refactor(betterer 🔧): use Promises.withResolvers instead of custom defer

packages/betterer/src/reporters/reporter.ts

@@ -14,6 +14,7 @@ export class BettererReporterΩ implements BettererReporter {
   }
 
   async contextStart(context: BettererContext, lifecycle: Promise<BettererContextSummary>): Promise<void> {
+    defaultLifecycleCatch(lifecycle);
     await Promise.all(this._reporters.map((r) => r.contextStart?.(context, lifecycle)));
   }
 
@@ -26,6 +27,7 @@ export class BettererReporterΩ implements BettererReporter {
   }
 
   async suiteStart(suite: BettererSuite, lifecycle: Promise<BettererSuiteSummary>): Promise<void> {
+    defaultLifecycleCatch(lifecycle);
     await Promise.all(this._reporters.map((r) => r.suiteStart?.(suite, lifecycle)));
   }
 
@@ -38,6 +40,7 @@ export class BettererReporterΩ implements BettererReporter {
   }
 
   async runStart(run: BettererRun, lifecycle: Promise<BettererRunSummary>): Promise<void> {
+    defaultLifecycleCatch(lifecycle);
     await Promise.all(this._reporters.map((r) => r.runStart?.(run, lifecycle)));
   }
 
@@ -49,3 +52,8 @@ export class BettererReporterΩ implements BettererReporter {
     await Promise.all(this._reporters.map((r) => r.runError?.(run, error)));
   }
 }
+
+function defaultLifecycleCatch(lifecycle: Promise<unknown>): void {
+  // Just in case no-one handles this error in a reporter:
+  lifecycle.catch(() => void 0);
+}

packages/betterer/src/run/run-obsolete.ts

@@ -1,7 +1,6 @@
 import type { BettererResult } from '../results/index.js';
 import type { BettererRun, BettererRunSummary } from './types.js';
 
-import { defer } from '../utils.js';
 import { BettererRunSummaryΩ } from './run-summary.js';
 
 export class BettererRunObsoleteΩ implements BettererRun {
@@ -12,7 +11,7 @@ export class BettererRunObsoleteΩ implements BettererRun {
   public readonly isOnly = false;
   public readonly isRemoved: boolean;
   public readonly isSkipped = false;
-  public readonly lifecycle = defer<BettererRunSummary>();
+  public readonly lifecycle = Promise.withResolvers<BettererRunSummary>();
 
   constructor(
     public readonly name: string,

packages/betterer/src/run/run.ts

@@ -10,11 +10,10 @@ import { getTimeΔ } from '@betterer/time';
 
 import { getGlobals } from '../globals.js';
 import { BettererResultΩ } from '../results/index.js';
-import { defer } from '../utils.js';
 import { BettererRunSummaryΩ } from './run-summary.js';
 
 export class BettererRunΩ implements BettererRun {
-  public readonly lifecycle = defer<BettererRunSummary>();
+  public readonly lifecycle = Promise.withResolvers<BettererRunSummary>();
   public readonly isNew: boolean;
   public readonly isObsolete = false;
   public readonly isOnly: boolean;

packages/betterer/src/runner/runner.ts

@@ -11,14 +11,14 @@ import { BettererError } from '@betterer/errors';
 
 import { BettererContextΩ } from '../context/index.js';
 import { createGlobals, destroyGlobals, getGlobals } from '../globals.js';
-import { defer, normalisedPath } from '../utils.js';
+import { normalisedPath } from '../utils.js';
 import { createWatcher, WATCHER_EVENTS } from './watcher.js';
 
 const DEBOUNCE_TIME = 200;
 
 export class BettererRunnerΩ implements BettererRunner {
   public config: BettererConfig;
-  public readonly lifecycle = defer<BettererContextSummary>();
+  public readonly lifecycle = Promise.withResolvers<BettererContextSummary>();
 
   private _reporterContextStart: Promise<void>;
   private _isRunOnce = false;

packages/betterer/src/suite/suite.ts

@@ -10,13 +10,12 @@ import { invariantΔ } from '@betterer/errors';
 import { getGlobals } from '../globals.js';
 import { BettererResultΩ } from '../results/index.js';
 import { BettererRunΩ, BettererRunObsoleteΩ } from '../run/index.js';
-import { defer } from '../utils.js';
 import { BettererSuiteSummaryΩ } from './suite-summary.js';
 
 const NEGATIVE_FILTER_TOKEN = '!';
 
 export class BettererSuiteΩ implements BettererSuite {
-  public readonly lifecycle = defer<BettererSuiteSummary>();
+  public readonly lifecycle = Promise.withResolvers<BettererSuiteSummary>();
 
   private constructor(
     public filePaths: BettererFilePaths,

packages/betterer/src/utils.ts

@@ -1,4 +1,3 @@
-import assert from 'node:assert';
 import path from 'node:path';
 
 export function isBoolean(value: unknown): value is boolean {
@@ -29,30 +28,6 @@ export function normalisedPath(filePath: string): string {
   return filePath.split(path.sep).join(path.posix.sep);
 }
 
-type Resolve<T> = (value: T) => void;
-type Reject = (error: Error) => void;
-
-/** @knipignore */
-export interface Defer<T> {
-  promise: Promise<T>;
-  resolve: Resolve<T>;
-  reject: Reject;
-}
-
-export function defer<T>(): Defer<T> {
-  let resolve: Resolve<T> | null = null;
-  let reject: Reject | null = null;
-  const promise = new Promise<T>((res, rej) => {
-    resolve = res;
-    reject = rej;
-  });
-  // Catch here to avoid global unhandledRejection:
-  promise.catch(() => void 0);
-  assert(resolve);
-  assert(reject);
-  return { promise, resolve, reject };
-}
-
 const NEW_LINE = '\n';
 const NEW_LINES = /\r\n|\r|\n/g;
 

packages/fixture/src/polyfills.ts

@@ -2,3 +2,6 @@
 
 // `structuredClone` is needed by ESLint and doesn't exist in node.js v16:
 import 'core-js/actual/structured-clone.js';
+
+// `Promise.withResolvers` is only a proposal but it's super useful:
+import 'core-js/proposals/promise-with-resolvers.js';

test/watch/watch-debounced.spec.ts

@@ -2,8 +2,6 @@ import type { BettererSuiteSummary } from '@betterer/betterer';
 
 import { describe, expect, it } from 'vitest';
 
-import assert from 'node:assert';
-
 import { createFixture } from '../fixture.js';
 
 describe('betterer.watch', () => {
@@ -28,7 +26,7 @@ export default {
     const filePath = resolve('./src/file.ts');
     const { cwd } = paths;
 
-    const suiteSummaryDefer = defer<BettererSuiteSummary>();
+    const suiteSummaryDefer = Promise.withResolvers<BettererSuiteSummary>();
 
     const runner = await watch({
       configPaths,
@@ -58,23 +56,3 @@ export default {
     await cleanup();
   });
 });
-
-type Resolve<T> = (value: T) => void;
-type Reject = (error: Error) => void;
-interface Defer<T> {
-  promise: Promise<T>;
-  resolve: Resolve<T>;
-  reject: Reject;
-}
-
-function defer<T>(): Defer<T> {
-  let resolve: Resolve<T> | null = null;
-  let reject: Reject | null = null;
-  const promise = new Promise<T>((res, rej) => {
-    resolve = res;
-    reject = rej;
-  });
-  assert(resolve);
-  assert(reject);
-  return { promise, resolve, reject };
-}

test/watch/watch-ignored.spec.ts

@@ -2,8 +2,6 @@ import type { BettererSuiteSummary } from '@betterer/betterer';
 
 import { describe, expect, it } from 'vitest';
 
-import assert from 'node:assert';
-
 import { createFixture } from '../fixture.js';
 
 describe('betterer.watch', () => {
@@ -35,7 +33,7 @@ ignored.ts
     const nestedPath = resolve('./src/nested/ignored.ts');
     const { cwd } = paths;
 
-    const suiteSummaryDefer = defer<BettererSuiteSummary>();
+    const suiteSummaryDefer = Promise.withResolvers<BettererSuiteSummary>();
 
     const runner = await betterer.watch({
       configPaths,
@@ -68,23 +66,3 @@ ignored.ts
     await cleanup();
   });
 });
-
-type Resolve<T> = (value: T) => void;
-type Reject = (error: Error) => void;
-interface Defer<T> {
-  promise: Promise<T>;
-  resolve: Resolve<T>;
-  reject: Reject;
-}
-
-function defer<T>(): Defer<T> {
-  let resolve: Resolve<T> | null = null;
-  let reject: Reject | null = null;
-  const promise = new Promise<T>((res, rej) => {
-    resolve = res;
-    reject = rej;
-  });
-  assert(resolve);
-  assert(reject);
-  return { promise, resolve, reject };
-}

test/watch/watch-quit.spec.ts

@@ -1,5 +1,3 @@
-import assert from 'node:assert';
-
 import { describe, expect, it } from 'vitest';
 
 import { createFixture } from '../fixture.js';
@@ -27,8 +25,8 @@ export default {
 
     const { cwd } = paths;
 
-    const suiteEndDefer = defer();
-    const contextEndDefer = defer();
+    const suiteEndDefer = Promise.withResolvers<void>();
+    const contextEndDefer = Promise.withResolvers<void>();
 
     await betterer.watch({
       configPaths,
@@ -62,23 +60,3 @@ export default {
     await cleanup();
   });
 });
-
-type Resolve<T> = (value: T) => void;
-type Reject = (error: Error) => void;
-interface Defer<T = void> {
-  promise: Promise<T>;
-  resolve: Resolve<T>;
-  reject: Reject;
-}
-
-function defer<T = void>(): Defer<T> {
-  let resolve: Resolve<T> | null = null;
-  let reject: Reject | null = null;
-  const promise = new Promise<T>((res, rej) => {
-    resolve = res;
-    reject = rej;
-  });
-  assert(resolve);
-  assert(reject);
-  return { promise, resolve, reject };
-}

test/watch/watch.spec.ts

@@ -2,8 +2,6 @@ import type { BettererSuiteSummary } from '@betterer/betterer';
 
 import { describe, expect, it } from 'vitest';
 
-import assert from 'node:assert';
-
 import { createFixture } from '../fixture.js';
 
 describe('betterer.watch', () => {
@@ -32,9 +30,9 @@ export default {
     await betterer({ configPaths, resultsPath, cwd, workers: false });
 
     const suiteSummaryDefers = [
-      defer<BettererSuiteSummary>(),
-      defer<BettererSuiteSummary>(),
-      defer<BettererSuiteSummary>()
+      Promise.withResolvers<BettererSuiteSummary>(),
+      Promise.withResolvers<BettererSuiteSummary>(),
+      Promise.withResolvers<BettererSuiteSummary>()
     ];
     const [worse, same, better] = suiteSummaryDefers;
 
@@ -83,23 +81,3 @@ export default {
     await cleanup();
   });
 });
-
-type Resolve<T> = (value: T) => void;
-type Reject = (error: Error) => void;
-interface Defer<T> {
-  promise: Promise<T>;
-  resolve: Resolve<T>;
-  reject: Reject;
-}
-
-function defer<T>(): Defer<T> {
-  let resolve: Resolve<T> | null = null;
-  let reject: Reject | null = null;
-  const promise = new Promise<T>((res, rej) => {
-    resolve = res;
-    reject = rej;
-  });
-  assert(resolve);
-  assert(reject);
-  return { promise, resolve, reject };
-}