Fix RESP3 double parsing returning positive INF for -inf (#1716)

parseDouble() returned positive INF for the RESP3 payload ',-inf',
inverting the sign. The value is reachable with protocol=3, for
example ZSCORE on a member whose score is -inf.

The existing infinity test asserted only is_infinite(), which cannot
detect the sign inversion, so it now checks exact values.

NaN payloads keep their current behavior; that is addressed
separately.

CHANGELOG.md

@@ -4,6 +4,7 @@
 ### Added
 ### Changed
 ### Fixed
+- Fixed RESP3 double parsing returning positive `INF` for `-inf` payloads (#1716)
 
 ## v3.6.0 (2026-08-14)
 ### Added

src/Protocol/Parser/Strategy/Resp3Strategy.php

@@ -63,10 +63,14 @@ class Resp3Strategy extends Resp2Strategy
      */
     protected function parseDouble(string $string): float
     {
-        if ($string === 'inf' || $string === '-inf') {
+        if ($string === 'inf') {
             return INF;
         }
 
+        if ($string === '-inf') {
+            return -INF;
+        }
+
         return (float) $string;
     }
 

tests/Predis/Protocol/Parser/Strategy/Resp3StrategyTest.php

@@ -60,11 +60,11 @@ class Resp3StrategyTest extends PredisTestCase
      * @param  string $data
      * @return void
      */
-    public function testParseDataReturnsFloatInfinityOnInfinityOrNegativeInfinity(string $data): void
+    public function testParseDataReturnsFloatInfinityOnInfinityOrNegativeInfinity(string $data, float $expectedValue): void
     {
         $actualResponse = $this->strategy->parseData($data);
 
-        $this->assertInfinite($actualResponse);
+        $this->assertSame($expectedValue, $actualResponse);
     }
 
     /**
@@ -166,8 +166,8 @@ class Resp3StrategyTest extends PredisTestCase
     public function infinityProvider(): array
     {
         return [
-            'positive infinity' => [",inf\r\n"],
-            'negative infinity' => [",-inf\r\n"],
+            'positive infinity' => [",inf\r\n", INF],
+            'negative infinity' => [",-inf\r\n", -INF],
         ];
     }