Add --lint flag for the 'deploy' action and a 'lint' action to validate the Docker compose/stack file

For this (optional) new feature, the 'docker-compose' tool must be installed,
see: https://docs.docker.com/compose/install/

psu

@@ -48,6 +48,7 @@ main() {
     "masked-variables;-m;--masked-variables;In debug and/or verbose mode, the value of sensitive variables will be hidden, useful in CI to avoid leaking passwords/tokens in logs. Possible values: true|extended|false. Defaults to false"
     "quiet;-q;--quiet;Display the minimum of information or nothing, UNIX/Linux friendly. Defaults to false"
     "strict;-t;--strict;Never updates an existent stack nor removes an inexistent one, and instead exits with an error. Defaults to false"
+    "lint;-L;--lint;Validate the Docker compose/stack file before deploying the stack (only used when action=deploy). Defaults to false"
     "help;-h;--help;Display help message. To display help of a given action, run: 'psu <action> --help'"
     "version;-V;--version;Display the version of this program"
     "secure;-s;--secure[=yes|no];DEPRECATED: Use the '--insecure' option instead. Enable or disable the host's SSL certificate verification. Defaults to 'yes'"
@@ -56,7 +57,7 @@ main() {
 
   ACTIONS_TABLE=(
     # action_name;description[;required_option_key1|required_option_key2...][;optional_option_key1|optional_option_key2...]
-    "deploy;Deploy the stack;url|user|password|name|compose-file;auth-token|endpoint|env-file|prune|insecure|verbose|debug|masked-variables|strict"
+    "deploy;Deploy the stack;url|user|password|name|compose-file;auth-token|endpoint|lint|env-file|prune|insecure|verbose|debug|masked-variables|strict"
     "undeploy;Undeploy/remove the stack;url|user|password|name;auth-token|endpoint|insecure|verbose|debug|masked-variables|strict"
     "login;Log in to a Portainer instance;url|user|password;insecure|verbose|debug|masked-variables"
     "list;Lists of the stacks already deployed;url|user|password;auth-token|endpoint|quiet|insecure|verbose|debug|masked-variables|help"
@@ -67,14 +68,15 @@ main() {
     "tasks;Lists tasks for the current stack;url|user|password|name;auth-token|endpoint|service|detect-job|timeout|quiet|insecure|verbose|debug|masked-variables"
     "tasks:healthy;Lists tasks who are running correctly for the current stack;url|user|password|name;auth-token|endpoint|service|detect-job|timeout|quiet|insecure|verbose|debug|masked-variables"
     "containers;Lists containers running for the current stack;url|user|password|name;auth-token|endpoint|service|quiet|insecure|verbose|debug|masked-variables"
-    "actions;Lists available actions of this program;;verbose|debug|masked-variables"
+    "lint;Validate the Docker compose/stack file;compose-file;verbose|debug"
+    "actions;Lists available actions of this program;;verbose|debug"
     "help;Display help message"
     "version;Display this program version"
   )
 
   # Special actions who display text only
-  # No HTTP requests are done
+  # No HTTP requests will be made
-  ACTIONS_TEXT_ONLY="actions help version"
+  ACTIONS_TEXT_ONLY="actions lint help version"
 
   # Aliases of default actions
   # NOTICE: This is an experimental feature
@@ -325,6 +327,12 @@ main() {
     exit 0
   fi
 
+  # Lint the Docker compose/stack file
+  if [ $ACTION == "lint" ]; then
+    lint
+    exit 0
+  fi
+
   # Get list of all actions who can be used for this program
   if [ $ACTION == "actions" ]; then
     echo "Portainer Stack Utils, version $VERSION"
@@ -350,6 +358,7 @@ main() {
 #   PORTAINER_STACK_NAME       #
 #   PORTAINER_SERVICE_NAME     #
 #   DOCKER_COMPOSE_FILE        #
+#   DOCKER_COMPOSE_LINT        #
 #   ENVIRONMENT_VARIABLES_FILE #
 #   PORTAINER_ENDPOINT         #
 #   PORTAINER_PRUNE            #
@@ -378,6 +387,7 @@ set_globals() {
   PORTAINER_STACK_NAME=${PORTAINER_STACK_NAME}
   PORTAINER_SERVICE_NAME=${PORTAINER_SERVICE_NAME}
   DOCKER_COMPOSE_FILE=${DOCKER_COMPOSE_FILE}
+  DOCKER_COMPOSE_LINT=${DOCKER_COMPOSE_LINT:-"false"}
   ENVIRONMENT_VARIABLES_FILE=${ENVIRONMENT_VARIABLES_FILE}
   PORTAINER_ENDPOINT=${PORTAINER_ENDPOINT:-"1"}
   PORTAINER_PRUNE=${PORTAINER_PRUNE:-"false"}
@@ -402,6 +412,7 @@ set_globals() {
   echo_debug "PORTAINER_STACK_NAME -> $PORTAINER_STACK_NAME"
   echo_debug "PORTAINER_SERVICE_NAME -> $PORTAINER_SERVICE_NAME"
   echo_debug "DOCKER_COMPOSE_FILE -> $DOCKER_COMPOSE_FILE"
+  echo_debug "DOCKER_COMPOSE_LINT -> $DOCKER_COMPOSE_LINT"
   echo_debug "ENVIRONMENT_VARIABLES_FILE -> $ENVIRONMENT_VARIABLES_FILE"
   echo_debug "PORTAINER_ENDPOINT -> $PORTAINER_ENDPOINT"
   echo_debug "PORTAINER_PRUNE -> $PORTAINER_PRUNE"
@@ -423,8 +434,8 @@ set_globals() {
     fi
     check_argument "$PORTAINER_URL" "portainer url" "PORTAINER_URL" "l" "url"
   fi
-  if [ "$ACTION" == "deploy" ]; then
+  if [ "$ACTION" == "deploy" ] || [ "$ACTION" == "lint" ]; then
-    check_argument "$DOCKER_COMPOSE_FILE" "docker stack file" "DOCKER_COMPOSE_FILE" "f" "stack-file"
+    check_argument "$DOCKER_COMPOSE_FILE" "docker compose file" "DOCKER_COMPOSE_FILE" "c" "compose-file"
     if [ -n "$ENVIRONMENT_VARIABLES_FILE" ] && [[ ! -f "$ENVIRONMENT_VARIABLES_FILE" ]]; then
       echo_error "Error: File path \"$ENVIRONMENT_VARIABLES_FILE\" not found for \"ENVIRONMENT_VARIABLES_FILE\" environment variable or the \"-g\" flag or the \"--env-file\" option."
       exit 1
@@ -488,6 +499,13 @@ inputs() {
           shift
         fi
         ;;
+      -L|--lint|-L=*|--lint=*)
+        DOCKER_COMPOSE_LINT=$(input_flag "$1" "$2")
+        if [ -n "$2" ] && [[ ! $2 =~ ^-.+$ ]] ; then
+          # When the second argument is the value of the current option
+          shift
+        fi
+        ;;
       -g=*|--env-file=*|-g|--env-file)
         ENVIRONMENT_VARIABLES_FILE=$(input_option "$1" "$2")
         if [ -n "$2" ] && [[ ! $2 =~ ^-.+$ ]] ; then
@@ -910,6 +928,7 @@ mask_variables() {
 # Globals:                     #
 #   STACK                      #
 #   DOCKER_COMPOSE_FILE        #
+#   DOCKER_COMPOSE_LINT        #
 #   PORTAINER_STACK_NAME       #
 #   PORTAINER_URL              #
 #   ENVIRONMENT_VARIABLES_FILE #
@@ -922,6 +941,10 @@ mask_variables() {
 #   None                       #
 ################################
 deploy() {
+  # Lint docker-compose file if --lint option is "true"
+  if [ "$DOCKER_COMPOSE_LINT" == "true" ]; then
+    lint
+  fi
   # Read docker-compose file content
   local docker_compose_file_content
   docker_compose_file_content="$( jq -Rscjr '{StackFileContent: . }' $DOCKER_COMPOSE_FILE | tail -c +2 | head -c -1 )"
@@ -1236,6 +1259,29 @@ containers() {
   echo "$containers"
 }
 
+lint() {
+  local docker_stack_error
+  local docker_stack_validation
+
+  if [ -x "$(command -v docker-compose)" ]; then
+    echo_verbose "Linting Docker compose/stack file..."
+    docker_stack_error="error_docker_stack_is_invalid"
+    docker_stack_validation=$(docker-compose -f "$DOCKER_COMPOSE_FILE" config -q > docker_stack_validation_report 2>&1 || echo $docker_stack_error)
+    if [[ $docker_stack_validation =~ $docker_stack_error$ ]]; then
+      echo_error "Error: The '$DOCKER_COMPOSE_FILE' Docker compose/stack file is invalid:"
+      echo_error "$(cat docker_stack_validation_report)"
+      rm -f docker_stack_validation_report
+      exit 1
+    else
+      echo "[OK]"
+      echo_verbose "The '$DOCKER_COMPOSE_FILE' Docker compose/stack file is valid"
+    fi
+  else
+    echo "WARNING: Cannot validate '$DOCKER_COMPOSE_FILE' file, 'docker-compose' is not installed or not executable."
+    echo_verbose "For more informations, see: https://docs.docker.com/compose/install/"
+  fi || true
+}
+
 display_options_message() {
   echo "Options:"
   local table