It should be possible to specify `JsonIgnoreCondition`'s on the type level

[eiriktsarpalis]

Motivation

There's a substantial amount of duplication in the following code:

class MyPoco
{
    [JsonIgnore(JsonIgnoreCondition.WhenWritingNull)]
    public string? PropA { get; set; }

    [JsonIgnore(JsonIgnoreCondition.WhenWritingNull)]
    public string? PropB { get; set; }

    [JsonIgnore(JsonIgnoreCondition.WhenWritingNull)]
    public string? PropC { get; set; }
}

that could be eliminated using a type-level declaration:

[JsonIgnore(JsonIgnoreCondition.WhenWritingNull)]
class MyPoco
{
    public string? PropA { get; set; }

    public string? PropB { get; set; }

    public string? PropC { get; set; }
}

API Proposal

namespace System.Text.Json.Serialization;

-[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Interface | AttributeTargets.AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
public partial class JsonIgnoreAttribute;

cc @stephentoub

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[terrajobst]

Video

• Looks good as proposed

namespace System.Text.Json.Serialization;

// Before:
//
// [AttributeUsage(AttributeTargets.Property |
//                 AttributeTargets.Field, AllowMultiple = false)]
//
[AttributeUsage(AttributeTargets.Class |
                AttributeTargets.Struct |
                AttributeTargets.Interface |
                AttributeTargets.Property |
                AttributeTargets.Field, AllowMultiple = false)]
public partial class JsonIgnoreAttribute;