fix shallow copy, improve docs

Author: khvn26

Flagsmith.Engine/EvaluationContext/EvaluationContext.cs

@@ -37,9 +37,18 @@ public partial class EvaluationContext<SegmentMetadataT, FeatureMetadataT>
         [JsonProperty("segments", Required = Required.DisallowNull, NullValueHandling = NullValueHandling.Ignore)]
         public Dictionary<string, SegmentContext<SegmentMetadataT, FeatureMetadataT>> Segments { get; set; }
 
+
+        /// <summary>
+        /// Creates a copy of the EvaluationContext object
+        /// for internal use in the engine.
+        /// Optimised to avoid deep cloning where possible.
+        /// </summary>
+        /// <returns>EvaluationContext</returns>
         public EvaluationContext<SegmentMetadataT, FeatureMetadataT> Clone()
         {
-            return (EvaluationContext<SegmentMetadataT, FeatureMetadataT>)MemberwiseClone();
+            var clone = (EvaluationContext<SegmentMetadataT, FeatureMetadataT>)MemberwiseClone();
+            clone.Identity = clone.Identity?.Clone();
+            return clone;
         }
     }
 
@@ -166,6 +175,16 @@ public partial class IdentityContext
         /// </summary>
         [JsonProperty("traits", Required = Required.DisallowNull, NullValueHandling = NullValueHandling.Ignore)]
         public Dictionary<string, object> Traits { get; set; }
+
+        /// <summary>
+        /// Creates a copy of the IdentityContext object
+        /// for internal use in the engine.
+        /// </summary>
+        /// <returns>IdentityContext</returns>
+        public IdentityContext Clone()
+        {
+            return (IdentityContext)MemberwiseClone();
+        }
     }
 
     /// <summary>

Flagsmith.EngineTest/EngineTestV2.cs

@@ -62,5 +62,33 @@ public static IEnumerable<object[]> ExtractTestCaseFilenames()
             }
             return testCases;
         }
+
+        [Fact]
+        public void TestGetEvaluationResult_ShouldNotMutateOriginalContextIdentity()
+        {
+            // Arrange
+            var engine = new Engine();
+            var context = new EvaluationContext<object, object>
+            {
+                Environment = new EnvironmentContext
+                {
+                    Key = "test-env",
+                    Name = "Test Environment"
+                },
+                Identity = new IdentityContext
+                {
+                    Identifier = "user-123",
+                    Key = null  // Empty Key triggers the clone+mutate logic in GetEnrichedEvaluationContext
+                },
+                Features = new Dictionary<string, FeatureContext<object>>(),
+                Segments = new Dictionary<string, SegmentContext<object, object>>()
+            };
+
+            // Act
+            var result = engine.GetEvaluationResult(context);
+
+            // Assert: The original context's Identity.Key should still be null
+            Assert.Null(context.Identity.Key);
+        }
     }
-}
+}