Generate genrule modules for merged api txts

Add a soong plugin that can generate the genrule definitions for the
merged api txt files. This will allow removing a lot of duplicated
lists in the Android.bp and simplify adding new modules.

Bug: 169103987
Test: follow-up that uses these rules (branch dependent)
Change-Id: I0c7a9921b7f4c5b74f8b652cb357abf9444ce93f

1 files changed, 224 insertions, 0 deletions

diff --git a/api/api.go b/api/api.go
new file mode 100644
index 000000000000..976b140f407f
--- /dev/null
+++ b/api/api.go
@@ -0,0 +1,224 @@
+// Copyright (C) 2021 The Android Open Source Project
+//
+// 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 api
+
+import (
+	"github.com/google/blueprint/proptools"
+
+	"android/soong/android"
+	"android/soong/genrule"
+)
+
+// The intention behind this soong plugin is to generate a number of "merged"
+// API-related modules that would otherwise require a large amount of very
+// similar Android.bp boilerplate to define. For example, the merged current.txt
+// API definitions (created by merging the non-updatable current.txt with all
+// the module current.txts). This simplifies the addition of new android
+// modules, by reducing the number of genrules etc a new module must be added to.
+
+// The properties of the combined_apis module type.
+type CombinedApisProperties struct {
+	// Module libraries that have public APIs
+	Public []string
+	// Module libraries that have system APIs
+	System []string
+	// Module libraries that have module_library APIs
+	Module_lib []string
+	// Module libraries that have system_server APIs
+	System_server []string
+	// ART module library. The only API library not removed from the filtered api database, because
+	// 1) ART apis are available by default to all modules, while other module-to-module deps are
+	//    explicit and probably receive more scrutiny anyway
+	// 2) The number of ART/libcore APIs is large, so not linting them would create a large gap
+	// 3) It's a compromise. Ideally we wouldn't be filtering out any module APIs, and have
+	//    per-module lint databases that excludes just that module's APIs. Alas, that's more
+	//    difficult to achieve.
+	Art_module string
+}
+
+type CombinedApis struct {
+	android.ModuleBase
+
+	properties CombinedApisProperties
+}
+
+func init() {
+	registerBuildComponents(android.InitRegistrationContext)
+}
+
+func registerBuildComponents(ctx android.RegistrationContext) {
+	ctx.RegisterModuleType("combined_apis", combinedApisModuleFactory)
+}
+
+var PrepareForCombinedApisTest = android.FixtureRegisterWithContext(registerBuildComponents)
+
+func (a *CombinedApis) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+}
+
+type genruleProps struct {
+	Name       *string
+	Cmd        *string
+	Dists      []android.Dist
+	Out        []string
+	Srcs       []string
+	Tools      []string
+	Visibility []string
+}
+
+// Struct to pass parameters for the various merged [current|removed].txt file modules we create.
+type MergedTxtDefinition struct {
+	// "current.txt" or "removed.txt"
+	TxtFilename string
+	// The module for the non-updatable / non-module part of the api.
+	BaseTxt string
+	// The list of modules that are relevant for this merged txt.
+	Modules []string
+	// The output tag for each module to use.e.g. {.public.api.txt} for current.txt
+	ModuleTag string
+	// public, system, module-lib or system-server
+	Scope string
+}
+
+func createMergedTxt(ctx android.LoadHookContext, txt MergedTxtDefinition) {
+	metalavaCmd := "$(location metalava)"
+	// Silence reflection warnings. See b/168689341
+	metalavaCmd += " -J--add-opens=java.base/java.util=ALL-UNNAMED "
+	metalavaCmd += " --quiet --no-banner --format=v2 "
+
+	filename := txt.TxtFilename
+	if txt.Scope != "public" {
+		filename = txt.Scope + "-" + filename
+	}
+
+	props := genruleProps{}
+	props.Name = proptools.StringPtr(ctx.ModuleName() + "-" + filename)
+	props.Tools = []string{"metalava"}
+	props.Out = []string{txt.TxtFilename}
+	props.Cmd = proptools.StringPtr(metalavaCmd + "$(in) --api $(out)")
+	props.Srcs = createSrcs(txt.BaseTxt, txt.Modules, txt.ModuleTag)
+	props.Dists = []android.Dist{
+		{
+			Targets: []string{"droidcore"},
+			Dir:     proptools.StringPtr("api"),
+			Dest:    proptools.StringPtr(filename),
+		},
+		{
+			Targets: []string{"sdk"},
+			Dir:     proptools.StringPtr("apistubs/android/" + txt.Scope + "/api"),
+			Dest:    proptools.StringPtr(txt.TxtFilename),
+		},
+	}
+	props.Visibility = []string{"//visibility:public"}
+	ctx.CreateModule(genrule.GenRuleFactory, &props)
+}
+
+func createMergedStubsSrcjar(ctx android.LoadHookContext, modules []string) {
+	props := genruleProps{}
+	props.Name = proptools.StringPtr(ctx.ModuleName() + "-current.srcjar")
+	props.Tools = []string{"merge_zips"}
+	props.Out = []string{"current.srcjar"}
+	props.Cmd = proptools.StringPtr("$(location merge_zips) $(out) $(in)")
+	props.Srcs = createSrcs(":api-stubs-docs-non-updatable", modules, "{.public.stubs.source}")
+	props.Visibility = []string{"//visibility:private"} // Used by make module in //development, mind
+	ctx.CreateModule(genrule.GenRuleFactory, &props)
+}
+
+func createFilteredApiVersions(ctx android.LoadHookContext, modules []string) {
+	props := genruleProps{}
+	props.Name = proptools.StringPtr("api-versions-xml-public-filtered")
+	props.Tools = []string{"api_versions_trimmer"}
+	props.Out = []string{"api-versions-public-filtered.xml"}
+	props.Cmd = proptools.StringPtr("$(location api_versions_trimmer) $(out) $(in)")
+	// Note: order matters: first parameter is the full api-versions.xml
+	// after that the stubs files in any order
+	// stubs files are all modules that export API surfaces EXCEPT ART
+	props.Srcs = createSrcs(":framework-doc-stubs{.api_versions.xml}", modules, ".stubs{.jar}")
+	props.Dists = []android.Dist{{Targets: []string{"sdk"}}}
+	ctx.CreateModule(genrule.GenRuleFactory, &props)
+}
+
+func createSrcs(base string, modules []string, tag string) []string {
+	a := make([]string, 0, len(modules)+1)
+	a = append(a, base)
+	for _, module := range modules {
+		a = append(a, ":"+module+tag)
+	}
+	return a
+}
+
+func remove(s []string, v string) []string {
+	s2 := make([]string, 0, len(s))
+	for _, sv := range s {
+		if sv != v {
+			s2 = append(s2, sv)
+		}
+	}
+	return s2
+}
+
+func createMergedTxts(ctx android.LoadHookContext, props CombinedApisProperties) {
+	var textFiles []MergedTxtDefinition
+	tagSuffix := []string{".api.txt}", ".removed-api.txt}"}
+	for i, f := range []string{"current.txt", "removed.txt"} {
+		textFiles = append(textFiles, MergedTxtDefinition{
+			TxtFilename: f,
+			BaseTxt:     ":non-updatable-" + f,
+			Modules:     props.Public,
+			ModuleTag:   "{.public" + tagSuffix[i],
+			Scope:       "public",
+		})
+		textFiles = append(textFiles, MergedTxtDefinition{
+			TxtFilename: f,
+			BaseTxt:     ":non-updatable-system-" + f,
+			Modules:     props.System,
+			ModuleTag:   "{.system" + tagSuffix[i],
+			Scope:       "system",
+		})
+		textFiles = append(textFiles, MergedTxtDefinition{
+			TxtFilename: f,
+			BaseTxt:     ":non-updatable-module-lib-" + f,
+			Modules:     props.Module_lib,
+			ModuleTag:   "{.module-lib" + tagSuffix[i],
+			Scope:       "module-lib",
+		})
+		textFiles = append(textFiles, MergedTxtDefinition{
+			TxtFilename: f,
+			BaseTxt:     ":non-updatable-system-server-" + f,
+			Modules:     props.System_server,
+			ModuleTag:   "{.system-server" + tagSuffix[i],
+			Scope:       "system-server",
+		})
+	}
+	for _, txt := range textFiles {
+		createMergedTxt(ctx, txt)
+	}
+}
+
+func (a *CombinedApis) createInternalModules(ctx android.LoadHookContext) {
+	createMergedTxts(ctx, a.properties)
+
+	createMergedStubsSrcjar(ctx, a.properties.Public)
+
+	// For the filtered api versions, we prune all APIs except art module's APIs.
+	createFilteredApiVersions(ctx, remove(a.properties.Public, a.properties.Art_module))
+}
+
+func combinedApisModuleFactory() android.Module {
+	module := &CombinedApis{}
+	module.AddProperties(&module.properties)
+	android.InitAndroidModule(module)
+	android.AddLoadHook(module, func(ctx android.LoadHookContext) { module.createInternalModules(ctx) })
+	return module
+}