHash.to_string(SRI),
-                lazyInput->lockedInput.info.narHash.to_string(SRI));
-
-        // FIXME: check all the other attributes in lockedInput.info
-        // once we've dropped support for lock file version 4.
-
-        assert(sourceInfo.storePath == lazyInput->lockedInput.computeStorePath(*state.store));
-
-        state.mkAttrs(v, 8);
-
-        assert(state.store->isValidPath(sourceInfo.storePath));
-
-        auto pathS = state.store->printStorePath(sourceInfo.storePath);
-
-        mkString(*state.allocAttr(v, state.sOutPath), pathS, {pathS});
-
-        emitSourceInfoAttrs(state, lockedRef, sourceInfo, v);
-
-        v.attrs->sort();
-    }
-}
-
 void callFlake(EvalState & state,
     const Flake & flake,
     const LockedInputs & lockedInputs,
-    Value & vResFinal)
+    Value & vRes)
 {
-    auto & vRes = *state.allocValue();
+    auto vCallFlake = state.allocValue();
-    auto & vInputs = *state.allocValue();
+    auto vLocks = state.allocValue();
+    auto vRootSrc = state.allocValue();
+    auto vTmp = state.allocValue();
 
-    state.mkAttrs(vInputs, flake.inputs.size() + 1);
+    mkString(*vLocks, lockedInputs.to_string());
 
-    for (auto & [inputId, input] : flake.inputs) {
+    emitTreeAttrs(state, *flake.sourceInfo, flake.lockedRef.input, *vRootSrc);
-        auto vFlake = state.allocAttr(vInputs, inputId);
-        auto vPrimOp = state.allocValue();
-        static auto primOp = new PrimOp(prim_callFlake, 1, state.symbols.create("callFlake"));
-        vPrimOp->type = tPrimOp;
-        vPrimOp->primOp = primOp;
-        auto vArg = state.allocValue();
-        vArg->type = tNull;
-        auto lockedInput = lockedInputs.inputs.find(inputId);
-        assert(lockedInput != lockedInputs.inputs.end());
-        // FIXME: leak
-        vArg->attrs = (Bindings *) new LazyInput{input.isFlake, lockedInput->second};
-        mkApp(*vFlake, *vPrimOp, *vArg);
-    }
 
-    auto & vSourceInfo = *state.allocValue();
+    state.evalFile(canonPath(settings.nixDataDir + "/nix/corepkgs/call-flake.nix", true), *vCallFlake);
-    state.mkAttrs(vSourceInfo, 8);
+    state.callFunction(*vCallFlake, *vLocks, *vTmp, noPos);
-    emitSourceInfoAttrs(state, flake.lockedRef, *flake.sourceInfo, vSourceInfo);
+    state.callFunction(*vTmp, *vRootSrc, vRes, noPos);
-    vSourceInfo.attrs->sort();
-
-    vInputs.attrs->push_back(Attr(state.sSelf, &vRes));
-
-    vInputs.attrs->sort();
-
-    /* For convenience, put the outputs directly in the result, so you
-       can refer to an output of an input as 'inputs.foo.bar' rather
-       than 'inputs.foo.outputs.bar'. */
-    auto vCall = *state.allocValue();
-    state.eval(state.parseExprFromString(
-            "outputsFun: inputs: sourceInfo: let outputs = outputsFun inputs; in "
-            "outputs // sourceInfo // { inherit inputs; inherit outputs; inherit sourceInfo; }", "/"), vCall);
-
-    auto vCall2 = *state.allocValue();
-    auto vCall3 = *state.allocValue();
-    state.callFunction(vCall, *flake.vOutputs, vCall2, noPos);
-    state.callFunction(vCall2, vInputs, vCall3, noPos);
-    state.callFunction(vCall3, vSourceInfo, vRes, noPos);
-
-    vResFinal = vRes;
 }
 
 void callFlake(EvalState & state,
@@ -767,7 +644,6 @@ void callFlake(EvalState & state,
     callFlake(state, lockedFlake.flake, lockedFlake.lockFile, v);
 }
 
-// This function is exposed to be used in nix files.
 static void prim_getFlake(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     callFlake(state,

src/libexpr/flake/flake.hh

@@ -107,4 +107,10 @@ void callFlake(
 
 }
 
+void emitTreeAttrs(
+    EvalState & state,
+    const fetchers::Tree & tree,
+    std::shared_ptr<const fetchers::Input> input,
+    Value & v);
+
 }

src/libexpr/flake/lockfile.cc

@@ -123,6 +123,11 @@ nlohmann::json LockedInputs::toJson() const
     return json;
 }
 
+std::string LockedInputs::to_string() const
+{
+    return toJson().dump(2);
+}
+
 bool LockedInputs::isImmutable() const
 {
     for (auto & i : inputs)

src/libexpr/flake/lockfile.hh

@@ -27,6 +27,8 @@ struct LockedInputs
 
     nlohmann::json toJson() const;
 
+    std::string to_string() const;
+
     bool isImmutable() const;
 
     std::optional<LockedInput *> findInput(const InputPath & path);

src/libexpr/primops.hh

@@ -20,6 +20,7 @@ struct RegisterPrimOp
    them. */
 /* Load a ValueInitializer from a DSO and return whatever it initializes */
 void prim_importNative(EvalState & state, const Pos & pos, Value * * args, Value & v);
+
 /* Execute a program and parse its output */
 void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v);
 

src/libexpr/primops/fetchTree.cc

@@ -4,11 +4,45 @@
 #include "fetchers/fetchers.hh"
 #include "fetchers/registry.hh"
 
+#include <ctime>
+#include <iomanip>
+
 namespace nix {
 
+void emitTreeAttrs(
+    EvalState & state,
+    const fetchers::Tree & tree,
+    std::shared_ptr<const fetchers::Input> input,
+    Value & v)
+{
+    state.mkAttrs(v, 8);
+
+    auto storePath = state.store->printStorePath(tree.storePath);
+
+    mkString(*state.allocAttr(v, state.sOutPath), storePath, PathSet({storePath}));
+
+    assert(tree.info.narHash);
+    mkString(*state.allocAttr(v, state.symbols.create("narHash")),
+        tree.info.narHash.to_string(SRI));
+
+    if (input->getRev()) {
+        mkString(*state.allocAttr(v, state.symbols.create("rev")), input->getRev()->gitRev());
+        mkString(*state.allocAttr(v, state.symbols.create("shortRev")), input->getRev()->gitShortRev());
+    }
+
+    if (tree.info.revCount)
+        mkInt(*state.allocAttr(v, state.symbols.create("revCount")), *tree.info.revCount);
+
+    if (tree.info.lastModified)
+        mkString(*state.allocAttr(v, state.symbols.create("lastModified")),
+            fmt("%s", std::put_time(std::gmtime(&*tree.info.lastModified), "%Y%m%d%H%M%S")));
+
+    v.attrs->sort();
+}
+
 static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    settings.requireExperimentalFeature("fetch-tree");
+    settings.requireExperimentalFeature("flakes");
 
     std::shared_ptr<const fetchers::Input> input;
     PathSet context;
@@ -25,7 +59,8 @@ static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, V
             if (attr.value->type == tString)
                 attrs.emplace(attr.name, attr.value->string.s);
             else
-                throw Error("unsupported attribute type");
+                throw TypeError("fetchTree argument '%s' is %s while a string is expected",
+                    attr.name, showType(*attr.value));
         }
 
         if (!attrs.count("type"))
@@ -43,19 +78,10 @@ static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, V
 
     auto [tree, input2] = input->fetchTree(state.store);
 
-    state.mkAttrs(v, 8);
-    auto storePath = state.store->printStorePath(tree.storePath);
-    mkString(*state.allocAttr(v, state.sOutPath), storePath, PathSet({storePath}));
-    if (input2->getRev()) {
-        mkString(*state.allocAttr(v, state.symbols.create("rev")), input2->getRev()->gitRev());
-        mkString(*state.allocAttr(v, state.symbols.create("shortRev")), input2->getRev()->gitShortRev());
-    }
-    if (tree.info.revCount)
-        mkInt(*state.allocAttr(v, state.symbols.create("revCount")), *tree.info.revCount);
-    v.attrs->sort();
-
     if (state.allowedPaths)
         state.allowedPaths->insert(tree.actualPath);
+
+    emitTreeAttrs(state, tree, input2, v);
 }
 
 static RegisterPrimOp r("fetchTree", 1, prim_fetchTree);

tests/tarball.sh

@@ -27,10 +27,10 @@ test_tarball() {
 
     nix-build -o $TEST_ROOT/result -E "import (fetchTarball file://$tarball)"
 
-    nix-build --experimental-features fetch-tree -o $TEST_ROOT/result -E "import (fetchTree file://$tarball)"
+    nix-build --experimental-features flakes -o $TEST_ROOT/result -E "import (fetchTree file://$tarball)"
-    nix-build --experimental-features fetch-tree -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; })"
+    nix-build --experimental-features flakes -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; })"
-    nix-build --experimental-features fetch-tree -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"$hash\"; })"
+    nix-build --experimental-features flakes -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"$hash\"; })"
-    nix-build --experimental-features fetch-tree -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"sha256-xdKv2pq/IiwLSnBBJXW8hNowI4MrdZfW+SYqDQs7Tzc=\"; })" 2>&1 | grep 'NAR hash mismatch in input'
+    nix-build --experimental-features flakes -o $TEST_ROOT/result -E "import (fetchTree { type = \"tarball\"; url = file://$tarball; narHash = \"sha256-xdKv2pq/IiwLSnBBJXW8hNowI4MrdZfW+SYqDQs7Tzc=\"; })" 2>&1 | grep 'NAR hash mismatch in input'
 
     nix-instantiate --eval -E '1 + 2' -I fnord=file://no-such-tarball.tar$ext
     nix-instantiate --eval -E 'with <fnord/xyzzy>; 1 + 2' -I fnord=file://no-such-tarball$ext