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JsonNull return false when comparing against null #842

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Dec 18, 2019
Merged

JsonNull return false when comparing against null #842

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JsonNull return false when comparing against null
henrikse55 Dec 13, 2019
45a1816
Updated xml comments to reflect my changes
henrikse55 Dec 17, 2019
1074418
Applied suggested change
henrikse55 Dec 18, 2019
01a6555
Applied Suggested change
henrikse55 Dec 18, 2019
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17 changes: 14 additions & 3 deletions src/libraries/System.Text.Json/src/System/Text/Json/Node/JsonNull.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,23 +43,34 @@ public JsonNull() { }
/// </summary>
/// <param name="other">The JSON null to compare against.</param>
/// <returns><see langword="true"/></returns>
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public bool Equals(JsonNull other) => true;
public bool Equals(JsonNull other) => !(other is null);
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/// <summary>
/// Compares values of two JSON nulls.
/// </summary>
/// <param name="left">The JSON null to compare.</param>
/// <param name="right">The JSON null to compare.</param>
/// <returns><see langword="true"/></returns>
public static bool operator ==(JsonNull left, JsonNull right) => true;
public static bool operator ==(JsonNull left, JsonNull right)
{
// Test "right" first to allow branch elimination when inlined for null checks (== null)
// so it can become a simple test
if (right is null)
{
// return true/false not the test result https://github.com/dotnet/coreclr/issues/914
return (left is null) ? true : false;
}

return right.Equals(left);
}

/// <summary>
/// Compares values of two JSON nulls.
/// </summary>
/// <param name="left">The JSON null to compare.</param>
/// <param name="right">The JSON null to compare.</param>
/// <returns><see langword="false"/></returns>
public static bool operator !=(JsonNull left, JsonNull right) => false;
public static bool operator !=(JsonNull left, JsonNull right) => !(left == right);

/// <summary>
/// Creates a new JSON null that is a copy of the current instance.
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20 changes: 10 additions & 10 deletions src/libraries/System.Text.Json/tests/JsonNullTests.cs
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Expand Up @@ -46,16 +46,16 @@ public static void TestEquals()
Assert.False(jsonNull1.Equals(new Exception()));

// Null comparisons behave this way because of implicit conversion from null to JsonNull:
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Assert.True(jsonNull1.Equals(null));
Assert.True(jsonNull1 == null);
Assert.False(jsonNull1 != null);

Assert.False(jsonNull1.Equals(null));
Assert.False(jsonNull1 == null);
Assert.True(jsonNull1 != null);

JsonNull jsonNullNull = null;

Assert.True(jsonNull1.Equals(jsonNullNull));
Assert.True(jsonNull1 == jsonNullNull);
Assert.False(jsonNull1 != jsonNullNull);
Assert.False(jsonNull1.Equals(jsonNullNull));
Assert.False(jsonNull1 == jsonNullNull);
Assert.True(jsonNull1 != jsonNullNull);

JsonNull otherJsonNullNull = null;
Assert.True(jsonNullNull == otherJsonNullNull);
Expand All @@ -64,7 +64,7 @@ public static void TestEquals()

JsonNode jsonNodeNull = null;
Assert.False(jsonNull1.Equals(jsonNodeNull));

JsonArray jsonArrayNull = null;
Assert.False(jsonNull1.Equals(jsonArrayNull));
}
Expand All @@ -75,10 +75,10 @@ public static void TestGetHashCode()
var jsonNull = new JsonNull();

Assert.Equal(jsonNull.GetHashCode(), new JsonNull().GetHashCode());

JsonNode jsonNodeNull = new JsonNull();
Assert.Equal(jsonNull.GetHashCode(), jsonNodeNull.GetHashCode());

IEquatable<JsonNull> jsonNullIEquatable = new JsonNull();
Assert.Equal(jsonNull.GetHashCode(), jsonNullIEquatable.GetHashCode());

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