[Fedora-packaging] Scripting language dependencies

[Toshio Kuratomi]

On Fri, Feb 17, 2012 at 10:10:48AM -0500, Tom Lane wrote:
> Bill Nottingham <notting at redhat.com> writes:
> > OK, so how about:
> 
> > Scripting inside of spec files
> 
> > Inside of a spec file, sometimes it is necessary to call a programming or
> > scripting language during %setup, %build, or %install. In Fedora, spec
> > files may in general only use the following languages for this purpose:
> 
> > 1. Python
> > 2. Perl
> > 3. awk/sed
> 
> > Also, if your package already BuildRequires a specific scripting language
> > (such as Ruby, or Tcl) as part of its normal compile process, it may also be
> > called from the spec file.
> 
> Couple of questions:
> 
> 1. Which of the above alternatives demand a BuildRequires for the
> language?  (Is BuildRequires the right thing for calls that aren't in
> %build?)
> 
Technically, only python.  For good practice I would say both perl and
python.  I would never say awk/sed.

Which reminds me... maybe we need to specify gawk rather than awk... if
someone wrote something that worked only with mawk we wouldn't like that
either.

BuildRequires is correct for %setup, %build, %install, and %check... the
sections that are run when building a package.  %pre/%post/etc would use
a form of Requires([pre,post,etc]): instead as they are run on the end
user's system at package install time.

> 2. Can we put even stricter limits on scripting language calls from
> macro definitions?  As an example, the specfile for python-psycopg2
> contains
> 
> %{expand: %%define py3ver %(python3 -c 'import sys;print(sys.version[0:3])')}
> 
> which I find to be a perpetual annoyance because I don't have python3
> installed on my system, and so *any* tool that parses the specfile burps
> out an error message, for example pretty nearly any fedpkg command
>
The very general approach of using a scripting language that the package (or
a subpackage) is building for seems valid.  So I don't think that this
should be restricted here.

That macro could be better, though.  For instance, if you use this:
%{!?py3ver: %global py3ver %(%{__python3} -c 'import sys; print(sys.version[0:3])')}

You won't get the errors that are coming from that %{expand} line.

However, that won't prevent you from having other errors/warnings like this:
sh: /usr/bin/python3: No such file or directory

Without python3 installed, macros in the spec file can't be expanded
correctly (because their definitions depend on python3).  The spec file is
BuildRequireing python3 so it shouldn't be expected that you can operate on
the spec file without python3 installed.

-Toshio
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