src/Application.ts

@@ -13,7 +13,7 @@ import Controller from "./Controller.js";
 import Migration, {MigrationType} from "./db/Migration.js";
 import MysqlConnectionManager from "./db/MysqlConnectionManager.js";
 import {ValidationBag, ValidationError} from "./db/Validator.js";
-import Extendable from "./Extendable.js";
+import Extendable, {MissingComponentError} from "./Extendable.js";
 import {BadRequestError, HttpError, NotFoundHttpError, ServerError, ServiceUnavailableHttpError} from "./HttpError.js";
 import {logger, loggingContextMiddleware} from "./Logger.js";
 import SecurityError from "./SecurityError.js";
@@ -384,6 +384,16 @@ export default abstract class Application implements Extendable<ApplicationCompo
         return module ? module as C : null;
     }
 
+    public has<C extends ApplicationComponent | WebSocketListener<Application>>(type: Type<C>): boolean {
+        return !!this.asOptional(type);
+    }
+
+    public require<C extends ApplicationComponent | WebSocketListener<Application>>(type: Type<C>): void {
+        if (!this.has(type)) {
+            throw new MissingComponentError(type);
+        }
+    }
+
     public async isInNodeModules(): Promise<boolean> {
         return await doesFileExist('node_modules/swaf');
     }

src/Extendable.ts

@@ -4,4 +4,17 @@ export default interface Extendable<ComponentClass> {
     as<C extends ComponentClass>(type: Type<C>): C;
 
     asOptional<C extends ComponentClass>(type: Type<C>): C | null;
+
+    has<C extends ComponentClass>(type: Type<C>): boolean;
+
+    /**
+     * @throws MissingComponentError
+     */
+    require<C extends ComponentClass>(type: Type<C>): void;
+}
+
+export class MissingComponentError<ComponentClass> extends Error {
+    public constructor(type: Type<ComponentClass>) {
+        super(`Required component ${type.name} was not found.`);
+    }
 }

src/db/Model.ts

@@ -1,7 +1,7 @@
 import {Request} from "express";
 import {Connection} from "mysql";
 
-import Extendable from "../Extendable.js";
+import Extendable, {MissingComponentError} from "../Extendable.js";
 import {Type} from "../Utils.js";
 import ModelComponent from "./ModelComponent.js";
 import ModelFactory, {PrimaryKeyValue} from "./ModelFactory.js";
@@ -99,6 +99,16 @@ export default abstract class Model implements Extendable<ModelComponent<Model>>
         return null;
     }
 
+    public has<C extends ModelComponent<Model>>(type: Type<C>): boolean {
+        return !!this.asOptional(type);
+    }
+
+    public require<C extends ModelComponent<Model>>(type: Type<C>): void {
+        if (!this.has(type)) {
+            throw new MissingComponentError(type);
+        }
+    }
+
     public updateWithData(data: Pick<this, keyof this> | Record<string, unknown>): void {
         for (const property of this._properties) {
             if (data[property] !== undefined) {