cc/tidy.go - platform/build/soong - Git at Google

 // Copyright 2016 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 cc

 import (
 	"fmt"
 	"path/filepath"
 	"regexp"
 	"strings"

 	"github.com/google/blueprint/proptools"

 	"android/soong/android"
 	"android/soong/cc/config"
 )

 type TidyProperties struct {
 	// whether to run clang-tidy over C-like sources.
 	Tidy *bool

 	// Extra flags to pass to clang-tidy
 	Tidy_flags []string

 	// Extra checks to enable or disable in clang-tidy
 	Tidy_checks []string

 	// Checks that should be treated as errors.
 	Tidy_checks_as_errors []string
 }

 type tidyFeature struct {
 	Properties TidyProperties
 }

 var quotedFlagRegexp, _ = regexp.Compile(`^-?-[^=]+=('|").*('|")$`)

 // When passing flag -name=value, if user add quotes around 'value',
 // the quotation marks will be preserved by NinjaAndShellEscapeList
 // and the 'value' string with quotes won't work like the intended value.
 // So here we report an error if -*='*' is found.
 func checkNinjaAndShellEscapeList(ctx ModuleContext, prop string, slice []string) []string {
 	for _, s := range slice {
 		if quotedFlagRegexp.MatchString(s) {
 			ctx.PropertyErrorf(prop, "Extra quotes in: %s", s)
 		}
 	}
 	return proptools.NinjaAndShellEscapeList(slice)
 }

 func (tidy *tidyFeature) props() []interface{} {
 	return []interface{}{&tidy.Properties}
 }

 // Set this const to true when all -warnings-as-errors in tidy_flags
 // are replaced with tidy_checks_as_errors.
 // Then, that old style usage will be obsolete and an error.
 const NoWarningsAsErrorsInTidyFlags = true

 // keep this up to date with https://cs.android.com/android/platform/superproject/+/master:build/bazel/rules/cc/clang_tidy.bzl
 func (tidy *tidyFeature) flags(ctx ModuleContext, flags Flags) Flags {
 	CheckBadTidyFlags(ctx, "tidy_flags", tidy.Properties.Tidy_flags)
 	CheckBadTidyChecks(ctx, "tidy_checks", tidy.Properties.Tidy_checks)

 	// Check if tidy is explicitly disabled for this module
 	if tidy.Properties.Tidy != nil && !*tidy.Properties.Tidy {
 		return flags
 	}
 	// Some projects like external/* and vendor/* have clang-tidy disabled by default,
 	// unless they are enabled explicitly with the "tidy:true" property or
 	// when TIDY_EXTERNAL_VENDOR is set to true.
 	if !proptools.Bool(tidy.Properties.Tidy) &&
 		config.NoClangTidyForDir(
 			ctx.Config().IsEnvTrue("TIDY_EXTERNAL_VENDOR"),
 			ctx.ModuleDir()) {
 		return flags
 	}
 	// If not explicitly disabled, set flags.Tidy to generate .tidy rules.
 	// Note that libraries and binaries will depend on .tidy files ONLY if
 	// the global WITH_TIDY or module 'tidy' property is true.
 	flags.Tidy = true

 	// If explicitly enabled, by global WITH_TIDY or local tidy:true property,
 	// set flags.NeedTidyFiles to make this module depend on .tidy files.
 	// Note that locally set tidy:true is ignored if ALLOW_LOCAL_TIDY_TRUE is not set to true.
 	if ctx.Config().IsEnvTrue("WITH_TIDY") || (ctx.Config().IsEnvTrue("ALLOW_LOCAL_TIDY_TRUE") && Bool(tidy.Properties.Tidy)) {
 		flags.NeedTidyFiles = true
 	}

 	// Add global WITH_TIDY_FLAGS and local tidy_flags.
 	withTidyFlags := ctx.Config().Getenv("WITH_TIDY_FLAGS")
 	if len(withTidyFlags) > 0 {
 		flags.TidyFlags = append(flags.TidyFlags, withTidyFlags)
 	}
 	esc := checkNinjaAndShellEscapeList
 	flags.TidyFlags = append(flags.TidyFlags, esc(ctx, "tidy_flags", tidy.Properties.Tidy_flags)...)
 	// If TidyFlags does not contain -header-filter, add default header filter.
 	// Find the substring because the flag could also appear as --header-filter=...
 	// and with or without single or double quotes.
 	if !android.SubstringInList(flags.TidyFlags, "-header-filter=") {
 		defaultDirs := ctx.Config().Getenv("DEFAULT_TIDY_HEADER_DIRS")
 		headerFilter := "-header-filter="
 		// Default header filter should include only the module directory,
 		// not the out/soong/.../ModuleDir/...
 		// Otherwise, there will be too many warnings from generated files in out/...
 		// If a module wants to see warnings in the generated source files,
 		// it should specify its own -header-filter flag.
 		if defaultDirs == "" {
 			headerFilter += "^" + ctx.ModuleDir() + "/"
 		} else {
 			headerFilter += "\"(^" + ctx.ModuleDir() + "/|" + defaultDirs + ")\""
 		}
 		flags.TidyFlags = append(flags.TidyFlags, headerFilter)
 	}
 	// Work around RBE bug in parsing clang-tidy flags, replace "--flag" with "-flag".
 	// Some C/C++ modules added local tidy flags like --header-filter= and --extra-arg-before=.
 	doubleDash := regexp.MustCompile("^('?)--(.*)$")
 	for i, s := range flags.TidyFlags {
 		flags.TidyFlags[i] = doubleDash.ReplaceAllString(s, "$1-$2")
 	}

 	// If clang-tidy is not enabled globally, add the -quiet flag.
 	if !ctx.Config().ClangTidy() {
 		flags.TidyFlags = append(flags.TidyFlags, "-quiet")
 		flags.TidyFlags = append(flags.TidyFlags, "-extra-arg-before=-fno-caret-diagnostics")
 	}

 	for _, f := range config.TidyExtraArgFlags() {
 		flags.TidyFlags = append(flags.TidyFlags, "-extra-arg-before="+f)
 	}

 	tidyChecks := "-checks="
 	if checks := ctx.Config().TidyChecks(); len(checks) > 0 {
 		tidyChecks += checks
 	} else {
 		tidyChecks += config.TidyChecksForDir(ctx.ModuleDir())
 	}
 	if len(tidy.Properties.Tidy_checks) > 0 {
 		// If Tidy_checks contains "-*", ignore all checks before "-*".
 		localChecks := tidy.Properties.Tidy_checks
 		ignoreGlobalChecks := false
 		for n, check := range tidy.Properties.Tidy_checks {
 			if check == "-*" {
 				ignoreGlobalChecks = true
 				localChecks = tidy.Properties.Tidy_checks[n:]
 			}
 		}
 		if ignoreGlobalChecks {
 			tidyChecks = "-checks=" + strings.Join(esc(ctx, "tidy_checks",
 				config.ClangRewriteTidyChecks(localChecks)), ",")
 		} else {
 			tidyChecks = tidyChecks + "," + strings.Join(esc(ctx, "tidy_checks",
 				config.ClangRewriteTidyChecks(localChecks)), ",")
 		}
 	}
 	tidyChecks = tidyChecks + config.TidyGlobalNoChecks()
 	if ctx.Windows() {
 		// https://b.corp.google.com/issues/120614316
 		// mingw32 has cert-dcl16-c warning in NO_ERROR,
 		// which is used in many Android files.
 		tidyChecks += ",-cert-dcl16-c"
 	}

 	flags.TidyFlags = append(flags.TidyFlags, tidyChecks)

 	// Embedding -warnings-as-errors in tidy_flags is error-prone.
 	// It should be replaced with the tidy_checks_as_errors list.
 	for i, s := range flags.TidyFlags {
 		if strings.Contains(s, "-warnings-as-errors=") {
 			if NoWarningsAsErrorsInTidyFlags {
 				ctx.PropertyErrorf("tidy_flags", "should not contain "+s+"; use tidy_checks_as_errors instead.")
 			} else {
 				fmt.Printf("%s: warning: module %s's tidy_flags should not contain %s, which is replaced with -warnings-as-errors=-*; use tidy_checks_as_errors for your own as-error warnings instead.\n",
 					ctx.BlueprintsFile(), ctx.ModuleName(), s)
 				flags.TidyFlags[i] = "-warnings-as-errors=-*"
 			}
 			break // there is at most one -warnings-as-errors
 		}
 	}
 	// Default clang-tidy flags does not contain -warning-as-errors.
 	// If a module has tidy_checks_as_errors, add the list to -warnings-as-errors
 	// and then append the TidyGlobalNoErrorChecks.
 	if len(tidy.Properties.Tidy_checks_as_errors) > 0 {
 		tidyChecksAsErrors := "-warnings-as-errors=" +
 			strings.Join(esc(ctx, "tidy_checks_as_errors", tidy.Properties.Tidy_checks_as_errors), ",") +
 			config.TidyGlobalNoErrorChecks()
 		flags.TidyFlags = append(flags.TidyFlags, tidyChecksAsErrors)
 	}
 	return flags
 }

 func init() {
 	android.RegisterSingletonType("tidy_phony_targets", TidyPhonySingleton)
 }

 // This TidyPhonySingleton generates both tidy-* and obj-* phony targets for C/C++ files.
 func TidyPhonySingleton() android.Singleton {
 	return &tidyPhonySingleton{}
 }

 type tidyPhonySingleton struct{}

 // Given a final module, add its tidy/obj phony targets to tidy/objModulesInDirGroup.
 func collectTidyObjModuleTargets(ctx android.SingletonContext, module android.Module,
 	tidyModulesInDirGroup, objModulesInDirGroup map[string]map[string]android.Paths) {
 	allObjFileGroups := make(map[string]android.Paths)     // variant group name => obj file Paths
 	allTidyFileGroups := make(map[string]android.Paths)    // variant group name => tidy file Paths
 	subsetObjFileGroups := make(map[string]android.Paths)  // subset group name => obj file Paths
 	subsetTidyFileGroups := make(map[string]android.Paths) // subset group name => tidy file Paths

 	// (1) Collect all obj/tidy files into OS-specific groups.
 	ctx.VisitAllModuleVariants(module, func(variant android.Module) {
 		if ctx.Config().KatiEnabled() && android.ShouldSkipAndroidMkProcessing(variant) {
 			return
 		}
 		if m, ok := variant.(*Module); ok {
 			osName := variant.Target().Os.Name
 			addToOSGroup(osName, m.objFiles, allObjFileGroups, subsetObjFileGroups)
 			addToOSGroup(osName, m.tidyFiles, allTidyFileGroups, subsetTidyFileGroups)
 		}
 	})

 	// (2) Add an all-OS group, with "" or "subset" name, to include all os-specific phony targets.
 	addAllOSGroup(ctx, module, allObjFileGroups, "", "obj")
 	addAllOSGroup(ctx, module, allTidyFileGroups, "", "tidy")
 	addAllOSGroup(ctx, module, subsetObjFileGroups, "subset", "obj")
 	addAllOSGroup(ctx, module, subsetTidyFileGroups, "subset", "tidy")

 	tidyTargetGroups := make(map[string]android.Path)
 	objTargetGroups := make(map[string]android.Path)
 	genObjTidyPhonyTargets(ctx, module, "obj", allObjFileGroups, objTargetGroups)
 	genObjTidyPhonyTargets(ctx, module, "obj", subsetObjFileGroups, objTargetGroups)
 	genObjTidyPhonyTargets(ctx, module, "tidy", allTidyFileGroups, tidyTargetGroups)
 	genObjTidyPhonyTargets(ctx, module, "tidy", subsetTidyFileGroups, tidyTargetGroups)

 	moduleDir := ctx.ModuleDir(module)
 	appendToModulesInDirGroup(tidyTargetGroups, moduleDir, tidyModulesInDirGroup)
 	appendToModulesInDirGroup(objTargetGroups, moduleDir, objModulesInDirGroup)
 }

 func (m *tidyPhonySingleton) GenerateBuildActions(ctx android.SingletonContext) {
 	// For tidy-* directory phony targets, there are different variant groups.
 	// tidyModulesInDirGroup[G][D] is for group G, directory D, with Paths
 	// of all phony targets to be included into direct dependents of tidy-D_G.
 	tidyModulesInDirGroup := make(map[string]map[string]android.Paths)
 	// Also for obj-* directory phony targets.
 	objModulesInDirGroup := make(map[string]map[string]android.Paths)

 	// Collect tidy/obj targets from the 'final' modules.
 	ctx.VisitAllModules(func(module android.Module) {
 		if module == ctx.FinalModule(module) {
 			collectTidyObjModuleTargets(ctx, module, tidyModulesInDirGroup, objModulesInDirGroup)
 		}
 	})

 	suffix := ""
 	if ctx.Config().KatiEnabled() {
 		suffix = "-soong"
 	}
 	generateObjTidyPhonyTargets(ctx, suffix, "obj", objModulesInDirGroup)
 	generateObjTidyPhonyTargets(ctx, suffix, "tidy", tidyModulesInDirGroup)
 }

 // The name for an obj/tidy module variant group phony target is Name_group-obj/tidy,
 func objTidyModuleGroupName(module android.Module, group string, suffix string) string {
 	if group == "" {
 		return module.Name() + "-" + suffix
 	}
 	return module.Name() + "_" + group + "-" + suffix
 }

 // Generate obj-* or tidy-* phony targets.
 func generateObjTidyPhonyTargets(ctx android.SingletonContext, suffix string, prefix string, objTidyModulesInDirGroup map[string]map[string]android.Paths) {
 	// For each variant group, create a <prefix>-<directory>_group target that
 	// depends on all subdirectories and modules in the directory.
 	for group, modulesInDir := range objTidyModulesInDirGroup {
 		groupSuffix := ""
 		if group != "" {
 			groupSuffix = "_" + group
 		}
 		mmTarget := func(dir string) string {
 			return prefix + "-" + strings.Replace(filepath.Clean(dir), "/", "-", -1) + groupSuffix
 		}
 		dirs, topDirs := android.AddAncestors(ctx, modulesInDir, mmTarget)
 		// Create a <prefix>-soong_group target that depends on all <prefix>-dir_group of top level dirs.
 		var topDirPaths android.Paths
 		for _, dir := range topDirs {
 			topDirPaths = append(topDirPaths, android.PathForPhony(ctx, mmTarget(dir)))
 		}
 		ctx.Phony(prefix+suffix+groupSuffix, topDirPaths...)
 		// Create a <prefix>-dir_group target that depends on all targets in modulesInDir[dir]
 		for _, dir := range dirs {
 			if dir != "." && dir != "" {
 				ctx.Phony(mmTarget(dir), modulesInDir[dir]...)
 			}
 		}
 	}
 }

 // Append (obj|tidy)TargetGroups[group] into (obj|tidy)ModulesInDirGroups[group][moduleDir].
 func appendToModulesInDirGroup(targetGroups map[string]android.Path, moduleDir string, modulesInDirGroup map[string]map[string]android.Paths) {
 	for group, phonyPath := range targetGroups {
 		if _, found := modulesInDirGroup[group]; !found {
 			modulesInDirGroup[group] = make(map[string]android.Paths)
 		}
 		modulesInDirGroup[group][moduleDir] = append(modulesInDirGroup[group][moduleDir], phonyPath)
 	}
 }

 // Add given files to the OS group and subset group.
 func addToOSGroup(osName string, files android.Paths, allGroups, subsetGroups map[string]android.Paths) {
 	if len(files) > 0 {
 		subsetName := osName + "_subset"
 		allGroups[osName] = append(allGroups[osName], files...)
 		// Now include only the first variant in the subsetGroups.
 		// If clang and clang-tidy get faster, we might include more variants.
 		if _, found := subsetGroups[subsetName]; !found {
 			subsetGroups[subsetName] = files
 		}
 	}
 }

 // Add an all-OS group, with groupName, to include all os-specific phony targets.
 func addAllOSGroup(ctx android.SingletonContext, module android.Module, phonyTargetGroups map[string]android.Paths, groupName string, objTidyName string) {
 	if len(phonyTargetGroups) > 0 {
 		var targets android.Paths
 		for group, _ := range phonyTargetGroups {
 			targets = append(targets, android.PathForPhony(ctx, objTidyModuleGroupName(module, group, objTidyName)))
 		}
 		phonyTargetGroups[groupName] = targets
 	}
 }

 // Create one phony targets for each group and add them to the targetGroups.
 func genObjTidyPhonyTargets(ctx android.SingletonContext, module android.Module, objTidyName string, fileGroups map[string]android.Paths, targetGroups map[string]android.Path) {
 	for group, files := range fileGroups {
 		groupName := objTidyModuleGroupName(module, group, objTidyName)
 		ctx.Phony(groupName, files...)
 		targetGroups[group] = android.PathForPhony(ctx, groupName)
 	}
 }
	// Copyright 2016 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 cc

	import (
	"fmt"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/google/blueprint/proptools"

	"android/soong/android"
	"android/soong/cc/config"
	)

	type TidyProperties struct {
	// whether to run clang-tidy over C-like sources.
	Tidy *bool

	// Extra flags to pass to clang-tidy
	Tidy_flags []string

	// Extra checks to enable or disable in clang-tidy
	Tidy_checks []string

	// Checks that should be treated as errors.
	Tidy_checks_as_errors []string
	}

	type tidyFeature struct {
	Properties TidyProperties
	}

	var quotedFlagRegexp, _ = regexp.Compile(`^-?-[^=]+=('\|").*('\|")$`)

	// When passing flag -name=value, if user add quotes around 'value',
	// the quotation marks will be preserved by NinjaAndShellEscapeList
	// and the 'value' string with quotes won't work like the intended value.
	// So here we report an error if -='' is found.
	func checkNinjaAndShellEscapeList(ctx ModuleContext, prop string, slice []string) []string {
	for _, s := range slice {
	if quotedFlagRegexp.MatchString(s) {
	ctx.PropertyErrorf(prop, "Extra quotes in: %s", s)
	}
	}
	return proptools.NinjaAndShellEscapeList(slice)
	}

	func (tidy *tidyFeature) props() []interface{} {
	return []interface{}{&tidy.Properties}
	}

	// Set this const to true when all -warnings-as-errors in tidy_flags
	// are replaced with tidy_checks_as_errors.
	// Then, that old style usage will be obsolete and an error.
	const NoWarningsAsErrorsInTidyFlags = true

	// keep this up to date with https://cs.android.com/android/platform/superproject/+/master:build/bazel/rules/cc/clang_tidy.bzl
	func (tidy *tidyFeature) flags(ctx ModuleContext, flags Flags) Flags {
	CheckBadTidyFlags(ctx, "tidy_flags", tidy.Properties.Tidy_flags)
	CheckBadTidyChecks(ctx, "tidy_checks", tidy.Properties.Tidy_checks)

	// Check if tidy is explicitly disabled for this module
	if tidy.Properties.Tidy != nil && !*tidy.Properties.Tidy {
	return flags
	}
	// Some projects like external/* and vendor/* have clang-tidy disabled by default,
	// unless they are enabled explicitly with the "tidy:true" property or
	// when TIDY_EXTERNAL_VENDOR is set to true.
	if !proptools.Bool(tidy.Properties.Tidy) &&
	config.NoClangTidyForDir(
	ctx.Config().IsEnvTrue("TIDY_EXTERNAL_VENDOR"),
	ctx.ModuleDir()) {
	return flags
	}
	// If not explicitly disabled, set flags.Tidy to generate .tidy rules.
	// Note that libraries and binaries will depend on .tidy files ONLY if
	// the global WITH_TIDY or module 'tidy' property is true.
	flags.Tidy = true

	// If explicitly enabled, by global WITH_TIDY or local tidy:true property,
	// set flags.NeedTidyFiles to make this module depend on .tidy files.
	// Note that locally set tidy:true is ignored if ALLOW_LOCAL_TIDY_TRUE is not set to true.
	if ctx.Config().IsEnvTrue("WITH_TIDY") \|\| (ctx.Config().IsEnvTrue("ALLOW_LOCAL_TIDY_TRUE") && Bool(tidy.Properties.Tidy)) {
	flags.NeedTidyFiles = true
	}

	// Add global WITH_TIDY_FLAGS and local tidy_flags.
	withTidyFlags := ctx.Config().Getenv("WITH_TIDY_FLAGS")
	if len(withTidyFlags) > 0 {
	flags.TidyFlags = append(flags.TidyFlags, withTidyFlags)
	}
	esc := checkNinjaAndShellEscapeList
	flags.TidyFlags = append(flags.TidyFlags, esc(ctx, "tidy_flags", tidy.Properties.Tidy_flags)...)
	// If TidyFlags does not contain -header-filter, add default header filter.
	// Find the substring because the flag could also appear as --header-filter=...
	// and with or without single or double quotes.
	if !android.SubstringInList(flags.TidyFlags, "-header-filter=") {
	defaultDirs := ctx.Config().Getenv("DEFAULT_TIDY_HEADER_DIRS")
	headerFilter := "-header-filter="
	// Default header filter should include only the module directory,
	// not the out/soong/.../ModuleDir/...
	// Otherwise, there will be too many warnings from generated files in out/...
	// If a module wants to see warnings in the generated source files,
	// it should specify its own -header-filter flag.
	if defaultDirs == "" {
	headerFilter += "^" + ctx.ModuleDir() + "/"
	} else {
	headerFilter += "\"(^" + ctx.ModuleDir() + "/\|" + defaultDirs + ")\""
	}
	flags.TidyFlags = append(flags.TidyFlags, headerFilter)
	}
	// Work around RBE bug in parsing clang-tidy flags, replace "--flag" with "-flag".
	// Some C/C++ modules added local tidy flags like --header-filter= and --extra-arg-before=.
	doubleDash := regexp.MustCompile("^('?)--(.*)$")
	for i, s := range flags.TidyFlags {
	flags.TidyFlags[i] = doubleDash.ReplaceAllString(s, "$1-$2")
	}

	// If clang-tidy is not enabled globally, add the -quiet flag.
	if !ctx.Config().ClangTidy() {
	flags.TidyFlags = append(flags.TidyFlags, "-quiet")
	flags.TidyFlags = append(flags.TidyFlags, "-extra-arg-before=-fno-caret-diagnostics")
	}

	for _, f := range config.TidyExtraArgFlags() {
	flags.TidyFlags = append(flags.TidyFlags, "-extra-arg-before="+f)
	}

	tidyChecks := "-checks="
	if checks := ctx.Config().TidyChecks(); len(checks) > 0 {
	tidyChecks += checks
	} else {
	tidyChecks += config.TidyChecksForDir(ctx.ModuleDir())
	}
	if len(tidy.Properties.Tidy_checks) > 0 {
	// If Tidy_checks contains "-", ignore all checks before "-".
	localChecks := tidy.Properties.Tidy_checks
	ignoreGlobalChecks := false
	for n, check := range tidy.Properties.Tidy_checks {
	if check == "-*" {
	ignoreGlobalChecks = true
	localChecks = tidy.Properties.Tidy_checks[n:]
	}
	}
	if ignoreGlobalChecks {
	tidyChecks = "-checks=" + strings.Join(esc(ctx, "tidy_checks",
	config.ClangRewriteTidyChecks(localChecks)), ",")
	} else {
	tidyChecks = tidyChecks + "," + strings.Join(esc(ctx, "tidy_checks",
	config.ClangRewriteTidyChecks(localChecks)), ",")
	}
	}
	tidyChecks = tidyChecks + config.TidyGlobalNoChecks()
	if ctx.Windows() {
	// https://b.corp.google.com/issues/120614316
	// mingw32 has cert-dcl16-c warning in NO_ERROR,
	// which is used in many Android files.
	tidyChecks += ",-cert-dcl16-c"
	}

	flags.TidyFlags = append(flags.TidyFlags, tidyChecks)

	// Embedding -warnings-as-errors in tidy_flags is error-prone.
	// It should be replaced with the tidy_checks_as_errors list.
	for i, s := range flags.TidyFlags {
	if strings.Contains(s, "-warnings-as-errors=") {
	if NoWarningsAsErrorsInTidyFlags {
	ctx.PropertyErrorf("tidy_flags", "should not contain "+s+"; use tidy_checks_as_errors instead.")
	} else {
	fmt.Printf("%s: warning: module %s's tidy_flags should not contain %s, which is replaced with -warnings-as-errors=-*; use tidy_checks_as_errors for your own as-error warnings instead.\n",
	ctx.BlueprintsFile(), ctx.ModuleName(), s)
	flags.TidyFlags[i] = "-warnings-as-errors=-*"
	}
	break // there is at most one -warnings-as-errors
	}
	}
	// Default clang-tidy flags does not contain -warning-as-errors.
	// If a module has tidy_checks_as_errors, add the list to -warnings-as-errors
	// and then append the TidyGlobalNoErrorChecks.
	if len(tidy.Properties.Tidy_checks_as_errors) > 0 {
	tidyChecksAsErrors := "-warnings-as-errors=" +
	strings.Join(esc(ctx, "tidy_checks_as_errors", tidy.Properties.Tidy_checks_as_errors), ",") +
	config.TidyGlobalNoErrorChecks()
	flags.TidyFlags = append(flags.TidyFlags, tidyChecksAsErrors)
	}
	return flags
	}

	func init() {
	android.RegisterSingletonType("tidy_phony_targets", TidyPhonySingleton)
	}

	// This TidyPhonySingleton generates both tidy-* and obj-* phony targets for C/C++ files.
	func TidyPhonySingleton() android.Singleton {
	return &tidyPhonySingleton{}
	}

	type tidyPhonySingleton struct{}

	// Given a final module, add its tidy/obj phony targets to tidy/objModulesInDirGroup.
	func collectTidyObjModuleTargets(ctx android.SingletonContext, module android.Module,
	tidyModulesInDirGroup, objModulesInDirGroup map[string]map[string]android.Paths) {
	allObjFileGroups := make(map[string]android.Paths) // variant group name => obj file Paths
	allTidyFileGroups := make(map[string]android.Paths) // variant group name => tidy file Paths
	subsetObjFileGroups := make(map[string]android.Paths) // subset group name => obj file Paths
	subsetTidyFileGroups := make(map[string]android.Paths) // subset group name => tidy file Paths

	// (1) Collect all obj/tidy files into OS-specific groups.
	ctx.VisitAllModuleVariants(module, func(variant android.Module) {
	if ctx.Config().KatiEnabled() && android.ShouldSkipAndroidMkProcessing(variant) {
	return
	}
	if m, ok := variant.(*Module); ok {
	osName := variant.Target().Os.Name
	addToOSGroup(osName, m.objFiles, allObjFileGroups, subsetObjFileGroups)
	addToOSGroup(osName, m.tidyFiles, allTidyFileGroups, subsetTidyFileGroups)
	}
	})

	// (2) Add an all-OS group, with "" or "subset" name, to include all os-specific phony targets.
	addAllOSGroup(ctx, module, allObjFileGroups, "", "obj")
	addAllOSGroup(ctx, module, allTidyFileGroups, "", "tidy")
	addAllOSGroup(ctx, module, subsetObjFileGroups, "subset", "obj")
	addAllOSGroup(ctx, module, subsetTidyFileGroups, "subset", "tidy")

	tidyTargetGroups := make(map[string]android.Path)
	objTargetGroups := make(map[string]android.Path)
	genObjTidyPhonyTargets(ctx, module, "obj", allObjFileGroups, objTargetGroups)
	genObjTidyPhonyTargets(ctx, module, "obj", subsetObjFileGroups, objTargetGroups)
	genObjTidyPhonyTargets(ctx, module, "tidy", allTidyFileGroups, tidyTargetGroups)
	genObjTidyPhonyTargets(ctx, module, "tidy", subsetTidyFileGroups, tidyTargetGroups)

	moduleDir := ctx.ModuleDir(module)
	appendToModulesInDirGroup(tidyTargetGroups, moduleDir, tidyModulesInDirGroup)
	appendToModulesInDirGroup(objTargetGroups, moduleDir, objModulesInDirGroup)
	}

	func (m *tidyPhonySingleton) GenerateBuildActions(ctx android.SingletonContext) {
	// For tidy-* directory phony targets, there are different variant groups.
	// tidyModulesInDirGroup[G][D] is for group G, directory D, with Paths
	// of all phony targets to be included into direct dependents of tidy-D_G.
	tidyModulesInDirGroup := make(map[string]map[string]android.Paths)
	// Also for obj-* directory phony targets.
	objModulesInDirGroup := make(map[string]map[string]android.Paths)

	// Collect tidy/obj targets from the 'final' modules.
	ctx.VisitAllModules(func(module android.Module) {
	if module == ctx.FinalModule(module) {
	collectTidyObjModuleTargets(ctx, module, tidyModulesInDirGroup, objModulesInDirGroup)
	}
	})

	suffix := ""
	if ctx.Config().KatiEnabled() {
	suffix = "-soong"
	}
	generateObjTidyPhonyTargets(ctx, suffix, "obj", objModulesInDirGroup)
	generateObjTidyPhonyTargets(ctx, suffix, "tidy", tidyModulesInDirGroup)
	}

	// The name for an obj/tidy module variant group phony target is Name_group-obj/tidy,
	func objTidyModuleGroupName(module android.Module, group string, suffix string) string {
	if group == "" {
	return module.Name() + "-" + suffix
	}
	return module.Name() + "_" + group + "-" + suffix
	}

	// Generate obj-* or tidy-* phony targets.
	func generateObjTidyPhonyTargets(ctx android.SingletonContext, suffix string, prefix string, objTidyModulesInDirGroup map[string]map[string]android.Paths) {
	// For each variant group, create a <prefix>-<directory>_group target that
	// depends on all subdirectories and modules in the directory.
	for group, modulesInDir := range objTidyModulesInDirGroup {
	groupSuffix := ""
	if group != "" {
	groupSuffix = "_" + group
	}
	mmTarget := func(dir string) string {
	return prefix + "-" + strings.Replace(filepath.Clean(dir), "/", "-", -1) + groupSuffix
	}
	dirs, topDirs := android.AddAncestors(ctx, modulesInDir, mmTarget)
	// Create a <prefix>-soong_group target that depends on all <prefix>-dir_group of top level dirs.
	var topDirPaths android.Paths
	for _, dir := range topDirs {
	topDirPaths = append(topDirPaths, android.PathForPhony(ctx, mmTarget(dir)))
	}
	ctx.Phony(prefix+suffix+groupSuffix, topDirPaths...)
	// Create a <prefix>-dir_group target that depends on all targets in modulesInDir[dir]
	for _, dir := range dirs {
	if dir != "." && dir != "" {
	ctx.Phony(mmTarget(dir), modulesInDir[dir]...)
	}
	}
	}
	}

	// Append (obj\|tidy)TargetGroups[group] into (obj\|tidy)ModulesInDirGroups[group][moduleDir].
	func appendToModulesInDirGroup(targetGroups map[string]android.Path, moduleDir string, modulesInDirGroup map[string]map[string]android.Paths) {
	for group, phonyPath := range targetGroups {
	if _, found := modulesInDirGroup[group]; !found {
	modulesInDirGroup[group] = make(map[string]android.Paths)
	}
	modulesInDirGroup[group][moduleDir] = append(modulesInDirGroup[group][moduleDir], phonyPath)
	}
	}

	// Add given files to the OS group and subset group.
	func addToOSGroup(osName string, files android.Paths, allGroups, subsetGroups map[string]android.Paths) {
	if len(files) > 0 {
	subsetName := osName + "_subset"
	allGroups[osName] = append(allGroups[osName], files...)
	// Now include only the first variant in the subsetGroups.
	// If clang and clang-tidy get faster, we might include more variants.
	if _, found := subsetGroups[subsetName]; !found {
	subsetGroups[subsetName] = files
	}
	}
	}

	// Add an all-OS group, with groupName, to include all os-specific phony targets.
	func addAllOSGroup(ctx android.SingletonContext, module android.Module, phonyTargetGroups map[string]android.Paths, groupName string, objTidyName string) {
	if len(phonyTargetGroups) > 0 {
	var targets android.Paths
	for group, _ := range phonyTargetGroups {
	targets = append(targets, android.PathForPhony(ctx, objTidyModuleGroupName(module, group, objTidyName)))
	}
	phonyTargetGroups[groupName] = targets
	}
	}

	// Create one phony targets for each group and add them to the targetGroups.
	func genObjTidyPhonyTargets(ctx android.SingletonContext, module android.Module, objTidyName string, fileGroups map[string]android.Paths, targetGroups map[string]android.Path) {
	for group, files := range fileGroups {
	groupName := objTidyModuleGroupName(module, group, objTidyName)
	ctx.Phony(groupName, files...)
	targetGroups[group] = android.PathForPhony(ctx, groupName)
	}
	}