Switch to System.Text.Json for (de)serialization

[kipusoep]

We're using the new System.Text.Json namespace for WebApi JSON serialization (I think it's OOTB like this nowadays).
TimeSpan objects are serialized in the format 23:59:59 and Newtonsoft.Json is unable to deserialize this.
It would be nice if the generated Open API code would use System.Text.Json instead.

[christianhelle]

@kipusoep Thanks for taking the time to report this

Which code generator are you thinking of? I have 100% control over Refitter since I wrote the tool and NSwag features the option to configure which JSON serialization library to use. I have very little control over the other code generators since I just piggyback over them

[kipusoep]

The Open API generator.

[christianhelle]

@kipusoep There's a similar issue on the OpenAPI Generator repo and one of the comments is about a fork that implements this. Hopefully, this becomes a pull request and ends up in the OpenAPI Generator itself. Otherwise, someone should implement this, that could be me, you, or someone else

[rasmusrim]

Here is the fork. It has worked well on several of my projects so far: https://github.com/rasmusrim/openapi-generator-csharp-system-text-json

[kipusoep]

Is there a relatively easy way to use your fork with the VS tool?

[christianhelle]

@kipusoep The mentioned fork looks like Mustache templates to me, and my extension supports using custom mustache templates. You can try to clone that repo to a local folder like C:\mustache-templates\system-text-json and then configure the OpenAPI Generator options in my extension to something like this:

[christianhelle]

@kipusoep @rasmusrim The mustache templates can be used to generate code, but the generated code doesn't build. At least not out-out-of-the-box. I guess some tweaking of the templates would help

Here's the output:
OpenAPI-Generator-Output.zip

The immediate problems that I noticed are the following:

• Enums are decorated with [JsonConverer(typeof(JsonStringEnumMemberConverter)) but JsonStringEnumMemberConverter doesn't exist
• Both Newtonsoft.Json and System.Text.Json are being used

Mustache templates are hard to work with when starting from scratch but they are not that hard to modify, so maybe a few tweaks would make this work.

Eventually this fork, once it works, should be merged into OpenAPI Generator itself