Handle store symlinks in flake directories

E.g. 'nix path-info ./result' inside a flake directory now works
again.

src/libexpr/flake/flakeref.cc

@@ -143,6 +143,14 @@ FlakeRef::FlakeRef(const std::string & uri_, bool allowRelative)
         IsPath d;
         if (allowRelative) {
             d.path = absPath(uri);
+            try {
+                if (!S_ISDIR(lstat(d.path).st_mode))
+                    throw BadFlakeRef("path '%s' is not a flake (sub)directory");
+            } catch (SysError & e) {
+                if (e.errNo == ENOENT || e.errNo == EISDIR)
+                    throw BadFlakeRef("flake '%s' does not exist");
+                throw;
+            }
             while (true) {
                 if (pathExists(d.path + "/.git")) break;
                 subdir = baseNameOf(d.path) + (subdir.empty() ? "" : "/" + subdir);

src/libstore/store-api.cc

@@ -55,7 +55,7 @@ Path Store::followLinksToStore(const Path & _path) const
         path = absPath(target, dirOf(path));
     }
     if (!isInStore(path))
-        throw Error(format("path '%1%' is not in the Nix store") % path);
+        throw NotInStore("path '%1%' is not in the Nix store", path);
     return path;
 }
 

src/libstore/store-api.hh

@@ -26,6 +26,7 @@ MakeError(InvalidPath, Error)
 MakeError(Unsupported, Error)
 MakeError(SubstituteGone, Error)
 MakeError(SubstituterDisabled, Error)
+MakeError(NotInStore, Error)
 
 
 struct BasicDerivation;

src/nix/installables.cc

@@ -394,9 +394,18 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
 
     } else {
 
+        auto follow = [&](const std::string & s) -> std::optional<Path> {
+            try {
+                return store->followLinksToStorePath(s);
+            } catch (NotInStore &) {
+                return {};
+            }
+        };
+
         for (auto & s : ss) {
 
             size_t colon;
+            std::optional<Path> storePath;
 
             if (s.compare(0, 1, "(") == 0)
                 result.push_back(std::make_shared<InstallableExpr>(*this, s));
@@ -422,17 +431,8 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                         getDefaultFlakeAttrPathPrefixes()));
             }
 
-            else if (s.find('/') != std::string::npos || s == ".") {
+            else if (s.find('/') != std::string::npos && (storePath = follow(s)))
-                Path storePath;
+                result.push_back(std::make_shared<InstallableStorePath>(*storePath));
-                try {
-                    storePath = store->toStorePath(store->followLinksToStore(s));
-                } catch (Error) { }
-                if (storePath != "")
-                    result.push_back(std::make_shared<InstallableStorePath>(storePath));
-                else
-                    result.push_back(std::make_shared<InstallableFlake>(*this, FlakeRef(s, true),
-                            getDefaultFlakeAttrPaths()));
-            }
 
             else
                 throw Error("unsupported argument '%s'", s);

tests/flakes.sh

@@ -149,6 +149,10 @@ nix build -o $TEST_ROOT/result --flake-registry $registry flake1
 nix build -o $TEST_ROOT/result --flake-registry $registry $flake1Dir
 nix build -o $TEST_ROOT/result --flake-registry $registry file://$flake1Dir
 
+# CHeck that store symlinks inside a flake are not interpreted as flakes.
+nix build -o $flake1Dir/result --flake-registry $registry file://$flake1Dir
+nix path-info $flake1Dir/result
+
 # Building a flake with an unlocked dependency should fail in pure mode.
 (! nix eval "(builtins.getFlake "$flake2Dir")")