Infinite recursion on model_json_schema() if recusive model is a field in another model

[Matthew-Burkard]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

Calling model_json_schema() on a model with a recursive field results in a recursion error if the recursive model is used as a type in another model field.

Example error:

Traceback (most recent call last):
  File "/home/matthew/Projects/PyCharm/openrpc/error.py", line 14, in <module>
    RecursiveModel.model_json_schema()
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/main.py", line 385, in model_json_schema
    return model_json_schema(
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 2153, in model_json_schema
    return schema_generator_instance.generate(cls.__pydantic_core_schema__, mode=mode)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 432, in generate
    json_schema = definitions_remapping.remap_json_schema(json_schema)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 214, in remap_json_schema
    schema['$defs'] = {
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 215, in <dictcomp>
    self.remap_defs_ref(DefsRef(key)): self.remap_json_schema(value)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 214, in remap_json_schema
...
... (stack trace repeats for a couple thousand lines here)
...
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 214, in remap_json_schema
    schema['$defs'] = {
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 215, in <dictcomp>
    self.remap_defs_ref(DefsRef(key)): self.remap_json_schema(value)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 219, in remap_json_schema
    schema[key] = self.remap_json_schema(value)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 219, in remap_json_schema
    schema[key] = self.remap_json_schema(value)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 219, in remap_json_schema
    schema[key] = self.remap_json_schema(value)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 208, in remap_json_schema
    return [self.remap_json_schema(item) for item in schema]
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 208, in <listcomp>
    return [self.remap_json_schema(item) for item in schema]
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 219, in remap_json_schema
    schema[key] = self.remap_json_schema(value)
  File "/home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic/json_schema.py", line 206, in remap_json_schema
    return self.remap_json_ref(JsonRef(schema))
RecursionError: maximum recursion depth exceeded

Example Code

from typing import Optional
from pydantic import BaseModel

class RecursiveModel(BaseModel):
    recursive_field: Optional["RecursiveModel"]

class AnotherModel(BaseModel):
    field: RecursiveModel

RecursiveModel.model_json_schema()

Python, Pydantic & OS Version

pydantic version: 2.4.1
        pydantic-core version: 2.10.1
          pydantic-core build: profile=release pgo=true
                 install path: /home/matthew/.cache/pypoetry/virtualenvs/openrpc-pwkskCd0-py3.10/lib/python3.10/site-packages/pydantic
               python version: 3.10.12 (main, Jun 11 2023, 05:26:28) [GCC 11.4.0]
                     platform: Linux-6.4.6-76060406-generic-x86_64-with-glibc2.35
             related packages: mypy-1.5.1 typing_extensions-4.8.0

[sydney-runkle]

Hi @Matthew-Burkard,

Thanks for reporting this issue. Looks like this is working in v 2.3.0 and v 2.4.0, so the issue likely has to do with our 2.4.1 patch release or the 2.10.1 pydantic-core release.

I'll log this on our known list of issues + we'll address this issue promptly!

[sydney-runkle]

Alright - a similar issue was reported in #7645, which we have a fix for in #7653. We'll have that across the line shortly 😄

[sydney-runkle]

Closing bc this is effectively a duplicate of #7645