findAlongAttrPath(): Return position

(cherry picked from commit 0b013a54dc)

src/libexpr/attr-path.cc

@@ -32,7 +32,7 @@ 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);
@@ -41,6 +41,7 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
         Error(format("attribute selection path '%1%' does not match expression") % attrPath);
 
     Value * v = &vIn;
+    Pos pos = noPos;
 
     for (auto & attr : tokens) {
 
@@ -72,6 +73,7 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
             if (a == v->attrs->end())
                 throw AttrPathNotFound("attribute '%1%' in selection path '%2%' not found", attr, attrPath);
             v = &*a->value;
+            pos = *a->pos;
         }
 
         else if (apType == apIndex) {
@@ -85,11 +87,12 @@ Value * findAlongAttrPath(EvalState & state, const string & 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};
 }
 
 
@@ -98,7 +101,7 @@ 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);
     }

src/libexpr/attr-path.hh

@@ -9,7 +9,7 @@ namespace nix {
 
 MakeError(AttrPathNotFound, Error);
 
-Value * findAlongAttrPath(EvalState & state, const string & attrPath,
+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/nix-build/nix-build.cc

@@ -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-env/nix-env.cc

@@ -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;

src/nix-instantiate/nix-instantiate.cc

@@ -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

@@ -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/installables.cc

@@ -193,7 +193,7 @@ struct InstallableAttrPath : InstallableValue
 
         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;

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));
     }