Handle positional-only args in class methods (fixes #157)

bugbear.py

@@ -459,7 +459,7 @@ def check_for_b902(self, node):
                 expected_first_args = B902.self
                 kind = "instance"
 
-        args = node.args.args
+        args = getattr(node.args, "posonlyargs", []) + node.args.args
         vararg = node.args.vararg
         kwarg = node.args.kwarg
         kwonlyargs = node.args.kwonlyargs

tests/b902_py38.py

@@ -0,0 +1,102 @@
+def not_a_method(arg1, /):
+    ...
+
+
+class NoWarnings:
+    def __init__(self, /):
+        def not_a_method_either(arg1, /):
+            ...
+
+    def __new__(cls, /, *args, **kwargs):
+        ...
+
+    def method(self, arg1, /, *, yeah):
+        ...
+
+    async def async_method(self, arg1, /, *, yeah):
+        ...
+
+    @classmethod
+    def someclassmethod(cls, arg1, with_default=None, /):
+        ...
+
+    @staticmethod
+    def not_a_problem(arg1, /):
+        ...
+
+
+class Warnings:
+    def __init__(i_am_special, /):
+        ...
+
+    def almost_a_class_method(cls, arg1, /):
+        ...
+
+    def almost_a_static_method():
+        ...
+
+    @classmethod
+    def wat(self, i_like_confusing_people, /):
+        ...
+
+    def i_am_strange(*args, **kwargs):
+        self = args[0]
+
+    def defaults_anyone(self=None, /):
+        ...
+
+    def invalid_kwargs_only(**kwargs):
+        ...
+
+    def invalid_keyword_only(*, self):
+        ...
+
+    async def async_invalid_keyword_only(*, self):
+        ...
+
+
+class Meta(type):
+    def __init__(cls, name, bases, d, /):
+        ...
+
+    @classmethod
+    def __prepare__(metacls, name, bases, /):
+        return {}
+
+
+class OtherMeta(type):
+    def __init__(self, name, bases, d, /):
+        ...
+
+    @classmethod
+    def __prepare__(cls, name, bases, /):
+        return {}
+
+    @classmethod
+    def first_arg_mcs_allowed(mcs, value, /):
+        ...
+
+
+def type_factory():
+    return object
+
+
+class CrazyBases(Warnings, type_factory(), metaclass=type):
+    def __init__(self):
+        ...
+
+
+class RuntimeError("This is not a base"):
+    def __init__(self):
+        ...
+
+
+class ImplicitClassMethods:
+    def __new__(cls, /, *args, **kwargs):
+        ...
+
+    def __init_subclass__(cls, /, *args, **kwargs):
+        ...
+
+    def __class_getitem__(cls, key, /):
+        ...

tests/test_bugbear.py

@@ -3,6 +3,7 @@
 from pathlib import Path
 import site
 import subprocess
+import sys
 import unittest
 
 from hypothesis import HealthCheck, given, settings
@@ -260,6 +261,27 @@ def test_b902(self):
             ),
         )
 
+    @unittest.skipIf(sys.version_info < (3, 8), "requires 3.8+")
+    def test_b902_py38(self):
+        filename = Path(__file__).absolute().parent / "b902_py38.py"
+        bbc = BugBearChecker(filename=str(filename))
+        errors = list(bbc.run())
+        self.assertEqual(
+            errors,
+            self.errors(
+                B902(29, 17, vars=("'i_am_special'", "instance", "self")),
+                B902(32, 30, vars=("'cls'", "instance", "self")),
+                B902(35, 4, vars=("(none)", "instance", "self")),
+                B902(39, 12, vars=("'self'", "class", "cls")),
+                B902(42, 22, vars=("*args", "instance", "self")),
+                B902(48, 30, vars=("**kwargs", "instance", "self")),
+                B902(51, 32, vars=("*, self", "instance", "self")),
+                B902(54, 44, vars=("*, self", "instance", "self")),
+                B902(68, 17, vars=("'self'", "metaclass instance", "cls")),
+                B902(72, 20, vars=("'cls'", "metaclass class", "metacls")),
+            ),
+        )
+
     def test_b903(self):
         filename = Path(__file__).absolute().parent / "b903.py"
         bbc = BugBearChecker(filename=str(filename))