Revert "Various fixups to warnings flags (#9344)" (#10037)

This reverts commit 448d421.

Unfortunately we have to revert this because we're finding that it
introduces too much new build log spam for existing proto files that are
out of compliance with the warnings. We might be able to roll it forward
again if we can figure out a way to do so without so many new log
messages.

src/google/protobuf/compiler/command_line_interface_unittest.cc

@@ -1217,8 +1217,7 @@ TEST_F(CommandLineInterfaceTest, InsertWithAnnotationFixup) {
       "--plug_out=insert_endlines=test_generator,test_plugin:$tmpdir "
       "--proto_path=$tmpdir foo.proto");
 
-  ExpectWarningSubstring(
-      "foo.proto:2:36: warning: Message name should be in UpperCamelCase.");
+  ExpectNoErrors();
   CheckGeneratedAnnotations("test_generator", "foo.proto");
   CheckGeneratedAnnotations("test_plugin", "foo.proto");
 }
@@ -2372,21 +2371,6 @@ TEST_F(CommandLineInterfaceTest, Warnings) {
   ExpectErrorSubstring("foo.proto:2:1: warning: Import bar.proto is unused.");
 }
 
-TEST_F(CommandLineInterfaceTest, ParserWarnings) {
-  // Test that parser warnings are propagated. See #9343.
-
-  CreateTempFile("foo.proto",
-                 "syntax = \"proto2\";\n"
-                 "message bad_to_the_bone {};\n");
-
-  Run("protocol_compiler --test_out=$tmpdir "
-      "--proto_path=$tmpdir foo.proto");
-  ExpectCapturedStderrSubstringWithZeroReturnCode(
-      "foo.proto:2:25: warning: Message name should be in UpperCamelCase. "
-      "Found: bad_to_the_bone. "
-      "See https://developers.google.com/protocol-buffers/docs/style");
-}
-
 // -------------------------------------------------------------------
 // Flag parsing tests
 
@@ -2707,6 +2691,7 @@ TEST_P(EncodeDecodeTest, Encode) {
   EXPECT_TRUE(Run(args + " --encode=protobuf_unittest.TestAllTypes"));
   ExpectStdoutMatchesBinaryFile(TestUtil::GetTestDataPath(
       "third_party/protobuf/testdata/golden_message_oneof_implemented"));
+  ExpectStderrMatchesText("");
 }
 
 TEST_P(EncodeDecodeTest, Decode) {
@@ -2718,6 +2703,7 @@ TEST_P(EncodeDecodeTest, Decode) {
   ExpectStdoutMatchesTextFile(TestUtil::GetTestDataPath(
       "third_party/protobuf/"
       "testdata/text_format_unittest_data_oneof_implemented.txt"));
+  ExpectStderrMatchesText("");
 }
 
 TEST_P(EncodeDecodeTest, Partial) {
@@ -2726,7 +2712,7 @@ TEST_P(EncodeDecodeTest, Partial) {
       Run(TestUtil::MaybeTranslatePath("net/proto2/internal/unittest.proto") +
           " --encode=protobuf_unittest.TestRequired"));
   ExpectStdoutMatchesText("");
-  ExpectStderrContainsText(
+  ExpectStderrMatchesText(
       "warning:  Input message is missing required fields:  a, b, c\n");
 }
 
@@ -2750,7 +2736,7 @@ TEST_P(EncodeDecodeTest, UnknownType) {
       Run(TestUtil::MaybeTranslatePath("net/proto2/internal/unittest.proto") +
           " --encode=NoSuchType"));
   ExpectStdoutMatchesText("");
-  ExpectStderrContainsText("Type not defined: NoSuchType\n");
+  ExpectStderrMatchesText("Type not defined: NoSuchType\n");
 }
 
 TEST_P(EncodeDecodeTest, ProtoParseError) {
@@ -2775,6 +2761,7 @@ TEST_P(EncodeDecodeTest, EncodeDeterministicOutput) {
       args + " --encode=protobuf_unittest.TestAllTypes --deterministic_output"));
   ExpectStdoutMatchesBinaryFile(TestUtil::GetTestDataPath(
       "third_party/protobuf/testdata/golden_message_oneof_implemented"));
+  ExpectStderrMatchesText("");
 }
 
 TEST_P(EncodeDecodeTest, DecodeDeterministicOutput) {

src/google/protobuf/compiler/importer.cc

@@ -105,12 +105,6 @@ class SourceTreeDescriptorDatabase::SingleFileErrorCollector
     had_errors_ = true;
   }
 
-  void AddWarning(int line, int column, const std::string& message) override {
-    if (multi_file_error_collector_ != NULL) {
-      multi_file_error_collector_->AddWarning(filename_, line, column, message);
-    }
-  }
-
  private:
   std::string filename_;
   MultiFileErrorCollector* multi_file_error_collector_;

src/google/protobuf/compiler/parser.cc

@@ -643,11 +643,10 @@ bool Parser::Parse(io::Tokenizer* input, FileDescriptorProto* file) {
       // Store the syntax into the file.
       if (file != nullptr) file->set_syntax(syntax_identifier_);
     } else if (!stop_after_syntax_identifier_) {
-      AddWarning(
-        "No syntax specified. Please use 'syntax = \"proto2\";' or "
-        "'syntax = \"proto3\";' to specify a syntax version. "
-        "(Defaulted to proto2 syntax.)"
-      );
+      GOOGLE_LOG(WARNING) << "No syntax specified for the proto file: " << file->name()
+                   << ". Please use 'syntax = \"proto2\";' "
+                   << "or 'syntax = \"proto3\";' to specify a syntax "
+                   << "version. (Defaulted to proto2 syntax.)";
       syntax_identifier_ = "proto2";
     }
 
@@ -1020,8 +1019,7 @@ bool Parser::ParseMessageFieldNoLabel(
     location.RecordLegacyLocation(field, DescriptorPool::ErrorCollector::NAME);
     DO(ConsumeIdentifier(field->mutable_name(), "Expected field name."));
 
-    if (field->type() != FieldDescriptorProto::TYPE_GROUP &&
-        !IsLowerUnderscore(field->name())) {
+    if (!IsLowerUnderscore(field->name())) {
       AddWarning(
           "Field name should be lowercase. Found: " + field->name() +
           ". See: https://developers.google.com/protocol-buffers/docs/style");

src/google/protobuf/compiler/parser_unittest.cc

@@ -221,8 +221,9 @@ TEST_F(ParserTest, StopAfterSyntaxIdentifierWithErrors) {
 TEST_F(ParserTest, WarnIfSyntaxIdentifierOmmitted) {
   SetupParser("message A {}");
   FileDescriptorProto file;
+  CaptureTestStderr();
   EXPECT_TRUE(parser_->Parse(input_.get(), &file));
-  EXPECT_TRUE(error_collector_.warning_.find("No syntax specified") !=
+  EXPECT_TRUE(GetCapturedTestStderr().find("No syntax specified") !=
               std::string::npos);
 }