Add filegroup_defaults module

Allows specifying shared filegroup attributes in a central place.

Test: filegroup_test.go
Change-Id: I82feac37ae6998313a0004f8af58f3decf7a514e

android/filegroup_test.go

@@ -58,3 +58,24 @@ func TestFileGroupWithPathProp(t *testing.T) {
 		AssertStringEquals(t, "src full path", expectedOutputfile, fg.srcs[0].String())
 	}
 }
+
+func TestFilegroupDefaults(t *testing.T) {
+	bp := FixtureAddTextFile("p/Android.bp", `
+		filegroup_defaults {
+			name: "defaults",
+			visibility: ["//x"],
+		}
+		filegroup {
+			name: "foo",
+			defaults: ["defaults"],
+			visibility: ["//y"],
+		}
+	`)
+	result := GroupFixturePreparers(
+		PrepareForTestWithFilegroup,
+		PrepareForTestWithDefaults,
+		PrepareForTestWithVisibility,
+		bp).RunTest(t)
+	rules := effectiveVisibilityRules(result.Config, qualifiedModuleName{pkg: "p", name: "foo"})
+	AssertDeepEquals(t, "visibility", []string{"//x", "//y"}, rules.Strings())
+}