Passing arguments to the PEP517 sipbuild.api backend

[Michał Górny]

On Sat, 2022-05-07 at 10:54 +0100, Phil Thompson wrote:
> On 07/05/2022 10:33, Michał Górny wrote:
> > On Sat, 2022-05-07 at 10:12 +0100, Phil Thompson wrote:
> > > On 06/05/2022 14:51, Michał Górny wrote:
> > > > Hello,
> > > > 
> > > > I'm one of the maintainers of Python packages in Gentoo.  Lately we've
> > > > been working on transitioning from the legacy "setup.py install"
> > > > workflow to PEP517 build backends.  As part of that, I'd like to work
> > > > on switching the packages relying on sip -- starting with recently
> > > > released update to python-poppler-qt5 but eventually including PyQt.
> > > > 
> > > > Unfortunately, I can't find a way to pass options to the PEP517 backend
> > > > in the way that it is possible to the sip-build executable.  Is it
> > > > possible to inject options currently?  If not, could you please add
> > > > such
> > > > a possibility?  The config_settings dictionary of build_wheel() method
> > > > seems to be the usual method of doing that (cf. setuptools accepting
> > > > {"--global_option": [...]}, though admittedly that double-dash is weird
> > > > there).
> > > > 
> > > > TIA.
> > > 
> > > The sipbuild.api backend currently ignores any config settings because
> > > (as it says in the comments) I wasn't aware of a frontend that seemed 
> > > to
> > > support the feature so I couldn't test it properly.
> > > 
> > > Do you have your own frontend or are you using pip (or similar)?
> > > 
> > 
> > Yes-ish.  I've written gpep517 for our needs [1] but the more common
> > build [2] package also supports passing config settings, e.g.:
> > 
> >   gpep517 build-wheel --output-fd 1 --wheel-dir dist/ \
> >     --config-json '{"--global-option": ["--foo"]}'
> > 
> >   python -m build -nw --config-setting=--global-option=--foo
> > 
> > [1] https://pypi.org/project/gpep517/
> > [2] https://pypi.org/project/build/
> 
> So the config_settings argument passed to build_sdist() and 
> build_wheel() would be...
> 
> {'--global-option': '--foo'}

For build case, yes, this.  If I add a debug print into build_meta:

  {'--global-option': '--foo'}

However, if you pass multiple arguments with the same key, it turns into
a list, e.g.:

  $ python -m build -nw --config-setting=--global-option=--foo \
      --config-setting=--global-option=--bar

yields:

  {'--global-option': ['--foo', '--bar']}

To account for this weird syntax, the setuptools backend checks
if "--global-option" is a string, and converts it to list.

gpep517 passes the literal dict from unserialized JSON.

I'd imagine sipbuild would need to use a similar logic, i.e. something
like:

  args = config_settings.get("args", [])
  if isinstance(args, str):
    args = [args]

if you want to support build as it currently works.  Personally, I just
need gpep517 support, so the hack wouldn't be necessary.


-- 
Best regards,
Michał Górny