server: Enable lua legacy float response for RESP3 (#5754)

* server: Enable lua legacy float response for RESP3

Previously when the lua legacy float flag was set, doubles would be sent
as floats for RESP2 but for RESP3 this behavior was skipped. This
changeset extends the behavior to RESP3 as well.

Signed-off-by: Abhijat Malviya <abhijat@dragonflydb.io>

Author: abhijat

src/server/dragonfly_test.cc

@@ -837,7 +837,7 @@ TEST_F(DflyEngineTest, Latency) {
 
 TEST_F(DflyEngineTest, EvalBug2664) {
   absl::FlagSaver fs;
-  absl::SetFlag(&FLAGS_lua_resp2_legacy_float, true);
+  SetFlag(&FLAGS_lua_resp2_legacy_float, true);
 
   auto resp = Run({"eval", "return 42.9", "0"});
   EXPECT_THAT(resp, IntArg(42));
@@ -848,7 +848,7 @@ TEST_F(DflyEngineTest, EvalBug2664) {
   ASSERT_THAT(resp, ArrLen(14));
 
   resp = Run({"eval", "return 42.9", "0"});
-  EXPECT_THAT(resp, DoubleArg(42.9));
+  EXPECT_THAT(resp, IntArg(42));
 }
 
 TEST_F(DflyEngineTest, MemoryUsage) {

src/server/main_service.cc

@@ -348,11 +348,11 @@ class EvalSerializer : public ObjectExplorer {
   }
 
   void OnDouble(double d) final {
-    if (rb_->IsResp3() || !GetFlag(FLAGS_lua_resp2_legacy_float)) {
-      rb_->SendDouble(d);
-    } else {
-      long val = d >= 0 ? static_cast<long>(floor(d)) : static_cast<long>(ceil(d));
+    if (GetFlag(FLAGS_lua_resp2_legacy_float)) {
+      const long val = d >= 0 ? static_cast<long>(floor(d)) : static_cast<long>(ceil(d));
       rb_->SendLong(val);
+    } else {
+      rb_->SendDouble(d);
     }
   }