[Distutils] PEP 517 again

[xoviat]

The issue is about exceptions bubbling up to the interface level, not about
crashing pip. For example, if some class raises notimplemented error and
pip interprets that to mean it should call build_wheel.

On Aug 25, 2017 1:23 PM, "Paul Moore" <p.f.moore at gmail.com> wrote:

> On 25 August 2017 at 18:06, xoviat <xoviat at gmail.com> wrote:
> > Is pip going to fall back to building a wheel directly if any other
> error is
> > raised? That's what happens with setup.py install. If so, then it may be
> > fine if unexpected exceptions bubble up.
>
> Given that hooks need to be called in a subprocess (see
> https://www.python.org/dev/peps/pep-0517/#id15, "Frontends should call
> each hook in a fresh subprocess, so that backends are free to change
> process global state") there's no "bubbling up" involved at all. The
> frontend code would be something along the lines of
>
> hook_stub = '''
> import backend
> try:
>     backend.build_sdist(...)
> except NotImplementedError:
>     sys.exit(1)
> sys.exit(0)
> '''
> # Or...
> hook_stub = '''
> import backend
> if backend.build_sdist(...) == NotImplemented:
>     sys.exit(1)
> sys.exit(0)
> '''
>
> if subprocess.call([sys.executable, "-c", hook_stub]) != 0:
>     # We didn't build a sdist
>
> There's little or no opportunity here for letting exceptions bubble up
> to the user, or passing complex data back to the frontend. Ultimately,
> it's pretty much immaterial which form of reporting is used.
>
> Paul
>
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