feat: use getOwnMetadata to prevent parent class mutation in decorators

Author: nicosammito

ts/src/decorators/event.dec.ts

@@ -2,7 +2,9 @@ import {EventSettingProps} from "../models/event.model";
 
 export const EventSetting = (setting: EventSettingProps): ClassDecorator =>
     (target) => {
-        const settings = Reflect.getMetadata('hercules:flow_settings', target) || [];
+        // getOwnMetadata: getMetadata would return the parent class's array on subclasses,
+        // and unshift would mutate the parent's settings.
+        const settings = Reflect.getOwnMetadata('hercules:flow_settings', target) || [];
         settings.unshift(setting);
         Reflect.defineMetadata('hercules:flow_settings', settings, target);
     }

ts/src/decorators/function.dec.ts

@@ -11,7 +11,9 @@ export const ThrowsError = (throwsError: boolean = true): ClassDecorator =>
 
 export const Parameter = (parameter: FunctionParameterProps): ClassDecorator =>
     (target) => {
-        const parameters = Reflect.getMetadata('hercules:function_parameters', target) || [];
+        // getOwnMetadata: getMetadata would return the parent class's array on subclasses,
+        // and unshift would mutate the parent's parameters.
+        const parameters = Reflect.getOwnMetadata('hercules:function_parameters', target) || [];
         parameters.unshift(parameter);
         Reflect.defineMetadata('hercules:function_parameters', parameters, target);
     }