Re: [PATCH v2 4/5] meson: replace Perl usage with Python

[Marc-André Lureau]

Hi

On Mon, Jan 9, 2023 at 10:52 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Mon, 9 Jan 2023 at 18:16, <marcandre.lureau@redhat.com> wrote:
> >
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > Let's try to remove Perl usage during build time.
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> >  tests/qapi-schema/meson.build | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/tests/qapi-schema/meson.build b/tests/qapi-schema/meson.build
> > index 9dfe98bc9a..d85b14f28c 100644
> > --- a/tests/qapi-schema/meson.build
> > +++ b/tests/qapi-schema/meson.build
> > @@ -259,22 +259,23 @@ if build_docs
> >    # Fix possible inconsistency in line endings in generated output and
> >    # in the golden reference (which could otherwise cause test failures
> >    # on Windows hosts). Unfortunately diff --strip-trailing-cr
> > -  # is GNU-diff only. The odd-looking perl is because we must avoid
> > +  # is GNU-diff only. The odd-looking python is because we must avoid
> >    # using an explicit '\' character in the command arguments to
> >    # a custom_target(), as Meson will unhelpfully replace it with a '/'
> >    # (https://github.com/mesonbuild/meson/issues/1564)
>
> This comment is not applicable to your Python rewrite of this.

To my interpretation, the comment still applies. I would have written
a much simpler sed invocation if we were allowed to use backslashes.

> It's talking about the way that the Perl code has to create
> a variable with a '\r' value in a weird way (using "$x = chr 13")
> and then do a substitution using that variable, rather than the obvious
> direct s// command ("s/\r//"), to work around a meson bug if the code
> has a literal \ character in it. Your python has no '\'s in it.
>
> > +  remove_cr = [python, '-c', 'import 
> > sys;[sys.stdout.write(line.replace(chr(13), "")) for line in sys.stdin]']
> >    qapi_doc_out_nocr = custom_target('QAPI rST doc newline-sanitized',
> >                                      output: ['doc-good.txt.nocr'],
> >                                      input: qapi_doc_out[0],
> >                                      build_by_default: true,
> > -                                    command: ['perl', '-pe', '$x = chr 13; 
> > s/$x$//', '@INPUT@'],
> > +                                    command: [remove_cr, '@INPUT@'],
> >                                      capture: true)
> >
> >    qapi_doc_ref_nocr = custom_target('QAPI rST doc reference 
> > newline-sanitized',
> >                                      output: ['doc-good.ref.nocr'],
> >                                      input: files('doc-good.txt'),
> >                                      build_by_default: true,
> > -                                    command: ['perl', '-pe', '$x = chr 13; 
> > s/$x$//', '@INPUT@'],
> > +                                    command: [remove_cr, '@INPUT@'],
> >                                      capture: true)
> >
> >    test('QAPI rST doc', diff, args: ['-u', qapi_doc_ref_nocr[0], 
> > qapi_doc_out_nocr[0]],
> > --
> > 2.39.0
>
> Maybe we should consider putting the Python into a script in
> scripts/ ? "Remove \r characters" is pretty trivial, but on the
> other hand I think this is the only Meson custom_target() we
> have where we directly invoke a script interpreter with a
> bit of inline script, and inline bits of script doesn't really
> seem to be a style Meson encourages (unlike Make).

It's a quite simple one-liner, and I hope we can drop it when meson
fix the mentionned bug. But I am fine putting it in a script, if that
can help.

-- 
Marc-André Lureau