Re: [PATCH 02/29] configure: Check that sphinx-build is using Python 3

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> On Fri, 7 Feb 2020 at 16:18, Markus Armbruster <address@hidden> wrote:
>>
>> Peter Maydell <address@hidden> writes:
>>
>> > Currently configure's has_sphinx_build() check simply runs a dummy
>> > sphinx-build and either passes or fails.  This means that "no
>> > sphinx-build at all" and "sphinx-build exists but is too old" are
>> > both reported the same way.
>> >
>> > Further, we want to assume that all the Python we write is running
>> > with at least Python 3.5; configure checks that for our scripts, but
>> > Sphinx extensions run with whatever Python version sphinx-build
>> > itself is using.
>> >
>> > Add a check to our conf.py which makes sphinx-build fail if it would
>> > be running our extensions with an old Python, and handle this
>> > in configure so we can report failure helpfully to the user.
>> > This will mean that configure --enable-docs will fail like this
>> > if the sphinx-build provided is not suitable:
>> >
>> > Warning: sphinx-build exists but it is either too old or uses too old a 
>> > Python version
>> >
>> > ERROR: User requested feature docs
>> >        configure was not able to find it.
>> >        Install texinfo, Perl/perl-podlators and a Python 3 version of 
>> > python-sphinx
>> >
>> > (As usual, the default is to simply not build the docs, as we would
>> > if sphinx-build wasn't present at all.)
>> >
>> > Signed-off-by: Peter Maydell <address@hidden>
>> > Reviewed-by: Alex Bennée <address@hidden>
>> > Reviewed-by: Wainer dos Santos Moschetta <address@hidden>
>> > ---
>> >  configure    | 12 ++++++++++--
>> >  docs/conf.py | 10 ++++++++++
>> >  2 files changed, 20 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/configure b/configure
>> > index 0aceb8e50db..2c5cad13edd 100755
>> > --- a/configure
>> > +++ b/configure
>>
>> Any particular reason for having $sphinx_build default to the
>> indeterminate version sphinx-build rather than sphinx-build-3?
>
> Because that's the binary we were using before this patch.
> "Allow the user to specify" shouldn't be tangled up with
> "and also change the default".
>
> It might be sphinx-build-3 on RH, but on Debian/Ubuntu it's
> just 'sphinx-build' assuming you installed the python3-sphinx
> and not the python2-sphinx, or you can run it directly out of
> /usr/share/sphinx/scripts/python3/sphinx-build, or (like
> me) you might have a locally installed 'sphinx-build' which
> is using Python 3. My assumption is that once the python2->3
> transition has faded into the rear view mirror most distros
> will just have a /usr/bin/sphinx-build that's a Python 3 one.

Defaulting to sphinx-build-3 if it exists, else sphinx-build would be
nicer for users on some common systems, and wouldn't hurt users on the
other common systems.  It's what we do for Python.