Crash on forward references in pydantic and django plugins

Crash Report

Mypy was working fine on my django project until about a week ago, when I started getting this error. I'm not sure what caused it. My python code used to be in the root directory of my project and now I moved it to the backend/ directory, and the problem started around then, but I'm not sure whether that is related.

I am using pre-commit and have mypy set up in my .pre-commit-config.yaml. The error actually only happens when I run mypy as part of pre-commit. If I just run mypy . from the command line, it works fine.

Presently, whenever I run pre-commit, I get an INTERNAL ERROR (details below).

Traceback

/home/travis/Repos/bethpage/backend/bethpage/models.py:23: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.16.0+dev.23e2d0f8cbaa2f4874d8f6a6bee3756922c78407
Traceback (most recent call last):
  File "/home/travis/Repos/bethpage/.tox/py312/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/__main__.py", line 15, in console_entry
    main()
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/main.py", line 119, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/main.py", line 203, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/build.py", line 191, in build
    result = _build(
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/build.py", line 267, in _build
    graph = dispatch(sources, manager, stdout)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/build.py", line 2937, in dispatch
    process_graph(graph, manager)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/build.py", line 3335, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/build.py", line 3430, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal_main.py", line 94, in semantic_analysis_for_scc
    process_functions(graph, scc, patches)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal_main.py", line 252, in process_functions
    process_top_level_function(
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal_main.py", line 291, in process_top_level_function
    deferred, incomplete, progress = semantic_analyze_target(
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal_main.py", line 351, in semantic_analyze_target
    analyzer.refresh_partial(
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal.py", line 655, in refresh_partial
    self.accept(node)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal.py", line 7254, in accept
    node.accept(self)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/nodes.py", line 811, in accept
    return visitor.visit_func_def(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal.py", line 913, in visit_func_def
    self.analyze_func_def(defn)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal.py", line 958, in analyze_func_def
    self.defer(defn)
  File "/home/travis/Repos/bethpage/.tox/py312/lib/python3.12/site-packages/mypy/semanal.py", line 6900, in defer
    assert not self.final_iteration, "Must not defer during final iteration"
           ^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Must not defer during final iteration
/home/travis/Repos/bethpage/backend/bethpage/models.py:23: : note: use --pdb to drop into pdb

To Reproduce

This crash happens any time I change any file in my backend/ directory and then run git add -A; pre-commit.

It does not happen if I just run cd backend; mypy .

If I use the --no-incremental flag or delete the cache directory, the problem still persists.

If I open up backend/bethpage/models.py and add a line that just says "pass" somewhere above line 23 (the line cited in the error), then run git add -A; pre-commit, it actually works fine and completes without errors. The next time I need to commit something, I'll get the error again, but I can just remove that "pass" line and once again, the error goes away.

Here is the beginning of that /backend/bethpage/models.py file:

import uuid
from typing import (
    Any,
    ClassVar,
    Dict,
    Generic,
    Iterable,
    List,
    Mapping,
    Optional,
    Self,
    Tuple,
    TypeVar,
)

from django.db import models, transaction
from django.db.models.fields.reverse_related import ForeignObjectRel
from django.utils import timezone

T = TypeVar("T", bound="BaseModel")


class BaseQuerySet(models.QuerySet[T], Generic[T]):

    def bulk_create(self, objs: Iterable[T], *args: Any, **kwargs: Any) -> List[T]:
        for obj in objs:
            obj.full_clean()
        return super().bulk_create(objs, *args, **kwargs)
...etc...

Your Environment

• Mypy version used: I have tried versions of mypy from 1.0.0 to 1.14.1 and have also tried using the master branch on github, always with the same error.
• Python version used: 3.12
• Operating system: Arch Linux

.pre-commit-config.yaml

repos:
  - repo: local
    hooks:
      - id: mypy
        name: mypy
        entry: mypy
        language: system
        types: [python]
        args:
          - --config-file=backend/mypy.ini
          - --show-traceback
...etc...

mypy.ini

[mypy]
python_version = 3.12
mypy_path = backend
plugins =
  mypy_django_plugin.main,
  mypy_drf_plugin.main
strict = True
show_error_codes = True
disallow_untyped_calls = True
disallow_untyped_defs = True
disallow_incomplete_defs = True
disallow_any_unimported = True
check_untyped_defs = True
no_implicit_optional = True
warn_unused_ignores = True
warn_return_any = True
warn_unreachable = True

[mypy.plugins.django-stubs]
django_settings_module = bethpage.settings

Reproduce the crash by running the local mypy pre-commit hook with backend/mypy.ini, then compare it with cd backend; mypy . and the --no-incremental case. Start at mypy/semanal.py around the final-iteration assertion and use backend/bethpage/models.py as the trigger; done means the pre-commit run completes without the INTERNAL ERROR.