fix: zdiff WITHSCORES param and resp3 response (#6013)

Author: BorysTheDev

src/server/zset_family.cc

@@ -2318,9 +2318,12 @@ void ZSetFamily::ZDiff(CmdArgList args, const CommandContext& cmd_cntx) {
     return;
   }
 
-  const bool with_scores = ArgS(args, args.size() - 1) == "WITHSCORES";
-  rb->StartArray(smvec.size() * (with_scores ? 2 : 1));
+  const bool with_scores = absl::EqualsIgnoreCase(ArgS(args, args.size() - 1), "WITHSCORES");
+  bool is_resp3 = rb->IsResp3();
+  rb->StartArray(smvec.size() * ((with_scores && !is_resp3) ? 2 : 1));
   for (const auto& [score, key] : smvec) {
+    if (is_resp3)
+      rb->StartArray(with_scores ? 2 : 1);
     rb->SendBulkString(key);
     if (with_scores) {
       rb->SendDouble(score);

src/server/zset_family_test.cc

@@ -1249,10 +1249,22 @@ TEST_F(ZSetFamilyTest, ZDiff) {
   resp = Run({"zdiff", "1", "z1", "WITHSCORES"});
   EXPECT_THAT(resp.GetVec(), ElementsAre("one", "1", "two", "2", "three", "3", "four", "4"));
 
-  resp = Run({"zdiff", "2", "z1", "z2", "WITHSCORES"});
+  resp = Run({"zdiff", "2", "z1", "z2", "withscores"});
   EXPECT_THAT(resp.GetVec(), ElementsAre("two", "2", "three", "3", "four", "4"));
 }
 
+TEST_F(ZSetFamilyTest, ZDiff_Resp3) {
+  Run({"hello", "3"});
+  EXPECT_EQ(4, CheckedInt({"zadd", "z1", "1", "one", "2", "two", "3", "three", "4", "four"}));
+
+  auto resp = Run({"zdiff", "1", "z1", "withscores"});
+  ASSERT_THAT(resp, ArrLen(4));
+  ASSERT_THAT(resp.GetVec()[0].GetVec(), ElementsAre("one", DoubleArg(1)));
+  ASSERT_THAT(resp.GetVec()[1].GetVec(), ElementsAre("two", DoubleArg(2)));
+  ASSERT_THAT(resp.GetVec()[2].GetVec(), ElementsAre("three", DoubleArg(3)));
+  ASSERT_THAT(resp.GetVec()[3].GetVec(), ElementsAre("four", DoubleArg(4)));
+}
+
 TEST_F(ZSetFamilyTest, ZDiffStoreError) {
   RespExpr resp;