Merge branch 'mysql-8.4' into mysql-trunk

Change-Id: Ie82c40386c39358ce971cf87b7c801f7920a27ab

Author: weigon

router/src/mysql_protocol/include/mysqlrouter/classic_protocol_codec_message.h

@@ -388,13 +388,16 @@ class Codec<borrowable::message::server::Ok<Borrowed>>
       }
     }
 
-    if (this->caps().test(capabilities::pos::session_track)) {
+    // if there is only empty "message" or "session-data", skip the rest.
+    const bool has_session_track_cap =
+        this->caps().test(capabilities::pos::session_track);
+
+    if (!v_.message().empty() || has_session_track_cap) {
       accu.step(bw::VarString<Borrowed>(v_.message()));
-      if (v_.status_flags().test(status::pos::session_state_changed)) {
+      if (has_session_track_cap &&
+          v_.status_flags().test(status::pos::session_state_changed)) {
         accu.step(bw::VarString<Borrowed>(v_.session_changes()));
       }
-    } else {
-      accu.step(bw::String<Borrowed>(v_.message()));
     }
 
     return accu.result();
@@ -460,24 +463,20 @@ class Codec<borrowable::message::server::Ok<Borrowed>>
       }
     }
 
-    stdx::expected<bw::String<Borrowed>, std::error_code> message_res;
     stdx::expected<bw::VarString<Borrowed>, std::error_code>
         session_changes_res;
-    if (caps[capabilities::pos::session_track]) {
-      // if there is more data.
-      const auto var_message_res =
-          accu.template try_step<bw::VarString<Borrowed>>();
-      if (var_message_res) {
-        // set the message from the var-string
-        message_res = var_message_res.value();
-      }
-
-      if (status_flags_res->value() &
-          status::session_state_changed.to_ulong()) {
-        session_changes_res = accu.template step<bw::VarString<Borrowed>>();
+    // if there is more data.
+    auto message_res = accu.template try_step<bw::VarString<Borrowed>>();
+    if (message_res) {
+      if (caps[capabilities::pos::session_track]) {
+        if (status_flags_res->value() &
+            status::session_state_changed.to_ulong()) {
+          session_changes_res = accu.template step<bw::VarString<Borrowed>>();
+        }
       }
     } else {
-      message_res = accu.template step<bw::String<Borrowed>>();
+      // no message field == empty message.
+      message_res = {};
     }
 
     if (!accu.result()) return stdx::unexpected(accu.result().error());

router/src/mysql_protocol/tests/test_classic_protocol_message.cc

@@ -138,6 +138,21 @@ const CodecParam<classic_protocol::message::server::Ok>
          {1, 3, classic_protocol::status::autocommit, 4},
          classic_protocol::capabilities::protocol_41,
          {0x00, 0x01, 0x03, 0x02, 0x00, 0x04, 0x00}},
+        {"with_message",
+         {
+             0x01,                                        // affected
+             0x00,                                        // last-insert-id
+             classic_protocol::status::autocommit,        // status
+             4,                                           // warning-count
+             "Rows matched: 1  Changed: 0  Warnings: 0",  // message
+             {},                                          // no session-info
+         },
+         classic_protocol::capabilities::protocol_41,
+         {0x00, 0x01, 0x00, 0x02, 0x00, 0x04, 0x00, 0x28, 0x52, 0x6f,
+          0x77, 0x73, 0x20, 0x6d, 0x61, 0x74, 0x63, 0x68, 0x65, 0x64,
+          0x3a, 0x20, 0x31, 0x20, 0x20, 0x43, 0x68, 0x61, 0x6e, 0x67,
+          0x65, 0x64, 0x3a, 0x20, 0x30, 0x20, 0x20, 0x57, 0x61, 0x72,
+          0x6e, 0x69, 0x6e, 0x67, 0x73, 0x3a, 0x20, 0x30}},
         {"with_session_state_info",
          {1,
           3,