Re: [PATCH v4] meson: woraround broken system PCRE2 dependency in macOS

> macOS provides a PCRE2 library in base that is not usable and not
> configured properly, as it installs a pkgconf module that
> points to a non existent pcre2.h header in /usr/local/include.
>
> Detect that case and allow a fallback to a wrapped submodule
> if the feature is enabled and that is possible, or print a
> warning and disable the feature if the feature was set to "auto".
> which is the new default.
>
> Suggested-by: Eli Schwartz <eschwartz@gentoo.org>
> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> ---

>  meson.build       | 20 +++++++++++++++++++-
>  meson_options.txt |  2 +-
>  2 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/meson.build b/meson.build
> index 596f5ac711..0e480e65cf 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1055,7 +1055,25 @@ else
>    build_options_config.set('NO_ICONV', '1')
>  endif
>  
> -pcre2 = dependency('libpcre2-8', required: get_option('pcre2'), default_options: ['default_library=static', 'test=false'])
> +pcre2_feature = get_option('pcre2')
> +pcre2 = dependency('libpcre2-8', required: pcre2_feature, default_options: ['default_library=static', 'test=false'])
> +if pcre2.found() and pcre2.type_name() != 'internal' and host_machine.system() == 'darwin'
> +  # macOS installs a broken system package, double check
> +  if not compiler.has_header('pcre2.h', dependencies: pcre2)
> +    if pcre2_feature.enabled()
> +      # Attempt to fallback
> +      pcre2 = dependency('libpcre2-8', required: true, method: 'builtin', default_options: ['default_library=static', 'test=false'])
> +      if not pcre2.found()
> +        error('only a broken pcre2 install found and pcre2 is required')
> +      endif
> +    elif pcre2_feature.auto()
> +      # Replace with not-found-dependency
> +      pcre2 = dependency('', required: false)
> +      warning('broken pcre2 install found, disabling pcre2 feature')
> +    endif
> +  endif
> +endif
> +
>  if pcre2.found()
>    libgit_dependencies += pcre2
>    libgit_c_args += '-DUSE_LIBPCRE2'
> diff --git a/meson_options.txt b/meson_options.txt
> index e7f768df24..1668f260a1 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -45,7 +45,7 @@ option('gitweb', type: 'feature', value: 'auto',
>    description: 'Build Git web interface. Requires Perl.')
>  option('iconv', type: 'feature', value: 'auto',
>    description: 'Support reencoding strings with different encodings.')
> -option('pcre2', type: 'feature', value: 'enabled',
> +option('pcre2', type: 'feature', value: 'auto',
>    description: 'Support Perl-compatible regular expressions in e.g. git-grep(1).')
>  option('perl', type: 'feature', value: 'auto',
>    description: 'Build tools written in Perl.')