moleculer-decorators/src/index.ts

decorators for moleculer

import {
  ServiceSchema,
  ActionSchema,
  ActionHandler,
  ServiceBroker,
  ServiceEventHandler,
  EventSchema,
} from "moleculer";
import * as _ from "./util";

const blacklist = [
  "created",
  "started",
  "stopped",
  "actions",
  "methods",
  "events",
  "broker",
  "logger",
];
const blacklist2 = ["metadata", "settings", "mixins", "name", "version"].concat(
  blacklist
);
const defaultServiceOptions: Options = {
  constructOverride: true,
  skipHandler: false, // not needed, just for clarity
};

export interface Options extends Partial<ServiceSchema> {
  name?: string;
  constructOverride?: boolean;
}

export interface ActionOptions extends Partial<ActionSchema> {
  name?: string;
  handler?: ActionHandler<any>; // Not really used
  skipHandler?: boolean;
}

export interface EventOptions extends Partial<EventSchema> {
  name?: string;
  group?: string;
  handler?: ServiceEventHandler; // not really used
}

export function Method(target, key: string, descriptor: PropertyDescriptor) {
  (target.methods || (target.methods = {}))[key] = descriptor.value;
}

export function Event(options?: EventOptions) {
  return function (target, key: string, descriptor: PropertyDescriptor) {
    (target.events || (target.events = {}))[key] = options
      ? {
          ...options,
          handler: descriptor.value,
        }
      : descriptor.value;
  };
}

export function Action(options: ActionOptions = {}) {
  return function (target, key: string, descriptor: PropertyDescriptor) {
    if (!options.skipHandler) {
      options.handler = descriptor.value;
    } else {
      delete options.skipHandler;
    }

    (target.actions || (target.actions = {}))[key] = options
      ? {
          ...options,
        }
      : options.skipHandler
      ? ""
      : descriptor.value;
  };
}

// Instead of using moleculer's ServiceBroker, we will fake the broker class to pass it to service constructor
const mockServiceBroker = new Object({ Promise });

export function Service<T extends Options>(opts: T = {} as T): Function {
  const options = opts || ({} as Options);
  return function (constructor: Function) {
    let base: ServiceSchema = {
      name: "", // will be overridden
    };
    const _options = Object.assign({}, defaultServiceOptions, options);

    Object.defineProperty(base, "name", {
      value: options.name || constructor.name,
      writable: false,
      enumerable: true,
    });

    if (options.name) {
      delete options.name; // not needed
    }

    Object.assign(base, _.omit(options, Object.keys(defaultServiceOptions))); // Apply

    const parentService = constructor.prototype;
    const vars = [];
    Object.getOwnPropertyNames(parentService).forEach(function (key) {
      if (key === "constructor") {
        if (_options.constructOverride) {
          // Override properties defined in @Service
          const ServiceClass = new parentService.constructor(mockServiceBroker);

          Object.getOwnPropertyNames(ServiceClass).forEach(function (key) {
            if (
              blacklist.indexOf(key) === -1 &&
              !_.isFunction(ServiceClass[key])
            ) {
              base[key] = Object.getOwnPropertyDescriptor(
                ServiceClass,
                key
              )!.value;
              if (blacklist2.indexOf(key) === -1) {
                // Needed, otherwize if the service is used as a mixin, these variables will overwrite the toplevel's
                vars[key] = Object.getOwnPropertyDescriptor(
                  ServiceClass,
                  key
                )!.value;
              }
            }
          });

          /* Insane hack below :D
           * It's needed since moleculer don't transfer all defined props in the schema to the actual service, so we have to do it.
           * Side note: This is quite hacky and would be a performance loss if the created function would be called over and over, since it's called once, it's more than fine :)
           */

          const bypass: any = Object.defineProperty; // typescript fix
          const obj: any = {}; // placeholder

          // Defining our 'own' created function
          bypass(obj, "created", {
            value: function created(broker: ServiceBroker) {
              for (let key in vars) {
                this[key] = vars[key];
              }

              // Check if user defined a created function, if so, we need to call it after ours.
              if (
                Object.getOwnPropertyDescriptor(parentService, "created") !=
                null
              ) {
                Object.getOwnPropertyDescriptor(
                  parentService,
                  "created"
                ).value.call(this, broker);
              }
            },
            writable: true,
            enumerable: true,
            configurable: true,
          });

          base["created"] = obj.created;
        }
        return;
      }

      const descriptor = Object.getOwnPropertyDescriptor(parentService, key)!;

      if (key === "created" && !_options.constructOverride) {
        base[key] = descriptor.value;
      }

      if (key === "started" || key === "stopped") {
        base[key] = descriptor.value;
        return;
      }

      if (key === "events" || key === "methods" || key === "actions") {
        base[key]
          ? Object.assign(base[key], descriptor.value)
          : (base[key] = descriptor.value);
        return;
      }

      // moleculer-db lifecycle methods (https://github.com/ColonelBundy/moleculer-decorators/issues/2)
      if (
        key === "afterConnected" ||
        key === "entityCreated" ||
        key === "entityUpdated" ||
        key === "entityRemoved"
      ) {
        base[key] = descriptor.value;
        return;
      }
    });

    return class extends parentService.constructor {
      constructor(broker, schema) {
        super(broker, schema);
        this.parseServiceSchema(base);
      }
    };
  };
}