Malformed api-docs JSON when StringHttpMessageConverter is not active

[micw]

Describe the bug

StringHttpMessageConverter unwraps a JSON string and delivers it's content a string. This may have some uses but it breaks JSON compatibility. If StringHttpMessageConverter is disabled, a JSON string is quoted properly.

In #624 the issue was already partially discussed. The only working solution is to use StringHttpMessageConverter. A real solution that works without StringHttpMessageConverter is needed, so that it works along with fully JSON compatible applications.

To Reproduce

Create an app with a WebMvcConfigurer with the following code:

	@Override
	public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
		converters.removeIf(c -> c instanceof StringHttpMessageConverter);
	}

Query for spec/v1.

Expected behavior

A Json should be returned. Instead a JSON quoted as JSON string is returned.

Edit:

The fix is trivial, see my comment in #624 (comment)

[bnasslahsen]

@micw,

The problem with the fix, is the potential regressions.
I am adding it to the master.

Please do not hesitate to propose a PR for your proposals

[micw]

@bnasslahsen Thank you for making me happy :-)

Edit: what do you mean with regressions? The fix changes from "works sometimes under certain conditions" to "works always" - regressions are very unlikely.

[bnasslahsen]

@micw,

It means that you might find developers that were using a use-case that you haven't thought about it.
For this case, changing the return type will be with impacts for people not relying on the response type only! And who have chosen to override the springdoc-openapi controllers.
Let's see if there so many people complaining about the change, or maybe more people getting happy.
Only the futur will let us know.