Merge pull request #8006 from bluetech/export-MonkeyPatch

bluetech · web-flow · commit e986d84466df · 2020-11-09T11:45:38.000+02:00
Export MonkeyPatch as pytest.MonkeyPatch
diff --git a/changelog/8006.feature.rst b/changelog/8006.feature.rst
@@ -0,0 +1,8 @@
+It is now possible to construct a :class:`~pytest.MonkeyPatch` object directly as ``pytest.MonkeyPatch()``,
+in cases when the :fixture:`monkeypatch` fixture cannot be used. Previously some users imported it
+from the private `_pytest.monkeypatch.MonkeyPatch` namespace.
+
+Additionally, :meth:`MonkeyPatch.context <pytest.MonkeyPatch.context>` is now a classmethod,
+and can be used as ``with MonkeyPatch.context() as mp: ...``. This is the recommended way to use
+``MonkeyPatch`` directly, since unlike the ``monkeypatch`` fixture, an instance created directly
+is not ``undo()``-ed automatically.
diff --git a/doc/en/reference.rst b/doc/en/reference.rst
@@ -486,16 +486,14 @@ caplog
 monkeypatch
 ~~~~~~~~~~~
 
-.. currentmodule:: _pytest.monkeypatch
-
 **Tutorial**: :doc:`monkeypatch`.
 
 .. autofunction:: _pytest.monkeypatch.monkeypatch()
     :no-auto-options:
 
-    Returns a :class:`MonkeyPatch` instance.
+    Returns a :class:`~pytest.MonkeyPatch` instance.
 
-.. autoclass:: _pytest.monkeypatch.MonkeyPatch
+.. autoclass:: pytest.MonkeyPatch
     :members:
 
 
diff --git a/src/_pytest/monkeypatch.py b/src/_pytest/monkeypatch.py
@@ -111,17 +111,27 @@ def __repr__(self) -> str:
 
 @final
 class MonkeyPatch:
-    """Object returned by the ``monkeypatch`` fixture keeping a record of
-    setattr/item/env/syspath changes."""
+    """Helper to conveniently monkeypatch attributes/items/environment
+    variables/syspath.
+
+    Returned by the :fixture:`monkeypatch` fixture.
+
+    :versionchanged:: 6.2
+        Can now also be used directly as `pytest.MonkeyPatch()`, for when
+        the fixture is not available. In this case, use
+        :meth:`with MonkeyPatch.context() as mp: <context>` or remember to call
+        :meth:`undo` explicitly.
+    """
 
     def __init__(self) -> None:
         self._setattr: List[Tuple[object, str, object]] = []
         self._setitem: List[Tuple[MutableMapping[Any, Any], object, object]] = ([])
         self._cwd: Optional[str] = None
         self._savesyspath: Optional[List[str]] = None
 
+    @classmethod
     @contextmanager
-    def context(self) -> Generator["MonkeyPatch", None, None]:
+    def context(cls) -> Generator["MonkeyPatch", None, None]:
         """Context manager that returns a new :class:`MonkeyPatch` object
         which undoes any patching done inside the ``with`` block upon exit.
 
@@ -140,7 +150,7 @@ def test_partial(monkeypatch):
         such as mocking ``stdlib`` functions that might break pytest itself if mocked (for examples
         of this see `#3290 <https://github.com/pytest-dev/pytest/issues/3290>`_.
         """
-        m = MonkeyPatch()
+        m = cls()
         try:
             yield m
         finally:
diff --git a/src/pytest/__init__.py b/src/pytest/__init__.py
@@ -19,6 +19,7 @@
 from _pytest.main import Session
 from _pytest.mark import MARK_GEN as mark
 from _pytest.mark import param
+from _pytest.monkeypatch import MonkeyPatch
 from _pytest.nodes import Collector
 from _pytest.nodes import File
 from _pytest.nodes import Item
@@ -74,6 +75,7 @@
     "main",
     "mark",
     "Module",
+    "MonkeyPatch",
     "Package",
     "param",
     "PytestAssertRewriteWarning",
diff --git a/testing/test_monkeypatch.py b/testing/test_monkeypatch.py
@@ -409,6 +409,16 @@ def test_context() -> None:
     assert inspect.isclass(functools.partial)
 
 
+def test_context_classmethod() -> None:
+    class A:
+        x = 1
+
+    with MonkeyPatch.context() as m:
+        m.setattr(A, "x", 2)
+        assert A.x == 2
+    assert A.x == 1
+
+
 def test_syspath_prepend_with_namespace_packages(
     testdir: Testdir, monkeypatch: MonkeyPatch
 ) -> None:
