Enable flake8-bugbear rule

notes-to-self/graceful-shutdown-idea.py

@@ -44,7 +44,7 @@ async def stream_handler(stream):
 # To trigger the shutdown:
 async def listen_for_shutdown_signals():
     with trio.open_signal_receiver(signal.SIGINT, signal.SIGTERM) as signal_aiter:
-        async for sig in signal_aiter:
+        async for _sig in signal_aiter:
             gsm.start_shutdown()
             break
         # TODO: it'd be nice to have some logic like "if we get another

notes-to-self/how-does-windows-so-reuseaddr-work.py

@@ -26,7 +26,7 @@ def bind(sock, bind_type):
     elif bind_type == "specific":
         sock.bind(("127.0.0.1", 12345))
     else:
-        assert False
+        raise AssertionError()
 
 
 def table_entry(mode1, bind_type1, mode2, bind_type2):
@@ -53,7 +53,7 @@ def table_entry(mode1, bind_type1, mode2, bind_type2):
 )
 
 print("""                              """, end="")
-for mode in modes:
+for _ in modes:
     print(" | " + " | ".join(["%8s" % bind_type for bind_type in bind_types]), end="")
 
 print(

notes-to-self/socketpair-buffering.py

@@ -27,11 +27,11 @@
         b.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, bufsize)
 
     try:
-        for i in range(10000000):
+        for _count in range(10000000):
             a.send(b"\x00")
     except BlockingIOError:
-        pass
+        break
 
-    print(f"setsockopt bufsize {bufsize}: {i}")
+    print(f"setsockopt bufsize {bufsize}: {_count}")
     a.close()
     b.close()

notes-to-self/ssl-close-notify/ssl-close-notify.py

@@ -73,6 +73,6 @@ def server_thread_fn():
 except ssl.SSLWantReadError:
     print("client got SSLWantReadError as expected")
 else:
-    assert False
+    raise AssertionError()
 client.close()
 client_done.set()

notes-to-self/thread-closure-bug-demo.py

@@ -35,9 +35,7 @@ def traced_looper():
         # Force w_locals to be instantiated (only matters on PyPy; on CPython
         # you can comment this line out and everything stays the same)
         print(locals())
-        # Force x to be closed over (could use 'nonlocal' on py3)
-        if False:
-            x
+        nonlocal x  # Force x to be closed over
         # Random nonsense whose only purpose is to trigger lots of calls to
         # the trace func
         count = 0

pyproject.toml

@@ -23,9 +23,11 @@ src = ["trio", "notes-to-self"]
 
 select = [
   "RUF",  # Ruff-specific rules
-  "E",  # Error
   "F",  # pyflakes
+  "E",  # Error
+  "W",  # Warning
   "I",  # isort
+  "B",  # flake8-bugbear
   "YTT",  # flake8-2020
 ]
 extend-ignore = [

trio/_abc.py

@@ -80,9 +80,11 @@ class Instrument(metaclass=ABCMeta):
 
     def before_run(self) -> None:
         """Called at the beginning of :func:`trio.run`."""
+        return
 
     def after_run(self) -> None:
         """Called just before :func:`trio.run` returns."""
+        return
 
     def task_spawned(self, task: Task) -> None:
         """Called when the given task is created.
@@ -91,6 +93,7 @@ def task_spawned(self, task: Task) -> None:
             task (trio.lowlevel.Task): The new task.
 
         """
+        return
 
     def task_scheduled(self, task: Task) -> None:
         """Called when the given task becomes runnable.
@@ -102,6 +105,7 @@ def task_scheduled(self, task: Task) -> None:
             task (trio.lowlevel.Task): The task that became runnable.
 
         """
+        return
 
     def before_task_step(self, task: Task) -> None:
         """Called immediately before we resume running the given task.
@@ -110,6 +114,7 @@ def before_task_step(self, task: Task) -> None:
             task (trio.lowlevel.Task): The task that is about to run.
 
         """
+        return
 
     def after_task_step(self, task: Task) -> None:
         """Called when we return to the main run loop after a task has yielded.
@@ -118,6 +123,7 @@ def after_task_step(self, task: Task) -> None:
             task (trio.lowlevel.Task): The task that just ran.
 
         """
+        return
 
     def task_exited(self, task: Task) -> None:
         """Called when the given task exits.
@@ -126,6 +132,7 @@ def task_exited(self, task: Task) -> None:
             task (trio.lowlevel.Task): The finished task.
 
         """
+        return
 
     def before_io_wait(self, timeout: float) -> None:
         """Called before blocking to wait for I/O readiness.
@@ -134,6 +141,7 @@ def before_io_wait(self, timeout: float) -> None:
             timeout (float): The number of seconds we are willing to wait.
 
         """
+        return
 
     def after_io_wait(self, timeout: float) -> None:
         """Called after handling pending I/O.
@@ -144,6 +152,7 @@ def after_io_wait(self, timeout: float) -> None:
                 whether any I/O was ready.
 
         """
+        return
 
 
 class HostnameResolver(metaclass=ABCMeta):
@@ -679,7 +688,7 @@ async def __anext__(self) -> ReceiveType:
         try:
             return await self.receive()
         except trio.EndOfChannel:
-            raise StopAsyncIteration
+            raise StopAsyncIteration from None
 
 
 class Channel(SendChannel[T], ReceiveChannel[T]):

trio/_core/_io_windows.py

@@ -368,7 +368,7 @@ def _get_base_socket(sock: _HasFileNo | int | Handle) -> Handle:
                     "https://github.com/python-trio/trio/issues/new, "
                     "and include the output of running: "
                     "netsh winsock show catalog"
-                )
+                ) from ex
             # Otherwise we've gotten at least one layer deeper, so
             # loop back around to keep digging.
             sock = next_sock