From af95a7c16b0fc0b033a7191f686fe98b2015162f Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Wed, 8 Jul 2020 15:38:01 -0400
Subject: [PATCH 01/12] Add name to BasicDerivation

We always have a name for BasicDerivation, since we have a derivation
store path that has a name.
---
 src/libexpr/primops.cc      |  6 ++++--
 src/libstore/daemon.cc      |  2 +-
 src/libstore/derivations.cc | 16 ++++++++++------
 src/libstore/derivations.hh |  5 +++--
 src/nix-store/nix-store.cc  |  4 ++--
 src/nix/repl.cc             |  2 +-
 6 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index dec917b38..da1937e6b 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -102,9 +102,11 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args
 
     Path realPath = state.checkSourcePath(state.toRealPath(path, context));
 
+    StorePath storePath = state.store->parseStorePath(path);
+
     // FIXME
-    if (state.store->isStorePath(path) && state.store->isValidPath(state.store->parseStorePath(path)) && isDerivation(path)) {
-        Derivation drv = readDerivation(*state.store, realPath);
+    if (state.store->isStorePath(path) && state.store->isValidPath(storePath) && isDerivation(path)) {
+        Derivation drv = readDerivation(*state.store, realPath, std::string(storePath.name()));
         Value & w = *state.allocValue();
         state.mkAttrs(w, 3 + drv.outputs.size());
         Value * v2 = state.allocAttr(w, state.sDrvPath);
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index ebc4d0285..4cf67064a 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -474,7 +474,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     case wopBuildDerivation: {
         auto drvPath = store->parseStorePath(readString(from));
         BasicDerivation drv;
-        readDerivation(from, *store, drv);
+        readDerivation(from, *store, drv, std::string(drvPath.name()));
         BuildMode buildMode = (BuildMode) readInt(from);
         logger->startWork();
         if (!trusted)
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 42551ef6b..bdc6f4f68 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -129,9 +129,11 @@ static DerivationOutput parseDerivationOutput(const Store & store, istringstream
 }
 
 
-static Derivation parseDerivation(const Store & store, const string & s)
+static Derivation parseDerivation(const Store & store, const string & s, string name)
 {
     Derivation drv;
+    drv.name = name;
+
     istringstream_nocopy str(s);
     expect(str, "Derive([");
 
@@ -175,10 +177,10 @@ static Derivation parseDerivation(const Store & store, const string & s)
 }
 
 
-Derivation readDerivation(const Store & store, const Path & drvPath)
+Derivation readDerivation(const Store & store, const Path & drvPath, std::string name)
 {
     try {
-        return parseDerivation(store, readFile(drvPath));
+        return parseDerivation(store, readFile(drvPath), name);
     } catch (FormatError & e) {
         throw Error("error parsing derivation '%1%': %2%", drvPath, e.msg());
     }
@@ -196,7 +198,7 @@ Derivation Store::readDerivation(const StorePath & drvPath)
 {
     auto accessor = getFSAccessor();
     try {
-        return parseDerivation(*this, accessor->readFile(printStorePath(drvPath)));
+        return parseDerivation(*this, accessor->readFile(printStorePath(drvPath)), std::string(drvPath.name()));
     } catch (FormatError & e) {
         throw Error("error parsing derivation '%s': %s", printStorePath(drvPath), e.msg());
     }
@@ -369,7 +371,7 @@ Hash hashDerivationModulo(Store & store, const Derivation & drv, bool maskOutput
         if (h == drvHashes.end()) {
             assert(store.isValidPath(i.first));
             h = drvHashes.insert_or_assign(i.first, hashDerivationModulo(store,
-                store.readDerivation(i.first), false)).first;
+                    store.readDerivation(i.first), false)).first;
         }
         inputs2.insert_or_assign(h->second.to_string(Base16, false), i.second);
     }
@@ -435,8 +437,10 @@ StringSet BasicDerivation::outputNames() const
 }
 
 
-Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv)
+Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, string name)
 {
+    drv.name = name;
+
     drv.outputs.clear();
     auto nr = readNum<size_t>(in);
     for (size_t n = 0; n < nr; n++) {
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 68c53c1ff..f9d328196 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -35,6 +35,7 @@ struct BasicDerivation
     Path builder;
     Strings args;
     StringPairs env;
+    string name;
 
     BasicDerivation() { }
     virtual ~BasicDerivation() { };
@@ -76,7 +77,7 @@ StorePath writeDerivation(ref<Store> store,
     const Derivation & drv, std::string_view name, RepairFlag repair = NoRepair);
 
 /* Read a derivation from a file. */
-Derivation readDerivation(const Store & store, const Path & drvPath);
+Derivation readDerivation(const Store & store, const Path & drvPath, string name);
 
 // FIXME: remove
 bool isDerivation(const string & fileName);
@@ -93,7 +94,7 @@ bool wantOutput(const string & output, const std::set<string> & wanted);
 struct Source;
 struct Sink;
 
-Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv);
+Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, string name);
 void writeDerivation(Sink & out, const Store & store, const BasicDerivation & drv);
 
 std::string hashPlaceholder(const std::string & outputName);
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 7d81bf54f..9a8cf0f2f 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -914,9 +914,9 @@ static void opServe(Strings opFlags, Strings opArgs)
 
                 if (!writeAllowed) throw Error("building paths is not allowed");
 
-                auto drvPath = store->parseStorePath(readString(in)); // informational only
+                auto drvPath = store->parseStorePath(readString(in));
                 BasicDerivation drv;
-                readDerivation(in, *store, drv);
+                readDerivation(in, *store, drv, std::string(drvPath.name()));
 
                 getBuildSettings();
 
diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index fdacf604b..a3d85ed31 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -483,7 +483,7 @@ bool NixRepl::processLine(string line)
                but doing it in a child makes it easier to recover from
                problems / SIGINT. */
             if (runProgram(settings.nixBinDir + "/nix", Strings{"build", "--no-link", drvPath}) == 0) {
-                auto drv = readDerivation(*state->store, drvPath);
+                auto drv = readDerivation(*state->store, drvPath, std::string(state->store->parseStorePath(drvPath).name()));
                 std::cout << std::endl << "this derivation produced the following outputs:" << std::endl;
                 for (auto & i : drv.outputs)
                     std::cout << fmt("  %s -> %s\n", i.first, state->store->printStorePath(i.second.path));

From 8e0d0689be797f9e42f9b43b06f50c1af7f20b4a Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Wed, 8 Jul 2020 19:11:39 -0400
Subject: [PATCH 02/12] Only store hash of fixed derivation output
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

we don’t need a full storepath for a fixedoutput derivation. So just
putting the ingestion method + the hash is sufficient.
---
 perl/lib/Nix/Store.xs             |   2 +-
 src/libexpr/get-drvs.cc           |   2 +-
 src/libexpr/primops.cc            |  27 ++++----
 src/libstore/build.cc             |  76 ++++++++++++-----------
 src/libstore/builtins/fetchurl.cc |  21 ++++---
 src/libstore/derivations.cc       | 100 +++++++++++++++++++-----------
 src/libstore/derivations.hh       |  18 ++++--
 src/libstore/local-store.cc       |  11 +---
 src/libstore/misc.cc              |   4 +-
 src/nix-env/nix-env.cc            |   2 +-
 src/nix-store/nix-store.cc        |   6 +-
 src/nix/develop.cc                |   4 +-
 src/nix/repl.cc                   |   2 +-
 src/nix/show-derivation.cc        |   8 +--
 14 files changed, 162 insertions(+), 121 deletions(-)

diff --git a/perl/lib/Nix/Store.xs b/perl/lib/Nix/Store.xs
index 945ed49c7..6dba07549 100644
--- a/perl/lib/Nix/Store.xs
+++ b/perl/lib/Nix/Store.xs
@@ -304,7 +304,7 @@ SV * derivationFromPath(char * drvPath)
 
             HV * outputs = newHV();
             for (auto & i : drv.outputs)
-                hv_store(outputs, i.first.c_str(), i.first.size(), newSVpv(store()->printStorePath(i.second.path).c_str(), 0), 0);
+                hv_store(outputs, i.first.c_str(), i.first.size(), newSVpv(store()->printStorePath(i.second.path(store(), drv.name)).c_str(), 0), 0);
             hv_stores(hash, "outputs", newRV((SV *) outputs));
 
             AV * inputDrvs = newAV();
diff --git a/src/libexpr/get-drvs.cc b/src/libexpr/get-drvs.cc
index 9055f59a1..5d6e39aa0 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -39,7 +39,7 @@ DrvInfo::DrvInfo(EvalState & state, ref<Store> store, const std::string & drvPat
     if (i == drv.outputs.end())
         throw Error("derivation '%s' does not have output '%s'", store->printStorePath(drvPath), outputName);
 
-    outPath = store->printStorePath(i->second.path);
+    outPath = store->printStorePath(i->second.path(*store, drv.name));
 }
 
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index da1937e6b..9b613eef9 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -64,7 +64,7 @@ void EvalState::realiseContext(const PathSet & context)
                 DerivationOutputs::iterator i = drv.outputs.find(outputName);
                 if (i == drv.outputs.end())
                     throw Error("derivation '%s' does not have an output named '%s'", ctxS, outputName);
-                allowedPaths->insert(store->printStorePath(i->second.path));
+                allowedPaths->insert(store->printStorePath(i->second.path(*store, drv.name)));
             }
         }
     }
@@ -120,7 +120,7 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args
 
         for (const auto & o : drv.outputs) {
             v2 = state.allocAttr(w, state.symbols.create(o.first));
-            mkString(*v2, state.store->printStorePath(o.second.path), {"!" + o.first + "!" + path});
+            mkString(*v2, state.store->printStorePath(o.second.path(*state.store, drv.name)), {"!" + o.first + "!" + path});
             outputsVal->listElems()[outputs_index] = state.allocValue();
             mkString(*(outputsVal->listElems()[outputs_index++]), o.first);
         }
@@ -778,11 +778,12 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
         auto outPath = state.store->makeFixedOutputPath(ingestionMethod, h, drvName);
         if (!jsonObject) drv.env["out"] = state.store->printStorePath(outPath);
         drv.outputs.insert_or_assign("out", DerivationOutput {
-            .path = std::move(outPath),
-            .hash = FixedOutputHash {
-                .method = ingestionMethod,
-                .hash = std::move(h),
-            },
+                .output = DerivationOutputFixed {
+                    .hash = FixedOutputHash {
+                        .method = ingestionMethod,
+                        .hash = std::move(h),
+                    },
+                },
         });
     }
 
@@ -797,8 +798,9 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             if (!jsonObject) drv.env[i] = "";
             drv.outputs.insert_or_assign(i,
                 DerivationOutput {
-                    .path = StorePath::dummy,
-                    .hash = std::optional<FixedOutputHash> {},
+                    .output = DerivationOutputIntensional {
+                        .path = StorePath::dummy,
+                    },
                 });
         }
 
@@ -809,8 +811,9 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             if (!jsonObject) drv.env[i] = state.store->printStorePath(outPath);
             drv.outputs.insert_or_assign(i,
                 DerivationOutput {
-                    .path = std::move(outPath),
-                    .hash = std::optional<FixedOutputHash>(),
+                    .output = DerivationOutputIntensional {
+                        .path = std::move(outPath),
+                    },
                 });
         }
     }
@@ -831,7 +834,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
     mkString(*state.allocAttr(v, state.sDrvPath), drvPathS, {"=" + drvPathS});
     for (auto & i : drv.outputs) {
         mkString(*state.allocAttr(v, state.symbols.create(i.first)),
-            state.store->printStorePath(i.second.path), {"!" + i.first + "!" + drvPathS});
+            state.store->printStorePath(i.second.path(*state.store, drv.name)), {"!" + i.first + "!" + drvPathS});
     }
     v.attrs->sort();
 }
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 0ef2f288f..bf7d4c2f9 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1047,7 +1047,7 @@ DerivationGoal::DerivationGoal(const StorePath & drvPath, const BasicDerivation
 {
     this->drv = std::make_unique<BasicDerivation>(BasicDerivation(drv));
     state = &DerivationGoal::haveDerivation;
-    name = fmt("building of %s", worker.store.showPaths(drv.outputPaths()));
+    name = fmt("building of %s", worker.store.showPaths(drv.outputPaths(worker.store)));
     trace("created");
 
     mcExpectedBuilds = std::make_unique<MaintainCount<uint64_t>>(worker.expectedBuilds);
@@ -1182,7 +1182,7 @@ void DerivationGoal::haveDerivation()
     retrySubstitution = false;
 
     for (auto & i : drv->outputs)
-        worker.store.addTempRoot(i.second.path);
+        worker.store.addTempRoot(i.second.path(worker.store, drv->name));
 
     /* Check what outputs paths are not already valid. */
     auto invalidOutputs = checkPathValidity(false, buildMode == bmRepair);
@@ -1290,12 +1290,12 @@ void DerivationGoal::repairClosure()
     StorePathSet outputClosure;
     for (auto & i : drv->outputs) {
         if (!wantOutput(i.first, wantedOutputs)) continue;
-        worker.store.computeFSClosure(i.second.path, outputClosure);
+        worker.store.computeFSClosure(i.second.path(worker.store, drv->name), outputClosure);
     }
 
     /* Filter out our own outputs (which we have already checked). */
     for (auto & i : drv->outputs)
-        outputClosure.erase(i.second.path);
+        outputClosure.erase(i.second.path(worker.store, drv->name));
 
     /* Get all dependencies of this derivation so that we know which
        derivation is responsible for which path in the output
@@ -1307,7 +1307,7 @@ void DerivationGoal::repairClosure()
         if (i.isDerivation()) {
             Derivation drv = worker.store.derivationFromPath(i);
             for (auto & j : drv.outputs)
-                outputsToDrv.insert_or_assign(j.second.path, i);
+                outputsToDrv.insert_or_assign(j.second.path(worker.store, drv.name), i);
         }
 
     /* Check each path (slow!). */
@@ -1379,7 +1379,7 @@ void DerivationGoal::inputsRealised()
             for (auto & j : i.second) {
                 auto k = inDrv.outputs.find(j);
                 if (k != inDrv.outputs.end())
-                    worker.store.computeFSClosure(k->second.path, inputPaths);
+                    worker.store.computeFSClosure(k->second.path(worker.store, inDrv.name), inputPaths);
                 else
                     throw Error(
                         "derivation '%s' requires non-existent output '%s' from input derivation '%s'",
@@ -1432,7 +1432,7 @@ void DerivationGoal::tryToBuild()
        goal can start a build, and if not, the main loop will sleep a
        few seconds and then retry this goal. */
     PathSet lockFiles;
-    for (auto & outPath : drv->outputPaths())
+    for (auto & outPath : drv->outputPaths(worker.store))
         lockFiles.insert(worker.store.Store::toRealPath(outPath));
 
     if (!outputLocks.lockPaths(lockFiles, "", false)) {
@@ -1460,16 +1460,16 @@ void DerivationGoal::tryToBuild()
         return;
     }
 
-    missingPaths = drv->outputPaths();
+    missingPaths = drv->outputPaths(worker.store);
     if (buildMode != bmCheck)
         for (auto & i : validPaths) missingPaths.erase(i);
 
     /* If any of the outputs already exist but are not valid, delete
        them. */
     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.Store::toRealPath(i.second.path));
+        if (worker.store.isValidPath(i.second.path(worker.store, drv->name))) continue;
+        debug("removing invalid path '%s'", worker.store.printStorePath(i.second.path(worker.store, drv->name)));
+        deletePath(worker.store.Store::toRealPath(i.second.path(worker.store, drv->name)));
     }
 
     /* Don't do a remote build if the derivation has the attribute
@@ -1692,7 +1692,7 @@ void DerivationGoal::buildDone()
                 fmt("running post-build-hook '%s'", settings.postBuildHook),
                 Logger::Fields{worker.store.printStorePath(drvPath)});
             PushActivity pact(act.id);
-            auto outputPaths = drv->outputPaths();
+            auto outputPaths = drv->outputPaths(worker.store);
             std::map<std::string, std::string> hookEnvironment = getEnv();
 
             hookEnvironment.emplace("DRV_PATH", worker.store.printStorePath(drvPath));
@@ -1920,7 +1920,7 @@ StorePathSet DerivationGoal::exportReferences(const StorePathSet & storePaths)
         if (j.isDerivation()) {
             Derivation drv = worker.store.derivationFromPath(j);
             for (auto & k : drv.outputs)
-                worker.store.computeFSClosure(k.second.path, paths);
+                worker.store.computeFSClosure(k.second.path(worker.store, drv.name), paths);
         }
     }
 
@@ -2015,7 +2015,7 @@ void DerivationGoal::startBuilder()
 
     /* Substitute output placeholders with the actual output paths. */
     for (auto & output : drv->outputs)
-        inputRewrites[hashPlaceholder(output.first)] = worker.store.printStorePath(output.second.path);
+        inputRewrites[hashPlaceholder(output.first)] = worker.store.printStorePath(output.second.path(worker.store, drv->name));
 
     /* Construct the environment passed to the builder. */
     initEnv();
@@ -2200,7 +2200,7 @@ void DerivationGoal::startBuilder()
            (typically the dependencies of /bin/sh).  Throw them
            out. */
         for (auto & i : drv->outputs)
-            dirsInChroot.erase(worker.store.printStorePath(i.second.path));
+            dirsInChroot.erase(worker.store.printStorePath(i.second.path(drv->name)));
 
 #elif __APPLE__
         /* We don't really have any parent prep work to do (yet?)
@@ -2613,7 +2613,7 @@ void DerivationGoal::writeStructuredAttrs()
     /* Add an "outputs" object containing the output paths. */
     nlohmann::json outputs;
     for (auto & i : drv->outputs)
-        outputs[i.first] = rewriteStrings(worker.store.printStorePath(i.second.path), inputRewrites);
+        outputs[i.first] = rewriteStrings(worker.store.printStorePath(i.second.path(worker.store, drv->name)), inputRewrites);
     json["outputs"] = outputs;
 
     /* Handle exportReferencesGraph. */
@@ -2818,7 +2818,7 @@ struct RestrictedStore : public LocalFSStore
                 auto drv = derivationFromPath(path.path);
                 for (auto & output : drv.outputs)
                     if (wantOutput(output.first, path.outputs))
-                        newPaths.insert(output.second.path);
+                        newPaths.insert(output.second.path(*this, drv.name));
             } else if (!goal.isAllowed(path.path))
                 throw InvalidPath("cannot build unknown path '%s' in recursive Nix", printStorePath(path.path));
         }
@@ -3580,7 +3580,7 @@ StorePathSet parseReferenceSpecifiers(Store & store, const BasicDerivation & drv
         if (store.isStorePath(i))
             result.insert(store.parseStorePath(i));
         else if (drv.outputs.count(i))
-            result.insert(drv.outputs.find(i)->second.path);
+            result.insert(drv.outputs.find(i)->second.path(store, drv.name));
         else throw BuildError("derivation contains an illegal reference specifier '%s'", i);
     }
     return result;
@@ -3618,7 +3618,7 @@ void DerivationGoal::registerOutputs()
     if (hook) {
         bool allValid = true;
         for (auto & i : drv->outputs)
-            if (!worker.store.isValidPath(i.second.path)) allValid = false;
+            if (!worker.store.isValidPath(i.second.path(worker.store, drv->name))) allValid = false;
         if (allValid) return;
     }
 
@@ -3639,23 +3639,23 @@ void DerivationGoal::registerOutputs()
        Nix calls. */
     StorePathSet referenceablePaths;
     for (auto & p : inputPaths) referenceablePaths.insert(p);
-    for (auto & i : drv->outputs) referenceablePaths.insert(i.second.path);
+    for (auto & i : drv->outputs) referenceablePaths.insert(i.second.path(worker.store, drv->name));
     for (auto & p : addedPaths) referenceablePaths.insert(p);
 
     /* Check whether the output paths were created, and grep each
        output path to determine what other paths it references.  Also make all
        output paths read-only. */
     for (auto & i : drv->outputs) {
-        auto path = worker.store.printStorePath(i.second.path);
-        if (!missingPaths.count(i.second.path)) continue;
+        auto path = worker.store.printStorePath(i.second.path(worker.store, drv->name));
+        if (!missingPaths.count(i.second.path(worker.store, drv->name))) continue;
 
         Path actualPath = path;
         if (needsHashRewrite()) {
-            auto r = redirectedOutputs.find(i.second.path);
+            auto r = redirectedOutputs.find(i.second.path(worker.store, drv->name));
             if (r != redirectedOutputs.end()) {
                 auto redirected = worker.store.Store::toRealPath(r->second);
                 if (buildMode == bmRepair
-                    && redirectedBadOutputs.count(i.second.path)
+                    && redirectedBadOutputs.count(i.second.path(worker.store, drv->name))
                     && pathExists(redirected))
                     replaceValidPath(path, redirected);
                 if (buildMode == bmCheck)
@@ -3724,7 +3724,9 @@ void DerivationGoal::registerOutputs()
 
         if (fixedOutput) {
 
-            if (i.second.hash->method == FileIngestionMethod::Flat) {
+            FixedOutputHash outputHash = std::get<DerivationOutputFixed>(i.second.output).hash;
+
+            if (outputHash.method == FileIngestionMethod::Flat) {
                 /* The output path should be a regular file without execute permission. */
                 if (!S_ISREG(st.st_mode) || (st.st_mode & S_IXUSR) != 0)
                     throw BuildError(
@@ -3735,13 +3737,13 @@ void DerivationGoal::registerOutputs()
 
             /* Check the hash. In hash mode, move the path produced by
                the derivation to its content-addressed location. */
-            Hash h2 = i.second.hash->method == FileIngestionMethod::Recursive
-                ? hashPath(*i.second.hash->hash.type, actualPath).first
-                : hashFile(*i.second.hash->hash.type, actualPath);
+            Hash h2 = outputHash.method == FileIngestionMethod::Recursive
+                ? hashPath(*outputHash.hash.type, actualPath).first
+                : hashFile(*outputHash.hash.type, actualPath);
 
-            auto dest = worker.store.makeFixedOutputPath(i.second.hash->method, h2, i.second.path.name());
+            auto dest = worker.store.makeFixedOutputPath(outputHash.method, h2, i.second.path(worker.store, drv->name).name());
 
-            if (i.second.hash->hash != h2) {
+            if (outputHash.hash != h2) {
 
                 /* Throw an error after registering the path as
                    valid. */
@@ -3749,7 +3751,7 @@ void DerivationGoal::registerOutputs()
                 delayedException = std::make_exception_ptr(
                     BuildError("hash mismatch in fixed-output derivation '%s':\n  wanted: %s\n  got:    %s",
                         worker.store.printStorePath(dest),
-                        i.second.hash->hash.to_string(SRI, true),
+                        outputHash.hash.to_string(SRI, true),
                         h2.to_string(SRI, true)));
 
                 Path actualDest = worker.store.Store::toRealPath(dest);
@@ -3771,7 +3773,7 @@ void DerivationGoal::registerOutputs()
                 assert(worker.store.parseStorePath(path) == dest);
 
             ca = FixedOutputHash {
-                .method = i.second.hash->method,
+                .method = outputHash.method,
                 .hash = h2,
             };
         }
@@ -3895,7 +3897,7 @@ void DerivationGoal::registerOutputs()
     /* If this is the first round of several, then move the output out of the way. */
     if (nrRounds > 1 && curRound == 1 && curRound < nrRounds && keepPreviousRound) {
         for (auto & i : drv->outputs) {
-            auto path = worker.store.printStorePath(i.second.path);
+            auto path = worker.store.printStorePath(i.second.path(worker.store, drv->name));
             Path prev = path + checkSuffix;
             deletePath(prev);
             Path dst = path + checkSuffix;
@@ -3913,7 +3915,7 @@ void DerivationGoal::registerOutputs()
        if the result was not determistic? */
     if (curRound == nrRounds) {
         for (auto & i : drv->outputs) {
-            Path prev = worker.store.printStorePath(i.second.path) + checkSuffix;
+            Path prev = worker.store.printStorePath(i.second.path(worker.store, drv->name)) + checkSuffix;
             deletePath(prev);
         }
     }
@@ -4214,9 +4216,9 @@ StorePathSet DerivationGoal::checkPathValidity(bool returnValid, bool checkHash)
     for (auto & i : drv->outputs) {
         if (!wantOutput(i.first, wantedOutputs)) continue;
         bool good =
-            worker.store.isValidPath(i.second.path) &&
-            (!checkHash || worker.pathContentsGood(i.second.path));
-        if (good == returnValid) result.insert(i.second.path);
+            worker.store.isValidPath(i.second.path(worker.store, drv->name)) &&
+            (!checkHash || worker.pathContentsGood(i.second.path(worker.store, drv->name)));
+        if (good == returnValid) result.insert(i.second.path(worker.store, drv->name));
     }
     return result;
 }
diff --git a/src/libstore/builtins/fetchurl.cc b/src/libstore/builtins/fetchurl.cc
index e630cf6f1..017a633b5 100644
--- a/src/libstore/builtins/fetchurl.cc
+++ b/src/libstore/builtins/fetchurl.cc
@@ -63,16 +63,19 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
     auto & output = drv.outputs.begin()->second;
 
     /* Try the hashed mirrors first. */
-    if (output.hash && output.hash->method == FileIngestionMethod::Flat)
-        for (auto hashedMirror : settings.hashedMirrors.get())
-            try {
-                if (!hasSuffix(hashedMirror, "/")) hashedMirror += '/';
-                auto & h = output.hash->hash;
-                fetch(hashedMirror + printHashType(*h.type) + "/" + h.to_string(Base16, false));
-                return;
-            } catch (Error & e) {
-                debug(e.what());
+    if (auto hash = std::get_if<DerivationOutputFixed>(&output.output)) {
+        if (hash->hash.method == FileIngestionMethod::Flat) {
+            for (auto hashedMirror : settings.hashedMirrors.get()) {
+                try {
+                    if (!hasSuffix(hashedMirror, "/")) hashedMirror += '/';
+                    fetch(hashedMirror + printHashType(*hash->hash.hash.type) + "/" + hash->hash.hash.to_string(Base16, false));
+                    return;
+                } catch (Error & e) {
+                    debug(e.what());
+                }
             }
+        }
+    }
 
     /* Otherwise try the specified URL. */
     fetch(mainUrl);
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index bdc6f4f68..ffeafea87 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -8,12 +8,28 @@
 
 namespace nix {
 
-const StorePath & BasicDerivation::findOutput(const string & id) const
+// FIXME Put this somewhere?
+template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
+template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
+
+StorePath DerivationOutput::path(const Store & store, string drvName) const
+{
+    return std::visit(overloaded {
+        [](DerivationOutputIntensional doi) {
+            return doi.path;
+        },
+        [&](DerivationOutputFixed dof) {
+            return store.makeFixedOutputPath(dof.hash.method, dof.hash.hash, drvName);
+        }
+    }, output);
+}
+
+const StorePath & BasicDerivation::findOutput(const Store & store, const string & id) const
 {
     auto i = outputs.find(id);
     if (i == outputs.end())
         throw Error("derivation has no output '%s'", id);
-    return i->second.path;
+    return i->second.path(store, name);
 }
 
 
@@ -108,7 +124,6 @@ static DerivationOutput parseDerivationOutput(const Store & store, istringstream
     expect(str, ","); const auto hash = parseString(str);
     expect(str, ")");
 
-    std::optional<FixedOutputHash> fsh;
     if (hashAlgo != "") {
         auto method = FileIngestionMethod::Flat;
         if (string(hashAlgo, 0, 2) == "r:") {
@@ -116,16 +131,21 @@ static DerivationOutput parseDerivationOutput(const Store & store, istringstream
             hashAlgo = string(hashAlgo, 2);
         }
         const HashType hashType = parseHashType(hashAlgo);
-        fsh = FixedOutputHash {
-            .method = std::move(method),
-            .hash = Hash(hash, hashType),
-        };
-    }
 
-    return DerivationOutput {
-        .path = std::move(path),
-        .hash = std::move(fsh),
-    };
+        return DerivationOutput {
+            .output = DerivationOutputFixed {
+                .hash = FixedOutputHash {
+                    .method = std::move(method),
+                    .hash = Hash(hash, hashType),
+                },
+            }
+        };
+    } else
+        return DerivationOutput {
+            .output = DerivationOutputIntensional {
+                .path = std::move(path),
+            }
+        };
 }
 
 
@@ -266,10 +286,14 @@ string Derivation::unparse(const Store & store, bool maskOutputs,
     for (auto & i : outputs) {
         if (first) first = false; else s += ',';
         s += '('; printUnquotedString(s, i.first);
-        s += ','; printUnquotedString(s, maskOutputs ? "" : store.printStorePath(i.second.path));
-        s += ','; printUnquotedString(s, i.second.hash ? i.second.hash->printMethodAlgo() : "");
-        s += ','; printUnquotedString(s,
-            i.second.hash ? i.second.hash->hash.to_string(Base16, false) : "");
+        s += ','; printUnquotedString(s, maskOutputs ? "" : store.printStorePath(i.second.path(store, name)));
+        if (auto hash = std::get_if<DerivationOutputFixed>(&i.second.output)) {
+            s += ','; printUnquotedString(s, hash->hash.printMethodAlgo());
+            s += ','; printUnquotedString(s, hash->hash.hash.to_string(Base16, false));
+        } else {
+            s += ','; printUnquotedString(s, "");
+            s += ','; printUnquotedString(s, "");
+        }
         s += ')';
     }
 
@@ -325,7 +349,7 @@ bool BasicDerivation::isFixedOutput() const
 {
     return outputs.size() == 1 &&
         outputs.begin()->first == "out" &&
-        outputs.begin()->second.hash;
+        std::holds_alternative<DerivationOutputFixed>(outputs.begin()->second.output);
 }
 
 
@@ -357,10 +381,11 @@ Hash hashDerivationModulo(Store & store, const Derivation & drv, bool maskOutput
     /* Return a fixed hash for fixed-output derivations. */
     if (drv.isFixedOutput()) {
         DerivationOutputs::const_iterator i = drv.outputs.begin();
+        auto hash = std::get<DerivationOutputFixed>(i->second.output);
         return hashString(htSHA256, "fixed:out:"
-            + i->second.hash->printMethodAlgo() + ":"
-            + i->second.hash->hash.to_string(Base16, false) + ":"
-            + store.printStorePath(i->second.path));
+            + hash.hash.printMethodAlgo() + ":"
+            + hash.hash.hash.to_string(Base16, false) + ":"
+            + store.printStorePath(i->second.path(store, drv.name)));
     }
 
     /* For other derivations, replace the inputs paths with recursive
@@ -394,11 +419,11 @@ bool wantOutput(const string & output, const std::set<string> & wanted)
 }
 
 
-StorePathSet BasicDerivation::outputPaths() const
+StorePathSet BasicDerivation::outputPaths(const Store & store) const
 {
     StorePathSet paths;
     for (auto & i : outputs)
-        paths.insert(i.second.path);
+        paths.insert(i.second.path(store, name));
     return paths;
 }
 
@@ -408,7 +433,6 @@ static DerivationOutput readDerivationOutput(Source & in, const Store & store)
     auto hashAlgo = readString(in);
     auto hash = readString(in);
 
-    std::optional<FixedOutputHash> fsh;
     if (hashAlgo != "") {
         auto method = FileIngestionMethod::Flat;
         if (string(hashAlgo, 0, 2) == "r:") {
@@ -416,16 +440,20 @@ static DerivationOutput readDerivationOutput(Source & in, const Store & store)
             hashAlgo = string(hashAlgo, 2);
         }
         auto hashType = parseHashType(hashAlgo);
-        fsh = FixedOutputHash {
-            .method = std::move(method),
-            .hash = Hash(hash, hashType),
+        return DerivationOutput {
+            .output = DerivationOutputFixed {
+                .hash = FixedOutputHash {
+                    .method = std::move(method),
+                    .hash = Hash(hash, hashType),
+                },
+            }
+        };
+    } else
+        return DerivationOutput {
+            .output = DerivationOutputIntensional {
+                .path = std::move(path),
+            }
         };
-    }
-
-    return DerivationOutput {
-        .path = std::move(path),
-        .hash = std::move(fsh),
-    };
 }
 
 StringSet BasicDerivation::outputNames() const
@@ -469,10 +497,10 @@ void writeDerivation(Sink & out, const Store & store, const BasicDerivation & dr
     out << drv.outputs.size();
     for (auto & i : drv.outputs) {
         out << i.first
-            << store.printStorePath(i.second.path);
-        if (i.second.hash) {
-            out << i.second.hash->printMethodAlgo()
-                << i.second.hash->hash.to_string(Base16, false);
+            << store.printStorePath(i.second.path(store, drv.name));
+        if (auto hash = std::get_if<DerivationOutputFixed>(&i.second.output)) {
+            out << hash->hash.printMethodAlgo()
+                << hash->hash.hash.to_string(Base16, false);
         } else {
             out << "" << "";
         }
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index f9d328196..d8cee0f34 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -13,10 +13,20 @@ namespace nix {
 
 /* Abstract syntax of derivations. */
 
-struct DerivationOutput
+struct DerivationOutputIntensional
 {
     StorePath path;
-    std::optional<FixedOutputHash> hash; /* hash used for expected hash computation */
+};
+
+struct DerivationOutputFixed
+{
+    FixedOutputHash hash; /* hash used for expected hash computation */
+};
+
+struct DerivationOutput
+{
+    std::variant<DerivationOutputIntensional, DerivationOutputFixed> output;
+    StorePath path(const Store & store, string drvName) const;
 };
 
 typedef std::map<string, DerivationOutput> DerivationOutputs;
@@ -42,7 +52,7 @@ struct BasicDerivation
 
     /* Return the path corresponding to the output identifier `id' in
        the given derivation. */
-    const StorePath & findOutput(const std::string & id) const;
+    const StorePath & findOutput(const Store & store, const std::string & id) const;
 
     bool isBuiltin() const;
 
@@ -50,7 +60,7 @@ struct BasicDerivation
     bool isFixedOutput() const;
 
     /* Return the output paths of a derivation. */
-    StorePathSet outputPaths() const;
+    StorePathSet outputPaths(const Store & store) const;
 
     /* Return the output names of a derivation. */
     StringSet outputNames() const;
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index eed225349..7ecaa8743 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -560,19 +560,12 @@ void LocalStore::checkDerivationOutputs(const StorePath & drvPath, const Derivat
         DerivationOutputs::const_iterator out = drv.outputs.find("out");
         if (out == drv.outputs.end())
             throw Error("derivation '%s' does not have an output named 'out'", printStorePath(drvPath));
-
-        check(
-            makeFixedOutputPath(
-                out->second.hash->method,
-                out->second.hash->hash,
-                drvName),
-            out->second.path, "out");
     }
 
     else {
         Hash h = hashDerivationModulo(*this, drv, true);
         for (auto & i : drv.outputs)
-            check(makeOutputPath(i.first, h, drvName), i.second.path, i.first);
+            check(makeOutputPath(i.first, h, drvName), i.second.path(*this, drv.name), i.first);
     }
 }
 
@@ -614,7 +607,7 @@ uint64_t LocalStore::addValidPath(State & state,
             state.stmtAddDerivationOutput.use()
                 (id)
                 (i.first)
-                (printStorePath(i.second.path))
+                (printStorePath(i.second.path(*this, drv.name)))
                 .exec();
         }
     }
diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index e68edb38c..c4d22a634 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -198,8 +198,8 @@ void Store::queryMissing(const std::vector<StorePathWithOutputs> & targets,
             PathSet invalid;
             for (auto & j : drv->outputs)
                 if (wantOutput(j.first, path.outputs)
-                    && !isValidPath(j.second.path))
-                    invalid.insert(printStorePath(j.second.path));
+                    && !isValidPath(j.second.path(*this, drv->name)))
+                    invalid.insert(printStorePath(j.second.path(*this, drv->name)));
             if (invalid.empty()) return;
 
             if (settings.useSubstitutes && parsedDrv.substitutesAllowed()) {
diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index c992b7d74..a42859fd0 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -381,7 +381,7 @@ static void queryInstSources(EvalState & state,
 
                 if (path.isDerivation()) {
                     elem.setDrvPath(state.store->printStorePath(path));
-                    elem.setOutPath(state.store->printStorePath(state.store->derivationFromPath(path).findOutput("out")));
+                    elem.setOutPath(state.store->printStorePath(state.store->derivationFromPath(path).findOutput(*state.store, "out")));
                     if (name.size() >= drvExtension.size() &&
                         string(name, name.size() - drvExtension.size()) == drvExtension)
                         name = string(name, 0, name.size() - drvExtension.size());
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 9a8cf0f2f..2a2f16ac1 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -77,7 +77,7 @@ static PathSet realisePath(StorePathWithOutputs path, bool build = true)
             if (i == drv.outputs.end())
                 throw Error("derivation '%s' does not have an output named '%s'",
                     store2->printStorePath(path.path), j);
-            auto outPath = store2->printStorePath(i->second.path);
+            auto outPath = store2->printStorePath(i->second.path(*store, drv.name));
             if (store2) {
                 if (gcRoot == "")
                     printGCWarning();
@@ -219,7 +219,7 @@ static StorePathSet maybeUseOutputs(const StorePath & storePath, bool useOutput,
         auto drv = store->derivationFromPath(storePath);
         StorePathSet outputs;
         for (auto & i : drv.outputs)
-            outputs.insert(i.second.path);
+            outputs.insert(i.second.path(*store, drv.name));
         return outputs;
     }
     else return {storePath};
@@ -313,7 +313,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
                 if (forceRealise) realisePath({i2});
                 Derivation drv = store->derivationFromPath(i2);
                 for (auto & j : drv.outputs)
-                    cout << fmt("%1%\n", store->printStorePath(j.second.path));
+                    cout << fmt("%1%\n", store->printStorePath(j.second.path(*store, drv.name)));
             }
             break;
         }
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index eb93f56fc..929fae5c4 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -135,7 +135,9 @@ StorePath getDerivationEnvironment(ref<Store> store, const StorePath & drvPath)
     drv.inputSrcs.insert(std::move(getEnvShPath));
     Hash h = hashDerivationModulo(*store, drv, true);
     auto shellOutPath = store->makeOutputPath("out", h, drvName);
-    drv.outputs.insert_or_assign("out", DerivationOutput { .path = shellOutPath });
+    drv.outputs.insert_or_assign("out", DerivationOutput { .output = DerivationOutputIntensional {
+                .path = shellOutPath
+            } });
     drv.env["out"] = store->printStorePath(shellOutPath);
     auto shellDrvPath2 = writeDerivation(store, drv, drvName);
 
diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index a3d85ed31..bd72a3b19 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -486,7 +486,7 @@ bool NixRepl::processLine(string line)
                 auto drv = readDerivation(*state->store, drvPath, std::string(state->store->parseStorePath(drvPath).name()));
                 std::cout << std::endl << "this derivation produced the following outputs:" << std::endl;
                 for (auto & i : drv.outputs)
-                    std::cout << fmt("  %s -> %s\n", i.first, state->store->printStorePath(i.second.path));
+                    std::cout << fmt("  %s -> %s\n", i.first, state->store->printStorePath(i.second.path(*state->store, drv.name)));
             }
         } else if (command == ":i") {
             runProgram(settings.nixBinDir + "/nix-env", Strings{"-i", drvPath});
diff --git a/src/nix/show-derivation.cc b/src/nix/show-derivation.cc
index 5d77cfdca..a868023d4 100644
--- a/src/nix/show-derivation.cc
+++ b/src/nix/show-derivation.cc
@@ -69,10 +69,10 @@ struct CmdShowDerivation : InstallablesCommand
                 auto outputsObj(drvObj.object("outputs"));
                 for (auto & output : drv.outputs) {
                     auto outputObj(outputsObj.object(output.first));
-                    outputObj.attr("path", store->printStorePath(output.second.path));
-                    if (output.second.hash) {
-                        outputObj.attr("hashAlgo", output.second.hash->printMethodAlgo());
-                        outputObj.attr("hash", output.second.hash->hash.to_string(Base16, false));
+                    outputObj.attr("path", store->printStorePath(output.second.path(*store, drv.name)));
+                    if (auto hash = std::get_if<DerivationOutputFixed>(&output.second.output)) {
+                        outputObj.attr("hashAlgo", hash->hash.printMethodAlgo());
+                        outputObj.attr("hash", hash->hash.hash.to_string(Base16, false));
                     }
                 }
             }

From 06a4e15478920bcf8d39c36abc1a73a1e83bc9b7 Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Wed, 8 Jul 2020 19:27:51 -0400
Subject: [PATCH 03/12] Fix build.cc on linux

---
 src/libstore/build.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index bf7d4c2f9..9a53d9df7 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -2200,7 +2200,7 @@ void DerivationGoal::startBuilder()
            (typically the dependencies of /bin/sh).  Throw them
            out. */
         for (auto & i : drv->outputs)
-            dirsInChroot.erase(worker.store.printStorePath(i.second.path(drv->name)));
+            dirsInChroot.erase(worker.store.printStorePath(i.second.path(worker.store, drv->name)));
 
 #elif __APPLE__
         /* We don't really have any parent prep work to do (yet?)

From a7884970c57f821e274fba20473d6fcce95ff6c8 Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Thu, 9 Jul 2020 11:37:18 -0400
Subject: [PATCH 04/12] Fix DerivationOutputExtensional name

---
 src/libexpr/primops.cc      | 4 ++--
 src/libstore/derivations.cc | 6 +++---
 src/libstore/derivations.hh | 4 ++--
 src/nix/develop.cc          | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 9b613eef9..bd7ec628c 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -798,7 +798,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             if (!jsonObject) drv.env[i] = "";
             drv.outputs.insert_or_assign(i,
                 DerivationOutput {
-                    .output = DerivationOutputIntensional {
+                    .output = DerivationOutputExtensional {
                         .path = StorePath::dummy,
                     },
                 });
@@ -811,7 +811,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             if (!jsonObject) drv.env[i] = state.store->printStorePath(outPath);
             drv.outputs.insert_or_assign(i,
                 DerivationOutput {
-                    .output = DerivationOutputIntensional {
+                    .output = DerivationOutputExtensional {
                         .path = std::move(outPath),
                     },
                 });
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index ffeafea87..86f55342d 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -15,7 +15,7 @@ template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 StorePath DerivationOutput::path(const Store & store, string drvName) const
 {
     return std::visit(overloaded {
-        [](DerivationOutputIntensional doi) {
+        [](DerivationOutputExtensional doi) {
             return doi.path;
         },
         [&](DerivationOutputFixed dof) {
@@ -142,7 +142,7 @@ static DerivationOutput parseDerivationOutput(const Store & store, istringstream
         };
     } else
         return DerivationOutput {
-            .output = DerivationOutputIntensional {
+            .output = DerivationOutputExtensional {
                 .path = std::move(path),
             }
         };
@@ -450,7 +450,7 @@ static DerivationOutput readDerivationOutput(Source & in, const Store & store)
         };
     } else
         return DerivationOutput {
-            .output = DerivationOutputIntensional {
+            .output = DerivationOutputExtensional {
                 .path = std::move(path),
             }
         };
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index d8cee0f34..2515188ec 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -13,7 +13,7 @@ namespace nix {
 
 /* Abstract syntax of derivations. */
 
-struct DerivationOutputIntensional
+struct DerivationOutputExtensional
 {
     StorePath path;
 };
@@ -25,7 +25,7 @@ struct DerivationOutputFixed
 
 struct DerivationOutput
 {
-    std::variant<DerivationOutputIntensional, DerivationOutputFixed> output;
+    std::variant<DerivationOutputExtensional, DerivationOutputFixed> output;
     StorePath path(const Store & store, string drvName) const;
 };
 
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 929fae5c4..e03d2e057 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -135,7 +135,7 @@ StorePath getDerivationEnvironment(ref<Store> store, const StorePath & drvPath)
     drv.inputSrcs.insert(std::move(getEnvShPath));
     Hash h = hashDerivationModulo(*store, drv, true);
     auto shellOutPath = store->makeOutputPath("out", h, drvName);
-    drv.outputs.insert_or_assign("out", DerivationOutput { .output = DerivationOutputIntensional {
+    drv.outputs.insert_or_assign("out", DerivationOutput { .output = DerivationOutputExtensional {
                 .path = shellOutPath
             } });
     drv.env["out"] = store->printStorePath(shellOutPath);

From abea26a9683d58e0bee43d9ededeb710f3617603 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 01:57:06 +0000
Subject: [PATCH 05/12] BasicDerivation::findOutput cannot return reference
 anymore

---
 src/libstore/derivations.cc | 2 +-
 src/libstore/derivations.hh | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 86f55342d..bde147502 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -24,7 +24,7 @@ StorePath DerivationOutput::path(const Store & store, string drvName) const
     }, output);
 }
 
-const StorePath & BasicDerivation::findOutput(const Store & store, const string & id) const
+const StorePath BasicDerivation::findOutput(const Store & store, const string & id) const
 {
     auto i = outputs.find(id);
     if (i == outputs.end())
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 2515188ec..4694ec0dd 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -52,7 +52,7 @@ struct BasicDerivation
 
     /* Return the path corresponding to the output identifier `id' in
        the given derivation. */
-    const StorePath & findOutput(const Store & store, const std::string & id) const;
+    const StorePath findOutput(const Store & store, const std::string & id) const;
 
     bool isBuiltin() const;
 

From 1c9bec226f9ff1a9586bfefcd0c3b66ed989b2d3 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 02:38:03 +0000
Subject: [PATCH 06/12] Don't improperly assume path is store path

---
 src/libexpr/primops.cc | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index bd7ec628c..4367f9b22 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -102,10 +102,17 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args
 
     Path realPath = state.checkSourcePath(state.toRealPath(path, context));
 
-    StorePath storePath = state.store->parseStorePath(path);
-
     // FIXME
-    if (state.store->isStorePath(path) && state.store->isValidPath(storePath) && isDerivation(path)) {
+    auto isValidDerivationInStore = [&]() -> std::optional<StorePath> {
+        if (!state.store->isStorePath(path))
+            return std::nullopt;
+        auto storePath = state.store->parseStorePath(path);
+        if (!(state.store->isValidPath(storePath) && isDerivation(path)))
+            return std::nullopt;
+        return storePath;
+    };
+    if (auto optStorePath = isValidDerivationInStore()) {
+        auto storePath = *optStorePath;
         Derivation drv = readDerivation(*state.store, realPath, std::string(storePath.name()));
         Value & w = *state.allocValue();
         state.mkAttrs(w, 3 + drv.outputs.size());

From 13ec627e0a46d26b5de227e193a05b51af7f55e5 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 03:03:12 +0000
Subject: [PATCH 07/12] Set derivation name in dervationStrict

---
 src/libexpr/primops.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 4367f9b22..14a7deed5 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -591,6 +591,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
 
     /* Build the derivation expression by processing the attributes. */
     Derivation drv;
+    drv.name = drvName;
 
     PathSet context;
 

From 5d0b75e5b6a1c70203257fecc25743e5a1e009cb Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 15:02:36 +0000
Subject: [PATCH 08/12] std::string_view for new derivation name parameters

---
 src/libstore/derivations.cc | 8 ++++----
 src/libstore/derivations.hh | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index bde147502..97fd21885 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -12,7 +12,7 @@ namespace nix {
 template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
 template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 
-StorePath DerivationOutput::path(const Store & store, string drvName) const
+StorePath DerivationOutput::path(const Store & store, std::string_view drvName) const
 {
     return std::visit(overloaded {
         [](DerivationOutputExtensional doi) {
@@ -149,7 +149,7 @@ static DerivationOutput parseDerivationOutput(const Store & store, istringstream
 }
 
 
-static Derivation parseDerivation(const Store & store, const string & s, string name)
+static Derivation parseDerivation(const Store & store, const string & s, std::string_view name)
 {
     Derivation drv;
     drv.name = name;
@@ -197,7 +197,7 @@ static Derivation parseDerivation(const Store & store, const string & s, string
 }
 
 
-Derivation readDerivation(const Store & store, const Path & drvPath, std::string name)
+Derivation readDerivation(const Store & store, const Path & drvPath, std::string_view name)
 {
     try {
         return parseDerivation(store, readFile(drvPath), name);
@@ -465,7 +465,7 @@ StringSet BasicDerivation::outputNames() const
 }
 
 
-Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, string name)
+Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, std::string_view name)
 {
     drv.name = name;
 
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 4694ec0dd..81c196ff7 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -26,7 +26,7 @@ struct DerivationOutputFixed
 struct DerivationOutput
 {
     std::variant<DerivationOutputExtensional, DerivationOutputFixed> output;
-    StorePath path(const Store & store, string drvName) const;
+    StorePath path(const Store & store, std::string_view drvName) const;
 };
 
 typedef std::map<string, DerivationOutput> DerivationOutputs;
@@ -45,7 +45,7 @@ struct BasicDerivation
     Path builder;
     Strings args;
     StringPairs env;
-    string name;
+    std::string name;
 
     BasicDerivation() { }
     virtual ~BasicDerivation() { };
@@ -87,7 +87,7 @@ StorePath writeDerivation(ref<Store> store,
     const Derivation & drv, std::string_view name, RepairFlag repair = NoRepair);
 
 /* Read a derivation from a file. */
-Derivation readDerivation(const Store & store, const Path & drvPath, string name);
+Derivation readDerivation(const Store & store, const Path & drvPath, std::string_view name);
 
 // FIXME: remove
 bool isDerivation(const string & fileName);
@@ -104,7 +104,7 @@ bool wantOutput(const string & output, const std::set<string> & wanted);
 struct Source;
 struct Sink;
 
-Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, string name);
+Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, std::string_view name);
 void writeDerivation(Sink & out, const Store & store, const BasicDerivation & drv);
 
 std::string hashPlaceholder(const std::string & outputName);

From 18152406ce9db9491385f2e67da6f7f78e8d98d5 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 15:26:30 +0000
Subject: [PATCH 09/12] String .drv suffix to create derivation name

---
 src/libexpr/primops.cc      |  2 +-
 src/libstore/daemon.cc      |  2 +-
 src/libstore/derivations.cc | 11 ++++++++++-
 src/libstore/derivations.hh |  2 ++
 src/nix-store/nix-store.cc  |  2 +-
 src/nix/repl.cc             |  2 +-
 6 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 14a7deed5..21bd4fb52 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -113,7 +113,7 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args
     };
     if (auto optStorePath = isValidDerivationInStore()) {
         auto storePath = *optStorePath;
-        Derivation drv = readDerivation(*state.store, realPath, std::string(storePath.name()));
+        Derivation drv = readDerivation(*state.store, realPath, Derivation::nameFromPath(storePath));
         Value & w = *state.allocValue();
         state.mkAttrs(w, 3 + drv.outputs.size());
         Value * v2 = state.allocAttr(w, state.sDrvPath);
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index 4cf67064a..2ff53c964 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -474,7 +474,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     case wopBuildDerivation: {
         auto drvPath = store->parseStorePath(readString(from));
         BasicDerivation drv;
-        readDerivation(from, *store, drv, std::string(drvPath.name()));
+        readDerivation(from, *store, drv, Derivation::nameFromPath(drvPath));
         BuildMode buildMode = (BuildMode) readInt(from);
         logger->startWork();
         if (!trusted)
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 97fd21885..a85a70c0a 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -218,7 +218,7 @@ Derivation Store::readDerivation(const StorePath & drvPath)
 {
     auto accessor = getFSAccessor();
     try {
-        return parseDerivation(*this, accessor->readFile(printStorePath(drvPath)), std::string(drvPath.name()));
+        return parseDerivation(*this, accessor->readFile(printStorePath(drvPath)), Derivation::nameFromPath(drvPath));
     } catch (FormatError & e) {
         throw Error("error parsing derivation '%s': %s", printStorePath(drvPath), e.msg());
     }
@@ -465,6 +465,15 @@ StringSet BasicDerivation::outputNames() const
 }
 
 
+std::string_view BasicDerivation::nameFromPath(const StorePath & drvPath) {
+    auto nameWithSuffix = drvPath.name();
+    constexpr std::string_view extension = ".drv";
+    assert(hasSuffix(nameWithSuffix, extension));
+    nameWithSuffix.remove_suffix(extension.size());
+    return nameWithSuffix;
+}
+
+
 Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, std::string_view name)
 {
     drv.name = name;
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 81c196ff7..6d3b54d3f 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -64,6 +64,8 @@ struct BasicDerivation
 
     /* Return the output names of a derivation. */
     StringSet outputNames() const;
+
+    static std::string_view nameFromPath(const StorePath & storePath);
 };
 
 struct Derivation : BasicDerivation
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 39a47e19a..9605e4b32 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -916,7 +916,7 @@ static void opServe(Strings opFlags, Strings opArgs)
 
                 auto drvPath = store->parseStorePath(readString(in));
                 BasicDerivation drv;
-                readDerivation(in, *store, drv, std::string(drvPath.name()));
+                readDerivation(in, *store, drv, Derivation::nameFromPath(drvPath));
 
                 getBuildSettings();
 
diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index bd72a3b19..74f0b3ec8 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -483,7 +483,7 @@ bool NixRepl::processLine(string line)
                but doing it in a child makes it easier to recover from
                problems / SIGINT. */
             if (runProgram(settings.nixBinDir + "/nix", Strings{"build", "--no-link", drvPath}) == 0) {
-                auto drv = readDerivation(*state->store, drvPath, std::string(state->store->parseStorePath(drvPath).name()));
+                auto drv = readDerivation(*state->store, drvPath, Derivation::nameFromPath(state->store->parseStorePath(drvPath)));
                 std::cout << std::endl << "this derivation produced the following outputs:" << std::endl;
                 for (auto & i : drv.outputs)
                     std::cout << fmt("  %s -> %s\n", i.first, state->store->printStorePath(i.second.path(*state->store, drv.name)));

From a8d4707107c39d0258fef17b531ac031dd16ec88 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 15:54:12 +0000
Subject: [PATCH 10/12] Undo erroneous indentation change

---
 src/libstore/derivations.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index a85a70c0a..f41edd81d 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -396,7 +396,7 @@ Hash hashDerivationModulo(Store & store, const Derivation & drv, bool maskOutput
         if (h == drvHashes.end()) {
             assert(store.isValidPath(i.first));
             h = drvHashes.insert_or_assign(i.first, hashDerivationModulo(store,
-                    store.readDerivation(i.first), false)).first;
+                store.readDerivation(i.first), false)).first;
         }
         inputs2.insert_or_assign(h->second.to_string(Base16, false), i.second);
     }

From 503b4256903b2cf414a6d697d19be40db299e2c6 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 15:56:20 +0000
Subject: [PATCH 11/12] DerivationOutputExtensional ->
 DerivationOutputInputAddressed

Thanks @regnat for the great name.
---
 src/libexpr/primops.cc      | 4 ++--
 src/libstore/derivations.cc | 6 +++---
 src/libstore/derivations.hh | 4 ++--
 src/nix/develop.cc          | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 21bd4fb52..5a9c17814 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -806,7 +806,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             if (!jsonObject) drv.env[i] = "";
             drv.outputs.insert_or_assign(i,
                 DerivationOutput {
-                    .output = DerivationOutputExtensional {
+                    .output = DerivationOutputInputAddressed {
                         .path = StorePath::dummy,
                     },
                 });
@@ -819,7 +819,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             if (!jsonObject) drv.env[i] = state.store->printStorePath(outPath);
             drv.outputs.insert_or_assign(i,
                 DerivationOutput {
-                    .output = DerivationOutputExtensional {
+                    .output = DerivationOutputInputAddressed {
                         .path = std::move(outPath),
                     },
                 });
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index f41edd81d..d267468af 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -15,7 +15,7 @@ template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 StorePath DerivationOutput::path(const Store & store, std::string_view drvName) const
 {
     return std::visit(overloaded {
-        [](DerivationOutputExtensional doi) {
+        [](DerivationOutputInputAddressed doi) {
             return doi.path;
         },
         [&](DerivationOutputFixed dof) {
@@ -142,7 +142,7 @@ static DerivationOutput parseDerivationOutput(const Store & store, istringstream
         };
     } else
         return DerivationOutput {
-            .output = DerivationOutputExtensional {
+            .output = DerivationOutputInputAddressed {
                 .path = std::move(path),
             }
         };
@@ -450,7 +450,7 @@ static DerivationOutput readDerivationOutput(Source & in, const Store & store)
         };
     } else
         return DerivationOutput {
-            .output = DerivationOutputExtensional {
+            .output = DerivationOutputInputAddressed {
                 .path = std::move(path),
             }
         };
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 6d3b54d3f..fd8828373 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -13,7 +13,7 @@ namespace nix {
 
 /* Abstract syntax of derivations. */
 
-struct DerivationOutputExtensional
+struct DerivationOutputInputAddressed
 {
     StorePath path;
 };
@@ -25,7 +25,7 @@ struct DerivationOutputFixed
 
 struct DerivationOutput
 {
-    std::variant<DerivationOutputExtensional, DerivationOutputFixed> output;
+    std::variant<DerivationOutputInputAddressed, DerivationOutputFixed> output;
     StorePath path(const Store & store, std::string_view drvName) const;
 };
 
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index e03d2e057..654f62f38 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -135,7 +135,7 @@ StorePath getDerivationEnvironment(ref<Store> store, const StorePath & drvPath)
     drv.inputSrcs.insert(std::move(getEnvShPath));
     Hash h = hashDerivationModulo(*store, drv, true);
     auto shellOutPath = store->makeOutputPath("out", h, drvName);
-    drv.outputs.insert_or_assign("out", DerivationOutput { .output = DerivationOutputExtensional {
+    drv.outputs.insert_or_assign("out", DerivationOutput { .output = DerivationOutputInputAddressed {
                 .path = shellOutPath
             } });
     drv.env["out"] = store->printStorePath(shellOutPath);

From 886c91dfcc462d157dc2ce5265800e98d1bc45dd Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 18:26:10 +0000
Subject: [PATCH 12/12] Try to fix perl bindings

---
 perl/lib/Nix/Store.xs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/perl/lib/Nix/Store.xs b/perl/lib/Nix/Store.xs
index 6dba07549..522de5802 100644
--- a/perl/lib/Nix/Store.xs
+++ b/perl/lib/Nix/Store.xs
@@ -304,7 +304,10 @@ SV * derivationFromPath(char * drvPath)
 
             HV * outputs = newHV();
             for (auto & i : drv.outputs)
-                hv_store(outputs, i.first.c_str(), i.first.size(), newSVpv(store()->printStorePath(i.second.path(store(), drv.name)).c_str(), 0), 0);
+                hv_store(
+                    outputs, i.first.c_str(), i.first.size(),
+                    newSVpv(store()->printStorePath(i.second.path(*store(), drv.name)).c_str(), 0),
+                    0);
             hv_stores(hash, "outputs", newRV((SV *) outputs));
 
             AV * inputDrvs = newAV();