Disallow -warnings-as-errors in tidy_flags

* Also remove the undocumented complicated
  experiment to overwrite local warnings-as-errors.

Bug: 229801437
Test: WITH_TIDY=1 make; make tidy-soong_subset
Change-Id: I2fb32146b4685ab9f5198724c15c303f799b7a14

cc/tidy.go

@@ -188,31 +188,14 @@ func (tidy *tidyFeature) flags(ctx ModuleContext, flags Flags) Flags {
 	tidyChecks = tidyChecks + ",-cert-err33-c"
 	flags.TidyFlags = append(flags.TidyFlags, tidyChecks)
 
-	if ctx.Config().IsEnvTrue("WITH_TIDY") {
-		// WITH_TIDY=1 enables clang-tidy globally. There could be many unexpected
-		// warnings from new checks and many local tidy_checks_as_errors and
-		// -warnings-as-errors can break a global build.
-		// So allow all clang-tidy warnings.
-		inserted := false
-		for i, s := range flags.TidyFlags {
-			if strings.Contains(s, "-warnings-as-errors=") {
-				// clang-tidy accepts only one -warnings-as-errors
-				// replace the old one
-				re := regexp.MustCompile(`'?-?-warnings-as-errors=[^ ]* *`)
-				newFlag := re.ReplaceAllString(s, "")
-				if newFlag == "" {
-					flags.TidyFlags[i] = "-warnings-as-errors=-*"
-				} else {
-					flags.TidyFlags[i] = newFlag + " -warnings-as-errors=-*"
-				}
-				inserted = true
-				break
-			}
+	// Embedding -warnings-as-errors in tidy_flags is error-prone.
+	// It should be replaced with the tidy_checks_as_errors list.
+	for _, s := range flags.TidyFlags {
+		if strings.Contains(s, "-warnings-as-errors=") {
+			ctx.PropertyErrorf("tidy_flags", "should not contain -warnings-as-errors, use tidy_checks_as_errors instead")
 		}
-		if !inserted {
-			flags.TidyFlags = append(flags.TidyFlags, "-warnings-as-errors=-*")
-		}
-	} else if len(tidy.Properties.Tidy_checks_as_errors) > 0 {
+	}
+	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), ",")
 		flags.TidyFlags = append(flags.TidyFlags, tidyChecksAsErrors)
 	}