Generating Json Schema for nested models that have overlapping model names.

[alexvoronov]

Bug

I'm trying to generate a schema that includes several models that have nested models. The inner-most models have identical name, Params, but since they are used only inside the class, there is no name clash. However, when adding outer models to the same schema, both inner-most Params models end up in the same ref location: {'$ref': '#/definitions/Params'}, which I believe causes the error I see: KeyError: <class '__main__.A.Params'>.

I believe some fully-qualified path in '$ref' would resolve this, something like:

{'$ref': '#/definitions/A/Params'}
{'$ref': '#/definitions/B/Params'}

As a workaround, I wonder if there a way I can adjust prefix of each model independently? Or is there a way to put schema of nested classes "in-place", without creating a "$ref"?

Here is a complete minimal example:

from pydantic import BaseModel, schema


class A(BaseModel):
    class Params(BaseModel):
        a: int

    params: Params  # A.Params

class B(BaseModel):
    class Params(BaseModel):
        b: int

    params: Params  # B.Params


schema.schema([A])  # Works fine.
schema.schema([B])  # Works fine.
try:
    schema.schema([A, B])  # Two schemas together - does not work.
except KeyError as e:
    print(f"{e.__class__.__name__}: {str(e)}")
    """
    KeyError: <class '__main__.A.Params'>
    """

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.6.1
            pydantic compiled: True
               python version: 3.7.8 | packaged by conda-forge | (default, Jul 31 2020, 02:25:08)  [GCC 7.5.0]
                     platform: Linux-3.10.0-957.27.2.el7.x86_64-x86_64-with-centos-7.6.1810-Core
     optional deps. installed: ['typing-extensions']

[jusexton]

It doesn't appear the ref string plays any role in this KeyError. Model names coming from the models themselves are conflicting. The code currently resolves conflicts but does not consider the possibility of nested class declarations. I can raise a PR to resolve the KeyError but it is unclear how the ref property should behave in this scenario.