fix: RedisValue/RedisResult: cast to double should respect special values

docs/ReleaseNotes.md

@@ -8,6 +8,8 @@ Current package versions:
 
 ## Unreleased
 
+- Fix `RedisValue` special-value (NaN, Inf, etc) handling when casting from raw/string values to `double` ([#2950 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2950))
+
 ## 2.9.11
 
 - Add `HGETDEL`, `HGETEX` and `HSETEX` support ([#2863 by atakavci](https://github.com/StackExchange/StackExchange.Redis/pull/2863))

src/StackExchange.Redis/RedisValue.cs

@@ -656,6 +656,10 @@ public static explicit operator double(RedisValue value)
                 StorageType.Int64 => value.OverlappedValueInt64,
                 StorageType.UInt64 => value.OverlappedValueUInt64,
                 StorageType.Double => value.OverlappedValueDouble,
+                // special values like NaN/Inf are deliberately not handled by Simplify, but need to be considered for casting
+                StorageType.String when Format.TryParseDouble((string)value._objectOrSentinel!, out var d) => d,
+                StorageType.Raw when TryParseDouble(value._memory.Span, out var d) => d,
+                // anything else: fail
                 _ => throw new InvalidCastException($"Unable to cast from {value.Type} to double: '{value}'"),
             };
         }

tests/StackExchange.Redis.Tests/RedisResultTests.cs

@@ -150,4 +150,48 @@ public void SingleResultConvertibleDirectViaChangeType_TypeCode()
         Assert.StrictEqual(123f, Convert.ChangeType(value, TypeCode.Single));
         Assert.StrictEqual(123d, Convert.ChangeType(value, TypeCode.Double));
     }
+
+    [Theory]
+    [InlineData(ResultType.Double)]
+    [InlineData(ResultType.BulkString)]
+    [InlineData(ResultType.SimpleString)]
+    public void RedisResultParseNaN(ResultType resultType)
+    {
+        // https://github.com/redis/NRedisStack/issues/439
+        var value = RedisResult.Create("NaN", resultType);
+        Assert.True(double.IsNaN(value.AsDouble()));
+    }
+
+    [Theory]
+    [InlineData(ResultType.Double)]
+    [InlineData(ResultType.BulkString)]
+    [InlineData(ResultType.SimpleString)]
+    public void RedisResultParseInf(ResultType resultType)
+    {
+        // https://github.com/redis/NRedisStack/issues/439
+        var value = RedisResult.Create("inf", resultType);
+        Assert.True(double.IsPositiveInfinity(value.AsDouble()));
+    }
+
+    [Theory]
+    [InlineData(ResultType.Double)]
+    [InlineData(ResultType.BulkString)]
+    [InlineData(ResultType.SimpleString)]
+    public void RedisResultParsePlusInf(ResultType resultType)
+    {
+        // https://github.com/redis/NRedisStack/issues/439
+        var value = RedisResult.Create("+inf", resultType);
+        Assert.True(double.IsPositiveInfinity(value.AsDouble()));
+    }
+
+    [Theory]
+    [InlineData(ResultType.Double)]
+    [InlineData(ResultType.BulkString)]
+    [InlineData(ResultType.SimpleString)]
+    public void RedisResultParseMinusInf(ResultType resultType)
+    {
+        // https://github.com/redis/NRedisStack/issues/439
+        var value = RedisResult.Create("-inf", resultType);
+        Assert.True(double.IsNegativeInfinity(value.AsDouble()));
+    }
 }