Re: [gentoo-dev] [PATCH 1/2] eapi8-dosym.eclass: New eclass.

[Alec Warner]

On Thu, Nov 19, 2020 at 2:32 AM Ulrich Müller <ulm@g.o> wrote:

> This implements the dosym command proposed for EAPI 8 (called dosym8
> because we cannot use the same name as the package-manager builtin).
>
> "dosym -r <target> <link>" will expand the (apparent) path of <target>
> relative to the (apparent) path of the directory containing <link>.
> The main aim of this is to allow for an absolute path to be specified
> as the link target, and the function will count path components and
> convert it into a relative path.
>
> Since we're inside ED at this point but the image will finally be
> installed in EROOT, we don't try to resolve any pre-existing symlinks
> in <target> or <link>. In other words, path expansion only looks at
> the specified apparent paths, without touching any actual files in ED
> or EROOT.
>
> Signed-off-by: Ulrich Müller <ulm@g.o>
> ---
>  eclass/eapi8-dosym.eclass | 108 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 108 insertions(+)
>  create mode 100644 eclass/eapi8-dosym.eclass
>
> diff --git a/eclass/eapi8-dosym.eclass b/eclass/eapi8-dosym.eclass
> new file mode 100644
> index 000000000000..52f0ffe3e62b
> --- /dev/null
> +++ b/eclass/eapi8-dosym.eclass
> @@ -0,0 +1,108 @@
> +# Copyright 2020 Gentoo Authors
> +# Distributed under the terms of the GNU General Public License v2
> +
> +# @ECLASS: eapi8-dosym.eclass
> +# @MAINTAINER:
> +# PMS team <pms@g.o>
> +# @AUTHOR:
> +# Ulrich Müller <ulm@g.o>
> +# @SUPPORTED_EAPIS: 5 6 7
> +# @BLURB: Testing implementation of EAPI 8 dosym -r option
> +# @DESCRIPTION:
> +# A stand-alone implementation of the dosym command aimed for EAPI 8.
> +# Intended to be used for wider testing of the proposed option and to
> +# allow ebuilds to switch to the new model early, with minimal change
> +# needed for actual EAPI 8.
> +#
> +# https://bugs.gentoo.org/708360
> +
> +case ${EAPI} in
> +       5|6|7) ;;
> +       *) die "${ECLASS}: EAPI=${EAPI:-0} not supported" ;;
> +esac
> +
> +# @FUNCTION: _dosym8_canonicalize
> +# @USAGE: <path>
> +# @INTERNAL
> +# @DESCRIPTION:
> +# Transparent bash-only replacement for GNU "realpath -m -s".
> +# Resolve references to "/./", "/../" and remove extra "/" characters
> +# from <path>, without touching any actual file.
>

Take this as a nit, but do we have any way to test this function
(particularly around edge cases.)
I see eclass/tests exists, could we add a couple for this?


> +_dosym8_canonicalize() {
>

in dosym8() you save and restore IFS, but you don't here, is there a reason
for that?


> +       local path slash i prev out IFS=/
> +
> +       path=( $1 )
> +       [[ $1 == /* ]] && slash=/
> +
> +       while true; do
> +               # Find first instance of non-".." path component followed
> by "..",
> +               # or as a special case, "/.." at the beginning of the path.
> +               # Also drop empty and "." path components as we go along.
> +               prev=
> +               for i in ${!path[@]}; do
> +                       if [[ -z ${path[i]} || ${path[i]} == . ]]; then
> +                               unset "path[i]"
> +                       elif [[ ${path[i]} != .. ]]; then
> +                               prev=${i}
> +                       elif [[ ${prev} || ${slash} ]]; then
> +                               # Found, remove path components and
> reiterate
> +                               [[ ${prev} ]] && unset "path[prev]"
> +                               unset "path[i]"
> +                               continue 2
> +                       fi
> +               done
> +               # No (further) instance found, so we're done
> +               break
> +       done
> +
> +       out="${slash}${path[*]}"
> +       echo "${out:-.}"
> +}
> +
> +# @FUNCTION: dosym8
> +# @USAGE: [-r] <target> <link>
> +# @DESCRIPTION:
> +# Create a symbolic link <link>, pointing to <target>.  If the
> +# directory containing the new link does not exist, create it.
> +#
> +# If called with option -r, expand <target> relative to the apparent
> +# path of the directory containing <link>.  For example, "dosym8 -r
> +# /bin/foo /usr/bin/foo" will create a link named "../../bin/foo".
> +dosym8() {
> +       local option_r
> +
> +       case $1 in
> +               -r) option_r=t; shift ;;
> +       esac
> +
> +       [[ $# -eq 2 ]] || die "${FUNCNAME}: bad number of arguments"
> +
> +       local target=$1 link=$2
> +
> +       if [[ ${option_r} ]]; then
> +               local linkdir comp
> +
> +               # Expansion makes sense only for an absolute target path
> +               [[ ${target} == /* ]] \
> +                       || die "${FUNCNAME}: -r specified but no absolute
> target path"
> +
> +               target=$(_dosym8_canonicalize "${target}")
> +               linkdir=$(_dosym8_canonicalize "/${link#/}")
> +               linkdir=${linkdir%/*}   # poor man's dirname(1)
> +               linkdir=${linkdir:-/}   # always keep the initial "/"
> +
> +               local ifs_save=${IFS-$' \t\n'} IFS=/
> +               for comp in ${linkdir}; do
> +                       if [[ ${target%%/*} == "${comp}" ]]; then
> +                               target=${target#"${comp}"}
> +                               target=${target#/}
> +                       else
> +                               target=..${target:+/}${target}
> +                       fi
> +               done
> +               IFS=${ifs_save}
> +               target=${target:-.}
> +       fi
> +
> +       dosym "${target}" "${link}"
> +}
> --
> 2.29.2
>
>
>