config: Tweak logic to return a validation error when custom validation fails

data/helpers.d/config

@@ -242,8 +242,20 @@ _ynh_app_config_validate() {
         fi
         if [ -n "$result" ]
         then
-            local key="YNH_ERROR_${short_setting}"
+            #
-            ynh_return "$key: \"$result\""
+            # Return a yaml such as:
+            #
+            # validation_errors:
+            #   some_key: "An error message"
+            #   some_other_key: "Another error message"
+            #
+            # We use changes_validated to know if this is
+            # the first validation error
+            if [[ "$changes_validated" == true ]]
+            then
+                ynh_return "validation_errors:"
+            fi
+            ynh_return "  ${short_setting}: \"$result\""
             changes_validated=false
         fi
     done

src/yunohost/app.py

@@ -1695,9 +1695,7 @@ def app_config_set(
 
     Question.operation_logger = operation_logger
 
-    result = config_.set(key, value, args, args_file, operation_logger=operation_logger)
+    return config_.set(key, value, args, args_file, operation_logger=operation_logger)
-
-    return result
 
 
 class AppConfigPanel(ConfigPanel):
@@ -1715,7 +1713,18 @@ class AppConfigPanel(ConfigPanel):
 
     def _apply(self):
         env = {key: str(value) for key, value in self.new_values.items()}
-        self.errors = self._call_config_script("apply", env=env)
+        return_content = self._call_config_script("apply", env=env)
+
+        # If the script returned validation error
+        # raise a ValidationError exception using
+        # the first key
+        if return_content:
+            for key, message in return_content.get("validation_errors").items():
+                raise YunohostValidationError(
+                    "app_argument_invalid",
+                    name=key,
+                    error=message,
+                )
 
     def _call_config_script(self, action, env={}):
         from yunohost.hook import hook_exec

src/yunohost/utils/config.py

@@ -135,6 +135,8 @@ class ConfigPanel:
 
         try:
             self._apply()
+        except YunohostError:
+            raise
         # Script got manually interrupted ...
         # N.B. : KeyboardInterrupt does not inherit from Exception
         except (KeyboardInterrupt, EOFError):
@@ -152,16 +154,10 @@ class ConfigPanel:
             # Delete files uploaded from API
             FileQuestion.clean_upload_dirs()
 
-        if self.errors:
-            return {
-                "errors": self.errors,
-            }
-
         self._reload_services()
 
         logger.success("Config updated as expected")
         operation_logger.success()
-        return {}
 
     def _get_toml(self):
         return read_toml(self.config_path)