Allow to install the library on systems without compilation toolset

[asvetlov]

Fixes #280

[webknjaz]

maybe we should also rely on MULTIDICT_NO_EXTENSIONS?

[asvetlov]

My strategy is:

• git clone is for development mode. Compilation toolset is required
• Users should install released versions from PyPI.
• Binary wheels are preferred, they don't execute setup.py code
• If a binary wheel for the target platform is not available source tarball is used regardless to MULTIDICT_NO_EXTENSIONS
• If the toolset is not available pure python installation is executed with a warning to stdout. Better to change stdout -> stderr as a minor improvement

Later I want to consider switching to pure python only if MULTIDICT_NO_EXTENSIONS is set to prevent silent performance lose. It enforces something like MULTIDICT_NO_EXTENSIONS=1 pip install multidict on machines without compilation toolset when a binary wheel is not available.

Thoughts?

[webknjaz]

Sounds fine, I think. I've pushed minor adjustments. Plz review

[webknjaz]

Hold on merging this. There's a chicken-egg problem to solve ;)

[webknjaz]

Some linters don't need such dependency, but this change this.
Like dist setup check, which only requires docutils==0.14.
I think we'll need to have some switch for this.

[asvetlov]

Well, if you want to support the env var in git clone mode -- I'm ok with it.

[webknjaz]

@asvetlov can we reuse MULTIDICT_NO_EXTENSIONS? is it's meaning strictly defined somewhere? Like affecting the build- or run- time.

[asvetlov]

I think reusing MULTIDICT_NO_EXTENSIONS is perfectly fine

[codecov]

Codecov Report

Merging #281 into master will decrease coverage by 0.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #281      +/-   ##
==========================================
- Coverage   99.71%   99.43%   -0.29%     
==========================================
  Files           4        4              
  Lines         355      355              
==========================================
- Hits          354      353       -1     
- Misses          1        2       +1

Impacted Files	Coverage Δ
multidict/__init__.py	87.5% <0%> (-12.5%)	⬇️

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[webknjaz]

@asvetlov there's copy-paste from multidict._compat module in place now. Do you think we can just import that? (Of course, this would mean banning _compat from importing anything from project to avoid cyclic dependency hell)

[webknjaz]

Maybe:

extra_ignore_exc = () if USE_CYTHON_EXTENSIONS else (CompilerError, )
...
# and then
except (*extra_ignore_exc, DistutilsExecError, DistutilsPlatformError, ValueError):
    ...

[asvetlov]

Please do it

[asvetlov]

I prefer don't import from a package in setup.py.
Copy-paste is fine for the case.

[webknjaz]

@asvetlov ready for review again

[asvetlov]

LGTM!

[asvetlov]

thank you

[jstriebel]

Seems like this is not yet published on pypi. Could you please publish it there?

[asvetlov]

Please wait for #284
I'd like to have fixed type hints in a new release