Analyzer/Code fix idea: JsonConverters applied to properties implementing a collection

[WhitWaldo]

Per #85479 and #54189 the preferred approach to apply a custom JsonConverter is to apply the converter type to the type being converted so that it's used whether (de)serializing a single entity or a collection of entities using that converter.

Having not realized that, I would propose that an analyzer (potentially with a code fix) be added that identifies when [JsonConverter] has been applied to a property that itself represents a collection of the type the JsonConverter is typed for since this will actually throw at runtime. The code fix should move the [JsonConverter] attribute from its position on any various properties to the type definition itself (when available in the same assembly) so it's applied consistently whether to a single or collection of the type.

Thank you for the consideration!

[ghost]

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Issue Details

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Per #85479 and #54189 the preferred approach to apply a custom JsonConverter is to apply the converter type to the type being converted so that it's used whether (de)serializing a single entity or a collection of entities using that converter.

Having not realized that, I would propose that an analyzer (potentially with a code fix) be added that identifies when [JsonConverter] has been applied to a property that itself represents a collection of the type the JsonConverter is typed for since this will actually throw at runtime. The code fix should move the [JsonConverter] attribute from its position on any various properties to the type definition itself (when available in the same assembly) so it's applied consistently whether to a single or collection of the type.

Thank you for the consideration!

Author:	WhitWaldo
Assignees:	-
Labels:	area-System.Text.Json
Milestone:	-

[eiriktsarpalis]

It's an interesting proposal, we could consider it in the future. Thanks!

[gpuchtel]

@eiriktsarpalis Why is this just "an interesting proposal?". This, IMO is a fundamental usage issue. I'm surprised (sad even) that Microsoft doesn't see it the same way.