flake8-bugbear

.flake8

@@ -4,6 +4,21 @@ max-line-length = 119
 ignore =
     # black disagrees with flake8 about these
     E203, E501, E701, E704, W503
+    # Assigning to `os.environ` doesn't clear the environment.
+    B003
+    # Do not use mutable data structures for argument defaults.
+    B006
+    # Loop control variable not used within the loop body.
+    B007
+    # Do not perform function calls in argument defaults.
+    B008
+    # return/continue/break inside finally blocks cause exceptions to be
+    # silenced.
+    B012
+    # Star-arg unpacking after a keyword argument is strongly discouraged
+    B026
+    # No explicit stacklevel argument found.
+    B028
     # docstring does contain unindexed parameters
     P102
     # other string does contain unindexed parameters

.pre-commit-config.yaml

@@ -9,6 +9,7 @@ repos:
   hooks:
   - id: flake8
     additional_dependencies:
+    - flake8-bugbear
     - flake8-comprehensions
     - flake8-debugger
     - flake8-docstrings

scrapy/pipelines/media.py

@@ -234,7 +234,7 @@ class MediaPipeline(ABC):
             # Exception Chaining (https://www.python.org/dev/peps/pep-3134/).
             context = getattr(result.value, "__context__", None)
             if isinstance(context, StopIteration):
-                setattr(result.value, "__context__", None)
+                result.value.__context__ = None
 
         info.downloading.remove(fp)
         info.downloaded[fp] = result  # cache result

scrapy/utils/defer.py

@@ -407,7 +407,7 @@ def maybeDeferred_coro(
     """Copy of defer.maybeDeferred that also converts coroutines to Deferreds."""
     try:
         result = f(*args, **kw)
-    except:  # noqa: E722
+    except:  # noqa: E722,B001
         return defer.fail(failure.Failure(captureVars=Deferred.debug))
 
     if isinstance(result, Deferred):

scrapy/utils/python.py

@@ -269,7 +269,7 @@ def get_spec(func: Callable[..., Any]) -> Tuple[List[str], Dict[str, Any]]:
 
     if inspect.isfunction(func) or inspect.ismethod(func):
         spec = inspect.getfullargspec(func)
-    elif hasattr(func, "__call__"):
+    elif hasattr(func, "__call__"):  # noqa: B004
         spec = inspect.getfullargspec(func.__call__)
     else:
         raise TypeError(f"{type(func)} is not callable")

scrapy/utils/signal.py

@@ -100,7 +100,10 @@ def send_catch_log_deferred(
         d.addErrback(logerror, receiver)
         # TODO https://pylint.readthedocs.io/en/latest/user_guide/messages/warning/cell-var-from-loop.html
         d.addBoth(
-            lambda result: (receiver, result)  # pylint: disable=cell-var-from-loop
+            lambda result: (
+                receiver,  # pylint: disable=cell-var-from-loop  # noqa: B023
+                result,
+            )
         )
         dfds.append(d)
     d = DeferredList(dfds)

tests/test_cmdline/__init__.py

@@ -20,7 +20,7 @@ class CmdlineTest(unittest.TestCase):
         self.env["SCRAPY_SETTINGS_MODULE"] = "tests.test_cmdline.settings"
 
     def _execute(self, *new_args, **kwargs):
-        encoding = getattr(sys.stdout, "encoding") or "utf-8"
+        encoding = sys.stdout.encoding or "utf-8"
         args = (sys.executable, "-m", "scrapy.cmdline") + new_args
         proc = Popen(args, stdout=PIPE, stderr=PIPE, env=self.env, **kwargs)
         comm = proc.communicate()[0].strip()

tests/test_command_version.py

@@ -12,7 +12,7 @@ class VersionTest(ProcessTest, unittest.TestCase):
 
     @defer.inlineCallbacks
     def test_output(self):
-        encoding = getattr(sys.stdout, "encoding") or "utf-8"
+        encoding = sys.stdout.encoding or "utf-8"
         _, out, _ = yield self.execute([])
         self.assertEqual(
             out.strip().decode(encoding),
@@ -21,7 +21,7 @@ class VersionTest(ProcessTest, unittest.TestCase):
 
     @defer.inlineCallbacks
     def test_verbose_output(self):
-        encoding = getattr(sys.stdout, "encoding") or "utf-8"
+        encoding = sys.stdout.encoding or "utf-8"
         _, out, _ = yield self.execute(["-v"])
         headers = [
             line.partition(":")[0].strip()

tests/test_commands.py

@@ -101,7 +101,7 @@ class ProjectTest(unittest.TestCase):
         def kill_proc():
             p.kill()
             p.communicate()
-            assert False, "Command took too much time to complete"
+            raise AssertionError("Command took too much time to complete")
 
         timer = Timer(15, kill_proc)
         try:

tests/test_downloader_handlers.py

@@ -892,7 +892,7 @@ class S3TestCase(unittest.TestCase):
         except Exception as e:
             self.assertIsInstance(e, (TypeError, NotConfigured))
         else:
-            assert False
+            raise AssertionError()
 
     def test_request_signing1(self):
         # gets an object from the johnsmith bucket.

tests/test_engine.py

@@ -459,7 +459,7 @@ class EngineTest(unittest.TestCase):
         def kill_proc():
             p.kill()
             p.communicate()
-            assert False, "Command took too much time to complete"
+            raise AssertionError("Command took too much time to complete")
 
         timer = Timer(15, kill_proc)
         try:

tests/test_request_dict.py

@@ -147,7 +147,7 @@ class RequestSerializationTest(unittest.TestCase):
 
         spider = MySpider()
         r = Request("http://www.example.com", callback=spider.parse)
-        setattr(spider, "parse", None)
+        spider.parse = None
         self.assertRaises(ValueError, r.to_dict, spider=spider)
 
     def test_callback_not_available(self):