Add pytest.register_fixture

changelog/12376.feature.rst

@@ -0,0 +1,7 @@
+Added :func:`pytest.register_fixture()` to register fixtures using an imperative interface.
+
+This is an advanced function intended for use by plugins.
+
+Normally, fixtures should be registered declaratively using the :func:`@pytest.fixture <pytest.fixture>` decorator.
+Pytest looks for these fixture definitions during the collection phase and registers them automatically.
+For some plugin usecases the declarative interface can be cumbersome or unviable, in which case this imperative interface can be used.

changelog/14004.deprecation.rst

@@ -2,5 +2,6 @@ Passing ``baseid`` to :class:`~pytest.FixtureDef` or ``nodeid`` strings to fixtu
 
 Use the ``node`` parameter instead for fixture scoping. This enables more robust node-based
 matching instead of string prefix matching.
+If you've used ``nodeid=None``, pass ``node=session`` instead.
 
 This will be removed in pytest 10.

changelog/14513.deprecation.rst

@@ -0,0 +1,2 @@
+The private ``FixtureDef.has_location`` attribute is now deprecated and will be removed in pytest 10.
+See :ref:`fixturedef-has-location-deprecated` for details.

changelog/14513.improvement.rst

@@ -0,0 +1,5 @@
+The order in which fixture definitions overriding each other are resolved is now determined first by their *visibility* in the collection tree rather than by the order in which they happened to be registered.
+
+A fixture defined for a more specific node (e.g. a module or an item) now always takes precedence over one with the same name defined for a more general node (e.g. the session), even when the more general one was registered later.
+Fixtures with non-comparable visibility keep the existing behavior of "last registered wins".
+This change is supposed to only affect plugins which register multiple fixtures programmatically with the same name.

doc/en/deprecations.rst

@@ -20,7 +20,7 @@ Below is a complete list of all pytest features which are considered deprecated.
 Passing ``baseid``/``nodeid`` strings to fixture registration APIs
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-.. deprecated:: 9.2
+.. deprecated:: 9.1
 
 Passing ``baseid`` to :class:`~pytest.FixtureDef` or ``nodeid`` strings to
 ``FixtureManager._register_fixture`` and ``FixtureManager.parsefactories``
@@ -37,11 +37,27 @@ node-based matching instead of fragile string prefix matching.
 
     # Use instead
     fixture_manager.parsefactories(holder=plugin_obj, node=directory_node)
-    fixture_manager._register_fixture(name="fix", func=func, node=directory_node)
+    pytest.register_fixture(name="fix", func=func, node=directory_node)
+
+The equivalent of passing ``nodeid=None`` (global visibility) is ``node=session``.
 
 In pytest 10, the ``baseid`` and ``nodeid`` string parameters will be removed.
 
 
+.. _fixturedef-has-location-deprecated:
+
+``FixtureDef.has_location``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. deprecated:: 9.1
+
+The private ``FixtureDef.has_location`` attribute is deprecated and will be removed in pytest 10.
+
+It indicated whether a fixture was found from a node or a conftest in the collection tree (as opposed to a non-conftest plugin).
+It was used to determine the override order of fixtures, pushing fixtures with "no location" to the front of the override chain (such that they are chosen last).
+The override order is now determined by the visibility of the fixtures in the collection tree, making this distinction obsolete.
+
+
 .. _console-main:
 
 ``pytest.console_main()``

src/_pytest/deprecated.py

@@ -123,6 +123,11 @@
     "Pass node instead for fixture scoping."
 )
 
+FIXTUREDEF_HAS_LOCATION_DEPRECATED = PytestRemovedIn10Warning(
+    "FixtureDef.has_location is deprecated and will be removed in pytest 10. "
+    "See https://docs.pytest.org/en/stable/deprecations.html#fixturedef-has-location-deprecated"
+)
+
 PARSEFACTORIES_NODEID_DEPRECATED = PytestRemovedIn10Warning(
     "Passing nodeid string to parsefactories is deprecated. "
     "Use parsefactories(holder=obj, node=node) instead."