commit f5e96331ea1f74fe956f0ef62a5e1ce4b81d8bc4
Author: Jan Schär <jan@monogon.tech>
Date:   Wed Jul 2 13:41:44 2025 +0000

    Request stdlib cache dir in gopackagesdriver
    
    The stdlib_json_file contains paths of compiled cgo files, which are in
    the stdlib cache_dir. The gopackagesdriver reads those files, but this
    dependency was not explicitly declared previously.
    
    Usually, it works despite the missing dependency. But when you have a
    Bazel cache configured, and then run `bazel clean` and run the
    gopackagesdriver again, Bazel will not restore the cache_dir from the
    Bazel cache. The gopackagesdriver then fails with an error like this:
    
    error: unable to load JSON files: unable to resolve imports: open
    [...]/bin/external/rules_go+/stdlib_/gocache/a4/a4f91e8314b27a4bce0e8fbc01bb9736cb9ed10da747af722c5a4f2fcb1213a3-d:
    no such file or directory
    
    This change adds a new output group containing the stdlib cache_dir,
    and requests this from the gopackagesdriver, fixing the problem.

    Upstream PR: https://github.com/bazel-contrib/rules_go/pull/4391

diff --git a/go/tools/gopackagesdriver/aspect.bzl b/go/tools/gopackagesdriver/aspect.bzl
index c6013d76..dbe56633 100644
--- a/go/tools/gopackagesdriver/aspect.bzl
+++ b/go/tools/gopackagesdriver/aspect.bzl
@@ -65,6 +65,7 @@ def make_pkg_json(ctx, name, pkg_info):
 def _go_pkg_info_aspect_impl(target, ctx):
     # Fetch the stdlib JSON file from the inner most target
     stdlib_json_file = None
+    stdlib_cache_dir = None
 
     transitive_json_files = []
     transitive_export_files = []
@@ -87,6 +88,7 @@ def _go_pkg_info_aspect_impl(target, ctx):
                 # Fetch the stdlib json from the first dependency
                 if not stdlib_json_file:
                     stdlib_json_file = pkg_info.stdlib_json_file
+                    stdlib_cache_dir = pkg_info.stdlib_cache_dir
 
     pkg_json_files = []
     compiled_go_files = []
@@ -113,9 +115,11 @@ def _go_pkg_info_aspect_impl(target, ctx):
     # current go_ node.
     if not stdlib_json_file:
         stdlib_json_file = ctx.attr._go_stdlib[GoStdLib]._list_json
+        stdlib_cache_dir = ctx.attr._go_stdlib[GoStdLib].cache_dir
 
     pkg_info = GoPkgInfo(
         stdlib_json_file = stdlib_json_file,
+        stdlib_cache_dir = stdlib_cache_dir,
         pkg_json_files = depset(
             direct = pkg_json_files,
             transitive = transitive_json_files,
@@ -137,6 +141,7 @@ def _go_pkg_info_aspect_impl(target, ctx):
             go_pkg_driver_srcs = pkg_info.compiled_go_files,
             go_pkg_driver_export_file = pkg_info.export_files,
             go_pkg_driver_stdlib_json_file = depset([pkg_info.stdlib_json_file] if pkg_info.stdlib_json_file else []),
+            go_pkg_driver_stdlib_cache_dir = pkg_info.stdlib_cache_dir or depset([]),
         ),
     ]
 
diff --git a/go/tools/gopackagesdriver/bazel_json_builder.go b/go/tools/gopackagesdriver/bazel_json_builder.go
index 76386332..bb50f7a0 100644
--- a/go/tools/gopackagesdriver/bazel_json_builder.go
+++ b/go/tools/gopackagesdriver/bazel_json_builder.go
@@ -159,7 +159,7 @@ func NewBazelJSONBuilder(bazel *Bazel, includeTests bool) (*BazelJSONBuilder, er
 }
 
 func (b *BazelJSONBuilder) outputGroupsForMode(mode packages.LoadMode) string {
-	og := "go_pkg_driver_json_file,go_pkg_driver_stdlib_json_file,go_pkg_driver_srcs"
+	og := "go_pkg_driver_json_file,go_pkg_driver_stdlib_json_file,go_pkg_driver_stdlib_cache_dir,go_pkg_driver_srcs"
 	if mode&packages.NeedExportsFile != 0 {
 		og += ",go_pkg_driver_export_file"
 	}