makepkg: provide a field for tracking generic metadata

The xdata field is an array of key=value entries that allow a packager to
include arbitrary metadata in the generated .PKGINFO.

Fixes #241.

Signed-off-by: Dominik Peteler <archlinux+gitlab@with-h.at>

doc/PKGBUILD.5.asciidoc

@@ -313,6 +313,15 @@ underscore and the architecture name e.g., 'replaces_x86_64=()'.
 		Enable building packages using link time optimization. Adds '-flto'
 		to both CFLAGS and CXXFLAGS.
 
+*xdata (array)*::
+	This array allows you to add additional metadata to the package.
+	This data is neither used by pacman nor by makepkg;
+	It has purely informational purpose, or may be interpreted by third-party tools.
++
+All entries in that array must have the form 'key=value', where
+'key' is an arbitrary non-empty string and 'value' must not contain an equal sign.
+Furthermore, the key ``pkgtype'' is reserved for the makepkg program.
+
 
 Packaging Functions
 -------------------

scripts/libmakepkg/lint_pkgbuild/meson.build

@@ -25,6 +25,7 @@ sources = [
   'source.sh.in',
   'util.sh.in',
   'variable.sh.in',
+  'xdata.sh.in',
 ]
 
 foreach src : sources

scripts/libmakepkg/lint_pkgbuild/xdata.sh.in

@@ -0,0 +1,58 @@
+#!/bin/bash
+#
+#   xdata.sh - Check the 'xdata' array conforms to requirements.
+#
+#   Copyright (c) 2014-2025 Pacman Development Team <pacman-dev@lists.archlinux.org>
+#
+#   This program is free software; you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation; either version 2 of the License, or
+#   (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+[[ -n "$LIBMAKEPKG_LINT_PKGBUILD_XDATA_SH" ]] && return
+LIBMAKEPKG_LINT_PKGBUILD_XDATA_SH=1
+
+MAKEPKG_LIBRARY=${MAKEPKG_LIBRARY:-'@libmakepkgdir@'}
+
+source "$MAKEPKG_LIBRARY/util/message.sh"
+source "$MAKEPKG_LIBRARY/util/pkgbuild.sh"
+
+
+lint_pkgbuild_functions+=('lint_xdata')
+
+
+lint_xdata() {
+	local xdata_list entry key value ret=0
+
+	get_pkgbuild_all_split_attributes xdata xdata_list
+
+	for entry in "${xdata_list[@]}"; do
+		key="${entry%%=*}"
+		value="${entry##*=}"
+
+		if [[ "${entry}" == "${key}=${value}" ]]; then
+			# Entries must contain exactly one equal sign.
+			error "$(gettext "%s array: Entries must contain exactly one equal sign, e.g. key=value.")" "xdata"
+			ret=1
+		elif [[ "${key}" == '' ]]; then
+			# Do not allow keys without values.
+			error "$(gettext "%s array: The key part of an entry must not be empty.")" "xdata"
+			ret=1
+		elif [[ "${key}" == "pkgtype" ]]; then
+			# The key "pkgtype" is reserved for makepkg.
+			error "$(gettext "%s array: The key 'pkgtype' is reserved for makepkg.")" "xdata"
+			ret=1
+		fi
+	done
+
+	return $ret
+}

scripts/libmakepkg/util/schema.sh.in

@@ -30,7 +30,7 @@ known_hash_algos=({ck,md5,sha{1,224,256,384,512},b2})
 
 pkgbuild_schema_arrays=(arch backup checkdepends conflicts depends groups
                         license makedepends noextract optdepends options
-                        provides replaces source validpgpkeys
+                        provides replaces source validpgpkeys xdata
                         "${known_hash_algos[@]/%/sums}")
 
 pkgbuild_schema_strings=(changelog epoch install pkgbase pkgdesc pkgrel pkgver

scripts/makepkg.sh.in

@@ -493,7 +493,7 @@ write_pkginfo() {
 
 	write_kv_pair "pkgname" "$pkgname"
 	write_kv_pair "pkgbase" "$pkgbase"
-	write_kv_pair "xdata" "pkgtype=$pkgtype"
+	write_kv_pair "xdata" "pkgtype=$pkgtype" "${xdata[@]}"
 
 	local fullver=$(get_full_version)
 	write_kv_pair "pkgver" "$fullver"