Improve startup and test-run performance

lib/assert.js

@@ -1,9 +1,10 @@
 import {isNativeError} from 'node:util/types';
 
-import concordance from 'concordance';
 import isPromise from 'is-promise';
 
+import {AssertionError, getAssertionStack} from './assertion-error.js';
 import concordanceOptions from './concordance-options.js';
+import concordance from './concordance.js';
 import {CIRCULAR_SELECTOR, isLikeSelector, selectComparable} from './like-selector.js';
 import {SnapshotError, VersionMismatchError} from './snapshot-manager.js';
 
@@ -13,19 +14,19 @@ function formatDescriptorDiff(actualDescriptor, expectedDescriptor, options) {
 	const {insertLine, deleteLine} = options.theme.string.diff;
 	return {
 		label: `Difference (${diffGutters.actual}${deleteLine.open}actual${deleteLine.close}, ${diffGutters.expected}${insertLine.open}expected${insertLine.close}):`,
-		formatted: concordance.diffDescriptors(actualDescriptor, expectedDescriptor, options),
+		formatted: concordance().diffDescriptors(actualDescriptor, expectedDescriptor, options),
 	};
 }
 
 function formatDescriptorWithLabel(label, descriptor) {
 	return {
 		label,
-		formatted: concordance.formatDescriptor(descriptor, concordanceOptions),
+		formatted: concordance().formatDescriptor(descriptor, concordanceOptions),
 	};
 }
 
 function formatWithLabel(label, value) {
-	return formatDescriptorWithLabel(label, concordance.describe(value, concordanceOptions));
+	return formatDescriptorWithLabel(label, concordance().describe(value, concordanceOptions));
 }
 
 const noop = () => {};
@@ -34,24 +35,6 @@ const notImplemented = () => {
 	throw new Error('not implemented');
 };
 
-export class AssertionError extends Error {
-	constructor(message = '', {
-		assertion,
-		assertionStack = getAssertionStack(AssertionError),
-		formattedDetails = [],
-		improperUsage = null,
-		cause,
-	} = {}) {
-		super(message, {cause});
-		this.name = 'AssertionError';
-
-		this.assertion = assertion;
-		this.assertionStack = assertionStack;
-		this.improperUsage = improperUsage;
-		this.formattedDetails = formattedDetails;
-	}
-}
-
 export function checkAssertionMessage(message, assertion) {
 	if (message === undefined || typeof message === 'string') {
 		return true;
@@ -63,15 +46,6 @@ export function checkAssertionMessage(message, assertion) {
 	});
 }
 
-export function getAssertionStack(constructorOpt = getAssertionStack) {
-	const {stackTraceLimit: limitBefore} = Error;
-	Error.stackTraceLimit = Number.POSITIVE_INFINITY;
-	const temporary = {};
-	Error.captureStackTrace(temporary, constructorOpt);
-	Error.stackTraceLimit = limitBefore;
-	return temporary.stack;
-}
-
 function validateExpectations(assertion, expectations, numberArgs) { // eslint-disable-line complexity
 	if (numberArgs === 1 || expectations === null || expectations === undefined) {
 		if (expectations === null) {
@@ -297,9 +271,9 @@ export class Assertions {
 				return pass();
 			}
 
-			const result = concordance.compare(actual, expected, concordanceOptions);
-			const actualDescriptor = result.actual ?? concordance.describe(actual, concordanceOptions);
-			const expectedDescriptor = result.expected ?? concordance.describe(expected, concordanceOptions);
+			const result = concordance().compare(actual, expected, concordanceOptions);
+			const actualDescriptor = result.actual ?? concordance().describe(actual, concordanceOptions);
+			const expectedDescriptor = result.expected ?? concordance().describe(expected, concordanceOptions);
 
 			if (result.pass) {
 				throw fail(new AssertionError(message, {
@@ -330,13 +304,13 @@ export class Assertions {
 		this.deepEqual = withSkip((actual, expected, message) => {
 			assertMessage(message, 't.deepEqual()');
 
-			const result = concordance.compare(actual, expected, concordanceOptions);
+			const result = concordance().compare(actual, expected, concordanceOptions);
 			if (result.pass) {
 				return pass();
 			}
 
-			const actualDescriptor = result.actual ?? concordance.describe(actual, concordanceOptions);
-			const expectedDescriptor = result.expected ?? concordance.describe(expected, concordanceOptions);
+			const actualDescriptor = result.actual ?? concordance().describe(actual, concordanceOptions);
+			const expectedDescriptor = result.expected ?? concordance().describe(expected, concordanceOptions);
 			throw fail(new AssertionError(message, {
 				assertion: 't.deepEqual()',
 				formattedDetails: [formatDescriptorDiff(actualDescriptor, expectedDescriptor)],
@@ -346,9 +320,9 @@ export class Assertions {
 		this.notDeepEqual = withSkip((actual, expected, message) => {
 			assertMessage(message, 't.notDeepEqual()');
 
-			const result = concordance.compare(actual, expected, concordanceOptions);
+			const result = concordance().compare(actual, expected, concordanceOptions);
 			if (result.pass) {
-				const actualDescriptor = result.actual ?? concordance.describe(actual, concordanceOptions);
+				const actualDescriptor = result.actual ?? concordance().describe(actual, concordanceOptions);
 				throw fail(new AssertionError(message, {
 					assertion: 't.notDeepEqual()',
 					formattedDetails: [formatDescriptorWithLabel('Value is deeply equal:', actualDescriptor)],
@@ -382,13 +356,13 @@ export class Assertions {
 				throw error;
 			}
 
-			const result = concordance.compare(comparable, selector, concordanceOptions);
+			const result = concordance().compare(comparable, selector, concordanceOptions);
 			if (result.pass) {
 				return pass();
 			}
 
-			const actualDescriptor = result.actual ?? concordance.describe(comparable, concordanceOptions);
-			const expectedDescriptor = result.expected ?? concordance.describe(selector, concordanceOptions);
+			const actualDescriptor = result.actual ?? concordance().describe(comparable, concordanceOptions);
+			const expectedDescriptor = result.expected ?? concordance().describe(selector, concordanceOptions);
 			throw fail(new AssertionError(message, {
 				assertion: 't.like()',
 				formattedDetails: [formatDescriptorDiff(actualDescriptor, expectedDescriptor)],
@@ -810,3 +784,5 @@ export class Assertions {
 		});
 	}
 }
+
+export {AssertionError, getAssertionStack} from './assertion-error.js';

lib/assertion-error.js

@@ -0,0 +1,26 @@
+export function getAssertionStack(constructorOpt = getAssertionStack) {
+	const {stackTraceLimit: limitBefore} = Error;
+	Error.stackTraceLimit = Number.POSITIVE_INFINITY;
+	const temporary = {};
+	Error.captureStackTrace(temporary, constructorOpt);
+	Error.stackTraceLimit = limitBefore;
+	return temporary.stack;
+}
+
+export class AssertionError extends Error {
+	constructor(message = '', {
+		assertion,
+		assertionStack = getAssertionStack(AssertionError),
+		formattedDetails = [],
+		improperUsage = null,
+		cause,
+	} = {}) {
+		super(message, {cause});
+		this.name = 'AssertionError';
+
+		this.assertion = assertion;
+		this.assertionStack = assertionStack;
+		this.improperUsage = improperUsage;
+		this.formattedDetails = formattedDetails;
+	}
+}

lib/concordance.js

@@ -0,0 +1,12 @@
+import {createRequire} from 'node:module';
+
+// Concordance (and its lodash dependency) is expensive to evaluate, so it's loaded lazily on first use.
+// Workers running passing simple assertions, plain `t.log` calls and snapshot-free files never touch it,
+// and the main process only needs it to format the occasional non-native error.
+const require = createRequire(import.meta.url);
+
+let concordance;
+export default function loadConcordance() {
+	concordance ??= require('concordance');
+	return concordance;
+}

lib/fork.js

@@ -64,9 +64,15 @@ export default function loadFork(file, options, execArgv = process.execArgv) {
 	let finished = false;
 
 	const emitter = new Emittery();
+	// `stateChange` is high-frequency and consumed synchronously, so it bypasses Emittery's per-emit async overhead.
+	// `connectSharedWorker` is rare and stays on Emittery.
+	const stateChangeListeners = new Set();
 	const emitStateChange = evt => {
 		if (!finished) {
-			emitter.emit('stateChange', Object.assign(evt, {testFile: file}));
+			const data = Object.assign(evt, {testFile: file});
+			for (const listener of stateChangeListeners) {
+				listener(data);
+			}
 		}
 	};
 
@@ -172,7 +178,8 @@ export default function loadFork(file, options, execArgv = process.execArgv) {
 		},
 
 		onStateChange(listener) {
-			return emitter.on('stateChange', ({data}) => listener(data));
+			stateChangeListeners.add(listener);
+			return () => stateChangeListeners.delete(listener);
 		},
 	};
 }

lib/provider-manager.js

@@ -1,4 +1,3 @@
-import * as globs from './globs.js';
 import pkg from './pkg.js';
 
 // Provides an integer representation of the protocol level. This is internal to a particular AVA installation, and
@@ -14,6 +13,8 @@ const levelsByProtocol = Object.assign(Object.create(null), {
 
 async function load(providerModule, projectDir, selectProtocol = () => true) {
 	const ava = {version: pkg.version};
+	// Loaded lazily so that workers running plain JavaScript don't pay for the glob stack they never use.
+	const globs = await import('./globs.js');
 	const {default: makeProvider} = await import(providerModule);
 
 	let fatal;

lib/run-status.js

@@ -1,8 +1,12 @@
-import v8 from 'node:v8';
-
 import Emittery from 'emittery';
 
-const copyStats = stats => v8.deserialize(v8.serialize(stats));
+// A purpose-built deep copy. The stats object is flat counters plus a `byFile` map of flat counters,
+// so this is far cheaper than a generic structured clone and runs on every state change.
+const copyStats = stats => ({
+	...stats,
+	byFile: new Map(Array.from(stats.byFile, ([file, fileStats]) => [file, {...fileStats}])),
+	parallelRuns: stats.parallelRuns && {...stats.parallelRuns},
+});
 
 export default class RunStatus extends Emittery {
 	constructor(files, parallelRuns, selectionInsights) {

lib/serialize-error.js

@@ -2,11 +2,11 @@ import path from 'node:path';
 import {pathToFileURL} from 'node:url';
 import {isNativeError} from 'node:util/types';
 
-import concordance from 'concordance';
 import StackUtils from 'stack-utils';
 
-import {AssertionError} from './assert.js';
+import {AssertionError} from './assertion-error.js';
 import concordanceOptions from './concordance-options.js';
+import concordance from './concordance.js';
 
 function isAvaAssertionError(source) {
 	return source instanceof AssertionError;
@@ -57,7 +57,7 @@ export default function serializeError(error, {testFile = null} = {}) {
 		return {
 			type: 'unknown',
 			originalError: error, // Note that the main process receives a structured clone.
-			formattedError: concordance.formatDescriptor(concordance.describe(error, concordanceOptions), concordanceOptions),
+			formattedError: concordance().formatDescriptor(concordance().describe(error, concordanceOptions), concordanceOptions),
 		};
 	}
 
@@ -90,7 +90,7 @@ export default function serializeError(error, {testFile = null} = {}) {
 		type: 'ava',
 		assertion: error.assertion,
 		improperUsage: error.improperUsage,
-		formattedCause: error.cause ? concordance.formatDescriptor(concordance.describe(error.cause, concordanceOptions), concordanceOptions) : null,
+		formattedCause: error.cause ? concordance().formatDescriptor(concordance().describe(error.cause, concordanceOptions), concordanceOptions) : null,
 		formattedDetails: error.formattedDetails,
 		source: extractSource(error.assertionStack, testFile),
 		stack: isNativeError(error.cause) ? error.cause.stack : error.assertionStack,

lib/snapshot-manager.js

@@ -9,13 +9,13 @@ import zlib from 'node:zlib';
 import {decode as decodeCbor, encode as encodeCbor, TypeEncoderMap} from 'cbor2';
 import {writeArray, writeUint8Array} from 'cbor2/encoder';
 import {sortLengthFirstDeterministic} from 'cbor2/sorts';
-import concordance from 'concordance';
 import indentString from 'indent-string';
 import memoize from 'memoize';
 import slash from 'slash';
 import writeFileAtomic from 'write-file-atomic';
 
 import {snapshotManager as concordanceOptions} from './concordance-options.js';
+import concordance from './concordance.js';
 
 // Increment if encoding layout or Concordance serialization versions change. Previous AVA versions will not be able to
 // decode buffers generated by a newer version, so changing this value will require a major version bump of AVA itself.
@@ -94,7 +94,7 @@ function formatEntry(snapshot, index) {
 	} = snapshot;
 
 	const description = data
-		? concordance.formatDescriptor(concordance.deserialize(Buffer.from(data.buffer, data.byteOffset, data.byteLength)), concordanceOptions)
+		? concordance().formatDescriptor(concordance().deserialize(Buffer.from(data.buffer, data.byteOffset, data.byteLength)), concordanceOptions)
 		: '<No Data>';
 
 	const blockquote = label.split(/\n/).map(line => '> ' + line).join('\n');
@@ -312,9 +312,9 @@ class Manager {
 			return {pass: true};
 		}
 
-		const actual = concordance.deserialize(Buffer.from(data.buffer, data.byteOffset, data.byteLength), concordanceOptions);
-		const expected = concordance.describe(options.expected, concordanceOptions);
-		const pass = concordance.compareDescriptors(actual, expected);
+		const actual = concordance().deserialize(Buffer.from(data.buffer, data.byteOffset, data.byteLength), concordanceOptions);
+		const expected = concordance().describe(options.expected, concordanceOptions);
+		const pass = concordance().compareDescriptors(actual, expected);
 
 		return {actual, expected, pass};
 	}
@@ -340,8 +340,8 @@ class Manager {
 
 	deferRecord(options) {
 		const {expected, belongsTo, label, index} = options;
-		const descriptor = concordance.describe(expected, concordanceOptions);
-		const buffer = concordance.serialize(descriptor);
+		const descriptor = concordance().describe(expected, concordanceOptions);
+		const buffer = concordance().serialize(descriptor);
 		const data = new Uint8Array(buffer.buffer, buffer.byteOffset, buffer.byteLength);
 
 		return () => { // Must be called in order!

lib/test.js

@@ -1,11 +1,11 @@
-import concordance from 'concordance';
 import isPromise from 'is-promise';
 import plur from 'plur';
 
 import {
 	AssertionError, Assertions, checkAssertionMessage, getAssertionStack,
 } from './assert.js';
 import concordanceOptions from './concordance-options.js';
+import concordance from './concordance.js';
 import * as nowAndTimers from './now-and-timers.js';
 import parseTestArgs from './parse-test-args.js';
 
@@ -24,7 +24,7 @@ function isExternalAssertError(error) {
 }
 
 function formatErrorValue(label, error) {
-	const formatted = concordance.format(error, concordanceOptions);
+	const formatted = concordance().format(error, concordanceOptions);
 	return {label, formatted};
 }
 
@@ -68,7 +68,7 @@ class ExecutionContext extends Assertions {
 		this.log = (...inputArgs) => {
 			const args = inputArgs.map(value => typeof value === 'string'
 				? value
-				: concordance.format(value, concordanceOptions));
+				: concordance().format(value, concordanceOptions));
 			if (args.length > 0) {
 				test.addLog(args.join(' '));
 			}