Cpp bindings: Return false from Validator::Accept() on unrecognized message or invalid flags

mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl

Index: mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
index 5214df9cfcc6bfb2cc8645ce8c53ff5f9b5080f8..5831423ef07875459b3f6bff18f0a33c50352b29 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
@@ -227,16 +227,25 @@ bool {{class_name}}Stub::AcceptWithResponder(
 
 bool {{class_name}}RequestValidator::Accept(mojo::Message* message) {
 {%- if interface.methods %}
+  if (message->has_flag(mojo::internal::kMessageIsResponse)) {
+    ReportValidationError(
+        mojo::internal::VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINATION);
+    return false;
+  }
   switch (message->header()->name) {
 {%-   for method in interface.methods %}
     case internal::k{{class_name}}_{{method.name}}_Name: {
 {%-     if method.response_parameters != None %}
-      if (!message->has_flag(mojo::internal::kMessageExpectsResponse))
-        break;
+      if (!message->has_flag(mojo::internal::kMessageExpectsResponse)) {
+        ReportValidationError(
+            mojo::internal::VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINATION);
+        return false;
+      }
 {%-     else %}
-      if (message->has_flag(mojo::internal::kMessageExpectsResponse) ||
-          message->has_flag(mojo::internal::kMessageIsResponse)) {
-        break;
+      if (message->has_flag(mojo::internal::kMessageExpectsResponse)) {
+        ReportValidationError(
+            mojo::internal::VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINATION);
+        return false;
       }
 {%-     endif %}
       mojo::internal::BoundsChecker bounds_checker(
@@ -249,6 +258,12 @@ bool {{class_name}}RequestValidator::Accept(mojo::Message* message) {
       break;
     }
 {%-   endfor %}
+    default: {
+      // Unrecognized message.
+      ReportValidationError(
+          mojo::internal::VALIDATION_ERROR_MESSAGE_HEADER_UNKNOWN_METHOD);
+      return false;
+    }
   }
 {%- endif %}
 
@@ -264,11 +279,14 @@ bool {{class_name}}RequestValidator::Accept(mojo::Message* message) {
 
 bool {{class_name}}ResponseValidator::Accept(mojo::Message* message) {
 {%- if interface.methods %}
+  if (!message->has_flag(mojo::internal::kMessageIsResponse)) {
+    ReportValidationError(
+        mojo::internal::VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINATION);
+    return false;
+  }
   switch (message->header()->name) {
 {%-   for method in interface.methods if method.response_parameters != None %}
     case internal::k{{class_name}}_{{method.name}}_Name: {
-      if (!message->has_flag(mojo::internal::kMessageIsResponse))
-        break;
       mojo::internal::BoundsChecker bounds_checker(
           message->payload(), message->payload_num_bytes(),
           message->handles()->size());
@@ -279,6 +297,12 @@ bool {{class_name}}ResponseValidator::Accept(mojo::Message* message) {
       break;
     }
 {%-   endfor %}
+    default: {
+      // Unrecognized message.
+      ReportValidationError(
+          mojo::internal::VALIDATION_ERROR_MESSAGE_HEADER_UNKNOWN_METHOD);
+      return false;
+    }
   }
 {%- endif %}