downgrade to a warning

src/google/protobuf/compiler/parser.cc

@@ -390,13 +390,16 @@ void Parser::AddError(const std::string& error) {
   AddError(input_->current().line, input_->current().column, error);
 }
 
-void Parser::AddWarning(const std::string& warning) {
+void Parser::AddWarning(int line, int column, const std::string& warning) {
   if (error_collector_ != nullptr) {
-    error_collector_->AddWarning(input_->current().line,
-                                 input_->current().column, warning);
+    error_collector_->AddWarning(line, column, warning);
   }
 }
 
+void Parser::AddWarning(const std::string& warning) {
+  AddWarning(input_->current().line, input_->current().column, warning);
+}
+
 // -------------------------------------------------------------------
 
 Parser::LocationRecorder::LocationRecorder(Parser* parser)
@@ -1736,7 +1739,7 @@ bool Parser::ParseReservedName(std::string* name, const char* error_message) {
   int col = input_->current().column;
   DO(ConsumeString(name, error_message));
   if (!io::Tokenizer::IsIdentifier(*name)) {
-    AddError(line, col, absl::StrFormat("Reserved name \"%s\" is not a valid identifier.", *name));
+    AddWarning(line, col, absl::StrFormat("Reserved name \"%s\" is not a valid identifier.", *name));
     return false;
   }
   return true;

src/google/protobuf/compiler/parser.h

@@ -213,6 +213,9 @@ class PROTOBUF_EXPORT Parser {
   // of the current token.
   void AddError(const std::string& error);
 
+  // Invokes error_collector_->AddWarning(), if error_collector_ is not NULL.
+  void AddWarning(int line, int column, const std::string& warning);
+
   // Invokes error_collector_->AddWarning() with the line and column number
   // of the current token.
   void AddWarning(const std::string& warning);

src/google/protobuf/compiler/parser_unittest.cc

@@ -147,6 +147,16 @@ class ParserTest : public testing::Test {
     EXPECT_EQ(io::Tokenizer::TYPE_END, input_->current().type);
   }
 
+  // Parse the text and expect that the given warnings are reported.
+  void ExpectHasWarnings(const char* text, const char* expected_warnings) {
+    SetupParser(text);
+    FileDescriptorProto file;
+    parser_->Parse(input_.get(), &file);
+    EXPECT_EQ(io::Tokenizer::TYPE_END, input_->current().type);
+    ASSERT_EQ("", error_collector_.text_);
+    EXPECT_EQ(expected_warnings, error_collector_.warning_);
+  }
+
   // Same as above but does not expect that the parser parses the complete
   // input.
   void ExpectHasEarlyExitErrors(const char* text, const char* expected_errors) {
@@ -1676,12 +1686,14 @@ TEST_F(ParseErrorTest, EnumReservedMissingQuotes) {
 }
 
 TEST_F(ParseErrorTest, EnumReservedInvalidIdentifier) {
-  ExpectHasErrors(
-      "enum TestEnum {\n"
-      "  FOO = 1;\n"
-      "  reserved \"foo bar\";\n"
-      "}\n",
-      "2:11: Reserved name \"foo bar\" is not a valid identifier.\n");
+  ExpectHasWarnings(
+      R"pb(
+      enum TestEnum {
+        FOO = 1;
+        reserved "foo bar";
+      }
+      )pb",
+      "3:17: Reserved name \"foo bar\" is not a valid identifier.\n");
 }
 
 // -------------------------------------------------------------------
@@ -1712,11 +1724,13 @@ TEST_F(ParseErrorTest, ReservedMissingQuotes) {
 }
 
 TEST_F(ParseErrorTest, ReservedInvalidIdentifier) {
-  ExpectHasErrors(
-      "message Foo {\n"
-      "  reserved \"foo bar\";\n"
-      "}\n",
-      "1:11: Reserved name \"foo bar\" is not a valid identifier.\n");
+  ExpectHasWarnings(
+      R"pb(
+      message Foo {
+        reserved "foo bar";
+      }
+      )pb",
+      "2:17: Reserved name \"foo bar\" is not a valid identifier.\n");
 }
 
 TEST_F(ParseErrorTest, ReservedNegativeNumber) {