typing: Testdir.__init__

src/_pytest/config/__init__.py

@@ -48,6 +48,13 @@
     from typing import Type
 
 
+_PluggyPlugin = object
+"""A type to represent plugin objects.
+Plugins can be any namespace, so we can't narrow it down much, but we use an
+alias to make the intent clear.
+Ideally this type would be provided by pluggy itself."""
+
+
 hookimpl = HookimplMarker("pytest")
 hookspec = HookspecMarker("pytest")
 

src/_pytest/pytester.py

@@ -29,12 +29,17 @@
 from _pytest.capture import MultiCapture
 from _pytest.capture import SysCapture
 from _pytest.compat import TYPE_CHECKING
+from _pytest.config import _PluggyPlugin
 from _pytest.fixtures import FixtureRequest
 from _pytest.main import ExitCode
 from _pytest.main import Session
 from _pytest.monkeypatch import MonkeyPatch
+from _pytest.nodes import Collector
+from _pytest.nodes import Item
 from _pytest.pathlib import Path
+from _pytest.python import Module
 from _pytest.reports import TestReport
+from _pytest.tmpdir import TempdirFactory
 
 if TYPE_CHECKING:
     from typing import Type
@@ -534,13 +539,15 @@ class Testdir:
     class TimeoutExpired(Exception):
         pass
 
-    def __init__(self, request, tmpdir_factory):
+    def __init__(self, request: FixtureRequest, tmpdir_factory: TempdirFactory) -> None:
         self.request = request
-        self._mod_collections = WeakKeyDictionary()
+        self._mod_collections = (
+            WeakKeyDictionary()
+        )  # type: WeakKeyDictionary[Module, List[Union[Item, Collector]]]
         name = request.function.__name__
         self.tmpdir = tmpdir_factory.mktemp(name, numbered=True)
         self.test_tmproot = tmpdir_factory.mktemp("tmp-" + name, numbered=True)
-        self.plugins = []
+        self.plugins = []  # type: List[Union[str, _PluggyPlugin]]
         self._cwd_snapshot = CwdSnapshot()
         self._sys_path_snapshot = SysPathsSnapshot()
         self._sys_modules_snapshot = self.__take_sys_modules_snapshot()
@@ -1064,7 +1071,9 @@ def getmodulecol(self, source, configargs=(), withinit=False):
         self.config = config = self.parseconfigure(path, *configargs)
         return self.getnode(config, path)
 
-    def collect_by_name(self, modcol, name):
+    def collect_by_name(
+        self, modcol: Module, name: str
+    ) -> Optional[Union[Item, Collector]]:
         """Return the collection node for name from the module collection.
 
         This will search a module collection node for a collection node
@@ -1073,13 +1082,13 @@ def collect_by_name(self, modcol, name):
         :param modcol: a module collection node; see :py:meth:`getmodulecol`
 
         :param name: the name of the node to return
-
         """
         if modcol not in self._mod_collections:
             self._mod_collections[modcol] = list(modcol.collect())
         for colitem in self._mod_collections[modcol]:
             if colitem.name == name:
                 return colitem
+        return None
 
     def popen(
         self,

testing/test_collection.py

@@ -9,6 +9,7 @@
 from _pytest.main import _in_venv
 from _pytest.main import ExitCode
 from _pytest.main import Session
+from _pytest.pytester import Testdir
 
 
 class TestCollector:
@@ -18,7 +19,7 @@ def test_collect_versus_item(self):
         assert not issubclass(Collector, Item)
         assert not issubclass(Item, Collector)
 
-    def test_check_equality(self, testdir):
+    def test_check_equality(self, testdir: Testdir) -> None:
         modcol = testdir.getmodulecol(
             """
             def test_pass(): pass
@@ -40,12 +41,15 @@ def test_fail(): assert 0
         assert fn1 != fn3
 
         for fn in fn1, fn2, fn3:
-            assert fn != 3
+            assert isinstance(fn, pytest.Function)
+            assert fn != 3  # type: ignore[comparison-overlap]  # noqa: F821
             assert fn != modcol
-            assert fn != [1, 2, 3]
-            assert [1, 2, 3] != fn
+            assert fn != [1, 2, 3]  # type: ignore[comparison-overlap]  # noqa: F821
+            assert [1, 2, 3] != fn  # type: ignore[comparison-overlap]  # noqa: F821
             assert modcol != fn
 
+        assert testdir.collect_by_name(modcol, "doesnotexist") is None
+
     def test_getparent(self, testdir):
         modcol = testdir.getmodulecol(
             """