new: [compose-core] add ``after`` option in relation definition

With ``after``, you can specify another relation name or a list of
relation names, after which the current relation must wait before
launching it's relation hook.

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

bin/compose-core

@@ -2423,10 +2423,33 @@ _out_new_relation_from_defs() {
     td=${td:-True}
     rc=$(merge_yaml_str "$rc_prov" "$rc") || return 1
 
-    printf "%s\0" "$service" "$relation_name" "$ts" "$rc" "$td"
+    after=$(_out_after_value_from_def "$service" "$rn" "$rel_def") || return 1
+    printf "%s\0" "$after" "$service" "$relation_name" "$ts" "$rc" "$td"
 }
 
 
+_out_after_value_from_def() {
+    local service="$1" relation_name="$2" relation_def="$3" after_t after
+    if after_t=$(echo "$relation_def" | shyaml get-type after 2>/dev/null); then
+        case "$after_t" in
+            sequence)
+                after="$(echo "$relation_def" | shyaml get-values after 2>/dev/null)" || return 1
+                after=",$service:${after//$'\n'/,$service:},"
+                ;;
+            struct)
+                err "Invalid type for ${WHITE}after${NORMAL}'s value in ${DARKBLUE}$relation_name${NORMAL}'s definition."
+                return 1
+                ;;
+            str)
+                after=",$service:$(echo "$relation_def" | shyaml get-value after "" 2>/dev/null)," || return 1
+                ;;
+        esac
+    else
+        after=""
+    fi
+    e "$after"
+}
+
 
 get_all_relations () {
     local cache_file="$state_tmpdir/$FUNCNAME.cache.$(H "$@" "$(declare -p without_relations)")" \
@@ -2460,7 +2483,8 @@ get_all_relations () {
                 debug "Ignoring compose $DARKYELLOW$service$NORMAL --$DARKBLUE$relation_name$NORMAL--> ${DARKYELLOW}$ts$NORMAL"
                 continue
             }
-            printf "%s\0" "$service" "$relation_name" "$ts" "$relation_config" "$tech_dep"
+            ## First is priority, that can be adjusted in second step
+            printf "%s\0" "" "$service" "$relation_name" "$ts" "$relation_config" "$tech_dep"
 
             ## adding target services ?
             [ "${services[$ts]}" ] && continue
@@ -2489,16 +2513,18 @@ get_all_relations () {
             }
 
             default_options=$(printf "%s" "$relation_def" | shyaml -y get-value "default-options" 2>/dev/null)
+            after=$(_out_after_value_from_def "$service" "$relation_name" "$relation_def") || return 1
             ## is this "use" declaration satisfied ?
             found=
-            while read-0 s rn ts rc td; do
+            while read-0 p s rn ts rc td; do
                 if [ -z "$found" -a "$service" == "$s" -a "$relation_name" == "$rn" ]; then
                     if [ "$default_options" ]; then
                         rc=$(merge_yaml_str "$default_options" "$rc") || return 1
                     fi
                     found="$ts"
+                    p="$after"
                 fi
-                printf "%s\0" "$s" "$rn" "$ts" "$rc" "$td"
+                printf "%s\0" "$p" "$s" "$rn" "$ts" "$rc" "$td"
             done < "${cache_file}.wip" > "${cache_file}.wip.new"
             mv "${cache_file}.wip.new" "${cache_file}.wip"
             if [ "$found" ]; then  ## this "use" declaration was satisfied
@@ -2638,8 +2664,60 @@ get_all_relations () {
         rm -f "${cache_file}"{,.wip,.wip.new}  ## no cache
         return 1
     fi
+
+    ##
+    ## Sort relations thanks to uses =metadata.yml= relations.
+    ##
+
+    mv "${cache_file}.wip"{,.in} &&
+    rm -f "${cache_file}.wip.final" &&
+    touch "${cache_file}.wip.final" || {
+        err "Unexpected error when mangling cache files."
+        return 1
+    }
+    declare -A relation_done=()
+    while true; do
+        had_remaining_relation=
+        had_new_relation=
+        while read-0 p s rn ts rc td; do
+            if [ -z "$p" ] || [ "$p" == "," ]; then
+                relation_done["$s:$rn"]=1
+                # printf "  ..  %-30s %-30s %-30s\n" "--" "$s" "$rn" >&2
+                printf "%s\0" "$s" "$rn" "$ts" "$rc" "$td" >> "${cache_file}.wip.final"
+                had_new_relation=1
+            else
+                # printf "  !!  %-30s %-30s %-30s\n" "$p" "$s" "$rn" >&2
+                printf "%s\0" "$p" "$s" "$rn" "$ts" "$rc" "$td" >> "${cache_file}.wip.out"
+                had_remaining_relation=1
+            fi
+        done < "${cache_file}.wip.in"
+        [ -z "$had_remaining_relation" ] && break
+        mv "${cache_file}.wip."{out,in}
+        while read-0 p s rn ts rc td; do
+            for rel in "${!relation_done[@]}"; do
+                p="${p//,$rel,/,}"
+            done
+            # printf "  CC  %-30s %-30s %-30s\n" "$p" "$s" "$rn" >&2
+            if [ -z "$had_new_relation" ]; then
+                err "${DARKYELLOW}$s${NORMAL} --${DARKBLUE}$rn${NORMAL}--> ${DARKYELLOW}$ts${NORMAL} missing required ${WHITE}after${NORMAL} relations:"
+                for rel in ${p//,/ }; do
+                    rel_s=${rel%%:*}
+                    rel_r=${rel##*:}
+                    echo "  - ${DARKYELLOW}$rel_s${NORMAL} --${DARKBLUE}$rel_r${NORMAL}--> ${DARKGRAY}*${NORMAL}" >&2
+                done
+            else
+                printf "%s\0" "$p" "$s" "$rn" "$ts" "$rc" "$td" >> "${cache_file}.wip.out"
+            fi
+        done < "${cache_file}.wip.in"
+        if [ -z "$had_new_relation" ]; then
+            rm -f "${cache_file}"{,.wip{,new,in,out,final}}  ## no cache
+            return 1
+        fi
+        mv "${cache_file}.wip."{out,in}
+    done
+
     export ALL_RELATIONS="$cache_file"
-    mv "${cache_file}"{.wip,}
+    mv "${cache_file}"{.wip.final,} || return 1
     cat "$cache_file"
 }
 export -f get_all_relations