Change default DEFAULT_TIDY_HEADER_DIRS to empty

* Default -header-filter will now contain only module directory.
  * In a clean build of aosp_x86_64-eng, this change can reduce
    the number of (duplicated) clang-tidy warnings by 77% or more.
* When compiled with WITH_TIDY=1, if DEFAULT_TIDY_HEADER_DIRS is
  not set, warnings from a header file will be shown only if
  the file is in a module's (sub)directory.
* Set DEFAULT_TIDY_HEADER_DIRS="bionic/|bootable/|build/|cts/|\
  dalvik/|developers/|development/|frameworks/|\
  libcore/|libnativehelper/|system/"
  will get before this change's -header-filter.
* Fix a bug: Default header-filter was not added when
  tidy_flags was defined in a module.
  With this fix, some incorrectly hidden header file tidy warnings
  will now show up.

Bug: 179530304
Test: make with WITH_TIDY=1 and various setting of DEFAULT_TIDY_HEADER_DIRS
Change-Id: Ia0c05349908a730862dae36be9a2dbe4f44fb6da

android/util.go

@@ -137,6 +137,16 @@ func HasAnyPrefix(s string, prefixList []string) bool {
 	return false
 }
 
+// Returns true if any string in the given list has the given substring.
+func SubstringInList(list []string, substr string) bool {
+	for _, s := range list {
+		if strings.Contains(s, substr) {
+			return true
+		}
+	}
+	return false
+}
+
 // Returns true if any string in the given list has the given prefix.
 func PrefixInList(list []string, prefix string) bool {
 	for _, s := range list {

cc/config/tidy.go

@@ -87,27 +87,11 @@ func init() {
 		}, ",")
 	})
 
-	// Give warnings to header files only in selected directories.
-	// Do not give warnings to external or vendor header files, which contain too
-	// many warnings.
+	// To reduce duplicate warnings from the same header files,
+	// header-filter will contain only the module directory and
+	// those specified by DEFAULT_TIDY_HEADER_DIRS.
 	pctx.VariableFunc("TidyDefaultHeaderDirs", func(ctx android.PackageVarContext) string {
-		if override := ctx.Config().Getenv("DEFAULT_TIDY_HEADER_DIRS"); override != "" {
-			return override
-		}
-		return strings.Join([]string{
-			"art/",
-			"bionic/",
-			"bootable/",
-			"build/",
-			"cts/",
-			"dalvik/",
-			"developers/",
-			"development/",
-			"frameworks/",
-			"libcore/",
-			"libnativehelper/",
-			"system/",
-		}, "|")
+		return ctx.Config().Getenv("DEFAULT_TIDY_HEADER_DIRS")
 	})
 
 	// Use WTIH_TIDY_FLAGS to pass extra global default clang-tidy flags.

cc/tidy.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/google/blueprint/proptools"
 
+	"android/soong/android"
 	"android/soong/cc/config"
 )
 
@@ -75,9 +76,17 @@ func (tidy *tidyFeature) flags(ctx ModuleContext, flags Flags) Flags {
 	}
 	esc := proptools.NinjaAndShellEscapeList
 	flags.TidyFlags = append(flags.TidyFlags, esc(tidy.Properties.Tidy_flags)...)
-	// If TidyFlags is empty, add default header filter.
-	if len(flags.TidyFlags) == 0 {
-		headerFilter := "-header-filter=\"(" + ctx.ModuleDir() + "|${config.TidyDefaultHeaderDirs})\""
+	// 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="
+		if defaultDirs == "" {
+			headerFilter += ctx.ModuleDir() + "/"
+		} else {
+			headerFilter += "\"(" + ctx.ModuleDir() + "/|" + defaultDirs + ")\""
+		}
 		flags.TidyFlags = append(flags.TidyFlags, headerFilter)
 	}