fix: script error reply (#5776)

* fix: script error reply


Co-authored-by: Roman Gershman <[email protected]>

Author: BorysTheDev

src/server/dragonfly_test.cc

@@ -149,6 +149,17 @@ TEST_F(SingleThreadDflyEngineTest, GlobalSingleThread) {
   Run({"move", "a", "1"});
 }
 
+TEST_F(DflyEngineTest, LuaErrors) {
+  auto resp = Run({"eval", "return redis.error_reply('some error')", "0"});
+  EXPECT_THAT(resp, ErrArg("some error"));
+
+  resp = Run({"eval", "return redis.pcall('foo', 'bar')", "0"});
+  EXPECT_THAT(resp, ErrArg("ERR unknown command"));
+
+  resp = Run({"eval", "return redis.pcall('incrby', 'foo', 'bar')", "1"});
+  EXPECT_THAT(resp, ErrArg("ERR Number of keys can't be greater than number of args"));
+}
+
 TEST_F(DflyEngineTest, EvalResp) {
   auto resp = Run({"eval", "return 43", "0"});
   EXPECT_THAT(resp, IntArg(43));

src/server/main_service.cc

@@ -383,7 +383,11 @@ class EvalSerializer : public ObjectExplorer {
   }
 
   void OnError(string_view str) {
-    rb_->SendError(str);
+    if (!str.empty() && str.front() != '-') {
+      rb_->SendError(absl::StrCat("-", str));
+    } else {
+      rb_->SendError(str);
+    }
   }
 
  private:
@@ -411,7 +415,11 @@ void InterpreterReplier::PostItem() {
 void InterpreterReplier::SendError(string_view str, std::string_view type) {
   DCHECK(array_len_.empty());
   DVLOG(1) << "Lua/df_call error " << str;
-  explr_->OnError(str);
+  if (!str.empty() && str.front() != '-') {
+    explr_->OnError(absl::StrCat("-ERR ", str));
+  } else {
+    explr_->OnError(str);
+  }
 }
 
 void InterpreterReplier::SendSimpleString(string_view str) {