Better error message for missing edition or syntax at the first line of proto files.

PiperOrigin-RevId: 842907062

Author: protobuf-github-bot

src/google/protobuf/compiler/parser.cc

@@ -654,8 +654,8 @@ bool Parser::ParseSyntaxIdentifier(const FileDescriptorProto* file,
     has_edition = true;
   } else {
     DO(Consume("syntax",
-               "File must begin with a syntax statement, e.g. 'syntax = "
-               "\"proto2\";'."));
+               "File must begin with an edition or syntax statement, e.g."
+               " 'edition = \"2023\";'."));
   }
 
   DO(Consume("="));

src/google/protobuf/compiler/parser_unittest.cc

@@ -1198,8 +1198,8 @@ TEST_F(ParseMessageTest, CanHandleErrorOnFirstToken) {
   ExpectHasEarlyExitErrors(
       "/",
       "0:0: Expected top-level statement (e.g. \"message\").\n"
-      "0:0: File must begin with a syntax statement, e.g. 'syntax = "
-      "\"proto2\";'.\n");
+      "0:0: File must begin with an edition or syntax statement, "
+      "e.g. 'edition = \"2023\";'.\n");
 }
 
 // ===================================================================
@@ -1562,9 +1562,10 @@ typedef ParserTest ParseErrorTest;
 
 TEST_F(ParseErrorTest, MissingSyntaxIdentifier) {
   require_syntax_identifier_ = true;
-  ExpectHasEarlyExitErrors("message TestMessage {}",
-                           "0:0: File must begin with a syntax statement, e.g. "
-                           "'syntax = \"proto2\";'.\n");
+  ExpectHasEarlyExitErrors(
+      "message TestMessage {}",
+      "0:0: File must begin with an edition or syntax statement, e.g. "
+      "'edition = \"2023\";'.\n");
   EXPECT_EQ("", parser_->GetSyntaxIdentifier());
 }