Initialize args and args_source during Config.__init__

Closes #10626

Co-authored-by: Bruno Oliveira <nicoddemus@gmail.com>

AUTHORS

@@ -290,6 +290,7 @@ Prashant Sharma
 Pulkit Goyal
 Punyashloka Biswal
 Quentin Pradet
+q0w
 Ralf Schmitt
 Ralph Giles
 Ram Rachum

changelog/10626.bugfix.rst

@@ -0,0 +1 @@
+Fix crash if ``--fixtures`` and ``--help`` are passed at the same time.

src/_pytest/config/__init__.py

@@ -1005,6 +1005,8 @@ class Config:
         self.hook.pytest_addoption.call_historic(
             kwargs=dict(parser=self._parser, pluginmanager=self.pluginmanager)
         )
+        self.args_source = Config.ArgsSource.ARGS
+        self.args: List[str] = []
 
         if TYPE_CHECKING:
             from _pytest.cacheprovider import Cache
@@ -1344,8 +1346,8 @@ class Config:
 
     def parse(self, args: List[str], addopts: bool = True) -> None:
         # Parse given cmdline arguments into this config object.
-        assert not hasattr(
-            self, "args"
+        assert (
+            self.args == []
         ), "can only parse cmdline args at most once per Config object"
         self.hook.pytest_addhooks.call_historic(
             kwargs=dict(pluginmanager=self.pluginmanager)

testing/python/fixtures.py

@@ -3338,6 +3338,10 @@ class TestShowFixtures:
         config = pytester.parseconfigure("--funcargs")
         assert config.option.showfixtures
 
+    def test_show_help(self, pytester: Pytester) -> None:
+        result = pytester.runpytest("--fixtures", "--help")
+        assert not result.ret
+
     def test_show_fixtures(self, pytester: Pytester) -> None:
         result = pytester.runpytest("--fixtures")
         result.stdout.fnmatch_lines(