Allow access to preparers that produced a TestResult am: 592518290f

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1645675

Change-Id: I7bde6493e80db34631ddac77b6405d5034d36886

android/fixture.go

@@ -458,15 +458,22 @@ func (f fixturePreparers) visit(visitor simpleFixturePreparerVisitor) {
 // preparers - a list of additional unflattened, undeduped preparers that will be applied after the
 //             base preparers.
 //
-// Returns a deduped and flattened list of the preparers minus any that exist in the base preparers.
+// Returns a deduped and flattened list of the preparers starting with the ones in base with any
+// additional ones from the preparers list added afterwards.
 func dedupAndFlattenPreparers(base []*simpleFixturePreparer, preparers fixturePreparers) []*simpleFixturePreparer {
-	var list []*simpleFixturePreparer
+	if len(preparers) == 0 {
+		return base
+	}
+
+	list := make([]*simpleFixturePreparer, len(base))
 	visited := make(map[*simpleFixturePreparer]struct{})
 
 	// Mark the already flattened and deduped preparers, if any, as having been seen so that
-	// duplicates of these in the additional preparers will be discarded.
-	for _, s := range base {
+	// duplicates of these in the additional preparers will be discarded. Add them to the output
+	// list.
+	for i, s := range base {
 		visited[s] = struct{}{}
+		list[i] = s
 	}
 
 	preparers.visit(func(preparer *simpleFixturePreparer) {
@@ -644,11 +651,8 @@ type fixtureFactory struct {
 }
 
 func (f *fixtureFactory) Extend(preparers ...FixturePreparer) FixtureFactory {
-	// Create a new slice to avoid accidentally sharing the preparers slice from this factory with
-	// the extending factories.
-	var all []*simpleFixturePreparer
-	all = append(all, f.preparers...)
-	all = append(all, dedupAndFlattenPreparers(f.preparers, preparers)...)
+	all := dedupAndFlattenPreparers(f.preparers, preparers)
+
 	// Copy the existing factory.
 	extendedFactory := &fixtureFactory{}
 	*extendedFactory = *f
@@ -667,10 +671,15 @@ func (f *fixtureFactory) Fixture(t *testing.T, preparers ...FixturePreparer) Fix
 		// Retrieve the buildDir from the supplier.
 		buildDir = *f.buildDirSupplier
 	}
+
+	// Construct an array of all preparers, those from this factory and the additional ones passed to
+	// this method.
+	all := dedupAndFlattenPreparers(f.preparers, preparers)
+
 	config := TestConfig(buildDir, nil, "", nil)
 	ctx := NewTestContext(config)
 	fixture := &fixture{
-		factory:      f,
+		preparers:    all,
 		t:            t,
 		config:       config,
 		ctx:          ctx,
@@ -678,11 +687,7 @@ func (f *fixtureFactory) Fixture(t *testing.T, preparers ...FixturePreparer) Fix
 		errorHandler: f.errorHandler,
 	}
 
-	for _, preparer := range f.preparers {
-		preparer.function(fixture)
-	}
-
-	for _, preparer := range dedupAndFlattenPreparers(f.preparers, preparers) {
+	for _, preparer := range all {
 		preparer.function(fixture)
 	}
 
@@ -730,8 +735,8 @@ func (f *fixtureFactory) RunTestWithConfig(t *testing.T, config Config) *TestRes
 }
 
 type fixture struct {
-	// The factory used to create this fixture.
-	factory *fixtureFactory
+	// The preparers used to create this fixture.
+	preparers []*simpleFixturePreparer
 
 	// The gotest state of the go test within which this was created.
 	t *testing.T
@@ -839,6 +844,21 @@ func (r *TestResult) NormalizePathsForTesting(paths Paths) []string {
 	return result
 }
 
+// Preparer will return a FixturePreparer encapsulating all the preparers used to create the fixture
+// that produced this result.
+//
+// e.g. assuming that this result was created by running:
+//     factory.Extend(preparer1, preparer2).RunTest(t, preparer3, preparer4)
+//
+// Then this method will be equivalent to running:
+//     GroupFixturePreparers(preparer1, preparer2, preparer3, preparer4)
+//
+// This is intended for use by tests whose output is Android.bp files to verify that those files
+// are valid, e.g. tests of the snapshots produced by the sdk module type.
+func (r *TestResult) Preparer() FixturePreparer {
+	return &compositeFixturePreparer{r.fixture.preparers}
+}
+
 // Module returns the module with the specific name and of the specified variant.
 func (r *TestResult) Module(name string, variant string) Module {
 	return r.ModuleForTests(name, variant).Module()