flakes: Ensure that self.outPath == ./.

Users expect `self` to refer to the directory where the `flake.nix`
file resides.

src/libexpr/flake/call-flake.nix

@@ -9,14 +9,18 @@ let
       (key: node:
         let
 
-          sourceInfo =
+          rawSourceInfo =
             if key == lockFile.root
             then rootSrc
             else fetchTree (node.info or {} // removeAttrs node.locked ["dir"]);
 
           subdir = if key == lockFile.root then rootSubdir else node.locked.dir or "";
 
-          flake = import (sourceInfo + (if subdir != "" then "/" else "") + subdir + "/flake.nix");
+          outPath = rawSourceInfo + ((if subdir == "" then "" else "/") + subdir);
+
+          sourceInfo = rawSourceInfo // { inherit outPath; };
+
+          flake = import (outPath + "/flake.nix");
 
           inputs = builtins.mapAttrs
             (inputName: inputSpec: allNodes.${resolveInput inputSpec})

tests/flakes/inputs.sh

@@ -0,0 +1,79 @@
+source ./common.sh
+
+requireGit
+
+
+test_subdir_self_path() {
+    baseDir=$TEST_ROOT/$RANDOM
+    flakeDir=$baseDir/b-low
+    mkdir -p $flakeDir
+    writeSimpleFlake $baseDir
+    writeSimpleFlake $flakeDir
+
+    echo all good > $flakeDir/message
+    cat > $flakeDir/flake.nix <<EOF
+{
+  outputs = inputs: rec {
+    packages.$system = rec {
+      default =
+        assert builtins.readFile ./message == "all good\n";
+        assert builtins.readFile (inputs.self + "/message") == "all good\n";
+        import ./simple.nix;
+    };
+  };
+}
+EOF
+    (
+        nix build $baseDir?dir=b-low --no-link
+    )
+}
+test_subdir_self_path
+
+
+test_git_subdir_self_path() {
+    repoDir=$TEST_ROOT/repo-$RANDOM
+    createGitRepo $repoDir
+    flakeDir=$repoDir/b-low
+    mkdir -p $flakeDir
+    writeSimpleFlake $repoDir
+    writeSimpleFlake $flakeDir
+
+    echo all good > $flakeDir/message
+    cat > $flakeDir/flake.nix <<EOF
+{
+  outputs = inputs: rec {
+    packages.$system = rec {
+      default =
+        assert builtins.readFile ./message == "all good\n";
+        assert builtins.readFile (inputs.self + "/message") == "all good\n";
+        import ./simple.nix;
+    };
+  };
+}
+EOF
+    (
+        cd $flakeDir
+        git add .
+        git commit -m init
+        # nix build
+    )
+
+    clientDir=$TEST_ROOT/client-$RANDOM
+    mkdir -p $clientDir
+    cat > $clientDir/flake.nix <<EOF
+{
+  inputs.inp = {
+    type = "git";
+    url = "file://$repoDir";
+    dir = "b-low";
+  };
+
+  outputs = inputs: rec {
+    packages = inputs.inp.packages;
+  };
+}
+EOF
+    nix build $clientDir --no-link
+
+}
+test_git_subdir_self_path

tests/local.mk

@@ -4,6 +4,7 @@ nix_tests = \
   flakes/mercurial.sh \
   flakes/circular.sh \
   flakes/init.sh \
+  flakes/inputs.sh \
   flakes/follow-paths.sh \
   flakes/bundle.sh \
   flakes/check.sh \