Add support for multiple inheritance

[wing328]

PR checklist

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• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
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Description of the PR

• add support for multiple inheritances: allParents tag
• bug fixes for allVars, vars
• fix allRequired
• fix property naming in mandatory, allMandatory
• add more test cases
• add isSelfReference flag to codegen property
• update run-in-docker.sh to use the local Maven cache

cc @OpenAPITools/generator-core-team

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[cbornet]

Didn't we already have supportsMixin for language that support "multiple inheritance" ?

[wing328]

@cbornet yup, only JS client generator uses that.

My current approach is to keep the "supportsMixin" and add new code, mustache tags to support mutiple inheritnance for other langauges as part of the code cleanup/refactoring.

[cbornet]

I mean, can't we reuse this option for other languages ?

[wing328]

Very good question. Ideally we should extend or reuse supportsMixin for other languages (in addition to JS) but when I read the following code:

openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

Lines 1652 to 1655 in 158760a

	if (modelImplCnt++ > 1) {
	LOGGER.warn("More than one inline schema specified in allOf:. Only the first one is recognized. All others are ignored.");
	break; // only one schema with discriminator allowed in allOf
	}

I couldn't understand why only the first model is considered in mixin (multiple inheritance) - shoudn't it consider all models defined in allOf as it's multiple inheritance?. I don't want to modify it least it break the JS API client. That's why I introduce a new option instead and add the allParents mustache tag should a language need multiple inheritance/mixins. We can later migrate JS to use supportsMultipleInheritance to migrate risks in breaking existing usage.

[cbornet]

Actually with your modifications supportsMixins doesn't have any effect anymore so it could just be removed...

[cbornet]

Also I prefer "mixin" over "multiple inheritance" as it better describe what is done. Multiple inheritance is bad and should be avoided at all cost while mixins are ok.

[wing328]

Also I prefer "mixin" over "multiple inheritance" as it better describe what is done. Multiple inheritance is bad and should be avoided at all cost while mixins are ok.

OK. I'll keep the supportsMixins name.

[cbornet]

👍 I wonder what's the effect of the modifications on the JS codegen ? I guess the mixin/multiple-inheritance shall be activated for this one.

[wing328]

I wonder what's the effect of the modifications on the JS codegen?

I've updated the JS samples and the tests passed. No visible code change which is expected as I try not to break backward compatibility at the moment.

[cbornet]

Also I don't think we have multiple inheritance in samples

[wing328]

@cbornet yup, I added several spec to test allOf, multiple inheritance, etc (e.g. allOfMultiParent.yaml). We'll add those to the fake petstore spec when more generators are ready for these new features. We'll test with these new spec individually for the time being.