MyPy plugin doesn't work with MyPy 0.750

[rafalp]

Bug

Please complete:

• OS: Debian Linux & MacOS
• Python version import sys; print(sys.version): 3.8
• Pydantic version import pydantic; print(pydantic.VERSION): 1.1, 1.2

MyPy 0.750 has just been released and it looks like it has changed plugin system, causing plugin to error:

mypy misago --ignore-missing-imports --show-traceback
/Users/rafalpiton/github/misago-starlette/venv/lib/python3.8/site-packages/mypy/typeshed/stdlib/3/typing.pyi:146: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.750
Traceback (most recent call last):
  File "mypy/semanal.py", line 4656, in accept
  File "mypy/nodes.py", line 939, in accept
  File "mypy/semanal.py", line 1029, in visit_class_def
  File "mypy/semanal.py", line 1106, in analyze_class
  File "mypy/semanal.py", line 1115, in analyze_class_body_common
  File "mypy/semanal.py", line 1173, in apply_class_plugin_hooks
  File "mypy/plugin.py", line 818, in get_base_class_hook
  File "mypy/plugin.py", line 830, in _find_hook
  File "mypy/plugin.py", line 818, in <lambda>
  File "mypy/plugin.py", line 743, in get_base_class_hook
  File "/Users/rafalpiton/github/misago-starlette/venv/lib/python3.8/site-packages/pydantic/mypy.py", line 79, in get_base_class_hook
    if any(base.fullname() == BASEMODEL_FULLNAME for base in sym.node.mro):
  File "/Users/rafalpiton/github/misago-starlette/venv/lib/python3.8/site-packages/pydantic/mypy.py", line 79, in <genexpr>
    if any(base.fullname() == BASEMODEL_FULLNAME for base in sym.node.mro):
TypeError: 'str' object is not callable
/Users/rafalpiton/github/misago-starlette/venv/lib/python3.8/site-packages/mypy/typeshed/stdlib/3/typing.pyi:146: : note: use --pdb to drop into pdb```

[dmontagu]

Thanks for reporting this. This is due to a noted breaking change in mypy 0.750. I’ll submit a patch PR shortly.

Any suggestions about how we could better handle breaking changes in mypy going forward would be appreciated!

[dmontagu]

In particular, it would be easy to log a warning if using a version of mypy that is not one against which the pydantic plugin has been tested. Would this be desirable?

[rafalp]

No opinion here. I'm just happy with value provided by Pydantic for me and reported this issues so you can fix the plugin when you have time for that :)

[stevebelskie]

A note in the docs page for the mypy plugin page noting the incompatibility would be helpful.

[samuelcolvin]

I guess we should just release a new version, I'll merge what I can and do a release soon.