Allow fixture and marker listing without required plugin options

AUTHORS

@@ -439,6 +439,7 @@ Russell Martin
 Ryan Puddephatt
 Ryan Wooden
 Sadra Barikbin
+Sagar
 Saiprasad Kale
 Samuel Colvin
 Samuel Dion-Girardeau

changelog/3042.bugfix.rst

@@ -0,0 +1 @@
+Allow ``--fixtures``, ``--funcargs``, ``--fixtures-per-test``, and ``--markers`` to run without supplying required plugin options. Required options remain enforced when running tests.

src/_pytest/config/argparsing.py

@@ -3,7 +3,10 @@
 
 import argparse
 from collections.abc import Callable
+from collections.abc import Iterable
+from collections.abc import Iterator
 from collections.abc import Sequence
+import contextlib
 import dataclasses
 import os
 import re
@@ -512,6 +515,42 @@ def __init__(
         # an usage error to provide more contextual information to the user.
         self.extra_info = extra_info
 
+    def parse_known_args(
+        self,
+        args: Iterable[str] | None = None,
+        namespace: Any = None,
+    ) -> tuple[Any, list[str]]:
+        with self._restore_required_options(namespace):
+            return super().parse_known_args(args, namespace)
+
+    def parse_known_intermixed_args(
+        self,
+        args: Iterable[str] | None = None,
+        namespace: Any = None,
+    ) -> tuple[Any, list[str]]:
+        with self._restore_required_options(namespace):
+            return super().parse_known_intermixed_args(args, namespace)
+
+    @contextlib.contextmanager
+    def _restore_required_options(
+        self, namespace: argparse.Namespace | None
+    ) -> Iterator[None]:
+        # Informational actions temporarily relax required options. Restore
+        # them even if parsing fails, so subsequent parses still enforce them.
+        required_actions = [action for action in self._actions if action.required]
+        if namespace is not None and any(
+            isinstance(action, InformationalAction)
+            and getattr(namespace, action.dest, False)
+            for action in self._actions
+        ):
+            for action in required_actions:
+                action.required = False
+        try:
+            yield
+        finally:
+            for action in required_actions:
+                action.required = True
+
     def error(self, message: str) -> NoReturn:
         """Transform argparse error message into UsageError."""
         # TODO(py313): Replace with `exit_on_error=False`. Note that while it
@@ -657,3 +696,15 @@ def __call__(
             current_overrides = []
         current_overrides.append(f"{self.ini_option}={self.ini_value}")
         setattr(namespace, "override_ini", current_overrides)
+
+
+class InformationalAction(argparse.Action):
+    """Set a listing flag without requiring options used to run tests."""
+
+    def __init__(self, option_strings, dest, default=False, **kwargs):
+        super().__init__(option_strings, dest, nargs=0, default=default, **kwargs)
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        setattr(namespace, self.dest, True)
+        for action in parser._actions:
+            action.required = False

src/_pytest/fixtures.py

@@ -54,6 +54,7 @@
 from _pytest.config import Config
 from _pytest.config import ExitCode
 from _pytest.config import hookimpl
+from _pytest.config.argparsing import InformationalAction
 from _pytest.config.argparsing import Parser
 from _pytest.deprecated import check_ispytest
 from _pytest.deprecated import CLASS_FIXTURE_INSTANCE_METHOD
@@ -1658,15 +1659,15 @@ def pytest_addoption(parser: Parser) -> None:
     group.addoption(
         "--fixtures",
         "--funcargs",
-        action="store_true",
+        action=InformationalAction,
         dest="showfixtures",
         default=False,
         help="Show available fixtures, sorted by plugin appearance "
         "(fixtures with leading '_' are only shown with '-v')",
     )
     group.addoption(
         "--fixtures-per-test",
-        action="store_true",
+        action=InformationalAction,
         dest="show_fixtures_per_test",
         default=False,
         help="Show fixtures per test",

src/_pytest/mark/__init__.py

@@ -25,6 +25,7 @@
 from _pytest.config import ExitCode
 from _pytest.config import hookimpl
 from _pytest.config import UsageError
+from _pytest.config.argparsing import InformationalAction
 from _pytest.config.argparsing import Parser
 from _pytest.stash import StashKey
 
@@ -118,7 +119,7 @@ def pytest_addoption(parser: Parser) -> None:
 
     group.addoption(
         "--markers",
-        action="store_true",
+        action=InformationalAction,
         help="show markers (builtin, plugin and per-project ones).",
     )
 

testing/test_config.py

@@ -3645,3 +3645,53 @@ def test_get_verbosity(self, pytester: Pytester) -> None:
         pytester.maketoml("[pytest]\nverbosity_assertions = 2\n")
         config = pytester.parseconfig()
         assert config.get_verbosity(Config.VERBOSITY_ASSERTIONS) == 2
+
+
+@pytest.mark.parametrize(
+    "flag", ["--fixtures", "--funcargs", "--fixtures-per-test", "--markers"]
+)
+@pytest.mark.parametrize("action", ["store", "store_true"])
+def test_information_with_required_option(
+    pytester: Pytester, flag: str, action: str
+) -> None:
+    pytester.makeconftest(
+        f"""
+        import pytest
+
+        def pytest_addoption(parser):
+            parser.addoption("--required", action="{action}", required=True)
+
+        @pytest.fixture
+        def example_fixture():
+            return 1
+        """
+    )
+    pytester.makepyfile(
+        """
+        def test_example(example_fixture):
+            assert example_fixture == 1
+        """
+    )
+    result = pytester.runpytest(flag)
+    assert result.ret == pytest.ExitCode.OK
+    expected = "@pytest.mark.skip" if flag == "--markers" else "example_fixture"
+    assert expected in result.stdout.str()
+
+
+@pytest.mark.parametrize("args", [[], ["--required", "present"]])
+def test_required_option_still_enforced(pytester: Pytester, args: list[str]) -> None:
+    pytester.makeconftest(
+        """
+        def pytest_addoption(parser):
+            parser.addoption("--required", required=True)
+        """
+    )
+    pytester.makepyfile("def test_example(): pass")
+    result = pytester.runpytest(*args)
+    if args:
+        result.assert_outcomes(passed=1)
+    else:
+        assert result.ret == pytest.ExitCode.USAGE_ERROR
+        result.stderr.fnmatch_lines(
+            ["*the following arguments are required: --required*"]
+        )

testing/test_parseopt.py

@@ -506,3 +506,50 @@ def test_does_not_break_on_hyphens(self) -> None:
 
     def test_empty_help(self) -> None:
         assert parseopt._split_help_text("", 40) == []
+
+
+@pytest.mark.parametrize("args", [["--list"], ["--list", "--required", "value"]])
+def test_informational_action_restores_required_options(parser, args):
+    parser.addoption("--list", action=parseopt.InformationalAction)
+    parser.addoption("--required", required=True)
+    namespace = parser.parse(args)
+    assert namespace.list is True
+    with pytest.raises(
+        UsageError, match="the following arguments are required: --required"
+    ):
+        parser.parse([])
+    assert parser.parse(["--required", "value"]).required == "value"
+
+
+@pytest.mark.parametrize(
+    "args", [["--list", "--choice", "bad"], ["--choice", "bad", "--list"]]
+)
+def test_informational_action_keeps_value_validation(parser, args):
+    parser.addoption("--list", action=parseopt.InformationalAction)
+    parser.addoption("--required", required=True)
+    parser.addoption("--choice", choices=["good"])
+    with pytest.raises(UsageError, match="invalid choice"):
+        parser.parse(args)
+    with pytest.raises(
+        UsageError, match="the following arguments are required: --required"
+    ):
+        parser.parse([])
+
+
+def test_informational_action_after_option_terminator(parser):
+    parser.addoption("--list", action=parseopt.InformationalAction)
+    parser.addoption("--required", required=True)
+    with pytest.raises(
+        UsageError, match="the following arguments are required: --required"
+    ):
+        parser.parse(["--", "--list"])
+
+
+# Older argparse versions read argument files without an explicit encoding.
+@pytest.mark.filterwarnings("ignore:'encoding' argument not specified:EncodingWarning")
+def test_informational_action_from_argument_file(parser, tmp_path):
+    parser.addoption("--list", action=parseopt.InformationalAction)
+    parser.addoption("--required", required=True)
+    args_file = tmp_path / "args.txt"
+    args_file.write_text("--list\n", encoding="utf-8")
+    assert parser.parse([f"@{args_file}"]).list is True