Re: [Buildroot] [PATCH v2 2/2] utils/scanpypi: add flit package support

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

On Sun, 13 Mar 2022 11:13:55 -0600
James Hilliard <james.hilliard1@gmail.com> wrote:

> +def toml_load(f):
> +    with open(f, 'rb') as fh:
> +        ex = None
> +
> +        # Try regular tomli first
> +        try:
> +            from tomli import load
> +            return load(fh)
> +        except ImportError as e:
> +            ex = e
> +
> +        # Try pip's vendored tomli
> +        try:
> +            from pip._vendor.tomli import load
> +            try:
> +                return load(fh)
> +            except TypeError:
> +                # Fallback to handle older version
> +                try:
> +                    fh.seek(0)
> +                    w = io.TextIOWrapper(fh, encoding="utf8", newline="")
> +                    return load(w)
> +                finally:
> +                    w.detach()
> +        except ImportError as e:
> +            pass
> +
> +        # Try regular toml last
> +        try:
> +            from toml import load
> +            fh.seek(0)
> +            w = io.TextIOWrapper(fh, encoding="utf8", newline="")
> +            try:
> +                return load(w)
> +            finally:
> +                w.detach()
> +        except ImportError:
> +            pass
> +
> +        print('This package needs tomli')
> +        raise ex

I'm confused by how "ex" gets used here. It's initially none, and it's
set to the ImportError exception if the tomli module couldn't be used.

>      def get_requirements(self, pkg_folder):
>          """
>          Retrieve dependencies from the metadata found in the setup.py script of
> @@ -694,9 +767,12 @@ def main():
>              except ImportError as err:
>                  if 'buildutils' in str(err):
>                      print('This package needs buildutils')
> +                    continue
>                  else:
> -                    raise
> -                continue
> +                    try:
> +                        package.load_pyproject()
> +                    except Exception as e:
> +                        raise

I really don't like the construction here. We're doing this:

	try:
		... do an attempt with traditional setup.py ...
	expect ImportError as err:
		...
		try:
			... do an attempt with pyproject.toml ...
		expect Exception as e:
			...

So, if get a third and then a fourth method of Python module packaging,
we will end up with:

	try:
		... do an attempt with traditional setup.py ...
	expect ImportError as err:
		...
		try:
			... do an attempt with pyproject.toml ...
		expect Exception as e:
			...
			try:
				... do an attempt with another method
			except:
				try:
					... do an attempt with another method
				except:

Clearly ugly. Can we have a better construct? I would know how to do
that in C, but I'm not very good at Python-ic constructs.
				
Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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