Add a new SingletonModule type

A SingletonModule is halfway between a Singleton and a Module.  It has
access to visiting other modules via its GenerateSingletonBuildActions
method, but must be defined in an Android.bp file and can also be
depended on like a module.

Bug: 176904285
Test: singleton_module_test.go
Change-Id: I1b2bfdfb3927c1eabf431c53213cb7c581e33ca4

android/singleton_module_test.go

@@ -0,0 +1,149 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package android
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+type testSingletonModule struct {
+	SingletonModuleBase
+	ops []string
+}
+
+func (tsm *testSingletonModule) GenerateAndroidBuildActions(ctx ModuleContext) {
+	tsm.ops = append(tsm.ops, "GenerateAndroidBuildActions")
+}
+
+func (tsm *testSingletonModule) GenerateSingletonBuildActions(ctx SingletonContext) {
+	tsm.ops = append(tsm.ops, "GenerateSingletonBuildActions")
+}
+
+func (tsm *testSingletonModule) MakeVars(ctx MakeVarsContext) {
+	tsm.ops = append(tsm.ops, "MakeVars")
+}
+
+func testSingletonModuleFactory() SingletonModule {
+	tsm := &testSingletonModule{}
+	InitAndroidSingletonModule(tsm)
+	return tsm
+}
+
+func runSingletonModuleTest(bp string) (*TestContext, []error) {
+	config := TestConfig(buildDir, nil, bp, nil)
+	// Enable Kati output to test SingletonModules with MakeVars.
+	config.katiEnabled = true
+	ctx := NewTestContext(config)
+	ctx.RegisterSingletonModuleType("test_singleton_module", testSingletonModuleFactory)
+	ctx.RegisterSingletonType("makevars", makeVarsSingletonFunc)
+	ctx.Register()
+
+	_, errs := ctx.ParseBlueprintsFiles("Android.bp")
+	if len(errs) > 0 {
+		return ctx, errs
+	}
+
+	_, errs = ctx.PrepareBuildActions(config)
+	return ctx, errs
+}
+
+func TestSingletonModule(t *testing.T) {
+	bp := `
+		test_singleton_module {
+			name: "test_singleton_module",
+		}
+	`
+	ctx, errs := runSingletonModuleTest(bp)
+	if len(errs) > 0 {
+		t.Fatal(errs)
+	}
+
+	ops := ctx.ModuleForTests("test_singleton_module", "").Module().(*testSingletonModule).ops
+	wantOps := []string{"GenerateAndroidBuildActions", "GenerateSingletonBuildActions", "MakeVars"}
+	if !reflect.DeepEqual(ops, wantOps) {
+		t.Errorf("Expected operations %q, got %q", wantOps, ops)
+	}
+}
+
+func TestDuplicateSingletonModule(t *testing.T) {
+	bp := `
+		test_singleton_module {
+			name: "test_singleton_module",
+		}
+
+		test_singleton_module {
+			name: "test_singleton_module2",
+		}
+	`
+	_, errs := runSingletonModuleTest(bp)
+	if len(errs) == 0 {
+		t.Fatal("expected duplicate SingletonModule error")
+	}
+	if len(errs) != 1 || !strings.Contains(errs[0].Error(), `Duplicate SingletonModule "test_singleton_module", previously used in`) {
+		t.Fatalf("expected duplicate SingletonModule error, got %q", errs)
+	}
+}
+
+func TestUnusedSingletonModule(t *testing.T) {
+	bp := ``
+	ctx, errs := runSingletonModuleTest(bp)
+	if len(errs) > 0 {
+		t.Fatal(errs)
+	}
+
+	singleton := ctx.SingletonForTests("test_singleton_module").Singleton()
+	sm := singleton.(*singletonModuleSingletonAdaptor).sm
+	ops := sm.(*testSingletonModule).ops
+	if ops != nil {
+		t.Errorf("Expected no operations, got %q", ops)
+	}
+}
+
+func testVariantSingletonModuleMutator(ctx BottomUpMutatorContext) {
+	if _, ok := ctx.Module().(*testSingletonModule); ok {
+		ctx.CreateVariations("a", "b")
+	}
+}
+
+func TestVariantSingletonModule(t *testing.T) {
+	bp := `
+		test_singleton_module {
+			name: "test_singleton_module",
+		}
+	`
+
+	config := TestConfig(buildDir, nil, bp, nil)
+	ctx := NewTestContext(config)
+	ctx.PreDepsMutators(func(ctx RegisterMutatorsContext) {
+		ctx.BottomUp("test_singleton_module_mutator", testVariantSingletonModuleMutator)
+	})
+	ctx.RegisterSingletonModuleType("test_singleton_module", testSingletonModuleFactory)
+	ctx.Register()
+
+	_, errs := ctx.ParseBlueprintsFiles("Android.bp")
+
+	if len(errs) == 0 {
+		_, errs = ctx.PrepareBuildActions(config)
+	}
+
+	if len(errs) == 0 {
+		t.Fatal("expected duplicate SingletonModule error")
+	}
+	if len(errs) != 1 || !strings.Contains(errs[0].Error(), `GenerateAndroidBuildActions already called for variant`) {
+		t.Fatalf("expected duplicate SingletonModule error, got %q", errs)
+	}
+}