Slightly reorganize initialization code

[asvetlov]

Curiously, #432 problem seems gone.
I don't understand clearly why but the code doesn't contain explicit tricks, it is clearly readable at least.

URL of RTD document: https://multidict.readthedocs.io/en/cleanup/

[codecov]

Codecov Report

Merging #438 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #438   +/-   ##
=======================================
  Coverage   75.97%   75.97%           
=======================================
  Files           5        5           
  Lines         487      487           
=======================================
  Hits          370      370           
  Misses        117      117

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[asvetlov]

Hmm, actually it doesn't fix but masks a problem.
Import error is raised and the system switches to pure python under pyinstaller.
The difference is that import doesn't crash now.

Need to investigate what behavior was in previous multidict versions? Maybe pyinstaller was never good with the multidict?

[iemelyanov]

Hmm, actually it doesn't fix but masks a problem.
Import error is raised and the system switches to pure python under pyinstaller.
The difference is that import doesn't crash now.

Need to investigate what behavior was in previous multidict versions? Maybe pyinstaller was never good with the multidict?

Previous versions v4.6.1 and lower works correct because pyinstaller not use C-extension.

[iemelyanov]

LGTM

[rtd-helper]

WebSocket is not open: readyState 3 (CLOSED)

[Varriount]

@asvetlov The fact that #432 is gone for no perceivable reason is worrying. To me, that indicates that there was some form of undefined behavior causing trouble. Do tests run with memory sanitizer/valgrind enabled?

[asvetlov]

@Varriount as I see the reason for the error is: pyinstaller splits multidict in two locations: Python files are bundled with all other sources into executable image and multidict folder with compiled shared library.
When the shared library tries to import multidict._multidict_base python module the import fails because of the split. Seems like pyinstaller supports a bunch of hooks for popular libraries to avoid this problem but I didn't dig into the project too deeply.

The PR "fixes" the problem to correctly process the import failure and switching back to pure-python implementation (which is much slower but still works).

Also, #443 has fixed another crash unrelated to this issue.

[asvetlov]

@Varriount as I see the reason for the error is: pyinstaller splits multidict in two locations: Python files are bundled with all other sources into executable image and multidict folder with compiled shared library.
When the shared library tries to import multidict._multidict_base python module the import fails because of the split. Seems like pyinstaller supports a bunch of hooks for popular libraries to avoid this problem but I didn't dig into the project too deeply.

The PR "fixes" the problem to correctly process the import failure and switching back to pure-python implementation (which is much slower but still works).

Also, #443 has fixed another crash unrelated to this issue.

[asvetlov]

The Inlining of pair_list adds 15-25% boost.
Other inlines seem don't add anything but I'll keep it for the sake of consistency.