[type/__localedef] Add state explorer

cdist/conf/type/__localedef/explorer/state

@@ -0,0 +1,71 @@
+#!/bin/sh -e
+#
+# 2020 Dennis Camera (dennis.camera at ssrq-sds-fds.ch)
+#
+# This file is part of cdist.
+#
+# cdist 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 3 of the License, or
+# (at your option) any later version.
+#
+# cdist 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 cdist. If not, see <http://www.gnu.org/licenses/>.
+#
+# This explorer determines if the locale is defined on the target system.
+# Will print nothing on error.
+#
+# Possible output:
+#  present:
+#    the main locale (and possibly aliases) is present
+#  absent:
+#    neither the main locale nor any aliases are present
+#
+
+command -v locale >/dev/null 2>&1 || exit 0
+
+locales=$(locale -a)
+
+parse_locale() {
+	# This function will split locales into their parts. Locale strings are
+	# usually of the form: [language[_territory][.codeset][@modifier]]
+	# For simplicity, language and territory are not separated by this function.
+	# Old Linux systems were also using "english" or "german" as locale strings.
+	# Usage: parse_locale locale_str lang_var codeset_var modifier_var
+	eval "${2:?}"="$(expr "$1" : '\([^.@]*\)')"
+	eval "${3:?}"="$(expr "$1" : '[^.]*\.\([^@]*\)')"
+	eval "${4:?}"="$(expr "$1" : '.*@\(.*\)$')"
+}
+
+format_locale() {
+	# Usage: format_locale language codeset modifier
+	printf '%s' "$1"
+	test -z "$2" || printf '.%s' "$2"
+	test -z "$3" || printf '@%s' "$3"
+	printf '\n'
+}
+
+gnu_normalize_codeset() {
+	# reimplementation of glibc/locale/programs/localedef.c normalize_codeset()
+	echo "$*" | tr '[:upper:]' '[:lower:]' | tr -cd '[:alnum:]'
+}
+
+locale_available() (
+	echo "${locales}" | grep -qxF "$1" || {
+		# glibc uses "normalized" locale names in archives.
+		# If a locale is stored in an archive, the normalized name will be
+		# printed by locale, so that needs to be checked, too.
+		localename=$(
+			parse_locale "$1" _lang _codeset _modifier \
+			&& format_locale "${_lang:?}" "$(gnu_normalize_codeset "${_codeset?}")" \
+			   "${_modifier?}")
+		echo "${locales}" | grep -qxF "${localename}"
+	}
+)
+
+locale_available "${__object_id:?}" && echo present || echo absent

cdist/conf/type/__localedef/gencode-remote

@@ -35,7 +35,8 @@ charmap=$(echo "$locale" | cut -d . -f 2)
 # W-T-F!
 locale_remove=$(echo "$locale" | sed 's/UTF-8/utf8/')
 
-state=$(cat "$__object/parameter/state")
+state_is=$(cat "${__object:?}/explorer/state")
+state_should=$(cat "${__object:?}/parameter/state")
 
 os=$(cat "$__global/explorer/os")
 
@@ -46,7 +47,15 @@ case "$os" in
         ;;
 esac
 
-case "$state" in
+# NOTE: If state explorer fails (e.g. locale(1) missing), the following check
+#       will always fail and let definition/removal run.
+if test "${state_is}" = "${state_should}"
+then
+	exit 0
+fi
+
+case ${state_should}
+in
     present)
         echo localedef -A "$alias" -f "$charmap" -i "$input" "$locale"
     ;;