Use issue_config_time_warning for the unset-loop-scope deprecation

changelog.d/1142.fixed.rst

@@ -0,0 +1 @@
+The deprecation warning for an unset `asyncio_default_fixture_loop_scope` is now visible to pytest: it appears in the warnings summary and can be filtered with `-W` and `filterwarnings`.

pytest_asyncio/plugin.py

@@ -297,7 +297,9 @@ def pytest_configure(config: Config) -> None:
     default_fixture_loop_scope = config.getini("asyncio_default_fixture_loop_scope")
     _validate_scope(default_fixture_loop_scope, "asyncio_default_fixture_loop_scope")
     if not default_fixture_loop_scope:
-        warnings.warn(PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET))
+        config.issue_config_time_warning(
+            PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET), stacklevel=2
+        )
 
     default_test_loop_scope = config.getini("asyncio_default_test_loop_scope")
     _validate_scope(default_test_loop_scope, "asyncio_default_test_loop_scope")

tests/test_fixture_loop_scopes.py

@@ -113,6 +113,54 @@ async def test_runs_in_fixture_loop(fixture_loop):
     result.assert_outcomes(passed=1)
 
 
+_UNSET_FIXTURE_LOOP_SCOPE_WARNING = (
+    "*PytestDeprecationWarning: The configuration option "
+    '"asyncio_default_fixture_loop_scope" is unset.*'
+)
+
+
+def test_unset_default_fixture_loop_scope_warning_appears_in_summary(
+    pytester: Pytester,
+):
+    """
+    The warning is emitted during configure, so it must still be recorded.
+
+    https://github.com/pytest-dev/pytest-asyncio/issues/1142
+    """
+    pytester.makepyfile("async def test_it(): pass")
+    result = pytester.runpytest("--asyncio-mode=auto")
+    result.assert_outcomes(passed=1, warnings=1)
+    result.stdout.fnmatch_lines(
+        ["*warnings summary*", _UNSET_FIXTURE_LOOP_SCOPE_WARNING]
+    )
+
+
+@pytest.mark.parametrize(
+    ("ini", "args"),
+    (
+        pytest.param(
+            "", ("-Wignore::pytest.PytestDeprecationWarning",), id="command-line-W"
+        ),
+        pytest.param(
+            "filterwarnings = ignore::pytest.PytestDeprecationWarning",
+            (),
+            id="filterwarnings-ini",
+        ),
+    ),
+)
+def test_unset_default_fixture_loop_scope_warning_is_filterable(
+    pytester: Pytester,
+    ini: str,
+    args: tuple[str, ...],
+):
+    """Being recorded properly also means users can silence it."""
+    pytester.makeini(f"[pytest]\n{ini}")
+    pytester.makepyfile("async def test_it(): pass")
+    result = pytester.runpytest("--asyncio-mode=auto", *args)
+    result.assert_outcomes(passed=1, warnings=0)
+    result.stdout.no_fnmatch_line(_UNSET_FIXTURE_LOOP_SCOPE_WARNING)
+
+
 def test_invalid_default_fixture_loop_scope_raises_error(pytester: Pytester):
     pytester.makeini("""\
         [pytest]