Categorize deprecation warnings to PytestRemovedInXWarning

Closes #7480.

This allows us to more easily follow our deprecation policy of turning
warnings into errors for the X.0 releases before complete removal in
X.1.

It also makes the deprecation timeline clear to both the users and
pytest developers -- it can be hard to keep track.

Note that the designation is not meant to be a binding contract - if the
time comes for removal of a specific deprecation but we decide it's too
soon, can just bump it to the next major.

Inspired by Django:
https://docs.djangoproject.com/en/dev/internals/contributing/writing-code/submitting-patches/#deprecating-a-feature

changelog/7480.improvement.rst

@@ -0,0 +1,5 @@
+A deprecation scheduled to be removed in a major version X (e.g. pytest 7, 8, 9, ...) now uses warning category `PytestRemovedInXWarning`,
+a subclass of :class:`~pytest.PytestDeprecationWarning`,
+instead of :class:`PytestDeprecationWarning` directly.
+
+See :ref:`backwards-compatibility` for more details.

doc/en/backwards-compatibility.rst

@@ -22,7 +22,9 @@ b) transitional: the old and new API don't conflict
 
    We will only start the removal of deprecated functionality in major releases (e.g. if we deprecate something in 3.0 we will start to remove it in 4.0), and keep it around for at least two minor releases (e.g. if we deprecate something in 3.9 and 4.0 is the next release, we start to remove it in 5.0, not in 4.0).
 
-   When the deprecation expires (e.g. 4.0 is released), we won't remove the deprecated functionality immediately, but will use the standard warning filters to turn them into **errors** by default. This approach makes it explicit that removal is imminent, and still gives you time to turn the deprecated feature into a warning instead of an error so it can be dealt with in your own time. In the next minor release (e.g. 4.1), the feature will be effectively removed.
+   A deprecated feature scheduled to be removed in major version X will use the warning class `PytestRemovedInXWarning` (a subclass of `~pytest.PytestDeprecationwarning`).
+
+   When the deprecation expires (e.g. 4.0 is released), we won't remove the deprecated functionality immediately, but will use the standard warning filters to turn `PytestRemovedInXWarning` (e.g. `PytestRemovedIn4Warning`) into **errors** by default. This approach makes it explicit that removal is imminent, and still gives you time to turn the deprecated feature into a warning instead of an error so it can be dealt with in your own time. In the next minor release (e.g. 4.1), the feature will be effectively removed.
 
 
 c) true breakage: should only be considered when normal transition is unreasonably unsustainable and would offset important development/features by years.

src/_pytest/deprecated.py

@@ -11,6 +11,8 @@
 from warnings import warn
 
 from _pytest.warning_types import PytestDeprecationWarning
+from _pytest.warning_types import PytestRemovedIn7Warning
+from _pytest.warning_types import PytestRemovedIn8Warning
 from _pytest.warning_types import UnformattedWarning
 
 # set of plugins which have been integrated into the core; we use this list to ignore
@@ -23,103 +25,106 @@
 
 
 FILLFUNCARGS = UnformattedWarning(
-    PytestDeprecationWarning,
+    PytestRemovedIn7Warning,
     "{name} is deprecated, use "
     "function._request._fillfixtures() instead if you cannot avoid reaching into internals.",
 )
 
 PYTEST_COLLECT_MODULE = UnformattedWarning(
-    PytestDeprecationWarning,
+    PytestRemovedIn7Warning,
     "pytest.collect.{name} was moved to pytest.{name}\n"
     "Please update to the new name.",
 )
 
+# This can be* removed pytest 8, but it's harmless and common, so no rush to remove.
+# * If you're in the future: "could have been".
 YIELD_FIXTURE = PytestDeprecationWarning(
     "@pytest.yield_fixture is deprecated.\n"
     "Use @pytest.fixture instead; they are the same."
 )
 
-MINUS_K_DASH = PytestDeprecationWarning(
+MINUS_K_DASH = PytestRemovedIn7Warning(
     "The `-k '-expr'` syntax to -k is deprecated.\nUse `-k 'not expr'` instead."
 )
 
-MINUS_K_COLON = PytestDeprecationWarning(
+MINUS_K_COLON = PytestRemovedIn7Warning(
     "The `-k 'expr:'` syntax to -k is deprecated.\n"
     "Please open an issue if you use this and want a replacement."
 )
 
-WARNING_CAPTURED_HOOK = PytestDeprecationWarning(
+WARNING_CAPTURED_HOOK = PytestRemovedIn7Warning(
     "The pytest_warning_captured is deprecated and will be removed in a future release.\n"
     "Please use pytest_warning_recorded instead."
 )
 
-WARNING_CMDLINE_PREPARSE_HOOK = PytestDeprecationWarning(
+WARNING_CMDLINE_PREPARSE_HOOK = PytestRemovedIn8Warning(
     "The pytest_cmdline_preparse hook is deprecated and will be removed in a future release. \n"
     "Please use pytest_load_initial_conftests hook instead."
 )
 
-FSCOLLECTOR_GETHOOKPROXY_ISINITPATH = PytestDeprecationWarning(
+FSCOLLECTOR_GETHOOKPROXY_ISINITPATH = PytestRemovedIn8Warning(
     "The gethookproxy() and isinitpath() methods of FSCollector and Package are deprecated; "
     "use self.session.gethookproxy() and self.session.isinitpath() instead. "
 )
 
-STRICT_OPTION = PytestDeprecationWarning(
+STRICT_OPTION = PytestRemovedIn8Warning(
     "The --strict option is deprecated, use --strict-markers instead."
 )
 
+# This deprecation is never really meant to be removed.
 PRIVATE = PytestDeprecationWarning("A private pytest class or function was used.")
 
-UNITTEST_SKIP_DURING_COLLECTION = PytestDeprecationWarning(
+UNITTEST_SKIP_DURING_COLLECTION = PytestRemovedIn8Warning(
     "Raising unittest.SkipTest to skip tests during collection is deprecated. "
     "Use pytest.skip() instead."
 )
 
-ARGUMENT_PERCENT_DEFAULT = PytestDeprecationWarning(
+ARGUMENT_PERCENT_DEFAULT = PytestRemovedIn8Warning(
     'pytest now uses argparse. "%default" should be changed to "%(default)s"',
 )
 
 ARGUMENT_TYPE_STR_CHOICE = UnformattedWarning(
-    PytestDeprecationWarning,
+    PytestRemovedIn8Warning,
     "`type` argument to addoption() is the string {typ!r}."
     " For choices this is optional and can be omitted, "
     " but when supplied should be a type (for example `str` or `int`)."
     " (options: {names})",
 )
 
 ARGUMENT_TYPE_STR = UnformattedWarning(
-    PytestDeprecationWarning,
+    PytestRemovedIn8Warning,
     "`type` argument to addoption() is the string {typ!r}, "
     " but when supplied should be a type (for example `str` or `int`)."
     " (options: {names})",
 )
 
 
 HOOK_LEGACY_PATH_ARG = UnformattedWarning(
-    PytestDeprecationWarning,
+    PytestRemovedIn8Warning,
     "The ({pylib_path_arg}: py.path.local) argument is deprecated, please use ({pathlib_path_arg}: pathlib.Path)\n"
     "see https://docs.pytest.org/en/latest/deprecations.html"
     "#py-path-local-arguments-for-hooks-replaced-with-pathlib-path",
 )
 
 NODE_CTOR_FSPATH_ARG = UnformattedWarning(
-    PytestDeprecationWarning,
+    PytestRemovedIn8Warning,
     "The (fspath: py.path.local) argument to {node_type_name} is deprecated. "
     "Please use the (path: pathlib.Path) argument instead.\n"
     "See https://docs.pytest.org/en/latest/deprecations.html"
     "#fspath-argument-for-node-constructors-replaced-with-pathlib-path",
 )
 
-WARNS_NONE_ARG = PytestDeprecationWarning(
+WARNS_NONE_ARG = PytestRemovedIn8Warning(
     "Passing None to catch any warning has been deprecated, pass no arguments instead:\n"
     " Replace pytest.warns(None) by simply pytest.warns()."
 )
 
 KEYWORD_MSG_ARG = UnformattedWarning(
-    PytestDeprecationWarning,
+    PytestRemovedIn8Warning,
     "pytest.{func}(msg=...) is now deprecated, use pytest.{func}(reason=...) instead",
 )
 
-INSTANCE_COLLECTOR = PytestDeprecationWarning(
+INSTANCE_COLLECTOR = PytestRemovedIn8Warning(
     "The pytest.Instance collector type is deprecated and is no longer used. "
     "See https://docs.pytest.org/en/latest/deprecations.html#the-pytest-instance-collector",
 )

src/_pytest/warning_types.py

@@ -42,13 +42,26 @@ class PytestCollectionWarning(PytestWarning):
     __module__ = "pytest"
 
 
-@final
 class PytestDeprecationWarning(PytestWarning, DeprecationWarning):
     """Warning class for features that will be removed in a future version."""
 
     __module__ = "pytest"
 
 
+@final
+class PytestRemovedIn7Warning(PytestDeprecationWarning):
+    """Warning class for features that will be removed in pytest 7."""
+
+    __module__ = "pytest"
+
+
+@final
+class PytestRemovedIn8Warning(PytestDeprecationWarning):
+    """Warning class for features that will be removed in pytest 8."""
+
+    __module__ = "pytest"
+
+
 @final
 class PytestExperimentalApiWarning(PytestWarning, FutureWarning):
     """Warning category used to denote experiments in pytest.

src/pytest/__init__.py

@@ -68,6 +68,8 @@
 from _pytest.warning_types import PytestConfigWarning
 from _pytest.warning_types import PytestDeprecationWarning
 from _pytest.warning_types import PytestExperimentalApiWarning
+from _pytest.warning_types import PytestRemovedIn7Warning
+from _pytest.warning_types import PytestRemovedIn8Warning
 from _pytest.warning_types import PytestUnhandledCoroutineWarning
 from _pytest.warning_types import PytestUnhandledThreadExceptionWarning
 from _pytest.warning_types import PytestUnknownMarkWarning
@@ -127,6 +129,8 @@
     "PytestConfigWarning",
     "PytestDeprecationWarning",
     "PytestExperimentalApiWarning",
+    "PytestRemovedIn7Warning",
+    "PytestRemovedIn8Warning",
     "Pytester",
     "PytestPluginManager",
     "PytestUnhandledCoroutineWarning",

testing/deprecated_test.py

@@ -115,7 +115,7 @@ def test_foo(): pass
     result.stdout.fnmatch_lines(
         [
             "'unknown' not found in `markers` configuration option",
-            "*PytestDeprecationWarning: The --strict option is deprecated, use --strict-markers instead.",
+            "*PytestRemovedIn8Warning: The --strict option is deprecated, use --strict-markers instead.",
         ]
     )
 
@@ -154,7 +154,7 @@ def test_raising_unittest_skiptest_during_collection_is_deprecated(
     result = pytester.runpytest()
     result.stdout.fnmatch_lines(
         [
-            "*PytestDeprecationWarning: Raising unittest.SkipTest*",
+            "*PytestRemovedIn8Warning: Raising unittest.SkipTest*",
         ]
     )
 
@@ -213,7 +213,7 @@ def test_skipping_msg():
         result = pytester.runpytest(p)
         result.stdout.fnmatch_lines(
             [
-                "*PytestDeprecationWarning: pytest.skip(msg=...) is now deprecated, "
+                "*PytestRemovedIn8Warning: pytest.skip(msg=...) is now deprecated, "
                 "use pytest.skip(reason=...) instead",
                 '*pytest.skip(msg="skippedmsg")*',
             ]
@@ -232,7 +232,7 @@ def test_failing_msg():
         result = pytester.runpytest(p)
         result.stdout.fnmatch_lines(
             [
-                "*PytestDeprecationWarning: pytest.fail(msg=...) is now deprecated, "
+                "*PytestRemovedIn8Warning: pytest.fail(msg=...) is now deprecated, "
                 "use pytest.fail(reason=...) instead",
                 '*pytest.fail(msg="failedmsg")',
             ]
@@ -251,7 +251,7 @@ def test_exit_msg():
         result = pytester.runpytest(p)
         result.stdout.fnmatch_lines(
             [
-                "*PytestDeprecationWarning: pytest.exit(msg=...) is now deprecated, "
+                "*PytestRemovedIn8Warning: pytest.exit(msg=...) is now deprecated, "
                 "use pytest.exit(reason=...) instead",
             ]
         )
@@ -269,7 +269,7 @@ def pytest_cmdline_preparse(config, args):
     result = pytester.runpytest()
     result.stdout.fnmatch_lines(
         [
-            "*PytestDeprecationWarning: The pytest_cmdline_preparse hook is deprecated*",
+            "*PytestRemovedIn8Warning: The pytest_cmdline_preparse hook is deprecated*",
             "*Please use pytest_load_initial_conftests hook instead.*",
         ]
     )