[libcamera-devel] [RFC 1/1] build: Preserve upstream git versioning using meson dist

[Laurent Pinchart]

Hi Naush,

Thank you for the patch.

On Wed, Oct 13, 2021 at 11:20:53AM +0100, Naushir Patuck wrote:
> On Wed, 13 Oct 2021 at 11:19, Naushir Patuck wrote:
> > When distributions build and package libcamera libraries, they may not
> > necessarily run the build in the upstream source tree. In these cases, the git
> > SHA1 versioning information will be lost.
> >
> > This change addresses that problem by requiring package managers to run
> > 'meson dist' to create a tarball of the source files and build from there.
> > On runing 'meson dist', the utils/run-dist.sh script will create a version.gen
> > file in the release tarball with the version string generated from the existing
> > utils/gen-version.sh script.
> >
> > The build system has been updated to check for the presence of this version.gen
> > file and read the version string from it. If the file is not present, the
> > version string is generated by running utils/gen-version.sh as it currently
> > does.
> >
> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > ---
> >  meson.build               | 30 ++++++++++++++++++++----------
> >  src/libcamera/meson.build | 11 +++++------
> >  utils/run-dist.sh         |  9 +++++++++
> >  3 files changed, 34 insertions(+), 16 deletions(-)
> >  create mode 100644 utils/run-dist.sh
> >
> > diff --git a/meson.build b/meson.build
> > index a49c484fe64e..f27bfd479a5c 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -10,20 +10,30 @@ project('libcamera', 'c', 'cpp',
> >      ],
> >      license : 'LGPL 2.1+')
> >
> > -# Generate version information. The libcamera_git_version variable contains the
> > -# full version with git patch count and SHA1 (e.g. 1.2.3+211-c94a24f4), while
> > -# the libcamera_version variable contains the major.minor.patch (e.g. 1.2.3)
> > -# only. If the source tree isn't under git control, or if it matches the last
> > -# git version tag, the build metadata (e.g. +211-c94a24f4) is omitted from
> > -# libcamera_git_version.
> > -libcamera_git_version = run_command('utils/gen-version.sh',
> > -                                    meson.build_root()).stdout().strip()
> > -if libcamera_git_version == ''
> > -    libcamera_git_version = meson.project_version()
> > +fs_mod = import('fs')
> > +if not fs_mod.is_file('version.gen')
> > +    # Generate version information. The libcamera_git_version variable contains the
> > +    # the full version with git patch count and SHA1 (e.g. 1.2.3+211-c94a24f4), while
> > +    # the libcamera_version variable contains the major.minor.patch (e.g. 1.2.3)
> > +    # only. If the source tree isn't under git control, or if it matches the last
> > +    # git version tag, the build metadata (e.g. +211-c94a24f4) is omitted from
> > +    # libcamera_git_version.
> > +    libcamera_git_version = run_command('utils/gen-version.sh',
> > +                                        meson.build_root()).stdout().strip()
> > +    if libcamera_git_version == ''
> > +        libcamera_git_version = meson.project_version()
> > +    endif
> > +else
> > +    # Read the version information from the file generated by the utils/run-dist.sh
> > +    # script on a 'meson dist' command.
> > +    libcamera_git_version = run_command(['cat', 'version.gen']).stdout().strip()
> >  endif
> 
> I've added an if clause here to check for the presence of the version file, but I
> could equally leave this as-is and check for the file in gen-version.sh. I don't have
> a strong preference either way.

I think I'd prefer handling this in gen-version.sh, as it will
centralize all the version handling code in a single place.

> >  libcamera_version = libcamera_git_version.split('+')[0]
> >
> > +# This script gererates the version.gen file on a 'meson dist' command.
> > +meson.add_dist_script('utils/run-dist.sh')
> > +
> >  # Configure the build environment.
> >  cc = meson.get_compiler('c')
> >  cxx = meson.get_compiler('cpp')
> > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> > index 243dd3c180eb..360eaf80ecf1 100644
> > --- a/src/libcamera/meson.build
> > +++ b/src/libcamera/meson.build
> > @@ -93,12 +93,11 @@ endforeach
> >
> >  libcamera_sources += control_sources
> >
> > -gen_version = meson.source_root() / 'utils' / 'gen-version.sh'
> > -
> > -version_cpp = vcs_tag(command : [gen_version, meson.build_root()],
> > -                      input : 'version.cpp.in',
> > -                      output : 'version.cpp',
> > -                      fallback : meson.project_version())
> > +version_data = configuration_data()
> > +version_data.set('VCS_TAG', libcamera_git_version)
> > +version_cpp = configure_file(input : 'version.cpp.in',
> > +                             output : 'version.cpp',
> > +                             configuration : version_data)
> >
> >  libcamera_sources += version_cpp
> >
> > diff --git a/utils/run-dist.sh b/utils/run-dist.sh
> > new file mode 100644
> > index 000000000000..1b2a6348c6bc
> > --- /dev/null
> > +++ b/utils/run-dist.sh
> > @@ -0,0 +1,9 @@
> > +#!/bin/sh
> > +
> > +# SPDX-License-Identifier: GPL-2.0-or-later
> > +#
> > +# On a meson dist run, generate the version string and store it in a file.
> > +# This will late be picked up by the build system and used in place of running

s/late/later/

> > +# the utils/gen-version.sh script again since we may not be running in the
> > +# upstream git source tree, and so version information would be lost.

A blank line here would be nice.

> > +"$MESON_DIST_ROOT"/utils/gen-version.sh > "$MESON_DIST_ROOT"/version.gen

Do we need to cd to MESON_SOURCE_ROOT first (or set GIT_DIR), or is
there a guarantee that this script will always run from a subdirectory
of MESON_SOURCE_ROOT ?

To end with some nitpicking, I wonder if there's a standard name for
files containing a version number (I initially thought about .version
but have no evidence that it would be better than version.gen).

-- 
Regards,

Laurent Pinchart