Merge branch 'pr/mopleen/5625'

src/libcmd/installables.cc

@@ -559,18 +559,39 @@ InstallableFlake::InstallableFlake(
         throw UsageError("'--arg' and '--argstr' are incompatible with flakes");
 }
 
-std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableFlake::toDerivation()
-{
-    auto lockedFlake = getLockedFlake();
+namespace {
+std::optional<Path> getSourceFilePathFromInStorePath(Store & store, const Path & file, const fetchers::Input & flakeInput) {
+    if (!store.isInStore(file)) {
+        return std::nullopt;
+    }
 
-    auto cache = openEvalCache(*state, lockedFlake);
+    auto [sourceStorePath, relPath] = store.toStorePath(file);
+    auto realPath = store.toRealPath(sourceStorePath);
+
+    auto maybeFlakeSource = flakeInput.getSourcePath();
+    if (!maybeFlakeSource) {
+        return std::nullopt;
+    }
+
+    auto betterFilePath = replaceStrings(file, realPath, *maybeFlakeSource);
+    if (!pathExists(betterFilePath)) {
+        return std::nullopt;
+    }
+
+    return betterFilePath;
+}
+
+std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> toDerivationImpl(InstallableFlake & flake) {
+    auto lockedFlake = flake.getLockedFlake();
+
+    auto cache = openEvalCache(*flake.state, lockedFlake);
     auto root = cache->getRoot();
 
-    for (auto & attrPath : getActualAttrPaths()) {
+    for (auto & attrPath : flake.getActualAttrPaths()) {
         debug("trying flake output attribute '%s'", attrPath);
 
         auto attr = root->findAlongAttrPath(
-            parseAttrPath(*state, attrPath),
+            parseAttrPath(*flake.state, attrPath),
             true
         );
 
@@ -581,17 +602,39 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableF
 
         auto drvPath = attr->forceDerivation();
 
-        auto drvInfo = DerivationInfo{
+        auto drvInfo = InstallableValue::DerivationInfo{
             std::move(drvPath),
-            state->store->maybeParseStorePath(attr->getAttr(state->sOutPath)->getString()),
-            attr->getAttr(state->sOutputName)->getString()
+            flake.state->store->maybeParseStorePath(attr->getAttr(flake.state->sOutPath)->getString()),
+            attr->getAttr(flake.state->sOutputName)->getString()
         };
 
         return {attrPath, lockedFlake->flake.lockedRef, std::move(drvInfo)};
     }
 
     throw Error("flake '%s' does not provide attribute %s",
-        flakeRef, showAttrPaths(getActualAttrPaths()));
+        flake.flakeRef, showAttrPaths(flake.getActualAttrPaths()));
+}
+
+template <class F>
+auto patchErrorSourceFile(Store & store, const fetchers::Input & flakeInput, F && func) {
+    try {
+        return func();
+    } catch (BaseError & e) {
+        if (auto pos = e.info().errPos) {
+            if (auto sourceFilePath = getSourceFilePathFromInStorePath(store, pos->file, flakeInput)) {
+                e.replacePosFile(*sourceFilePath);
+            }
+        }
+        throw;
+    }
+}
+}
+
+std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableFlake::toDerivation()
+{
+    return patchErrorSourceFile(*state->store, flakeRef.input, [&] {
+        return toDerivationImpl(*this);
+    });
 }
 
 std::vector<InstallableValue::DerivationInfo> InstallableFlake::toDerivations()

src/libutil/error.hh

@@ -164,6 +164,12 @@ public:
 
     const string & msg() const { return calcWhat(); }
     const ErrorInfo & info() const { calcWhat(); return err; }
+    
+    void replacePosFile(std::string file) {
+        if (err.errPos) {
+            err.errPos->file = std::move(file);
+        }
+    }
 
     template<typename... Args>
     BaseError & addTrace(std::optional<ErrPos> e, const string &fs, const Args & ... args)

tests/flake-print-local-path-error.sh

@@ -0,0 +1,14 @@
+source common.sh
+
+clearStore
+rm -rf $TEST_HOME/.cache $TEST_HOME/.config $TEST_HOME/.local
+
+cd $TEST_HOME
+
+cat <<EOF > flake.nix
+{
+    outputs = give me an error here;
+}
+EOF
+
+nix build |& grep $TEST_HOME || fail "Path should point to home, not to the store"

tests/local.mk

@@ -49,6 +49,7 @@ nix_tests = \
   flake-local-settings.sh \
   flake-searching.sh \
   flake-bundler.sh \
+  flake-print-local-path-error.sh \
   build.sh \
   repl.sh ca/repl.sh \
   ca/build.sh \