Add exclusions for B905 (#388)

Co-authored-by: Alexey Nikitin <[email protected]>

Author: NewGlad

README.rst

@@ -220,8 +220,11 @@ See `the exception chaining tutorial <https://docs.python.org/3/tutorial/errors.
 for details.
 
 **B905**: ``zip()`` without an explicit `strict=` parameter set. ``strict=True`` causes the resulting iterator
-to raise a ``ValueError`` if the arguments are exhausted at differing lengths. The ``strict=`` argument
-was added in Python 3.10, so don't enable this flag for code that should work on <3.10.
+to raise a ``ValueError`` if the arguments are exhausted at differing lengths.
+
+Exclusions are `itertools.count <https://docs.python.org/3/library/itertools.html#itertools.count>`_, `itertools.cycle <https://docs.python.org/3/library/itertools.html#itertools.cycle>`_ and `itertools.repeat <https://docs.python.org/3/library/itertools.html#itertools.repeat>`_ (with times=None) since they are infinite iterators.
+
+The ``strict=`` argument was added in Python 3.10, so don't enable this flag for code that should work on <3.10.
 For more information: https://peps.python.org/pep-0618/
 
 **B906**: ``visit_`` function with no further call to a ``visit`` function. This is often an error, and will stop the visitor from recursing into the subnodes of a visited node. Consider adding a call ``self.generic_visit(node)`` at the end of the function.

bugbear.py

@@ -1169,12 +1169,46 @@ def check_for_b025(self, node):
         for duplicate in duplicates:
             self.errors.append(B025(node.lineno, node.col_offset, vars=(duplicate,)))
 
-    def check_for_b905(self, node):
-        if (
-            isinstance(node.func, ast.Name)
-            and node.func.id == "zip"
-            and not any(kw.arg == "strict" for kw in node.keywords)
+    @staticmethod
+    def _is_infinite_iterator(node: ast.expr) -> bool:
+        if not (
+            isinstance(node, ast.Call)
+            and isinstance(node.func, ast.Attribute)
+            and isinstance(node.func.value, ast.Name)
+            and node.func.value.id == "itertools"
         ):
+            return False
+        if node.func.attr in {"cycle", "count"}:
+            return True
+        elif node.func.attr == "repeat":
+            if len(node.args) == 1 and len(node.keywords) == 0:
+                # itertools.repeat(iterable)
+                return True
+            if (
+                len(node.args) == 2
+                and isinstance(node.args[1], ast.Constant)
+                and node.args[1].value is None
+            ):
+                # itertools.repeat(iterable, None)
+                return True
+            for kw in node.keywords:
+                # itertools.repeat(iterable, times=None)
+                if (
+                    kw.arg == "times"
+                    and isinstance(kw.value, ast.Constant)
+                    and kw.value.value is None
+                ):
+                    return True
+
+        return False
+
+    def check_for_b905(self, node):
+        if not (isinstance(node.func, ast.Name) and node.func.id == "zip"):
+            return
+        for arg in node.args:
+            if self._is_infinite_iterator(arg):
+                return
+        if not any(kw.arg == "strict" for kw in node.keywords):
             self.errors.append(B905(node.lineno, node.col_offset))
 
     def check_for_b906(self, node: ast.FunctionDef):

tests/b905_py310.py

@@ -8,3 +8,15 @@
 zip(range(3), strict=True)
 zip("a", "b", strict=False)
 zip("a", "b", "c", strict=True)
+
+# infinite iterators from itertools module should not raise errors
+import itertools
+
+zip([1, 2, 3], itertools.cycle("ABCDEF"))
+zip([1, 2, 3], itertools.count())
+zip([1, 2, 3], itertools.repeat(1))
+zip([1, 2, 3], itertools.repeat(1, None))
+zip([1, 2, 3], itertools.repeat(1, times=None))
+
+zip([1, 2, 3], itertools.repeat(1, 1))
+zip([1, 2, 3], itertools.repeat(1, times=4))

tests/test_bugbear.py

@@ -700,6 +700,8 @@ def test_b905(self):
             B905(4, 15),
             B905(5, 4),
             B905(6, 0),
+            B905(21, 0),
+            B905(22, 0),
         ]
         self.assertEqual(errors, self.errors(*expected))