Failed CI legs doesn't look like caused from this PR changes, gonna merge this

Yay!

gonna merge this

Awesome! Thanks for your patience and effort in getting this merged, @buyaa-n. I appreciate you taking your time with it and getting the details right. Nullability annotations of a complex library like JSON hopefully help explore and refine the guidelines.

Awesome! Thanks for your patience and effort in getting this merged, @buyaa-n. I appreciate you taking your time with it and getting the details right. Nullability annotations of a complex library like JSON hopefully help explore and refine the guidelines.

Thanks for your delicate review, learnt a lot. Have fun with nullability aware coding 😄

Moving comment from #114 (comment) (since that PR was closed).

Highlighting the breaking change here (which became visible when enabling nullability analysis).

Deserializing into a char is now more strict to match user expectations. The payload must contain a single-character string for deserialization to succeed:

public class MyPoco
{
    public char Character { get; set; }
}

public static void TestDeserializeToChar()
{
    // Before (3.1): NullReferenceException
    // After (5.0): JsonException
    JsonSerializer.Deserialize<MyPoco>("{\"Character\": null}");

    // Before (3.1): IndexOutOfRangeException
    // After (5.0): JsonException
    JsonSerializer.Deserialize<MyPoco>("{\"Character\": \"\"}");

    // Before (3.1): Set Character to the first character - 'a'
    // After (5.0): JsonException
    JsonSerializer.Deserialize<MyPoco>("{\"Character\": \"abc\"}");
}

Passing in null for the Type parameter while serializing now correctly throws ArgumentNullException rather than returning "null" JSON:

public static void TestSerializeNullType()
{
    // Before (3.1): Returned a string with value "null"
    // After (5.0): ArgumentNullException: Value cannot be null. (Parameter 'type')
    JsonSerializer.Serialize(null, null);

    // Same with other Serialize{Async} overloads
    // Before (3.1): Returned a byte[] with value "null"
    // After (5.0): ArgumentNullException: Value cannot be null. (Parameter 'type')
    JsonSerializer.SerializeToUtf8Bytes(null, null);
}

@buyaa-n @layomia Does this need a breaking change issue?