mark: export pytest.MarkGenerator for typing purposes

The type cannot be constructed directly, but is exported for use in type
annotations, since it is reachable through existing public API.

2 files changed, 9 insertions, 4 deletions

diff --git a/src/_pytest/mark/structures.py b/src/_pytest/mark/structures.py
index 8bce33e68..ae6920735 100644
--- a/src/_pytest/mark/structures.py
+++ b/src/_pytest/mark/structures.py
@@ -488,9 +488,6 @@ class MarkGenerator:
     applies a 'slowtest' :class:`Mark` on ``test_function``.
     """
 
-    _config: Optional[Config] = None
-    _markers: Set[str] = set()
-
     # See TYPE_CHECKING above.
     if TYPE_CHECKING:
         skip: _SkipMarkDecorator
@@ -500,7 +497,13 @@ class MarkGenerator:
         usefixtures: _UsefixturesMarkDecorator
         filterwarnings: _FilterwarningsMarkDecorator
 
+    def __init__(self, *, _ispytest: bool = False) -> None:
+        check_ispytest(_ispytest)
+        self._config: Optional[Config] = None
+        self._markers: Set[str] = set()
+
     def __getattr__(self, name: str) -> MarkDecorator:
+        """Generate a new :class:`MarkDecorator` with the given name."""
         if name[0] == "_":
             raise AttributeError("Marker name must NOT start with underscore")
 
@@ -541,7 +544,7 @@ class MarkGenerator:
         return MarkDecorator(Mark(name, (), {}, _ispytest=True), _ispytest=True)
 
 
-MARK_GEN = MarkGenerator()
+MARK_GEN = MarkGenerator(_ispytest=True)
 
 
 @final
diff --git a/src/pytest/__init__.py b/src/pytest/__init__.py
index 1d5b38ee0..74cf00ee2 100644
--- a/src/pytest/__init__.py
+++ b/src/pytest/__init__.py
@@ -24,6 +24,7 @@ from _pytest.main import Session
 from _pytest.mark import Mark
 from _pytest.mark import MARK_GEN as mark
 from _pytest.mark import MarkDecorator
+from _pytest.mark import MarkGenerator
 from _pytest.mark import param
 from _pytest.monkeypatch import MonkeyPatch
 from _pytest.nodes import Collector
@@ -93,6 +94,7 @@ __all__ = [
     "mark",
     "Mark",
     "MarkDecorator",
+    "MarkGenerator",
     "Module",
     "MonkeyPatch",
     "Package",