cmd/api: explicit tagKey with GOOS and GOARCH

The origin tagKey is just dirname if no tags input which will cause
pkgCache missmatch if other imported pkg explicit on GOARCH or GOOS

This CL will add GOOS and GOARCH to tagKey

Fixes #8425
Fixes #21181

Change-Id: Ifc189cf6746d753ad7c7e5bb60621297fc0a4e35
Reviewed-on: https://go-review.googlesource.com/c/138315Reviewed-by: Robert Griesemer <gri@golang.org>

api/except.txt

@@ -6,6 +6,8 @@ pkg os, const ModeType = 2399141888
 pkg os, const ModeType = 2399666176
 pkg os (linux-arm), const O_SYNC = 4096
 pkg os (linux-arm-cgo), const O_SYNC = 4096
+pkg os (linux-arm), const O_SYNC = 1052672
+pkg os (linux-arm-cgo), const O_SYNC = 1052672
 pkg syscall (darwin-386), const ImplementsGetwd = false
 pkg syscall (darwin-386), func Fchflags(string, int) error
 pkg syscall (darwin-386-cgo), const ImplementsGetwd = false

src/cmd/api/goapi.go

@@ -385,9 +385,7 @@ func (w *Walker) parseFile(dir, file string) (*ast.File, error) {
 	return f, nil
 }
 
-// The package cache doesn't operate correctly in rare (so far artificial)
-// circumstances (issue 8425). Disable before debugging non-obvious errors
-// from the type-checker.
+// Disable before debugging non-obvious errors from the type-checker.
 const usePkgCache = true
 
 var (
@@ -398,7 +396,7 @@ var (
 // tagKey returns the tag-based key to use in the pkgCache.
 // It is a comma-separated string; the first part is dir, the rest tags.
 // The satisfied tags are derived from context but only those that
-// matter (the ones listed in the tags argument) are used.
+// matter (the ones listed in the tags argument plus GOOS and GOARCH) are used.
 // The tags list, which came from go/build's Package.AllTags,
 // is known to be sorted.
 func tagKey(dir string, context *build.Context, tags []string) string {
@@ -414,9 +412,17 @@ func tagKey(dir string, context *build.Context, tags []string) string {
 	}
 	// TODO: ReleaseTags (need to load default)
 	key := dir
+
+	// explicit on GOOS and GOARCH as global cache will use "all" cached packages for
+	// an indirect imported package. See https://github.com/golang/go/issues/21181
+	// for more detail.
+	tags = append(tags, context.GOOS, context.GOARCH)
+	sort.Strings(tags)
+
 	for _, tag := range tags {
 		if ctags[tag] {
 			key += "," + tag
+			ctags[tag] = false
 		}
 	}
 	return key

src/cmd/api/goapi_test.go

@@ -188,3 +188,18 @@ func BenchmarkAll(b *testing.B) {
 		}
 	}
 }
+
+func TestIssue21181(t *testing.T) {
+	for _, c := range contexts {
+		c.Compiler = build.Default.Compiler
+	}
+	for _, context := range contexts {
+		w := NewWalker(context, "testdata/src/issue21181")
+		pkg, err := w.Import("p")
+		if err != nil {
+			t.Fatalf("%s: (%s-%s) %s %v", err, context.GOOS, context.GOARCH,
+				pkg.Name(), w.imported)
+		}
+		w.export(pkg)
+	}
+}

src/cmd/api/testdata/src/issue21181/dep/p.go

+package dep
+
+type Interface interface {
+	N([]byte)
+}

src/cmd/api/testdata/src/issue21181/dep/p_amd64.go

+package dep

src/cmd/api/testdata/src/issue21181/indirect/p.go

+package indirect
+
+import "dep"
+
+func F(dep.Interface) {}

src/cmd/api/testdata/src/issue21181/p/p.go

+package p
+
+import (
+	"dep"
+)
+
+type algo struct {
+	indrt func(dep.Interface)
+}

src/cmd/api/testdata/src/issue21181/p/p_amd64.go

+package p
+
+import "indirect"
+
+var in = []algo{
+	{indirect.F},
+}

src/cmd/api/testdata/src/issue21181/p/p_generic.go

+// +build !amd64
+
+package p
+
+import (
+	"indirect"
+)
+
+var in = []algo{
+	{indirect.F},
+}