[Python] Inheritance doesn't work

[emreakca]

Description

The generated Python SubClass doesn't inherited from the BaseClass, when allOf is used.

SubClass:
  allOf:
    - $ref: '#/components/schemas/BaseClass'

The generated class shows

class SubClass(object):

instead of

class SubClass(BaseClass):

This issue was already posted (#453), but it's not solved nor answered.

openapi-generator version

3.1.1

Command line used for generation

java -jar ~/openapi-generator-cli-3.1.1.jar generate -g python -i openapi.json -o generated/python-client

Suggestion

Either do the inheritance correctly (as shown at the beginning), with the right constructors (__init__)
or add the Properties of the BaseClass to the SubClass, as in swagger 2.

[macjohnny]

@emreakca @poli-granot this could be fixed by applying the changes in swagger-api/swagger-codegen@843c638 to https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/python/model.mustache#L13 and other relevant files. would you like to file a PR for this?

[spacether]

I am working on a PR which will fix this issue. The problem is that the mustache files iterate through #vars per here: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/python/model.mustache#L36. #vars does not include the variables inherited from the allOf class. However, the requiredVars and optionalVars DO include those needed properties. My fix will iterate over the requiredVars and optionalVars.

[spacether]

composed schema inheritance is working in the python-experimental generator
Composed schema inheritance is implemented by storing instances of "ancestor" allOf models rather than using inherited classes.
This was done because multiple allOf models can contain the same property with differing enum and validation constraints on it.
Python class based inheritance generally assumes that a property has its definition/validation in one source of truth class location.