godoc/dl: don't display unstable releases under archive

If a release is unstable, don't consider adding it to archive or stable
lists as well. It should be present in the unstable list only.

Create and use test helper list to make tests more compact and thorough.

Also use a more consistent order of got, want in TestFilesToReleases.

Fixes golang/go#29669

Change-Id: I74cf1fa8ebf05b13a3a4c40b53442c50e0427302
Reviewed-on: https://go-review.googlesource.com/c/157499
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

godoc/dl/dl.go

@@ -203,6 +203,7 @@ func filesToReleases(fs []File) (stable, unstable, archive []Release) {
 				return
 			}
 			unstable = append(unstable, *r)
+			return
 		}
 
 		// Reports whether the release is the most recent minor version of the

godoc/dl/dl_test.go

@@ -86,21 +86,14 @@ func TestFilesToReleases(t *testing.T) {
 		{Version: "go1.5beta1", OS: "windows"},
 	}
 	stable, unstable, archive := filesToReleases(fs)
-	if got, want := len(stable), 2; want != got {
-		t.Errorf("len(stable): got %v, want %v", got, want)
-	} else {
-		if got, want := stable[0].Version, "go1.7.4"; want != got {
-			t.Errorf("stable[0].Version: got %v, want %v", got, want)
-		}
-		if got, want := stable[1].Version, "go1.6.2"; want != got {
-			t.Errorf("stable[1].Version: got %v, want %v", got, want)
-		}
+	if got, want := list(stable), "go1.7.4, go1.6.2"; got != want {
+		t.Errorf("stable = %q; want %q", got, want)
 	}
-	if got, want := len(unstable), 0; want != got {
-		t.Errorf("len(unstable): got %v, want %v", got, want)
+	if got, want := list(unstable), ""; got != want {
+		t.Errorf("unstable = %q; want %q", got, want)
 	}
-	if got, want := len(archive), 4; want != got {
-		t.Errorf("len(archive): got %v, want %v", got, want)
+	if got, want := list(archive), "go1.7, go1.6, go1.5.2, go1.5"; got != want {
+		t.Errorf("archive = %q; want %q", got, want)
 	}
 }
 
@@ -116,6 +109,28 @@ func TestOldUnstableNotShown(t *testing.T) {
 	}
 }
 
+// A new beta should show up under unstable, but not show up under archive. See golang.org/issue/29669.
+func TestNewUnstableShownOnce(t *testing.T) {
+	fs := []File{
+		{Version: "go1.12beta2"},
+		{Version: "go1.11.4"},
+		{Version: "go1.11"},
+		{Version: "go1.10.7"},
+		{Version: "go1.10"},
+		{Version: "go1.9"},
+	}
+	stable, unstable, archive := filesToReleases(fs)
+	if got, want := list(stable), "go1.11.4, go1.10.7"; got != want {
+		t.Errorf("stable = %q; want %q", got, want)
+	}
+	if got, want := list(unstable), "go1.12beta2"; got != want {
+		t.Errorf("unstable = %q; want %q", got, want)
+	}
+	if got, want := list(archive), "go1.11, go1.10, go1.9"; got != want {
+		t.Errorf("archive = %q; want %q", got, want)
+	}
+}
+
 func TestUnstableShown(t *testing.T) {
 	fs := []File{
 		{Version: "go1.8beta2"},
@@ -125,11 +140,20 @@ func TestUnstableShown(t *testing.T) {
 		{Version: "go1.7beta1"},
 	}
 	_, unstable, _ := filesToReleases(fs)
-	if got, want := len(unstable), 1; got != want {
-		t.Fatalf("len(unstable): got %v, want %v", got, want)
-	}
-	// show rcs ahead of betas.
-	if got, want := unstable[0].Version, "go1.8rc1"; got != want {
-		t.Fatalf("unstable[0].Version: got %v, want %v", got, want)
+	// Show RCs ahead of betas.
+	if got, want := list(unstable), "go1.8rc1"; got != want {
+		t.Errorf("unstable = %q; want %q", got, want)
 	}
 }
+
+// list returns a version list string for the given releases.
+func list(rs []Release) string {
+	var s string
+	for i, r := range rs {
+		if i > 0 {
+			s += ", "
+		}
+		s += r.Version
+	}
+	return s
+}