Invalid code generated for polymorphic array in Swagger spec

Describe the bug Invalid code generated for polymorphic array in Swagger spec.

To Reproduce Using the following Swagger YAML:

openapi: 3.0.0
info:
  title: datamodel-code-generator bug example
components:
  schemas:
    Container:
      allOf:
        - type: object
          required:
            - contents
          properties:
            contents:
              type: array
              items:
                anyOf:
                  - $ref: '#/components/schemas/Type1'
                  - $ref: '#/components/schemas/Type2'
    Type1:
      type: object
      properties:
        prop:
          type: string
    Type2:
      type: object
      properties:
        prop:
          type: string

The generated code:

# generated by datamodel-codegen:
#   filename:  swagger-borked.yaml
#   timestamp: 2020-06-10T22:51:26+00:00

from __future__ import annotations

from typing import List, Optional

from pydantic import BaseModel


class Type1(BaseModel):
    prop: Optional[str] = None


class Type2(BaseModel):
    prop: Optional[str] = None


class Container(BaseModel):
    contents: List[Type1, Type2]

The last line is invalid and causes a runtime error.

TypeError: Too many parameters for typing.List; actual 2, expected 1

Expected behavior The generated code should be a list containing a union of the types.

class Container(BaseModel):
    contents: List[Union[Type1, Type2]]

This occurs using the latest version of datamodel-code-generator, 0.5.2.

Thanks for the tool! It’s very handy. I tried to figure out how to fix this myself but found myself going in circles.

[FlorianLudwig]

I believe to properly support this (and all other nested possibilities) some refactoring is needed. Currently only a few cases are handled (see datamodel-code-generator/datamodel_code_generator/model/base.py function: DataModelFieldBase._get_type_hint).

DataModelFieldBase.data_types would need to be converted from a list to a tree, with nodes for Union, List, etc.

[koxudaxi]

Thank you. I have closed this issue. Please feel free to report them if you see any problem.