fixtures: exclude direct-param fixtures from --fixtures-per-test output

Fix #11295 by excluding from the --fixtures-per-test output any 'pseudo
fixture' that results from directy parametrizing a test e.g. with
``@pytest.mark.parametrize``.

The justification for removing these fixtures from the report is that

a) They are unintuitive. Their appearance in the fixtures-per-test
report confuses new users because the fixtures created via
``@pytest.mark.parametrize`` do not confrom to the expectations
established in the documentation; namely, that fixtures are
- richly reusable
- provide setup/teardown features
- created via the ``@pytest.fixture` decorator

b) They are an internal implementation detail. It is not the explicit
goal of the direct parametrization mark to create a fixture; instead,
pytest's internals leverages the fixture system to achieve the explicit
goal: a succinct batch execution syntax. Consequently, exposing the
fixtures that implement the batch execution behaviour reveal more about
pytest's internals than they do about the user's own design choices and
test dependencies.

Author: WarrenTheRabbit

AUTHORS

@@ -495,6 +495,7 @@ Vlad Radziuk
 Vladyslav Rachek
 Volodymyr Kochetkov
 Volodymyr Piskun
+Warren Markham
 Wei Lin
 Wil Cooley
 Will Riley

changelog/11295.improvement.rst

@@ -0,0 +1 @@
+Improved output of ``--fixtures-per-test`` by excluding internal-implementation fixtures generated by ``@pytest.mark.parametrize`` and similar.

src/_pytest/fixtures.py

@@ -1977,6 +1977,36 @@ def _pretty_fixture_path(invocation_dir: Path, func) -> str:
         return bestrelpath(invocation_dir, loc)
 
 
+def _get_fixtures_per_test(test: nodes.Item) -> Iterator[FixtureDef[object]]:
+    """Returns all fixtures used by the test item except for those created by
+    direct parametrization and those requested dynamically with
+    ``request.getfixturevalue``.
+
+    The justification for excluding fixtures created by direct parametrization
+    is that for users, they are internal implementation detail.
+
+    Dynamically requested fixtures are excluded because they are not known
+    statically.
+    """
+    from _pytest.python import DirectParamFixtureDef
+
+    # Custom Items may not have _fixtureinfo attribute.
+    fixture_info: FuncFixtureInfo | None = getattr(test, "_fixtureinfo", None)
+    if fixture_info is None:
+        return  # pragma: no cover
+
+    # dict key not used in loop but needed for sorting.
+    for argname, fixturedefs in sorted(fixture_info.name2fixturedefs.items()):
+        if not fixturedefs:
+            # Not supposed to be empty, but for safety.
+            continue  # pragma: no cover
+        # Last item is expected to be the one directly used by the test item.
+        fixturedef = fixturedefs[-1]
+        if isinstance(fixturedef, DirectParamFixtureDef):
+            continue
+        yield fixturedef
+
+
 def _show_fixtures_per_test(config: Config, session: Session) -> None:
     import _pytest.config
 
@@ -2009,22 +2039,18 @@ def write_fixture(fixture_def: FixtureDef[object]) -> None:
             tw.line("    no docstring available", red=True)
 
     def write_item(item: nodes.Item) -> None:
-        # Not all items have _fixtureinfo attribute.
-        info: FuncFixtureInfo | None = getattr(item, "_fixtureinfo", None)
-        if info is None or not info.name2fixturedefs:
+        fixturedefs = list(_get_fixtures_per_test(item))
+        if not fixturedefs:
             # This test item does not use any fixtures.
             return
+
         tw.line()
         tw.sep("-", f"fixtures used by {item.name}")
         # TODO: Fix this type ignore.
         tw.sep("-", f"({get_best_relpath(item.function)})")  # type: ignore[attr-defined]
-        # dict key not used in loop but needed for sorting.
-        for _, fixturedefs in sorted(info.name2fixturedefs.items()):
-            assert fixturedefs is not None
-            if not fixturedefs:
-                continue
-            # Last item is expected to be the one used by the test item.
-            write_fixture(fixturedefs[-1])
+
+        for fixturedef in fixturedefs:
+            write_fixture(fixturedef)
 
     for session_item in session.items:
         write_item(session_item)

testing/python/show_fixtures_per_test.py

@@ -3,7 +3,7 @@
 from _pytest.pytester import Pytester
 
 
-def test_no_items_should_not_show_output(pytester: Pytester) -> None:
+def test_should_show_no_output_when_zero_items(pytester: Pytester) -> None:
     result = pytester.runpytest("--fixtures-per-test")
     result.stdout.no_fnmatch_line("*fixtures used by*")
     assert result.ret == 0
@@ -254,3 +254,75 @@ def test_arg1(arg1):
             "    Docstring content that extends into a third paragraph.",
         ]
     )
+
+
+def test_should_not_show_direct_param_fixtures(pytester: Pytester) -> None:
+    """A direct-param fixture is a helper fixture created as an implementation
+    detail of direct parametrization.
+
+    These fixtures should not be included in the output because they don't
+    satisfy user expectations for how fixtures are created and used (#11295).
+    """
+    pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.mark.parametrize("x", [1])
+        def test_pseudo_fixture(x):
+            pass
+        """
+    )
+    result = pytester.runpytest("--fixtures-per-test")
+    result.stdout.no_fnmatch_line("*fixtures used by*")
+    assert result.ret == 0
+
+
+def test_should_show_parametrized_fixtures_used_by_test(pytester: Pytester) -> None:
+    """A fixture with parameters should be included if it was created using
+    the @pytest.fixture decorator, including those that are indirectly
+    parametrized."""
+    pytester.makepyfile(
+        '''
+        import pytest
+
+        @pytest.fixture(params=['a', 'b'])
+        def directly(request):
+            """parametrized fixture"""
+            return request.param
+
+        @pytest.fixture
+        def indirectly(request):
+            """indirectly parametrized fixture"""
+            return request.param
+
+        def test_directly_parametrized_fixture(directly):
+            pass
+
+        @pytest.mark.parametrize("indirectly", ["a", "b"], indirect=True)
+        def test_indirectly_parametrized_fixture(indirectly):
+            pass
+        '''
+    )
+    result = pytester.runpytest("--fixtures-per-test")
+    assert result.ret == 0
+
+    result.stdout.fnmatch_lines(
+        [
+            "*fixtures used by test_directly_parametrized_fixture*",
+            "*(test_should_show_parametrized_fixtures_used_by_test.py:14)*",
+            "directly -- test_should_show_parametrized_fixtures_used_by_test.py:4",
+            "    parametrized fixture",
+            "*fixtures used by test_directly_parametrized_fixture*",
+            "*(test_should_show_parametrized_fixtures_used_by_test.py:14)*",
+            "directly -- test_should_show_parametrized_fixtures_used_by_test.py:4",
+            "    parametrized fixture",
+            "*fixtures used by test_indirectly_parametrized_fixture*",
+            "*(test_should_show_parametrized_fixtures_used_by_test.py:17)*",
+            "indirectly -- test_should_show_parametrized_fixtures_used_by_test.py:9",
+            "    indirectly parametrized fixture",
+            "*fixtures used by test_indirectly_parametrized_fixture*",
+            "*(test_should_show_parametrized_fixtures_used_by_test.py:17)*",
+            "indirectly -- test_should_show_parametrized_fixtures_used_by_test.py:9",
+            "    indirectly parametrized fixture",
+        ]
+    )