[kotlin] enforce fields in data classes

[jaqxues]

Fix #14710

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[jaqxues]

Can anyone of you review quickly? Thanks!
(Random subset of 3, not sure if I should've tagged less or more)

Note: Maybe not using class at all but just "object" would be a good idea. Your call though

@dr4ke616 @stefankoppier @yutaka0m

[wing328]

can you please follow step 3 to update the samples so that the CI can test/verify the change?

cc @dr4ke616 (2018/08) @karismann (2019/03) @Zomzog (2019/04) @andrewemery (2019/10) @4brunu (2019/11) @yutaka0m (2020/03) @stefankoppier (2022/06)

[jaqxues]

@wing328 I ran the 3 commands when I made the commit already, and had no additional changes. Reran again now, git status remains clean.

Unless I should add additional things, I would say step 3 is handled.

[wing328]

you're right. samples are up-to-date

one thing i don't understand is how come there's no change in the samples as there are more test models with properties

i'll take another look later this week and run some tests

did you test the fix locally? I assume it works for your use cases

[jaqxues]

It does work.

Out of interest, what are you expecting to change? If there were a sample about empty data, someone would probably have noticed that it generates code that does not compile. (I am new to this project and do not have any profound knowledge about the CI setup etc)

[wing328]

@jaqxues the hasVars is true when the model has at least one property.

what I don't understand is there's no change to the samples (e.g. kotlin petstore client) given that the test petstore pet has at least one model with properties.

[jaqxues]

This fixes an issue with models without properties, so the opposite case. A data class in kotlin is not allowed to have no properties. So this compilation error is fixed by not making it data class in that special case. But I am not sure if it makes sense to change the class to object even in that special case.

[4brunu]

Thanks for the clarification 👍