Allow stdClass in XML responses

[provokateurin]

Summary

Allows returning \stdClass() in DataResponse that are encoded to XML.
JSON can already to it and converts it to {}, but for XML special handling is required.

This change is required in order to properly describe APIs using empty JSON objects ([] gets converted to [] in JSON instead of {}). XML just also needs to support it.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[ChristophWurst]

Could this be tested in \Test\AppFramework\Middleware\BaseResponseTest?

[AlexM4H]

Many thanks for the PR. A backport to Nextcloud 27.1.0 would be desirable.

[provokateurin]

@AlexM4H does it fix a bug for you? This was only meant as a feature, so it doesn't get any backport

[AlexM4H]

It fixes #1469 and #33330 for me.

Otherwise /api/v2.1/form/{id} returns an empty XML result.

[provokateurin]

On a technical level this is still a bug with the respective apps and not the core as this was never supported. @ChristophWurst @come-nc shall we backport it anyway?

[come-nc]

Hard to say. Backporting API change is always dangerous as it may trigger subtle sideeffects.
On the other hand if it fixes bugs…

Without this an stdClass is just stripped from XML output?

@provokateurin I think you’re more knowledgeable than me to decide whether to backport.

[provokateurin]

It's not breaking at all, but if an app returns stdClass the output without this patch would just be empty thus broken.

I still feel like the apps should fix it themselves as any version before this patch is broken. That would mean apps can't target <28 if they rely on this.

[AlexM4H]

Please keep in mind that Forms is a featured app. "Featured apps are developed by and in the community. They provide core functionality and are ready for production use."

The fix would be necessary for some app developers for NC 26 / 27, as NC 28 already includes the fix as a new feature.

[Chartman123]

What would we need to do to fix the problem in Forms?

[AlexM4H]

The corresponding issue is still open

nextcloud/forms#1469

[Chartman123]

@AlexM4H yes, I know. We're waiting for a server fix there 😆

My question was for @provokateurin 😉

[provokateurin]

Please keep in mind that Forms is a featured app. "Featured apps are developed by and in the community. They provide core functionality and are ready for production use."

@AlexM4H Sorry, this is not helpful. This is a bug with the app and not the core.

As I said the behavior the forms app is relying on was never intended to work (in previous versions). I added this as a feature but it is only available in >=28. If you target 28 and higher you can surely rely on it.

What would we need to do to fix the problem in Forms?

@Chartman123 For example Talk also had to work around it like this: https://github.com/nextcloud/spreed/blob/eaf04bbe5a7626cc1565cc455124f8a10b2ff078/lib/Model/Message.php#L163

cc @DaphneMuller

[Chartman123]

For example Talk also had to work around it like this

Thanks I'll have a look at it :)

[provokateurin]

In the future when you target >=28 you can of course drop the workaround.