Experimentally implement shared workers

ava.config.js

@@ -1,4 +1,9 @@
+const skipTests = [];
+if (process.versions.node < '12.17.0') {
+	skipTests.push('!test/shared-workers/!(requires-newish-node)/**');
+}
+
 export default {
-	files: ['test/**', '!test/**/{fixtures,helpers}/**'],
+	files: ['test/**', '!test/**/{fixtures,helpers}/**', ...skipTests],
 	ignoredByWatcher: ['{coverage,docs,media,test-d,test-tap}/**']
 };

lib/api.js

@@ -17,6 +17,7 @@ const RunStatus = require('./run-status');
 const fork = require('./fork');
 const serializeError = require('./serialize-error');
 const {getApplicableLineNumbers} = require('./line-numbers');
+const sharedWorkers = require('./shared-workers');
 
 function resolveModules(modules) {
 	return arrify(modules).map(name => {
@@ -231,6 +232,7 @@ class Api extends Emittery {
 
 				const worker = fork(file, options, apiOptions.nodeArguments);
 				runStatus.observeWorker(worker, file, {selectingLines: lineNumbers.length > 0});
+				sharedWorkers.observeWorkerProcess(worker, runStatus);
 
 				pendingWorkers.add(worker);
 				worker.promise.then(() => {

lib/fork.js

@@ -19,7 +19,55 @@ const serializeOptions = useAdvanced ?
 	options => JSON.parse(JSON.stringify(options)) : // Use JSON serialization to remove non-clonable values.
 	options => options;
 
+class SharedWorkerChannel extends Emittery {
+	constructor({channelId, filename, initialData}, sendToFork) {
+		super();
+
+		this.id = channelId;
+		this.filename = filename;
+		this.initialData = initialData;
+		this.sendToFork = sendToFork;
+	}
+
+	signalReady() {
+		this.sendToFork({
+			type: 'shared-worker-ready',
+			channelId: this.id
+		});
+	}
+
+	signalError() {
+		this.sendToFork({
+			type: 'shared-worker-error',
+			channelId: this.id
+		});
+	}
+
+	emitMessage({messageId, replyTo, data}) {
+		this.emit('message', {
+			messageId,
+			replyTo,
+			data
+		});
+	}
+
+	forwardMessageToFork({messageId, replyTo, data}) {
+		this.sendToFork({
+			type: 'shared-worker-message',
+			channelId: this.id,
+			messageId,
+			replyTo,
+			data
+		});
+	}
+}
+
+let forkCounter = 0;
+
 module.exports = (file, options, execArgv = process.execArgv) => {
+	const forkId = `fork/${++forkCounter}`;
+	const sharedWorkerChannels = new Map();
+
 	let finished = false;
 
 	const emitter = new Emittery();
@@ -32,6 +80,7 @@ module.exports = (file, options, execArgv = process.execArgv) => {
 	options = {
 		baseDir: process.cwd(),
 		file,
+		forkId,
 		...options
 	};
 
@@ -75,6 +124,16 @@ module.exports = (file, options, execArgv = process.execArgv) => {
 				case 'ready-for-options':
 					send({type: 'options', options: serializeOptions(options)});
 					break;
+				case 'shared-worker-connect': {
+					const channel = new SharedWorkerChannel(message.ava, send);
+					sharedWorkerChannels.set(channel.id, channel);
+					emitter.emit('connectSharedWorker', channel);
+					break;
+				}
+
+				case 'shared-worker-message':
+					sharedWorkerChannels.get(message.ava.channelId).emitMessage(message.ava);
+					break;
 				case 'ping':
 					send({type: 'pong'});
 					break;
@@ -105,6 +164,7 @@ module.exports = (file, options, execArgv = process.execArgv) => {
 
 	return {
 		file,
+		forkId,
 		promise,
 
 		exit() {
@@ -116,6 +176,10 @@ module.exports = (file, options, execArgv = process.execArgv) => {
 			send({type: 'peer-failed'});
 		},
 
+		onConnectSharedWorker(listener) {
+			return emitter.on('connectSharedWorker', listener);
+		},
+
 		onStateChange(listener) {
 			return emitter.on('stateChange', listener);
 		}

lib/load-config.js

@@ -7,7 +7,7 @@ const pkgConf = require('pkg-conf');
 
 const NO_SUCH_FILE = Symbol('no ava.config.js file');
 const MISSING_DEFAULT_EXPORT = Symbol('missing default export');
-const EXPERIMENTS = new Set(['disableSnapshotsInHooks', 'likeAssertion', 'reverseTeardowns']);
+const EXPERIMENTS = new Set(['disableSnapshotsInHooks', 'likeAssertion', 'reverseTeardowns', 'sharedWorkers']);
 
 // *Very* rudimentary support for loading ava.config.js files containing an `export default` statement.
 const evaluateJsConfig = configFile => {

lib/reporters/default.js

@@ -151,6 +151,7 @@ class Reporter {
 		this.internalErrors = [];
 		this.knownFailures = [];
 		this.lineNumberErrors = [];
+		this.sharedWorkerErrors = [];
 		this.uncaughtExceptions = [];
 		this.unhandledRejections = [];
 		this.unsavedSnapshots = [];
@@ -296,6 +297,19 @@ class Reporter {
 				break;
 			}
 
+			case 'shared-worker-error': {
+				this.sharedWorkerErrors.push(event);
+
+				if (this.verbose) {
+					this.lineWriter.ensureEmptyLine();
+					this.lineWriter.writeLine(colors.error(`${figures.cross} Error in shared worker`));
+					this.lineWriter.writeLine();
+					this.writeErr(event);
+				}
+
+				break;
+			}
+
 			case 'snapshot-error':
 				this.unsavedSnapshots.push(event);
 				break;
@@ -670,7 +684,7 @@ class Reporter {
 		}
 
 		if (this.failures.length > 0) {
-			const writeTrailingLines = this.internalErrors.length > 0 || this.uncaughtExceptions.length > 0 || this.unhandledRejections.length > 0;
+			const writeTrailingLines = this.internalErrors.length > 0 || this.sharedWorkerErrors.length > 0 || this.uncaughtExceptions.length > 0 || this.unhandledRejections.length > 0;
 
 			const lastFailure = this.failures[this.failures.length - 1];
 			for (const event of this.failures) {
@@ -694,7 +708,7 @@ class Reporter {
 
 		if (!this.verbose) {
 			if (this.internalErrors.length > 0) {
-				const writeTrailingLines = this.uncaughtExceptions.length > 0 || this.unhandledRejections.length > 0;
+				const writeTrailingLines = this.sharedWorkerErrors.length > 0 || this.uncaughtExceptions.length > 0 || this.unhandledRejections.length > 0;
 
 				const last = this.internalErrors[this.internalErrors.length - 1];
 				for (const event of this.internalErrors) {
@@ -716,6 +730,23 @@ class Reporter {
 				}
 			}
 
+			if (this.sharedWorkerErrors.length > 0) {
+				const writeTrailingLines = this.uncaughtExceptions.length > 0 || this.unhandledRejections.length > 0;
+
+				const last = this.sharedWorkerErrors[this.sharedWorkerErrors.length - 1];
+				for (const evt of this.sharedWorkerErrors) {
+					this.lineWriter.writeLine(colors.error(`${figures.cross} Error in shared worker`));
+					this.lineWriter.writeLine();
+					this.writeErr(evt.err);
+					if (evt !== last || writeTrailingLines) {
+						this.lineWriter.writeLine();
+						this.lineWriter.writeLine();
+					}
+
+					wroteSomething = true;
+				}
+			}
+
 			if (this.uncaughtExceptions.length > 0) {
 				const writeTrailingLines = this.unhandledRejections.length > 0;
 

lib/runner.js

@@ -42,6 +42,7 @@ class Runner extends Emittery {
 			serial: [],
 			todo: []
 		};
+		this.waitForReady = [];
 
 		const uniqueTestTitles = new Set();
 		this.registerUniqueTitle = title => {
@@ -444,6 +445,8 @@ class Runner extends Emittery {
 			});
 		}
 
+		await Promise.all(this.waitForReady);
+
 		if (concurrentTests.length === 0 && serialTests.length === 0) {
 			this.emit('finish');
 			// Don't run any hooks if there are no tests to run.