bp2build: add allowlist for package-level conversions.

This CL adds the support for specifying lists of directories in
build/soong/android/bazel.go, which are then written into
out/soong/bp2build/MANIFEST. Using this configuration,
modules/directories can either default to bp2build_available: true or
false, while still retaining the ability to opt-in or out at the module level.

It also ensures that ConvertWithBp2Build returns true iff the module
type has a registered bp2build converter.

Test: go tests
Test: demo.sh full
Test: TreeHugger presubmits for bp2build and mixed builds.

Change-Id: I0e0f6f4b1b2ec045f2f1c338f7084defc5d23a55
diff --git a/android/Android.bp b/android/Android.bp
index 2406321..4da0f4e 100644
--- a/android/Android.bp
+++ b/android/Android.bp
@@ -85,6 +85,7 @@
         "androidmk_test.go",
         "apex_test.go",
         "arch_test.go",
+        "bazel_test.go",
         "config_test.go",
         "csuite_config_test.go",
         "depset_test.go",
diff --git a/android/bazel.go b/android/bazel.go
index 683495b..9b06426 100644
--- a/android/bazel.go
+++ b/android/bazel.go
@@ -32,7 +32,13 @@
 
 	// If true, bp2build will generate the converted Bazel target for this module. Note: this may
 	// cause a conflict due to the duplicate targets if label is also set.
-	Bp2build_available bool
+	//
+	// This is a bool pointer to support tristates: true, false, not set.
+	//
+	// To opt-in a module, set bazel_module: { bp2build_available: true }
+	// To opt-out a module, set bazel_module: { bp2build_available: false }
+	// To defer the default setting for the directory, do not set the value.
+	Bp2build_available *bool
 }
 
 // Properties contains common module properties for Bazel migration purposes.
@@ -54,9 +60,9 @@
 	HasHandcraftedLabel() bool
 	HandcraftedLabel() string
 	GetBazelLabel(ctx BazelConversionPathContext, module blueprint.Module) string
-	ConvertWithBp2build() bool
+	ConvertWithBp2build(ctx BazelConversionPathContext) bool
 	GetBazelBuildFileContents(c Config, path, name string) (string, error)
-	ConvertedToBazel() bool
+	ConvertedToBazel(ctx BazelConversionPathContext) bool
 }
 
 // BazelModule is a lightweight wrapper interface around Module for Bazel-convertible modules.
@@ -91,15 +97,91 @@
 	if b.HasHandcraftedLabel() {
 		return b.HandcraftedLabel()
 	}
-	if b.ConvertWithBp2build() {
+	if b.ConvertWithBp2build(ctx) {
 		return bp2buildModuleLabel(ctx, module)
 	}
 	return "" // no label for unconverted module
 }
 
+// Configuration to decide if modules in a directory should default to true/false for bp2build_available
+type Bp2BuildConfig map[string]BazelConversionConfigEntry
+type BazelConversionConfigEntry int
+
+const (
+	// iota + 1 ensures that the int value is not 0 when used in the Bp2buildAllowlist map,
+	// which can also mean that the key doesn't exist in a lookup.
+
+	// all modules in this package and subpackages default to bp2build_available: true.
+	// allows modules to opt-out.
+	Bp2BuildDefaultTrueRecursively BazelConversionConfigEntry = iota + 1
+
+	// all modules in this package (not recursively) default to bp2build_available: false.
+	// allows modules to opt-in.
+	Bp2BuildDefaultFalse
+)
+
+var (
+	// Configure modules in these directories to enable bp2build_available: true or false by default.
+	bp2buildDefaultConfig = Bp2BuildConfig{
+		"bionic":                Bp2BuildDefaultTrueRecursively,
+		"system/core/libcutils": Bp2BuildDefaultTrueRecursively,
+		"system/logging/liblog": Bp2BuildDefaultTrueRecursively,
+	}
+)
+
 // ConvertWithBp2build returns whether the given BazelModuleBase should be converted with bp2build.
-func (b *BazelModuleBase) ConvertWithBp2build() bool {
-	return b.bazelProperties.Bazel_module.Bp2build_available
+func (b *BazelModuleBase) ConvertWithBp2build(ctx BazelConversionPathContext) bool {
+	// Ensure that the module type of this module has a bp2build converter. This
+	// prevents mixed builds from using auto-converted modules just by matching
+	// the package dir; it also has to have a bp2build mutator as well.
+	if ctx.Config().bp2buildModuleTypeConfig[ctx.ModuleType()] == false {
+		return false
+	}
+
+	packagePath := ctx.ModuleDir()
+	config := ctx.Config().bp2buildPackageConfig
+
+	// This is a tristate value: true, false, or unset.
+	propValue := b.bazelProperties.Bazel_module.Bp2build_available
+	if bp2buildDefaultTrueRecursively(packagePath, config) {
+		// Allow modules to explicitly opt-out.
+		return proptools.BoolDefault(propValue, true)
+	}
+
+	// Allow modules to explicitly opt-in.
+	return proptools.BoolDefault(propValue, false)
+}
+
+// bp2buildDefaultTrueRecursively checks that the package contains a prefix from the
+// set of package prefixes where all modules must be converted. That is, if the
+// package is x/y/z, and the list contains either x, x/y, or x/y/z, this function will
+// return true.
+//
+// However, if the package is x/y, and it matches a Bp2BuildDefaultFalse "x/y" entry
+// exactly, this module will return false early.
+//
+// This function will also return false if the package doesn't match anything in
+// the config.
+func bp2buildDefaultTrueRecursively(packagePath string, config Bp2BuildConfig) bool {
+	ret := false
+
+	if config[packagePath] == Bp2BuildDefaultFalse {
+		return false
+	}
+
+	packagePrefix := ""
+	// e.g. for x/y/z, iterate over x, x/y, then x/y/z, taking the final value from the allowlist.
+	for _, part := range strings.Split(packagePath, "/") {
+		packagePrefix += part
+		if config[packagePrefix] == Bp2BuildDefaultTrueRecursively {
+			// package contains this prefix and this prefix should convert all modules
+			return true
+		}
+		// Continue to the next part of the package dir.
+		packagePrefix += "/"
+	}
+
+	return ret
 }
 
 // GetBazelBuildFileContents returns the file contents of a hand-crafted BUILD file if available or
@@ -126,6 +208,6 @@
 
 // ConvertedToBazel returns whether this module has been converted to Bazel, whether automatically
 // or manually
-func (b *BazelModuleBase) ConvertedToBazel() bool {
-	return b.ConvertWithBp2build() || b.HasHandcraftedLabel()
+func (b *BazelModuleBase) ConvertedToBazel(ctx BazelConversionPathContext) bool {
+	return b.ConvertWithBp2build(ctx) || b.HasHandcraftedLabel()
 }
diff --git a/android/bazel_test.go b/android/bazel_test.go
new file mode 100644
index 0000000..e5d8fbb
--- /dev/null
+++ b/android/bazel_test.go
@@ -0,0 +1,134 @@
+// 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 "testing"
+
+func TestConvertAllModulesInPackage(t *testing.T) {
+	testCases := []struct {
+		prefixes   Bp2BuildConfig
+		packageDir string
+	}{
+		{
+			prefixes: Bp2BuildConfig{
+				"a": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b":   Bp2BuildDefaultTrueRecursively,
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"d/e/f": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultFalse,
+				"a/b":   Bp2BuildDefaultTrueRecursively,
+				"a/b/c": Bp2BuildDefaultFalse,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"a/b":   Bp2BuildDefaultFalse,
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a",
+		},
+	}
+
+	for _, test := range testCases {
+		if !bp2buildDefaultTrueRecursively(test.packageDir, test.prefixes) {
+			t.Errorf("Expected to convert all modules in %s based on %v, but failed.", test.packageDir, test.prefixes)
+		}
+	}
+}
+
+func TestModuleOptIn(t *testing.T) {
+	testCases := []struct {
+		prefixes   Bp2BuildConfig
+		packageDir string
+	}{
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b": Bp2BuildDefaultFalse,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":   Bp2BuildDefaultFalse,
+				"a/b": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a", // opt-in by default
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"d/e/f": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "foo/bar",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultTrueRecursively,
+				"a/b":   Bp2BuildDefaultFalse,
+				"a/b/c": Bp2BuildDefaultTrueRecursively,
+			},
+			packageDir: "a/b",
+		},
+		{
+			prefixes: Bp2BuildConfig{
+				"a":     Bp2BuildDefaultFalse,
+				"a/b":   Bp2BuildDefaultTrueRecursively,
+				"a/b/c": Bp2BuildDefaultFalse,
+			},
+			packageDir: "a",
+		},
+	}
+
+	for _, test := range testCases {
+		if bp2buildDefaultTrueRecursively(test.packageDir, test.prefixes) {
+			t.Errorf("Expected to allow module opt-in in %s based on %v, but failed.", test.packageDir, test.prefixes)
+		}
+	}
+}
diff --git a/android/config.go b/android/config.go
index 0de8928..5b82e3e 100644
--- a/android/config.go
+++ b/android/config.go
@@ -140,6 +140,9 @@
 	fs         pathtools.FileSystem
 	mockBpList string
 
+	bp2buildPackageConfig    Bp2BuildConfig
+	bp2buildModuleTypeConfig map[string]bool
+
 	// If testAllowNonExistentPaths is true then PathForSource and PathForModuleSrc won't error
 	// in tests when a path doesn't exist.
 	TestAllowNonExistentPaths bool
@@ -281,6 +284,8 @@
 
 	config.mockFileSystem(bp, fs)
 
+	config.bp2buildModuleTypeConfig = map[string]bool{}
+
 	return Config{config}
 }
 
@@ -452,6 +457,8 @@
 			Bool(config.productVariables.ClangCoverage))
 
 	config.BazelContext, err = NewBazelContext(config)
+	config.bp2buildPackageConfig = bp2buildDefaultConfig
+	config.bp2buildModuleTypeConfig = make(map[string]bool)
 
 	return Config{config}, err
 }
diff --git a/android/filegroup.go b/android/filegroup.go
index 2eb4741..abbb4d4 100644
--- a/android/filegroup.go
+++ b/android/filegroup.go
@@ -53,7 +53,7 @@
 
 func FilegroupBp2Build(ctx TopDownMutatorContext) {
 	fg, ok := ctx.Module().(*fileGroup)
-	if !ok || !fg.ConvertWithBp2build() {
+	if !ok || !fg.ConvertWithBp2build(ctx) {
 		return
 	}
 
diff --git a/android/mutator.go b/android/mutator.go
index 9552aa1..9e99bee 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -226,7 +226,7 @@
 
 var bp2buildPreArchMutators = []RegisterMutatorFunc{}
 var bp2buildDepsMutators = []RegisterMutatorFunc{}
-var bp2buildMutators = []RegisterMutatorFunc{}
+var bp2buildMutators = map[string]RegisterMutatorFunc{}
 
 // RegisterBp2BuildMutator registers specially crafted mutators for
 // converting Blueprint/Android modules into special modules that can
@@ -237,7 +237,7 @@
 	f := func(ctx RegisterMutatorsContext) {
 		ctx.TopDown(moduleType, m)
 	}
-	bp2buildMutators = append(bp2buildMutators, f)
+	bp2buildMutators[moduleType] = f
 }
 
 // PreArchBp2BuildMutators adds mutators to be register for converting Android Blueprint modules
diff --git a/android/paths.go b/android/paths.go
index f648c55..7a54e01 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -340,6 +340,7 @@
 
 	GetDirectDep(name string) (blueprint.Module, blueprint.DependencyTag)
 	Module() Module
+	ModuleType() string
 	OtherModuleName(m blueprint.Module) string
 	OtherModuleDir(m blueprint.Module) string
 }
@@ -450,7 +451,7 @@
 	// TODO(b/165114590): Convert tag (":name{.tag}") to corresponding Bazel implicit output targets.
 	b, ok := module.(Bazelable)
 	// TODO(b/181155349): perhaps return an error here if the module can't be/isn't being converted
-	if !ok || !b.ConvertedToBazel() {
+	if !ok || !b.ConvertedToBazel(ctx) {
 		return bp2buildModuleLabel(ctx, module)
 	}
 	return b.GetBazelLabel(ctx, module)
diff --git a/android/register.go b/android/register.go
index 900edfa..34ee0b4 100644
--- a/android/register.go
+++ b/android/register.go
@@ -174,7 +174,13 @@
 		t.register(ctx)
 	}
 
-	RegisterMutatorsForBazelConversion(ctx, bp2buildPreArchMutators, bp2buildDepsMutators, bp2buildMutators)
+	bp2buildMutatorList := []RegisterMutatorFunc{}
+	for t, f := range bp2buildMutators {
+		ctx.config.bp2buildModuleTypeConfig[t] = true
+		bp2buildMutatorList = append(bp2buildMutatorList, f)
+	}
+
+	RegisterMutatorsForBazelConversion(ctx, bp2buildPreArchMutators, bp2buildDepsMutators, bp2buildMutatorList)
 }
 
 // Register the pipeline of singletons, module types, and mutators for
diff --git a/android/testing.go b/android/testing.go
index f17de31..207c949 100644
--- a/android/testing.go
+++ b/android/testing.go
@@ -158,12 +158,17 @@
 	ctx.finalDeps = append(ctx.finalDeps, f)
 }
 
+func (ctx *TestContext) RegisterBp2BuildConfig(config Bp2BuildConfig) {
+	ctx.config.bp2buildPackageConfig = config
+}
+
 // RegisterBp2BuildMutator registers a BazelTargetModule mutator for converting a module
 // type to the equivalent Bazel target.
 func (ctx *TestContext) RegisterBp2BuildMutator(moduleType string, m func(TopDownMutatorContext)) {
 	f := func(ctx RegisterMutatorsContext) {
 		ctx.TopDown(moduleType, m)
 	}
+	ctx.config.bp2buildModuleTypeConfig[moduleType] = true
 	ctx.bp2buildMutators = append(ctx.bp2buildMutators, f)
 }