Fix sending zero byte files after sendfile changes

[bdraco]

What do these changes do?

Changing the sendfile implementation in #5157 caused a
regression with sending zero byte files, and the test
had too much mocking to expose the issue.

Are there changes in behavior for the user?

Bugfix only

Related issue number

#5157
#5124
home-assistant/core#42514

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[codecov]

Codecov Report

Merging #5380 (d1763e9) into master (3edc43c) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5380      +/-   ##
==========================================
- Coverage   97.16%   97.15%   -0.02%     
==========================================
  Files          41       41              
  Lines        8746     8746              
  Branches     1402     1402              
==========================================
- Hits         8498     8497       -1     
  Misses        129      129              
- Partials      119      120       +1     

Flag	Coverage Δ
unit	97.03% <100.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiohttp/web_fileresponse.py	99.18% <100.00%> (-0.82%)	⬇️

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[joshuaspence]

I'm thinking this will fix the following error that I am seeing a few times per day?

2021-02-08 13:26:25 ERROR (MainThread) [aiohttp.server] Unhandled exception
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_protocol.py", line 485, in start
    resp, reset = await task
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_protocol.py", line 440, in _handle_request
    reset = await self.finish_response(request, resp, start_time)
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_protocol.py", line 591, in finish_response
    await prepare_meth(request)
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_fileresponse.py", line 241, in prepare
    return await self._sendfile(request, fobj, offset, count)
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_fileresponse.py", line 96, in _sendfile
    await loop.sendfile(transport, fobj, offset, count)
  File "/usr/local/lib/python3.8/asyncio/base_events.py", line 1120, in sendfile
    return await self._sendfile_native(transport, file,
  File "/usr/local/lib/python3.8/asyncio/selector_events.py", line 578, in _sendfile_native
    return await self.sock_sendfile(transp._sock, file, offset, count,
  File "/usr/local/lib/python3.8/asyncio/base_events.py", line 836, in sock_sendfile
    self._check_sendfile_params(sock, file, offset, count)
  File "/usr/local/lib/python3.8/asyncio/base_events.py", line 889, in _check_sendfile_params
    raise ValueError(
ValueError: count must be a positive integer (got 0)

[bdraco]

ValueError: count must be a positive integer (got 0)

Yes it should

[djrm05]

ValueError: count must be a positive integer (got 0)

Yes it should

I was searching for the same issue and got this page. Could you pls let me know if this will be merge to the live version? I'm running HA 2021.2.3 in docker and seeing the above error in logs... Thanks!

[gralance]

Hello @asvetlov
will this fix be merged in the next release?

[cdonovan]

Hey @asvetlov, is there any chance this could get reviewed for release soon? I verified @bdraco's fix via Home Assistant (manually patched web_fileresponse.py in my docker container).

[asvetlov]

Thanks!

[patchback]

Backport to 3.8: 💚 backport PR created

✅ Backport PR branch: patchback/backports/3.8/11b46df4215d4802a0de9aa4f5b3d25a874431d0/pr-5380

Backported as #6145

🤖 @patchback
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