fix: stop aiohttp Socket Mode connect() retrying forever after close

[WilliamBergamin]

Summary

The aiohttp Socket Mode SocketModeClient.connect() looped with while True:, and its retry
handler never checked self.closed. If a connect/reconnect attempt was in flight when the client
was closed, every retry's ws_connect() raised RuntimeError: Session is closed, so the loop kept retrying at the ping_interval cadence forever.

The fix aligns connect() with the while not self.closed: idiom already used by its sibling loops (monitor_current_session, receive_messages, and the base process_messages), and returns from the retry handler once self.closed is set. A background task orphaned by shutdown now exits within one iteration instead of spinning forever; normal startup/reconnect is unchanged.

Closes #1913.

Testing

./scripts/run_tests.sh tests/slack_sdk_async/socket_mode/test_aiohttp.py

To watch it fail against the pre-fix code, restore the old connect() (keeping the new test), then
put the fix back:

git fetch origin
git checkout origin/main -- slack_sdk/socket_mode/aiohttp/__init__.py   # buggy `while True:` connect()
./scripts/run_tests.sh tests/slack_sdk_async/socket_mode/test_aiohttp.py
#  -> test_connect_returns_when_closed spins on the closed session;
#     asyncio.wait_for(..., timeout=1.0) raises TimeoutError -> FAIL

git checkout HEAD -- slack_sdk/socket_mode/aiohttp/__init__.py          # restore the fix
./scripts/run_tests.sh tests/slack_sdk_async/socket_mode/test_aiohttp.py   # PASS

(Equivalent manual repro: change while not self.closed: back to while True: and delete the
if self.closed: return guard in connect()'s except block.)

Category

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs (Documents)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.08%. Comparing base (9d1d6b9) to head (13bca88).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1956      +/-   ##
==========================================
+ Coverage   84.06%   84.08%   +0.01%     
==========================================
  Files         118      118              
  Lines       13505    13509       +4     
==========================================
+ Hits        11353    11359       +6     
+ Misses       2152     2150       -2     

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[zimeg]

@WilliamBergamin LGTM! I have one comment on logging but it's a ramble.

[zimeg]

🪬 note: I'm surprised self.logger.debug doesn't check this condition itself but I think this log is quite useful.

[WilliamBergamin]

This logic follows the existing pattern in the file, but I'm not sure why we have this condition, I need to take a deeper dive into it