[Scons-dev] Fwd: [Distutils] enscons, a prototype SCons-powered wheel & sdist builder

[Daniel Holth]

Here's the SConstruct I'm using to repackage SCons itself. I've taken
timj's Python 3 branch and SCons + __main__.py and packaged them as
import-scons-*.whl. I can have two totally different packages for Python 2
and 3, and the correct one is installed with 'pip install import-scons'.
Then you can type 'python -m SCons' to run. So far timj's Python 3 port
does everything I've asked it to do.

https://bitbucket.org/dholth/scons-wheel/src

On Mon, Jun 27, 2016 at 2:13 PM Bill Deegan <bill at baddogconsulting.com>
wrote:

> Forwarding from distutils mailing list.
> Thought it might be of interest to the community.
>
> -Bill
> Co-Manager SCons Project
> ---------- Forwarded message ----------
> From: Daniel Holth <dholth at gmail.com>
> Date: Sun, Jun 26, 2016 at 1:45 PM
> Subject: [Distutils] enscons, a prototype SCons-powered wheel & sdist
> builder
> To:
>
>
> I've been working on a prototype Python packaging system powered by SCons
> called enscons. https://bitbucket.org/dholth/enscons . It is designed to
> be an easier way to experiment with packaging compared to hacking on
> distutils or setuptools which are notoriously difficult to extend. Now it
> is at the very earliest state where it might be interesting to others who
> are less familiar with the details of pip and Python package formats.
>
> Enscons is able to create wheels and source distributions that can be
> installed by pip. Source distributions built with enscons use
> pyproject.toml from PEP 518 ( https://www.python.org/dev/peps/pep-0518/ )
> to install enscons before setup.py is run, and since pip does not yet
> implement PEP 518, include a setup.py shim for PEP 518. The same
> pyproject.toml includes most of the arguments normally passed to
> setuptools.setup(), which are used to create the metadata files needed by
> pip.
>
> Enscons converts pip's setup.py arguments to SCons ones and then invokes
> SCons, and the project's SConstruct does the rest. For a normal from-pypi
> installation, enscons generates just enough egg_info to let pip build a
> wheel, then pip builds and installs the wheel which has more complete
> metadata.
>
> Of course SCons is more interesting for more complicated projects. I've
> been working on building my pysdl2-cffi binding with SCons. It includes a
> custom Python code generation step that distutils knew nothing about. It's
> practically a one-liner to add my custom build step to SCons, and it knows
> how to rebuild each part of the project only when its dependencies have
> changed. I don't know how to do that with setuptools.
>
> It is still a very early prototype. Don't expect it to be very good. Here
> are some of its limitations:
>
>    - There is no error checking.
>    - The sdists can only be built inside virtualenvs; otherwise pip
>    complains that --user and --target cannot be used together.
>    - It also doesn't work if one of the pyproject.toml build requirements
>    conflicts with something that's already installed.
>    - 'pip install .' doesn't work; it still tries to invoke 'setup.py
>    install', which is not implemented.
>    - 'setup.py develop' is not implemented. Try PYTHONPATH.
>    - I am not an experienced SCons user.
>
> It also relies on what I'm sure will be a short-lived repackaging of SCons
> called 'import_scons' that makes 'python -m SCons' work, and includes a
> Python 3 version of SCons from github.com/timj/scons that seems to work
> well enough for my purposes.
>
> On the plus side, it's short.
>
> If you're interested in implementing Python packaging in SCons, or are
> interested in the straightforward but tedious task of copying just enough
> distutils trickery to implement a robust Python C extension compiler in
> SCons, then perhaps you should check out enscons.
>
> Here is a SConstruct for enscons itself:
>
> import pytoml as tomlimport ensconsmetadata = dict(toml.load(open('pyproject.toml')))['tool']['enscons']
> env = Environment(tools=['default', 'packaging', enscons.generate],                  PACKAGE_METADATA=metadata,                  WHEEL_TAG='py2.py3-none-any',                  ROOT_IS_PURELIB=True)py_source = Glob('enscons/*.py')
> sdist = env.Package(        NAME=env['PACKAGE_NAME'],        VERSION=env['PACKAGE_METADATA']['version'],        PACKAGETYPE='src_zip',        target=['dist/' + env['PACKAGE_NAME'] + '-' + env['PACKAGE_VERSION']],        source=FindSourceFiles() + ['PKG-INFO', 'setup.py'],        )
>
> env.NoClean(sdist)
>
> env.Alias('sdist', sdist)env.Whl('purelib', py_source, root='.')
>
>
>
> Thanks!
>
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