Add JsonIncludeAttribute & support for non-public accessors

[layomia]

Fixes #29743.
Fixes #34453 (since I'm in this code).

New API approved in #34558.

[Dotnet-GitSync-Bot]

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[steveharter]

Currently this PR assumes that the property is still public, correct?(meaning the setter or getter can be non-public, but not both). Do we have tests with a private property where both setter and getter are private to verify?

[layomia]

Yes, I added some tests showing that non-public properties (with various accessor visibility levels) are not included:

runtime/src/libraries/System.Text.Json/tests/Serialization/PropertyVisibilityTests.cs

Lines 869 to 891 in e4e0585

	[Fact]
	public static void NonPublicMembersAreNotIncluded()
	{
	Assert.Equal("{}", JsonSerializer.Serialize(new ClassWithNonPublicProperties()));
	string json = @"{""MyInt"":1,""MyString"":""Hello"",""MyFloat"":2,""MyDouble"":3}";
	var obj = JsonSerializer.Deserialize<ClassWithNonPublicProperties>(json);
	Assert.Equal(0, obj.MyInt);
	Assert.Null(obj.MyString);
	Assert.Equal(0, obj.GetMyFloat);
	Assert.Equal(0, obj.GetMyDouble);
	}
	private class ClassWithNonPublicProperties
	{
	internal int MyInt { get; set; }
	internal string MyString { get; private set; }
	internal float MyFloat { private get; set; }
	private double MyDouble { get; set; }
	internal float GetMyFloat => MyFloat;
	internal double GetMyDouble => MyDouble;
	}

These tests ensure that we throw IOE when [JsonInclude] is used on a non-public properties:

runtime/src/libraries/System.Text.Json/tests/Serialization/PropertyVisibilityTests.NonPublicAccessors.cs

Lines 295 to 330 in e4e0585

	[Theory]
	[InlineData(typeof(ClassWithPrivateProperty_WithJsonIncludeProperty))]
	[InlineData(typeof(ClassWithInternalProperty_WithJsonIncludeProperty))]
	[InlineData(typeof(ClassWithProtectedProperty_WithJsonIncludeProperty))]
	public static void NonPublicProperty_WithJsonInclude_Invalid(Type type)
	{
	InvalidOperationException ex = Assert.Throws<InvalidOperationException>(() => JsonSerializer.Deserialize("", type));
	string exAsStr = ex.ToString();
	Assert.Contains("MyString", exAsStr);
	Assert.Contains(type.ToString(), exAsStr);
	Assert.Contains("JsonIncludeAttribute", exAsStr);
	ex = Assert.Throws<InvalidOperationException>(() => JsonSerializer.Serialize(Activator.CreateInstance(type), type));
	exAsStr = ex.ToString();
	Assert.Contains("MyString", exAsStr);
	Assert.Contains(type.ToString(), exAsStr);
	Assert.Contains("JsonIncludeAttribute", exAsStr);
	}
	private class ClassWithPrivateProperty_WithJsonIncludeProperty
	{
	[JsonInclude]
	private string MyString { get; set; }
	}
	private class ClassWithInternalProperty_WithJsonIncludeProperty
	{
	[JsonInclude]
	internal string MyString { get; }
	}
	private class ClassWithProtectedProperty_WithJsonIncludeProperty
	{
	[JsonInclude]
	protected string MyString { get; private set; }
	}

[TanvirArjel]

@layomia Is this available on .NET 5.0 RC1, maybe not. My Project has been updated to .NET 5.0 RC1 but it's not working yet.

public class DataTableParamsDto
{
    public int Draw { get; set; }

    public int Start { get; set; }

    public int Length { get; set; }

    public List<ColumnRequestItem> Columns { get; private set; } // Not working

    public List<OrderRequestItem> Order { get; private set; } // Not working

    public SearchRequestItem Search { get; private set; } // Not working
}

[layomia]

@TanvirArjel the feature is in RC1, but it requires explicitly opting in with JsonIncludeAttribute:

public class DataTableParamsDto
{
    public int Draw { get; set; }

    public int Start { get; set; }

    public int Length { get; set; }

    [JsonInclude]
    public List<ColumnRequestItem> Columns { get; private set; }

    [JsonInclude]
    public List<OrderRequestItem> Order { get; private set; }

    [JsonInclude]
    public SearchRequestItem Search { get; private set; }
}