[Distutils] PEP 517: Build system API

[Daniel Holth]

I wouldn't be afraid of editable installs. They are trivial and involve
building the package in place and putting a .pth file where it will be
noticed. Specify editable packages can't necessarily be uninstalled in a
standard way and you are done.

The bespoke build tool tells pip where the package root is (where
.dist-info will be written), usually . or ./src, then pip does .pth.

On Wed, Nov 23, 2016, 17:16 Chris Barker <chris.barker at noaa.gov> wrote:

> On Wed, Nov 23, 2016 at 6:35 AM, Thomas Kluyver <thomas at kluyver.me.uk>
> wrote:
>
>
> Questions:
> 1. Editable installs. The PEP currenly specifies a hook to do an
> editable install (like 'pip install -e' or 'setup.py develop') into a
> given prefix. I don't think that specifying a prefix is sufficient to
> cover '--user' installation, which uses a different install scheme,
> especially on Windows and OSX framework builds. We can:
> a. Add an extra parameter 'user' to the hook, to override the prefix and
> do a user install.
> b. Leave it as is, and do not support editable user installation (which
> would make me sad, as I do editable user installs regularly)
>
>
> Please, please, let's figure SOMETHING our here - editable installs (or
> "develop" installs) are a critical tool. Frankly, I don't know how anyone
> can develop a package without them.
>
> Back in the day I struggle mightily with kludging sys.path, and, relative
> imports that never really worked right, and on and on -- it SUCKED.
>
> Then I discovered setuptools develop mode -- yeah! IN fact, I don't think
> I'd ever use setuptools at all if I didn't need it to get develop mode!
>
> c. Decide that editable installs are too fiddly to standardise, and
> leave it to users to invoke a tool directly to do an editable install.
>
>
> Not sure what that means -- does that mean that you couldn't get an
> editable isntall with pip? but rather you would do:
>
> setup.py develop   if you had setuptools as your build system, and
>
> some_other_command  if you had some other build tool?
>
> Not too bad, but why not have a standard way to invoke develop mode? If
> the tool can support it, why not have a way for pip to tell an arbitrary
> build system to "please install this package in develop mode"
>
> On the other hand:
>
> I've always thought we were moving toward proper separation of concerns,
> in which case, pip should be focused on resolving dependencies and finding
> and installing packages.
>
> Should it even be possible to build and install a package from source with
> pip?
>
> But if it is, then it might as well support editable installs as well.
>
> The complication I see here is that a tool can't know how to install in
> editable mode unless it knows about the python environment it it running in
> -- which is easy for a tool built with python, but a problem for a tool
> written some other way.
>
> However, I see from PEP 517:
>
>
> The build backend object is expected to have attributes which provide some
> or all of the following hooks. The commonconfig_settings argument is
> described after the individual hooks:
>
> def get_build_requires(config_settings):
>     ...
>
>
> So I guess we can count on a Python front end, at least, so 1(a) should be
> doable.
>
> In fact, is the user-install issue any different for editable installs
> than regular ones?
>
> -CHB
>
>
>
>
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>
>
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>
>
> 2. Dash vs. underscore, bikeshed reloaded! Currently,  the table name
> uses a dash: [build-system], but the key added by PEP 517 uses an
> underscore: build_backend. This seems a bit messy. I propose that we
> change build_backend to build-backend for consistency. Dashes and
> underscores can both be used in a TOML key without needing quoting.
>
> Thanks,
> Thomas
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>
>
>
> --
>
> Christopher Barker, Ph.D.
> Oceanographer
>
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> Chris.Barker at noaa.gov
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