Add optional resource getters to World

packages/ecs/src/world.js

@@ -366,27 +366,50 @@ export class World {
     return this.getResourceByTypeId(typeid(resourceType))
   }
 
+  /**
+   * @template T
+   * @param {Constructor<T>} resourceType
+   * @returns {T | undefined}
+   */
+  getOptionalResource(resourceType) {
+    return this.getOptionalResourceByTypeId(typeid(resourceType))
+  }
+
   /**
    * @template T
    * @param {TypeId} id
    * @returns {T}
    */
   getResourceByTypeId(id) {
+    const resource = this.getOptionalResourceByTypeId(id)
+
+    assert(resource, `The resource or resource alias \`${id}\` is non existent.`)
+
+    // SAFETY: The typeid should match the type, caller's responsibility
+    return /** @type {T}*/(resource)
+  }
+
+  /**
+   * @template T
+   * @param {TypeId} id
+   * @returns {T | undefined}
+   */
+  getOptionalResourceByTypeId(id) {
     const resource = this.resources.get(id)
 
-    if (resource) {
+    if (resource !== undefined) {
 
       // SAFETY: The typeid should match the type, caller's responsibility
       return /** @type {T}*/(resource)
     }
 
     const aliasedid = this.resourceAliases.get(id)
 
-    assert(aliasedid, `The resource or resource alias \`${id}\` is non existent.`)
+    if (aliasedid === undefined) return undefined
 
     const aliasedResource = this.resources.get(aliasedid)
 
-    assert(aliasedResource, `The resource alias \`${id}\` points to a non-existent resource \`${aliasedid}\`.`)
+    if (aliasedResource === undefined) return undefined
 
     // SAFETY: The aliased typeid should match the type, caller's responsibility
     return /** @type {T}*/(aliasedResource)

packages/ecs/tests/world.test.js

@@ -1,5 +1,5 @@
 import { test, describe } from "vitest";
-import { deepStrictEqual, throws } from "node:assert";
+import { deepStrictEqual, strictEqual, throws } from "node:assert";
 import { World } from "../src";
 import { typeid } from "@wimaengine/type";
 import { EntityHandle } from "../src/entities";
@@ -109,6 +109,30 @@ describe("Testing `World`", () => {
     deepStrictEqual(resource, new TestResource())
   })
 
+  test('Get optional correct resource on world.', () => {
+    const world = new World()
+    world.setResource(new TestResource())
+    const resource = world.getOptionalResource(TestResource)
+
+    deepStrictEqual(resource, new TestResource())
+  })
+
+  test('Optional resource lookup on world returns aliased resources.', () => {
+    const world = new World()
+    world.setResource(new TestResource())
+    world.setResourceAlias(typeid(TestResource), TestAlias)
+    const resource = world.getOptionalResource(TestAlias)
+
+    deepStrictEqual(resource, new TestResource())
+  })
+
+  test('Optional resource lookup on world returns undefined when missing.', () => {
+    const world = new World()
+
+    strictEqual(world.getOptionalResource(TestResource), undefined)
+    strictEqual(world.getOptionalResource(TestAlias), undefined)
+  })
+
   test('World has resource.', () => {
     const world = new World()
     world.setResource(new TestResource())