Fix IndexError on failure to close socket

[todddialpad]

What do these changes do?

It is possible for loop.sock_connect to fail in such a way that the wrapped socket no longer refers to a valid file descriptor. In this, the exception handler can fail on the attempt to call sock.close(). When this happens, start_connection can have sock == None and exceptions == []. This causes an IndexError because it assumes that exceptions always contains at least one exception instance.

Are there changes in behavior for the user?

I experienced crashes when handling connections with short timeouts.

Related issue number

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes

[bdraco]

Would you please post the full trace you get when it raises IndexError in the opening text.

I'll try to get the code coverage reporting fixed

[bdraco]

I bumped the codecov-action in #115 so hopefully codecov will work again once this PR has tests added

[webknjaz]

Will this fix #112 / #93? If so, they should be linked. Plus, I hope for some tests covering the new code too.

[bdraco]

codecov reporting should work now if you update with main

[todddialpad]

Will this fix #112 / #93? If so, they should be linked. Plus, I hope for some tests covering the new code too.

Ah yes, I believe this is the same issue.

This started happening to us in production and the closest I have been able to come to a standalone test case is to generate statistically similar traffic patterns (which in our case means fairly aggressive timeouts). I haven't been able yet to craft a self-contained unit test.

[codecov]

Codecov Report

Attention: Patch coverage is 40.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 97.44%. Comparing base (0653807) to head (fccce8d).

Files with missing lines	Patch %	Lines
src/aiohappyeyeballs/impl.py	40.00%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##              main     #114      +/-   ##
===========================================
- Coverage   100.00%   97.44%   -2.56%     
===========================================
  Files            5        5              
  Lines          227      235       +8     
  Branches        60       60              
===========================================
+ Hits           227      229       +2     
- Misses           0        6       +6     

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