JSON source gen doesn't detect [JsonNumberHandling] when applied to POCO

[steveharter]

The attribute is ignored, causing number-based properties to be written as integers, for example, instead of a string.

Repro:

using System.Text.Json;
using System.Text.Json.Serialization;

Console.WriteLine(JsonSerializer.Serialize(new MyPOCO(), MyContext.Default.MyPOCO));

[JsonSerializable(typeof(MyPOCO))]
public partial class MyContext : JsonSerializerContext { }

[JsonNumberHandling(JsonNumberHandling.WriteAsString)]
public class MyPOCO
{
    public int Id {  get; set; }
}

Outputs {"Id":0} instead of the expected {"Id":"0"}

Also when applying [JsonSourceGenerationOptions(GenerationMode =JsonSourceGenerationMode.Serialization)] to the context, a compile-time (or run-time based on current expected behavior) should occur since fast-path doesn't support number handling.

[ghost]

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Issue Details

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The attribute is ignored, causing number-based properties to be written as integers, for example, instead of a string.

Repro:

using System.Text.Json;
using System.Text.Json.Serialization;

Console.WriteLine(JsonSerializer.Serialize(new MyPOCO(), MyContext.Default.MyPOCO));

[JsonSerializable(typeof(MyPOCO))]
public partial class MyContext : JsonSerializerContext { }

[JsonNumberHandling(JsonNumberHandling.WriteAsString)]
public class MyPOCO
{
    public int Id {  get; set; }
}

Outputs {"Id":0} instead of the expected {"Id":"0"}

Also when applying [JsonSourceGenerationOptions(GenerationMode =JsonSourceGenerationMode.Serialization)] to the context, a compile-time (or run-time based on current expected behavior) should occur since fast-path doesn't support number handling.

Author:	steveharter
Assignees:	-
Labels:	area-System.Text.Json, blocking-release
Milestone:	6.0.0

[eiriktsarpalis]

The issue can be worked around by applying the attribute on the property level. As such I don't believe it meets the bar for a 6.0.0 fix. cc @ericstj