top-level/by-name-overlay: set meta.position

Author: rhendric

pkgs/by-name/sm/sm64baserom/package.nix

@@ -28,12 +28,10 @@ let
       }
       .${region};
   };
-  result = runCommand "baserom-${region}-safety-dir" { } ''
+  result = runCommand "baserom-${region}-safety-dir" { passthru = { inherit romPath; }; } ''
     mkdir $out
     ln -s ${file} $out/${file.name}
   '';
+  romPath = "${result.outPath}/${file.name}";
 in
 result
-// {
-  romPath = "${result.outPath}/${file.name}";
-}

pkgs/stdenv/generic/check-meta.nix

@@ -571,7 +571,8 @@ let
     // attrs.meta or { }
     // {
       # Fill `meta.position` to identify the source location of the package.
-      ${if pos == null then null else "position"} = pos.file + ":" + toString pos.line;
+      ${if pos == null || attrs ? meta.position then null else "position"} =
+        pos.file + ":" + toString pos.line;
 
       # Maintainers should be inclusive of teams.
       # Note that there may be external consumers of this API (repology, for instance) -

pkgs/top-level/by-name-overlay.nix

@@ -49,6 +49,16 @@ self: super:
   # and whether it's defined by this file here or `all-packages.nix`.
   # TODO: This can be removed once `pkgs/by-name` can handle custom `callPackage` arguments without `all-packages.nix` (or any other way of achieving the same result).
   # Because at that point the code in ./stage.nix can be changed to not allow definitions in `all-packages.nix` to override ones from `pkgs/by-name` anymore and throw an error if that happens instead.
-  _internalCallByNamePackageFile = file: self.callPackage file { };
+  _internalCallByNamePackageFile =
+    file:
+    (self.callPackage file { })
+    # Ensure that even a package that is a simple override of another package
+    # has a position that points to its own file.
+    .overrideAttrs
+      (old: {
+        meta = old.meta or { } // {
+          position = "${toString file}:1";
+        };
+      });
 }
 // mapAttrs (name: self._internalCallByNamePackageFile) packageFiles