From a37ccbfb28d16428247b3ac049f8804020aaf3eb Mon Sep 17 00:00:00 2001
From: Vladislav <vlad@dragonflydb.io>
Date: Wed, 8 Mar 2023 19:51:01 +0300
Subject: [PATCH] fix(core): Auto cast doubles to ints in lua scripts (#922)

fix(core): Auto convert double to integers in lua scripts
---
 src/core/interpreter.cc  | 17 ++++++++++++-----
 src/server/multi_test.cc | 10 ++++++++++
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/core/interpreter.cc b/src/core/interpreter.cc
index 4eae482c4..69cc8c167 100644
--- a/src/core/interpreter.cc
+++ b/src/core/interpreter.cc
@@ -84,13 +84,20 @@ void RedisTranslator::OnString(std::string_view str) {
   ArrayPost();
 }
 
-// Doubles are not supported by Redis, however we can support them.
-// Here is the use-case:
-// local foo = redis.call('zscore', 'myzset', 'one')
-// assert(type(foo) == "number")
 void RedisTranslator::OnDouble(double d) {
+  static constexpr double kConvertEps = std::numeric_limits<double>::epsilon();
+
+  double fractpart, intpart;
+  fractpart = modf(d, &intpart);
+
   ArrayPre();
-  lua_pushnumber(lua_, d);
+
+  // Convert to integer when possible to allow converting to string without trailing zeros.
+  if (abs(fractpart) < kConvertEps && intpart < std::numeric_limits<lua_Integer>::max() &&
+      intpart > std::numeric_limits<lua_Integer>::min())
+    lua_pushinteger(lua_, static_cast<lua_Integer>(d));
+  else
+    lua_pushnumber(lua_, d);
   ArrayPost();
 }
 
diff --git a/src/server/multi_test.cc b/src/server/multi_test.cc
index 1774c3f1b..915ecfdd6 100644
--- a/src/server/multi_test.cc
+++ b/src/server/multi_test.cc
@@ -381,6 +381,16 @@ TEST_F(MultiTest, Eval) {
   ASSERT_THAT(resp, ArrLen(3));
   const auto& arr = resp.GetVec();
   EXPECT_THAT(arr, ElementsAre("a", "b", "c"));
+
+  Run({"zadd", "z1", "123", "a", "12345678912345", "b", "12.5", "c"});
+  const char* kGetScore = "return redis.call('ZSCORE', KEYS[1], ARGV[1]) .. '-works'";
+
+  resp = Run({"eval", kGetScore, "1", "z1", "a"});
+  EXPECT_EQ(resp, "123-works");
+  resp = Run({"eval", kGetScore, "1", "z1", "b"});
+  EXPECT_EQ(resp, "12345678912345-works");
+  resp = Run({"eval", kGetScore, "1", "z1", "c"});
+  EXPECT_EQ(resp, "12.5-works");
 }
 
 TEST_F(MultiTest, Watch) {