Fix IdSpan equality violation: Create("") and default now correctly unequal

src/Orleans.Core.Abstractions/IDs/IdSpan.cs

@@ -94,7 +94,20 @@ private IdSpan(SerializationInfo info, StreamingContext context)
         public override bool Equals(object? obj) => obj is IdSpan kind && Equals(kind);
 
         /// <inheritdoc/>
-        public bool Equals(IdSpan obj) => _value == obj._value || _value.AsSpan().SequenceEqual(obj._value);
+        public bool Equals(IdSpan obj)
+        {
+            if (_value == obj._value)
+            {
+                return true;
+            }
+
+            if (_value is null || obj._value is null)
+            {
+                return false;
+            }
+
+            return _value.AsSpan().SequenceEqual(obj._value);
+        }
 
         /// <inheritdoc/>
         public override int GetHashCode() => _hashCode;
@@ -139,7 +152,20 @@ public void GetObjectData(SerializationInfo info, StreamingContext context)
         public static byte[]? UnsafeGetArray(IdSpan id) => id._value;
 
         /// <inheritdoc/>
-        public int CompareTo(IdSpan other) => _value.AsSpan().SequenceCompareTo(other._value.AsSpan());
+        public int CompareTo(IdSpan other)
+        {
+            if (_value is null)
+            {
+                return other._value is null ? 0 : -1;
+            }
+
+            if (other._value is null)
+            {
+                return 1;
+            }
+
+            return _value.AsSpan().SequenceCompareTo(other._value.AsSpan());
+        }
 
         /// <summary>
         /// Returns a string representation of this instance, decoding the value as UTF8.

test/NonSilo.Tests/IdSpanTests.cs

@@ -0,0 +1,123 @@
+using Orleans.Runtime;
+using Xunit;
+
+namespace NonSilo.Tests
+{
+    /// <summary>
+    /// Tests for IdSpan, a primitive type for identities representing a sequence of bytes.
+    /// Validates equality, hash code consistency, and proper handling of null vs empty arrays.
+    /// </summary>
+    [TestCategory("BVT")]
+    public class IdSpanTests
+    {
+        /// <summary>
+        /// Tests that IdSpan.Create(string.Empty) and default(IdSpan) are NOT equal.
+        /// They should have different internal states (empty array vs null) and should not be considered equal.
+        /// </summary>
+        [Fact]
+        public void IdSpan_CreateEmptyString_NotEqualToDefault()
+        {
+            IdSpan createdFromEmptyString = IdSpan.Create(string.Empty);
+            IdSpan defaultIdSpan = default;
+
+            Assert.NotEqual(createdFromEmptyString, defaultIdSpan);
+            Assert.False(createdFromEmptyString.Equals(defaultIdSpan));
+            Assert.False(createdFromEmptyString == defaultIdSpan);
+            Assert.True(createdFromEmptyString != defaultIdSpan);
+        }
+
+        /// <summary>
+        /// Tests that hash codes are consistent with equality.
+        /// If two IdSpans are equal, they must have the same hash code.
+        /// </summary>
+        [Fact]
+        public void IdSpan_HashCode_ConsistentWithEquality()
+        {
+            IdSpan id1 = IdSpan.Create("test");
+            IdSpan id2 = IdSpan.Create("test");
+            IdSpan id3 = IdSpan.Create("different");
+
+            // Equal objects must have equal hash codes
+            Assert.Equal(id1, id2);
+            Assert.Equal(id1.GetHashCode(), id2.GetHashCode());
+
+            // Not equal objects may have different hash codes (not required but expected)
+            Assert.NotEqual(id1, id3);
+        }
+
+        /// <summary>
+        /// Tests that default IdSpan has expected properties.
+        /// </summary>
+        [Fact]
+        public void IdSpan_Default_HasExpectedProperties()
+        {
+            IdSpan defaultIdSpan = default;
+
+            Assert.True(defaultIdSpan.IsDefault);
+            Assert.Equal(0, defaultIdSpan.GetHashCode());
+            Assert.Equal("", defaultIdSpan.ToString());
+        }
+
+        /// <summary>
+        /// Tests that IdSpan created from empty string has expected properties.
+        /// </summary>
+        [Fact]
+        public void IdSpan_CreateEmptyString_HasExpectedProperties()
+        {
+            IdSpan emptyStringIdSpan = IdSpan.Create(string.Empty);
+
+            Assert.True(emptyStringIdSpan.IsDefault);
+            Assert.Equal("", emptyStringIdSpan.ToString());
+            // Hash code should be computed from empty byte array, not 0
+            Assert.NotEqual(0, emptyStringIdSpan.GetHashCode());
+        }
+
+        /// <summary>
+        /// Tests that IdSpans with same content are equal.
+        /// </summary>
+        [Fact]
+        public void IdSpan_SameContent_AreEqual()
+        {
+            IdSpan id1 = IdSpan.Create("test123");
+            IdSpan id2 = IdSpan.Create("test123");
+
+            Assert.Equal(id1, id2);
+            Assert.True(id1 == id2);
+            Assert.False(id1 != id2);
+            Assert.Equal(id1.GetHashCode(), id2.GetHashCode());
+        }
+
+        /// <summary>
+        /// Tests that IdSpans with different content are not equal.
+        /// </summary>
+        [Fact]
+        public void IdSpan_DifferentContent_AreNotEqual()
+        {
+            IdSpan id1 = IdSpan.Create("test1");
+            IdSpan id2 = IdSpan.Create("test2");
+
+            Assert.NotEqual(id1, id2);
+            Assert.False(id1 == id2);
+            Assert.True(id1 != id2);
+        }
+
+        /// <summary>
+        /// Tests CompareTo behavior with null and empty arrays.
+        /// </summary>
+        [Fact]
+        public void IdSpan_CompareTo_HandlesNullAndEmpty()
+        {
+            IdSpan defaultIdSpan = default;
+            IdSpan emptyStringIdSpan = IdSpan.Create(string.Empty);
+            IdSpan normalIdSpan = IdSpan.Create("test");
+
+            // Default (null) should compare differently than empty string
+            Assert.NotEqual(0, defaultIdSpan.CompareTo(emptyStringIdSpan));
+            Assert.NotEqual(0, emptyStringIdSpan.CompareTo(defaultIdSpan));
+
+            // Both should be less than a normal span
+            Assert.True(defaultIdSpan.CompareTo(normalIdSpan) < 0);
+            Assert.True(emptyStringIdSpan.CompareTo(normalIdSpan) < 0);
+        }
+    }
+}