Merge pull request #314 from jakkdl/zip_require_strict

fixes #311

README.rst

@@ -200,6 +200,11 @@ or ``raise ... from None`` to distinguish them from errors in exception handling
 See `the exception chaining tutorial <https://docs.python.org/3/tutorial/errors.html#exception-chaining>`_
 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.
+For more information: https://peps.python.org/pep-0618/
+
 **B950**: Line too long. This is a pragmatic equivalent of
 ``pycodestyle``'s ``E501``: it considers "max-line-length" but only triggers
 when the value has been exceeded by **more than 10%**. You will no
@@ -299,7 +304,8 @@ Change Log
 
 Future
 ~~~~~~~~~
-* B027: ignore @overload when typing is import with other names
+* B027: ignore @overload when typing is imported with other names
+* Add B905: `zip()` without an explicit `strict=` parameter.
 
 22.10.27
 ~~~~~~~~~

bugbear.py

@@ -356,6 +356,7 @@ def visit_Call(self, node):
 
             self.check_for_b026(node)
 
+        self.check_for_b905(node)
         self.generic_visit(node)
 
     def visit_Assign(self, node):
@@ -960,6 +961,14 @@ 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)
+        ):
+            self.errors.append(B905(node.lineno, node.col_offset))
+
 
 def compose_call_path(node):
     if isinstance(node, ast.Attribute):
@@ -1360,6 +1369,8 @@ def visit_Lambda(self, node):
     )
 )
 
+B905 = Error(message="B905 `zip()` without an explicit `strict=` parameter.")
+
 B950 = Error(message="B950 line too long ({} > {} characters)")
 
-disabled_by_default = ["B901", "B902", "B903", "B904", "B950"]
+disabled_by_default = ["B901", "B902", "B903", "B904", "B905", "B950"]

tests/b905_py310.py

@@ -0,0 +1,10 @@
+zip()
+zip(range(3))
+zip("a", "b")
+zip("a", "b", *zip("c"))
+zip(zip("a"), strict=False)
+zip(zip("a", strict=True))
+
+zip(range(3), strict=True)
+zip("a", "b", strict=False)
+zip("a", "b", "c", strict=True)

tests/test_bugbear.py

@@ -42,6 +42,7 @@
     B902,
     B903,
     B904,
+    B905,
     B950,
     BugBearChecker,
     BugBearVisitor,
@@ -297,7 +298,7 @@ def test_b019(self):
     def test_b020(self):
         filename = Path(__file__).absolute().parent / "b020.py"
         bbc = BugBearChecker(filename=str(filename))
-        errors = list(bbc.run())
+        errors = list(e for e in bbc.run() if e[2][:4] == "B020")
         self.assertEqual(
             errors,
             self.errors(
@@ -484,6 +485,22 @@ def test_b904(self):
         ]
         self.assertEqual(errors, self.errors(*expected))
 
+    @unittest.skipIf(sys.version_info < (3, 10), "requires 3.10+")
+    def test_b905(self):
+        filename = Path(__file__).absolute().parent / "b905_py310.py"
+        bbc = BugBearChecker(filename=str(filename))
+        errors = list(bbc.run())
+        expected = [
+            B905(1, 0),
+            B905(2, 0),
+            B905(3, 0),
+            B905(4, 0),
+            B905(4, 15),
+            B905(5, 4),
+            B905(6, 0),
+        ]
+        self.assertEqual(errors, self.errors(*expected))
+
     def test_b950(self):
         filename = Path(__file__).absolute().parent / "b950.py"
         bbc = BugBearChecker(filename=str(filename))