Always report plugin support errors from protoc.

If a plugin doesn't support a feature used by a proto file, we can't trust any errors reported by that plugin.  We should always report these types of errors first.  There could be cases where the plugin doesn't correctly specify its support when it hits an error though, so we should *also* report any plugin errors to avoid masking them.

PiperOrigin-RevId: 639984803

src/google/protobuf/compiler/command_line_interface.cc

@@ -2872,23 +2872,24 @@ bool CommandLineInterface::GeneratePluginOutput(
   }
 
   // Check for errors.
-  if (!response.error().empty()) {
-    // Generator returned an error.
-    *error = response.error();
-    return false;
-  }
+  bool success = true;
   if (!EnforceProto3OptionalSupport(plugin_name, response.supported_features(),
                                     parsed_files)) {
-    return false;
+    success = false;
   }
   if (!EnforceEditionsSupport(plugin_name, response.supported_features(),
                               static_cast<Edition>(response.minimum_edition()),
                               static_cast<Edition>(response.maximum_edition()),
                               parsed_files)) {
-    return false;
+    success = false;
+  }
+  if (!response.error().empty()) {
+    // Generator returned an error.
+    *error = response.error();
+    success = false;
   }
 
-  return true;
+  return success;
 }
 
 bool CommandLineInterface::EncodeOrDecode(const DescriptorPool* pool) {

src/google/protobuf/compiler/command_line_interface_unittest.cc

@@ -1861,6 +1861,22 @@ TEST_F(CommandLineInterfaceTest, PluginNoEditionsSupport) {
       "code generator prefix-gen-plug hasn't been updated to support editions");
 }
 
+TEST_F(CommandLineInterfaceTest, PluginErrorAndNoEditionsSupport) {
+  CreateTempFile("foo.proto", R"schema(
+    edition = "2023";
+    message MockCodeGenerator_Error { }
+  )schema");
+
+  SetMockGeneratorTestCase("no_editions");
+  Run("protocol_compiler "
+      "--proto_path=$tmpdir foo.proto --plug_out=$tmpdir");
+
+  ExpectErrorSubstring(
+      "code generator prefix-gen-plug hasn't been updated to support editions");
+  ExpectErrorSubstring(
+      "--plug_out: foo.proto: Saw message type MockCodeGenerator_Error.");
+}
+
 TEST_F(CommandLineInterfaceTest, EditionDefaults) {
   CreateTempFile("google/protobuf/descriptor.proto",
                  google::protobuf::DescriptorProto::descriptor()->file()->DebugString());