fix: docker base image was wrong in image building charms having more than one layer.

bin/compose-core

@@ -1098,22 +1098,31 @@ service_base_docker_image() {
     }
     service_image=$(echo "$service_def" | shyaml get-value image 2>/dev/null)
     if [ "$?" != 0 ]; then
-        service_build=$(echo "$service_def" | shyaml get-value build 2>/dev/null)
-        if [ "$?" != 0 ]; then
-            err "Service $DARKYELLOW$service$NORMAL has no ${WHITE}image${NORMAL} nor ${WHITE}build${NORMAL} parameter."
-            echo "$service_def" >&2
-            return 1
-        fi
-        service_dockerfile="${service_build}"/Dockerfile
-        if ! [ -e "$service_dockerfile" ]; then
-            err "No Dockerfile found in '$service_dockerfile' location."
-            return 1
-        fi
+        ## According to https://stackoverflow.com/questions/32230577 , if there's a build,
+        ## then the builded image will get name ${project}_${service}
+        project=$(get_default_project_name) || return 1
+        image_name="${project}_${service}"
+        if ! docker_has_image "$image_name"; then
+            service_build=$(echo "$service_def" | shyaml get-value build 2>/dev/null)
+            if [ "$?" != 0 ]; then
+                err "Service $DARKYELLOW$service$NORMAL has no ${WHITE}image${NORMAL} nor ${WHITE}build${NORMAL} parameter."
+                echo "$service_def" >&2
+                return 1
+            fi
 
-        grep '^FROM' "$service_dockerfile" | xargs printf "%s " | cut -f 2 -d " "
+            docker build "$service_build" -t "${project}_${service}" >&2 || {
+                err "Failed to build image for ${DARKYELLOW}$service${NORMAL}."
+                return 1
+            }
+        fi
+        printf "%s" "${project}_${service}"
     else
-        echo "$service_image"
+        printf "%s" "${service_image}"
     fi | tee "$cache_file"
+    if [ "${PIPESTATUS[0]}" != 0 ]; then
+        rm "$cache_file"
+        return 1
+    fi
 
 }
 export -f service_base_docker_image