Wording in `mypy.plugin.Plugin.get_method[_signature]_hook` docstring

[bzoracler]

Documentation

The docstring of these plugin hook methods currently say:

https://github.com/python/mypy/blob/057508b4cb405fbc22e26b44f764b142352fcce5/mypy/plugin.py#L647-L648

...

https://github.com/python/mypy/blob/057508b4cb405fbc22e26b44f764b142352fcce5/mypy/plugin.py#L664

I understand this to mean that the argument to fullname will be "__main__.Base.method", because __main__.Base defines method.

However, this doesn't seem to be the case. Setting up the same example in the docstring:

• mypy.ini

  [mypy]
  plugins = plugin.py
  files = test.py
  

• plugin.py

  from mypy.plugin import Plugin
  
  def plugin(version):
      return TestPlugin
  
  class TestPlugin(Plugin):
      def get_method_signature_hook(self, fullname):
          if fullname.startswith("test."):
              print(f"Hook will be called with `{fullname}`")
  

• test.py

  from typing import Any
  
  class Base:
      def method(self, arg: Any) -> Any: ...
  
  class Derived(Base): ...
  
  var: Derived
  var.method(42)
  

$ mypy
Hook will be called with `test.Derived.method`

I installed as far back as mypy 0.9x and it was the same behaviour as described above, displaying test.Derived.method (not test.Base.method).

---

Is there something wrong with the docstring (perhaps from outdated behaviour that no longer applies), or have I misunderstood something?

[ilevkivskyi]

Hm, this is problematic. IIRC the intention was to actually pass Base names there. But changing the logic now may be risky, as many plugins will break. @JukkaL what do you think?

[JukkaL]

We could provide a flag to enable the new behavior to make it easier for plugins to switch to the new semantics. We'd then switch the default for the flag after at least a few releases. We don't promise that the plugin system remains backward compatible.