Fix Code.getargs() treating co_flags bitmask values as counts

changelog/14492.bugfix.rst

@@ -0,0 +1 @@
+Fixed ``Code.getargs()`` incorrectly including local variable names in the returned argument tuple for functions with ``*args`` and/or ``**kwargs``. The method was using ``co_flags`` bitmask values (``4`` and ``8``) directly as counts instead of converting them to ``1`` via ``bool()``.

src/_pytest/_code/code.py

@@ -121,8 +121,9 @@ def getargs(self, var: bool = False) -> tuple[str, ...]:
         raw = self.raw
         argcount = raw.co_argcount
         if var:
-            argcount += raw.co_flags & CO_VARARGS
-            argcount += raw.co_flags & CO_VARKEYWORDS
+            argcount += raw.co_kwonlyargcount
+            argcount += bool(raw.co_flags & CO_VARARGS)
+            argcount += bool(raw.co_flags & CO_VARKEYWORDS)
         return raw.co_varnames[:argcount]
 
 

testing/code/test_code.py

@@ -115,6 +115,20 @@ def f4(x, *y, **z):
     c4 = Code.from_function(f4)
     assert c4.getargs(var=True) == ("x", "y", "z")
 
+    def f5(x, *y, **z):
+        a1 = a2 = a3 = a4 = a5 = a6 = 1  # noqa: F841
+
+    c5 = Code.from_function(f5)
+    f5(1, 2, 3, z=4)  # cover function body
+    assert c5.getargs(var=True) == ("x", "y", "z")
+
+    def f6(x, *y, kw=1, **z):
+        a1 = a2 = a3 = a4 = a5 = a6 = 1  # noqa: F841
+
+    c6 = Code.from_function(f6)
+    f6(1, 2, kw=3, z=4)  # cover function body
+    assert c6.getargs(var=True) == ("x", "kw", "y", "z")
+
 
 def test_frame_getargs() -> None:
     def f1(x) -> FrameType: