From 3de1b5c59a9c16748186705f0f8afe6172c9a00b Mon Sep 17 00:00:00 2001
From: He-Pin <hepin1989@gmail.com>
Date: Mon, 29 Jun 2026 06:09:37 +0800
Subject: [PATCH] fix: preserve negative zero in std.round

---
 sjsonnet/src/sjsonnet/stdlib/MathModule.scala     |  3 ++-
 .../round_negative_zero_sign.jsonnet              | 15 +++++++++++++++
 .../round_negative_zero_sign.jsonnet.golden       |  9 +++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet
 create mode 100644 sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet.golden

diff --git a/sjsonnet/src/sjsonnet/stdlib/MathModule.scala b/sjsonnet/src/sjsonnet/stdlib/MathModule.scala
index 950f7bf3..65612cf8 100644
--- a/sjsonnet/src/sjsonnet/stdlib/MathModule.scala
+++ b/sjsonnet/src/sjsonnet/stdlib/MathModule.scala
@@ -318,7 +318,8 @@ object MathModule extends AbstractFunctionModule {
       // adding 0.5 would invoke IEEE 754 round-to-even and produce the wrong
       // result for odd inputs (e.g. 2^53 - 1). Short-circuit to avoid it.
       if (x != x || math.abs(x) >= 4503599627370496.0) x
-      else if (x >= 0) math.floor(x + 0.5)
+      else if (x == 0) x
+      else if (x > 0) math.floor(x + 0.5)
       else math.ceil(x - 0.5)
     },
     /**
diff --git a/sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet b/sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet
new file mode 100644
index 00000000..dcdb6a6c
--- /dev/null
+++ b/sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet
@@ -0,0 +1,15 @@
+{
+  // round(-0) should preserve negative zero sign
+  roundNegZero: std.round(-0),
+  // round(0) should stay positive zero
+  roundPosZero: std.round(0),
+  // round(-0.4) should produce -0
+  roundNegSmall: std.round(-0.4),
+  // round(0.5) should produce 1
+  roundHalfUp: std.round(0.5),
+  // round(-0.5) should produce -1
+  roundNegHalf: std.round(-0.5),
+  // atan2 verifies sign of zero
+  signNegZero: std.atan2(std.round(-0), -1) < 0,
+  signPosZero: std.atan2(std.round(0), -1) > 0,
+}
diff --git a/sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet.golden b/sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet.golden
new file mode 100644
index 00000000..1fca92fc
--- /dev/null
+++ b/sjsonnet/test/resources/new_test_suite/round_negative_zero_sign.jsonnet.golden
@@ -0,0 +1,9 @@
+{
+   "roundHalfUp": 1,
+   "roundNegHalf": -1,
+   "roundNegSmall": -0,
+   "roundNegZero": -0,
+   "roundPosZero": 0,
+   "signNegZero": true,
+   "signPosZero": true
+}