strict flake8-type-checking (#6866)

recent flake8-type-checking encourages cast() using the name of the
class rather than the actual class, presumably with the aim that you
might find more things you don't need to import at runtime

however here, consistent with other recent MRs, I've taken the view that
it's better to assert that you have the expected type than to trust that
it's so

.flake8

@@ -6,7 +6,7 @@ ban-relative-imports = true
 format-greedy = 1
 format-greedy = 1
 inline-quotes = double
 inline-quotes = double
 enable-extensions = TC, TC1
 enable-extensions = TC, TC1
-type-checking-exempt-modules = typing, typing-extensions
+type-checking-strict = true
 eradicate-whitelist-extend = ^-.*;
 eradicate-whitelist-extend = ^-.*;
 extend-ignore =
 extend-ignore =
     # E203: Whitespace before ':' (pycqa/pycodestyle#373)
     # E203: Whitespace before ':' (pycqa/pycodestyle#373)

.pre-commit-config.yaml

@@ -40,7 +40,7 @@ repos:
           - flake8-quotes==3.3.1
           - flake8-quotes==3.3.1
           - flake8-simplify==0.19.3
           - flake8-simplify==0.19.3
           - flake8-tidy-imports==4.8.0
           - flake8-tidy-imports==4.8.0
-          - flake8-type-checking==2.1.2
+          - flake8-type-checking==2.2.0
           - flake8-typing-imports==1.12.0
           - flake8-typing-imports==1.12.0
           - flake8-use-fstring==1.4
           - flake8-use-fstring==1.4
           - pep8-naming==0.13.1
           - pep8-naming==0.13.1

src/poetry/factory.py

@@ -257,7 +257,8 @@ class Factory(BaseFactory):
                     constraint["optional"] = True
                     constraint["optional"] = True
 
 
                 if len(constraint) == 1 and "version" in constraint:
                 if len(constraint) == 1 and "version" in constraint:
-                    constraint = cast(str, constraint["version"])
+                    assert isinstance(constraint["version"], str)
+                    constraint = constraint["version"]
                 elif not constraint:
                 elif not constraint:
                     constraint = "*"
                     constraint = "*"
 
 

src/poetry/installation/executor.py

@@ -13,7 +13,6 @@ from pathlib import Path
 from subprocess import CalledProcessError
 from subprocess import CalledProcessError
 from typing import TYPE_CHECKING
 from typing import TYPE_CHECKING
 from typing import Any
 from typing import Any
-from typing import cast
 
 
 from cleo.io.null_io import NullIO
 from cleo.io.null_io import NullIO
 from poetry.core.packages.file_dependency import FileDependency
 from poetry.core.packages.file_dependency import FileDependency
@@ -771,7 +770,8 @@ class Executor:
             for dist in self._env.site_packages.distributions(
             for dist in self._env.site_packages.distributions(
                 name=package.name, writable_only=True
                 name=package.name, writable_only=True
             ):
             ):
-                dist_path = cast(Path, dist._path)  # type: ignore[attr-defined]
+                dist_path = dist._path  # type: ignore[attr-defined]
+                assert isinstance(dist_path, Path)
                 url = dist_path / "direct_url.json"
                 url = dist_path / "direct_url.json"
                 url.write_text(json.dumps(url_reference), encoding="utf-8")
                 url.write_text(json.dumps(url_reference), encoding="utf-8")
 
 

src/poetry/mixology/failure.py

 from __future__ import annotations
 from __future__ import annotations
 
 
 from typing import TYPE_CHECKING
 from typing import TYPE_CHECKING
-from typing import cast
 
 
 from poetry.core.constraints.version import parse_constraint
 from poetry.core.constraints.version import parse_constraint
 
 
@@ -114,7 +113,8 @@ class _Writer:
         conjunction = "So," if conclusion or incompatibility == self._root else "And"
         conjunction = "So," if conclusion or incompatibility == self._root else "And"
         incompatibility_string = str(incompatibility)
         incompatibility_string = str(incompatibility)
 
 
-        cause: ConflictCause = cast(ConflictCause, incompatibility.cause)
+        cause = incompatibility.cause
+        assert isinstance(cause, ConflictCause)
 
 
         if isinstance(cause.conflict.cause, ConflictCause) and isinstance(
         if isinstance(cause.conflict.cause, ConflictCause) and isinstance(
             cause.other.cause, ConflictCause
             cause.other.cause, ConflictCause
@@ -198,7 +198,8 @@ class _Writer:
                     numbered=numbered,
                     numbered=numbered,
                 )
                 )
             elif self._is_collapsible(derived):
             elif self._is_collapsible(derived):
-                derived_cause: ConflictCause = cast(ConflictCause, derived.cause)
+                derived_cause = derived.cause
+                assert isinstance(derived_cause, ConflictCause)
                 if isinstance(derived_cause.conflict.cause, ConflictCause):
                 if isinstance(derived_cause.conflict.cause, ConflictCause):
                     collapsed_derived = derived_cause.conflict
                     collapsed_derived = derived_cause.conflict
                     collapsed_ext = derived_cause.other
                     collapsed_ext = derived_cause.other
@@ -233,7 +234,8 @@ class _Writer:
         if self._derivations[incompatibility] > 1:
         if self._derivations[incompatibility] > 1:
             return False
             return False
 
 
-        cause: ConflictCause = cast(ConflictCause, incompatibility.cause)
+        cause = incompatibility.cause
+        assert isinstance(cause, ConflictCause)
         if isinstance(cause.conflict.cause, ConflictCause) and isinstance(
         if isinstance(cause.conflict.cause, ConflictCause) and isinstance(
             cause.other.cause, ConflictCause
             cause.other.cause, ConflictCause
         ):
         ):

src/poetry/utils/helpers.py

@@ -12,7 +12,6 @@ from typing import TYPE_CHECKING
 from typing import Any
 from typing import Any
 from typing import Iterator
 from typing import Iterator
 from typing import Mapping
 from typing import Mapping
-from typing import cast
 
 
 from poetry.utils.constants import REQUESTS_TIMEOUT
 from poetry.utils.constants import REQUESTS_TIMEOUT
 
 
@@ -189,7 +188,8 @@ def _get_win_folder_from_registry(csidl_name: str) -> str:
     )
     )
     dir, type = _winreg.QueryValueEx(key, shell_folder_name)
     dir, type = _winreg.QueryValueEx(key, shell_folder_name)
 
 
-    return cast(str, dir)
+    assert isinstance(dir, str)
+    return dir
 
 
 
 
 def _get_win_folder_with_ctypes(csidl_name: str) -> str:
 def _get_win_folder_with_ctypes(csidl_name: str) -> str: