upd

internal/godoc/dochtml/dochtml.go

@@ -29,6 +29,8 @@ import (
 	"golang.org/x/pkgsite/internal"
 	"golang.org/x/pkgsite/internal/derrors"
 	"golang.org/x/pkgsite/internal/godoc/dochtml/internal/render"
+	"golang.org/x/pkgsite/internal/log"
+	"golang.org/x/pkgsite/internal/stdlib"
 	"golang.org/x/text/cases"
 	"golang.org/x/text/language"
 )
@@ -442,15 +444,21 @@ func buildNoteHeaders(notes map[string][]*doc.Note) map[string]noteHeader {
 }
 
 // versionedPkgPath transforms package paths to contain the same version as the
-// current module if the package belongs to the module. As a special case,
-// versionedPkgPath will not add versions to standard library packages.
+// current module if the package belongs to the module.
 func versionedPkgPath(pkgPath string, modInfo *ModuleInfo) string {
-	if modInfo == nil || !modInfo.ModulePackages[pkgPath] {
+	if modInfo != nil && modInfo.ModulePath == "std" {
+		tag, err := stdlib.TagForVersion(modInfo.ResolvedVersion)
+		if err != nil {
+			log.Errorf(context.TODO(), "goTagForVersion(%q): %v", modInfo.ResolvedVersion, err)
+			return pkgPath
+		}
+		return fmt.Sprintf("%s@%s", pkgPath, tag)
+	}
+
+	if modInfo == nil || (!modInfo.ModulePackages[pkgPath]) {
 		return pkgPath
 	}
-	// We don't need to do anything special here for standard library packages
-	// since pkgPath will never contain the "std/" module prefix, and
-	// modInfo.ModulePackages contains this prefix for standard library packages.
+
 	innerPkgPath := pkgPath[len(modInfo.ModulePath):]
 	return fmt.Sprintf("%s@%s%s", modInfo.ModulePath, modInfo.ResolvedVersion, innerPkgPath)
 }

internal/godoc/dochtml/dochtml_test.go

@@ -242,24 +242,24 @@ func TestVersionedPkgPath(t *testing.T) {
 		want    string
 	}{
 		{
-			name:    "builtin package is not versioned",
+			name:    "builtin package is versioned",
 			pkgPath: "builtin",
 			modInfo: &ModuleInfo{
 				ModulePath:      "std",
-				ResolvedVersion: "v1.14.4",
+				ResolvedVersion: "v1.14",
 				ModulePackages:  map[string]bool{"std/builtin": true, "std/net/http": true},
 			},
-			want: "builtin",
+			want: "builtin@go1.14",
 		},
 		{
-			name:    "std packages are not versioned",
+			name:    "std packages are versioned",
 			pkgPath: "net/http",
 			modInfo: &ModuleInfo{
 				ModulePath:      "std",
-				ResolvedVersion: "v1.14.4",
+				ResolvedVersion: "v1.23.0",
 				ModulePackages:  map[string]bool{"std/builtin": true, "std/net/http": true},
 			},
-			want: "net/http",
+			want: "net/http@go1.23.0",
 		},
 		{
 			name:    "imports from other modules are not versioned",