go/packages: add test that go list closes file handles

Updates golang/go#71544

Change-Id: I349f97a0c5eb679115ea251d37dbd56042c7679b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/647516
Reviewed-by: Robert Findley <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Commit-Queue: Alan Donovan <[email protected]>

Author: adonovan

go/packages/packages_test.go

@@ -28,7 +28,9 @@ import (
 	"time"
 
 	"github.com/google/go-cmp/cmp"
+	"golang.org/x/sync/errgroup"
 	"golang.org/x/tools/go/packages"
+	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/packagesinternal"
 	"golang.org/x/tools/internal/packagestest"
 	"golang.org/x/tools/internal/testenv"
@@ -3400,3 +3402,57 @@ func writeTree(t *testing.T, archive string) string {
 	}
 	return root
 }
+
+// This is not a test of go/packages at all: it's a test of whether it
+// is possible to delete the directory used by go list once it has
+// finished. It is intended to evaluate the hypothesis (to explain
+// issue #71544) that the go command, on Windows, occasionally fails
+// to release all its handles to the temporary directory even when it
+// should have finished. If this test ever fails, the go command has a bug.
+func TestRmdirAfterGoList(t *testing.T) {
+	testenv.NeedsExec(t)
+
+	dir := t.TempDir()
+	if err := os.Mkdir(filepath.Join(dir, "p"), 0777); err != nil {
+		t.Fatalf("mkdir p: %v", err)
+	}
+
+	// Create a go.mod file and 100 trivial Go files for the go command to read.
+	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module example.com"), 0666); err != nil {
+		t.Fatal(err)
+	}
+	for i := range 100 {
+		filename := filepath.Join(dir, fmt.Sprintf("p/%d.go", i))
+		if err := os.WriteFile(filename, []byte("package p"), 0666); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	runner := gocommand.Runner{}
+
+	g, ctx := errgroup.WithContext(context.Background())
+	for range 10 {
+		g.Go(func() error {
+			stdout, stderr, friendlyErr, err := runner.RunRaw(ctx, gocommand.Invocation{
+				Verb:       "list",
+				Args:       []string{"-json", "example.com/p"},
+				WorkingDir: dir,
+			})
+			if ctx.Err() != nil {
+				return nil // don't report error if canceled
+			}
+			if err != nil || friendlyErr != nil {
+				t.Fatalf("go list failed: %v, %v (stdout=%s stderr=%s)",
+					err, friendlyErr, stdout, stderr)
+			}
+			// Return an error so that concurrent invocations are canceled.
+			return fmt.Errorf("oops")
+		})
+	}
+	g.Wait() // ignore expected error
+
+	// This is the critical operation.
+	if err := os.RemoveAll(dir); err != nil {
+		t.Fatalf("failed to remove temp dir: %v", err)
+	}
+}