Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1097 insertions, 0 deletions

diff --git a/testing/web-platform/tests/resources/channel.sub.js b/testing/web-platform/tests/resources/channel.sub.js
new file mode 100644
index 0000000000..370d4f5905
--- /dev/null
+++ b/testing/web-platform/tests/resources/channel.sub.js
@@ -0,0 +1,1097 @@
+(function() {
+    function randInt(bits) {
+        if (bits < 1 || bits > 53) {
+            throw new TypeError();
+        } else {
+            if (bits >= 1 && bits <= 30) {
+                return 0 | ((1 << bits) * Math.random());
+            } else {
+                var high = (0 | ((1 << (bits - 30)) * Math.random())) * (1 << 30);
+                var low = 0 | ((1 << 30) * Math.random());
+                return  high + low;
+            }
+        }
+    }
+
+
+    function toHex(x, length) {
+        var rv = x.toString(16);
+        while (rv.length < length) {
+            rv = "0" + rv;
+        }
+        return rv;
+    }
+
+    function createUuid() {
+        return [toHex(randInt(32), 8),
+         toHex(randInt(16), 4),
+         toHex(0x4000 | randInt(12), 4),
+         toHex(0x8000 | randInt(14), 4),
+         toHex(randInt(48), 12)].join("-");
+    }
+
+
+    /**
+     * Cache of WebSocket instances per channel
+     *
+     * For reading there can only be one channel with each UUID, so we
+     * just have a simple map of {uuid: WebSocket}. The socket can be
+     * closed when the channel is closed.
+     *
+     * For writing there can be many channels for each uuid. Those can
+     * share a websocket (within a specific global), so we have a map
+     * of {uuid: [WebSocket, count]}.  Count is incremented when a
+     * channel is opened with a given uuid, and decremented when its
+     * closed. When the count reaches zero we can close the underlying
+     * socket.
+     */
+    class SocketCache {
+        constructor() {
+            this.readSockets = new Map();
+            this.writeSockets = new Map();
+        };
+
+        async getOrCreate(type, uuid, onmessage=null) {
+            function createSocket() {
+                let protocol = self.isSecureContext ? "wss" : "ws";
+                let port = self.isSecureContext? "{{ports[wss][0]}}" : "{{ports[ws][0]}}";
+                let url = `${protocol}://{{host}}:${port}/msg_channel?uuid=${uuid}&direction=${type}`;
+                let socket = new WebSocket(url);
+                if (onmessage !== null) {
+                    socket.onmessage = onmessage;
+                };
+                return new Promise(resolve => socket.addEventListener("open", () => resolve(socket)));
+            }
+
+            let socket;
+            if (type === "read") {
+                if (this.readSockets.has(uuid)) {
+                    throw new Error("Can't create multiple read sockets with same UUID");
+                }
+                socket = await createSocket();
+                // If the socket is closed by the server, ensure it's removed from the cache
+                socket.addEventListener("close", () => this.readSockets.delete(uuid));
+                this.readSockets.set(uuid, socket);
+            } else if (type === "write") {
+                let count;
+                if (onmessage !== null) {
+                    throw new Error("Can't set message handler for write sockets");
+                }
+                if (this.writeSockets.has(uuid)) {
+                    [socket, count] = this.writeSockets.get(uuid);
+                } else {
+                    socket = await createSocket();
+                    count = 0;
+                }
+                count += 1;
+                // If the socket is closed by the server, ensure it's removed from the cache
+                socket.addEventListener("close", () => this.writeSockets.delete(uuid));
+                this.writeSockets.set(uuid, [socket, count]);
+            } else {
+                throw new Error(`Unknown type ${type}`);
+            }
+            return socket;
+        };
+
+        async close(type, uuid) {
+            let target = type === "read" ? this.readSockets : this.writeSockets;
+            const data = target.get(uuid);
+            if (!data) {
+                return;
+            }
+            let count, socket;
+            if (type == "read") {
+                socket = data;
+                count = 0;
+            } else if (type === "write") {
+                [socket, count] = data;
+                count -= 1;
+                if (count > 0) {
+                    target.set(uuid, [socket, count]);
+                }
+            };
+            if (count <= 0 && socket) {
+                target.delete(uuid);
+                socket.close(1000);
+                await new Promise(resolve => socket.addEventListener("close", resolve));
+            }
+        };
+
+        async closeAll() {
+            let sockets = [];
+            this.readSockets.forEach(value => sockets.push(value));
+            this.writeSockets.forEach(value => sockets.push(value[0]));
+            let closePromises = sockets.map(socket =>
+                new Promise(resolve => socket.addEventListener("close", resolve)));
+            sockets.forEach(socket => socket.close(1000));
+            this.readSockets.clear();
+            this.writeSockets.clear();
+            await Promise.all(closePromises);
+        }
+    }
+
+    const socketCache = new SocketCache();
+
+    /**
+     * Abstract base class for objects that allow sending / receiving
+     * messages over a channel.
+     */
+    class Channel {
+        type = null;
+
+        constructor(uuid) {
+            /** UUID for the channel */
+            this.uuid = uuid;
+            this.socket = null;
+            this.eventListeners = {
+                connect: new Set(),
+                close: new Set()
+            };
+        }
+
+        hasConnection() {
+            return this.socket !== null && this.socket.readyState <= WebSocket.OPEN;
+        }
+
+        /**
+         * Connect to the channel.
+         *
+         * @param {Function} onmessage - Event handler function for
+         * the underlying websocket message.
+         */
+        async connect(onmessage) {
+            if (this.hasConnection()) {
+                return;
+            }
+            this.socket = await socketCache.getOrCreate(this.type, this.uuid, onmessage);
+            this._dispatch("connect");
+        }
+
+        /**
+         * Close the channel and underlying websocket connection
+         */
+        async close() {
+            this.socket = null;
+            await socketCache.close(this.type, this.uuid);
+            this._dispatch("close");
+        }
+
+        /**
+         * Add an event callback function. Supported message types are
+         * "connect", "close", and "message" (for ``RecvChannel``).
+         *
+         * @param {string} type - Message type.
+         * @param {Function} fn - Callback function. This is called
+         * with an event-like object, with ``type`` and ``data``
+         * properties.
+         */
+        addEventListener(type, fn) {
+            if (typeof type !== "string") {
+                throw new TypeError(`Expected string, got ${typeof type}`);
+            }
+            if (typeof fn !== "function") {
+                throw new TypeError(`Expected function, got ${typeof fn}`);
+            }
+            if (!this.eventListeners.hasOwnProperty(type)) {
+                throw new Error(`Unrecognised event type ${type}`);
+            }
+            this.eventListeners[type].add(fn);
+        };
+
+        /**
+         * Remove an event callback function.
+         *
+         * @param {string} type - Event type.
+         * @param {Function} fn - Callback function to remove.
+         */
+        removeEventListener(type, fn) {
+            if (!typeof type === "string") {
+                throw new TypeError(`Expected string, got ${typeof type}`);
+            }
+            if (typeof fn !== "function") {
+                throw new TypeError(`Expected function, got ${typeof fn}`);
+            }
+            let listeners = this.eventListeners[type];
+            if (listeners) {
+                listeners.delete(fn);
+            }
+        };
+
+        _dispatch(type, data) {
+            let listeners = this.eventListeners[type];
+            if (listeners) {
+                // If any listener throws we end up not calling the other
+                // listeners. This hopefully makes debugging easier, but
+                // is different to DOM event listeners.
+                listeners.forEach(fn => fn({type, data}));
+            }
+        };
+
+    }
+
+    /**
+     * Send messages over a channel
+     */
+    class SendChannel extends Channel {
+        type = "write";
+
+        /**
+         * Connect to the channel. Automatically called when sending the
+         * first message.
+         */
+        async connect() {
+            return super.connect(null);
+        }
+
+        async _send(cmd, body=null) {
+            if (!this.hasConnection()) {
+                await this.connect();
+            }
+            this.socket.send(JSON.stringify([cmd, body]));
+        }
+
+        /**
+         * Send a message. The message object must be JSON-serializable.
+         *
+         * @param {Object} msg - The message object to send.
+         */
+        async send(msg) {
+            await this._send("message", msg);
+        }
+
+        /**
+         * Disconnect the associated `RecvChannel <#RecvChannel>`_, if
+         * any, on the server side.
+         */
+        async disconnectReader() {
+            await this._send("disconnectReader");
+        }
+
+        /**
+         * Disconnect this channel on the server side.
+         */
+        async delete() {
+            await this._send("delete");
+        }
+    };
+    self.SendChannel = SendChannel;
+
+    const recvChannelsCreated = new Set();
+
+    /**
+     * Receive messages over a channel
+     */
+    class RecvChannel extends Channel {
+        type = "read";
+
+        constructor(uuid) {
+            if (recvChannelsCreated.has(uuid)) {
+                throw new Error(`Already created RecvChannel with id ${uuid}`);
+            }
+            super(uuid);
+            this.eventListeners.message = new Set();
+        }
+
+        async connect() {
+            if (this.hasConnection()) {
+                return;
+            }
+            await super.connect(event => this.readMessage(event.data));
+        }
+
+        readMessage(data) {
+            let msg = JSON.parse(data);
+            this._dispatch("message", msg);
+        }
+
+        /**
+         * Wait for the next message and return it (after passing it to
+         * existing handlers)
+         *
+         * @returns {Promise} - Promise that resolves to the message data.
+         */
+        nextMessage() {
+            return new Promise(resolve => {
+                let fn = ({data}) => {
+                    this.removeEventListener("message", fn);
+                    resolve(data);
+                };
+                this.addEventListener("message", fn);
+            });
+        }
+    }
+
+    /**
+     * Create a new channel pair
+     *
+     * @returns {Array} - Array of [RecvChannel, SendChannel] for the same channel.
+     */
+    self.channel = function() {
+        let uuid = createUuid();
+        let recvChannel = new RecvChannel(uuid);
+        let sendChannel = new SendChannel(uuid);
+        return [recvChannel, sendChannel];
+    };
+
+    /**
+     * Create an unconnected channel defined by a `uuid` in
+     * ``location.href`` for listening for `RemoteGlobal
+     * <#RemoteGlobal>`_ messages.
+     *
+     * @returns {RemoteGlobalCommandRecvChannel} - Disconnected channel
+     */
+    self.global_channel = function() {
+        let uuid = new URLSearchParams(location.search).get("uuid");
+        if (!uuid) {
+            throw new Error("URL must have a uuid parameter to use as a RemoteGlobal");
+        }
+        return new RemoteGlobalCommandRecvChannel(new RecvChannel(uuid));
+    };
+
+    /**
+     * Start listening for `RemoteGlobal <#RemoteGlobal>`_ messages on
+     * a channel defined by a `uuid` in `location.href`
+     *
+     * @returns {RemoteGlobalCommandRecvChannel} - Connected channel
+     */
+    self.start_global_channel = async function() {
+        let channel = self.global_channel();
+        await channel.connect();
+        return channel;
+    };
+
+    /**
+     * Close all WebSockets used by channels in the current realm.
+     *
+     */
+    self.close_all_channel_sockets = async function() {
+        await socketCache.closeAll();
+        // Spinning the event loop after the close events is necessary to
+        // ensure that the channels really are closed and don't affect
+        // bfcache behaviour in at least some implementations.
+        await new Promise(resolve => setTimeout(resolve, 0));
+    };
+
+    /**
+     * Handler for `RemoteGlobal <#RemoteGlobal>`_ commands.
+     *
+     * This can't be constructed directly but must be obtained from
+     * `global_channel() <#global_channel>`_ or
+     * `start_global_channel() <#start_global_channel>`_.
+     */
+    class RemoteGlobalCommandRecvChannel {
+        constructor(recvChannel) {
+            this.channel = recvChannel;
+            this.uuid = recvChannel.uuid;
+            this.channel.addEventListener("message", ({data}) => this.handleMessage(data));
+            this.messageHandlers = new Set();
+        };
+
+        /**
+         * Connect to the channel and start handling messages.
+         */
+        async connect() {
+            await this.channel.connect();
+        }
+
+        /**
+         * Close the channel and underlying websocket connection
+         */
+        async close() {
+            await this.channel.close();
+        }
+
+        async handleMessage(msg) {
+            const {id, command, params, respChannel} = msg;
+            let result = {};
+            let resp = {id, result};
+            if (command === "call") {
+                const fn = deserialize(params.fn);
+                const args = params.args.map(deserialize);
+                try {
+                    let resultValue = await fn(...args);
+                    result.result = serialize(resultValue);
+                } catch(e) {
+                    let exception = serialize(e);
+                    const getAsInt = (obj, prop) =>  {
+                        let value = prop in obj ? parseInt(obj[prop]) : 0;
+                        return Number.isNaN(value) ? 0 : value;
+                    };
+                    result.exceptionDetails = {
+                        text: e.toString(),
+                        lineNumber: getAsInt(e, "lineNumber"),
+                        columnNumber: getAsInt(e, "columnNumber"),
+                        exception
+                    };
+                }
+            } else if (command === "postMessage") {
+                this.messageHandlers.forEach(fn => fn(deserialize(params.msg)));
+            }
+            if (respChannel) {
+                let chan = deserialize(respChannel);
+                await chan.connect();
+                await chan.send(resp);
+            }
+        }
+
+        /**
+         * Add a handler for ``postMessage`` messages
+         *
+         * @param {Function} fn - Callback function that receives the
+         * message.
+         */
+        addMessageHandler(fn) {
+            this.messageHandlers.add(fn);
+        }
+
+        /**
+         * Remove a handler for ``postMessage`` messages
+         *
+         * @param {Function} fn - Callback function to remove
+         */
+        removeMessageHandler(fn) {
+            this.messageHandlers.delete(fn);
+        }
+
+        /**
+         * Wait for the next ``postMessage`` message and return it
+         * (after passing it to existing handlers)
+         *
+         * @returns {Promise} - Promise that resolves to the message.
+         */
+        nextMessage() {
+            return new Promise(resolve => {
+                let fn = (msg) => {
+                    this.removeMessageHandler(fn);
+                    resolve(msg);
+                };
+                this.addMessageHandler(fn);
+            });
+        }
+    }
+
+    class RemoteGlobalResponseRecvChannel {
+        constructor(recvChannel) {
+            this.channel = recvChannel;
+            this.channel.addEventListener("message", ({data}) => this.handleMessage(data));
+            this.responseHandlers = new Map();
+        }
+
+        setResponseHandler(commandId, fn) {
+            this.responseHandlers.set(commandId, fn);
+        }
+
+        handleMessage(msg) {
+            let {id, result} = msg;
+            let handler = this.responseHandlers.get(id);
+            if (handler) {
+                this.responseHandlers.delete(id);
+                handler(result);
+            }
+        }
+
+        close() {
+            return this.channel.close();
+        }
+    }
+
+    /**
+     * Object representing a remote global that has a
+     * `RemoteGlobalCommandRecvChannel
+     * <#RemoteGlobalCommandRecvChannel>`_
+     */
+    class RemoteGlobal {
+        /**
+         * Create a new RemoteGlobal object.
+         *
+         * This doesn't actually construct the global itself; that
+         * must be done elsewhere, with a ``uuid`` query parameter in
+         * its URL set to the same as the ``uuid`` property of this
+         * object.
+         *
+         * @param {SendChannel|string} [dest] - Either a SendChannel
+         * to the destination, or the UUID of the destination. If
+         * ommitted, a new UUID is generated, which can be used when
+         * constructing the URL for the global.
+         *
+         */
+        constructor(dest) {
+            if (dest === undefined || dest === null) {
+                dest = createUuid();
+            }
+            if (typeof dest == "string") {
+                /** UUID for the global */
+                this.uuid = dest;
+                this.sendChannel = new SendChannel(dest);
+            } else if (dest instanceof SendChannel) {
+                this.sendChannel = dest;
+                this.uuid = dest.uuid;
+            } else {
+                throw new TypeError("Unrecognised type, expected string or SendChannel");
+            }
+            this.recvChannel = null;
+            this.respChannel = null;
+            this.connected = false;
+            this.commandId = 0;
+        }
+
+        /**
+         * Connect to the channel. Automatically called when sending the
+         * first message
+         */
+        async connect() {
+            if (this.connected) {
+                return;
+            }
+            let [recvChannel, respChannel] = self.channel();
+            await Promise.all([this.sendChannel.connect(), recvChannel.connect()]);
+            this.recvChannel = new RemoteGlobalResponseRecvChannel(recvChannel);
+            this.respChannel = respChannel;
+            this.connected = true;
+        }
+
+        async sendMessage(command, params, hasResp=true) {
+            if (!this.connected) {
+                await this.connect();
+            }
+            let msg = {id: this.commandId++, command, params};
+            if (hasResp) {
+                msg.respChannel = serialize(this.respChannel);
+            }
+            let response;
+            if (hasResp) {
+                response = new Promise(resolve =>
+                    this.recvChannel.setResponseHandler(msg.id, resolve));
+            } else {
+                response = null;
+            }
+            this.sendChannel.send(msg);
+            return await response;
+        }
+
+        /**
+         * Run the function ``fn`` in the remote global, passing arguments
+         * ``args``, and return the result after awaiting any returned
+         * promise.
+         *
+         * @param {Function} fn - Function to run in the remote global.
+         * @param {...Any} args  - Arguments to pass to the function
+         * @returns {Promise} - Promise resolving to the return value
+         * of the function.
+         */
+        async call(fn, ...args) {
+            let result = await this.sendMessage("call", {fn: serialize(fn), args: args.map(x => serialize(x))}, true);
+            if (result.exceptionDetails) {
+                throw deserialize(result.exceptionDetails.exception);
+            }
+            return deserialize(result.result);
+        }
+
+        /**
+         * Post a message to the remote
+         *
+         * @param {Any} msg - The message to send.
+         */
+        async postMessage(msg) {
+            await this.sendMessage("postMessage", {msg: serialize(msg)}, false);
+        }
+
+        /**
+         * Disconnect the associated `RemoteGlobalCommandRecvChannel
+         * <#RemoteGlobalCommandRecvChannel>`_, if any, on the server
+         * side.
+         *
+         * @returns {Promise} - Resolved once the channel is disconnected.
+         */
+        disconnectReader() {
+            // This causes any readers to disconnect until they are explicitly reconnected
+            return this.sendChannel.disconnectReader();
+        }
+
+        /**
+         * Close the channel and underlying websocket connections
+         */
+        close() {
+            let closers = [this.sendChannel.close()];
+            if (this.recvChannel !== null) {
+                closers.push(this.recvChannel.close());
+            }
+            if (this.respChannel !== null) {
+                closers.push(this.respChannel.close());
+            }
+            return Promise.all(closers);
+        }
+    }
+
+    self.RemoteGlobal = RemoteGlobal;
+
+    function typeName(value) {
+        let type = typeof value;
+        if (type === "undefined" ||
+            type === "string" ||
+            type === "boolean" ||
+            type === "number" ||
+            type === "bigint" ||
+            type === "symbol" ||
+            type === "function") {
+            return type;
+        }
+
+        if (value === null) {
+            return "null";
+        }
+        // The handling of cross-global objects here is broken
+        if (value instanceof RemoteObject) {
+            return "remoteobject";
+        }
+        if (value instanceof SendChannel) {
+            return "sendchannel";
+        }
+        if (value instanceof RecvChannel) {
+            return "recvchannel";
+        }
+        if (value instanceof Error) {
+            return "error";
+        }
+        if (Array.isArray(value)) {
+            return "array";
+        }
+        let constructor = value.constructor && value.constructor.name;
+        if (constructor === "RegExp" ||
+            constructor === "Date" ||
+            constructor === "Map" ||
+            constructor === "Set" ||
+            constructor == "WeakMap" ||
+            constructor == "WeakSet") {
+            return constructor.toLowerCase();
+        }
+        // The handling of cross-global objects here is broken
+        if (typeof window == "object" && window === self) {
+            if (value instanceof Element) {
+                return "element";
+            }
+            if (value instanceof Document) {
+                return "document";
+            }
+            if (value instanceof Node) {
+                return "node";
+            }
+            if (value instanceof Window) {
+                return "window";
+            }
+        }
+        if (Promise.resolve(value) === value) {
+            return "promise";
+        }
+        return "object";
+    }
+
+    let remoteObjectsById = new Map();
+
+    function remoteId(obj) {
+        let rv;
+        rv = createUuid();
+        remoteObjectsById.set(rv, obj);
+        return rv;
+    }
+
+    /**
+     * Representation of a non-primitive type passed through a channel
+     */
+    class RemoteObject {
+        constructor(type, objectId) {
+            this.type = type;
+            this.objectId = objectId;
+        }
+
+        /**
+         * Create a RemoteObject containing a handle to reference obj
+         *
+         * @param {Any} obj - The object to reference.
+         */
+        static from(obj) {
+            let type = typeName(obj);
+            let id = remoteId(obj);
+            return new RemoteObject(type, id);
+        }
+
+        /**
+         * Return the local object referenced by the ``objectId`` of
+         * this ``RemoteObject``, or ``null`` if there isn't a such an
+         * object in this realm.
+         */
+        toLocal() {
+            if (remoteObjectsById.has(this.objectId)) {
+                return remoteObjectsById.get(this.objectId);
+            }
+            return null;
+        }
+
+        /**
+         * Remove the object from the local cache. This means that future
+         * calls to ``toLocal`` with the same objectId will always return
+         * ``null``.
+         */
+        delete() {
+            remoteObjectsById.delete(this.objectId);
+        }
+    }
+
+    self.RemoteObject = RemoteObject;
+
+    /**
+     * Serialize an object as a JSON-compatible representation.
+     *
+     * The format used is similar (but not identical to)
+     * `WebDriver-BiDi
+     * <https://w3c.github.io/webdriver-bidi/#data-types-protocolValue>`_.
+     *
+     * Each item to be serialized can have the following fields:
+     *
+     * type - The name of the type being represented e.g. "string", or
+     *  "map". For primitives this matches ``typeof``, but for
+     *  ``object`` types that have particular support in the protocol
+     *  e.g. arrays and maps, it is a custom value.
+     *
+     * value - A serialized representation of the object value. For
+     * container types this is a JSON container (i.e. an object or an
+     * array) containing a serialized representation of the child
+     * values.
+     *
+     * objectId - An integer used to handle object graphs. Where
+     * an object is present more than once in the serialization, the
+     * first instance has both ``value`` and ``objectId`` fields, but
+     * when encountered again, only ``objectId`` is present, with the
+     * same value as the first instance of the object.
+     *
+     * @param {Any} inValue - The value to be serialized.
+     * @returns {Object} - The serialized object value.
+     */
+    function serialize(inValue) {
+        const queue = [{item: inValue}];
+        let outValue = null;
+
+        // Map from container object input to output value
+        let objectsSeen = new Map();
+        let lastObjectId = 0;
+
+        /* Instead of making this recursive, use a queue holding the objects to be
+         * serialized. Each item in the queue can have the following properties:
+         *
+         * item (required) - the input item to be serialized
+         *
+         * target - For collections, the output serialized object to
+         * which the serialization of the current item will be added.
+         *
+         * targetName - For serializing object members, the name of
+         * the property. For serializing maps either "key" or "value",
+         * depending on whether the item represents a key or a value
+         * in the map.
+         */
+        while (queue.length > 0) {
+            const {item, target, targetName} = queue.shift();
+            let type = typeName(item);
+
+            let serialized = {type};
+
+            if (objectsSeen.has(item)) {
+                let outputValue = objectsSeen.get(item);
+                if (!outputValue.hasOwnProperty("objectId")) {
+                    outputValue.objectId = lastObjectId++;
+                }
+                serialized.objectId = outputValue.objectId;
+            } else {
+                switch (type) {
+                case "undefined":
+                case "null":
+                    break;
+                case "string":
+                case "boolean":
+                    serialized.value = item;
+                    break;
+                case "number":
+                    if (item !== item) {
+                        serialized.value = "NaN";
+                    } else if (item === 0 && 1/item == Number.NEGATIVE_INFINITY) {
+                        serialized.value = "-0";
+                    } else if (item === Number.POSITIVE_INFINITY) {
+                        serialized.value = "+Infinity";
+                    } else if (item === Number.NEGATIVE_INFINITY) {
+                        serialized.value = "-Infinity";
+                    } else {
+                        serialized.value = item;
+                    }
+                    break;
+                case "bigint":
+                case "function":
+                    serialized.value = item.toString();
+                    break;
+                case "remoteobject":
+                    serialized.value = {
+                        type: item.type,
+                        objectId: item.objectId
+                    };
+                    break;
+                case "sendchannel":
+                    serialized.value = item.uuid;
+                    break;
+                case "regexp":
+                    serialized.value = {
+                        pattern: item.source,
+                        flags: item.flags
+                    };
+                    break;
+                case "date":
+                    serialized.value = Date.prototype.toJSON.call(item);
+                    break;
+                case "error":
+                    serialized.value = {
+                        type: item.constructor.name,
+                        name: item.name,
+                        message: item.message,
+                        lineNumber: item.lineNumber,
+                        columnNumber: item.columnNumber,
+                        fileName: item.fileName,
+                        stack: item.stack,
+                    };
+                    break;
+                case "array":
+                case "set":
+                    serialized.value = [];
+                    for (let child of item) {
+                        queue.push({item: child, target: serialized});
+                    }
+                    break;
+                case "object":
+                    serialized.value = {};
+                    for (let [targetName, child] of Object.entries(item)) {
+                        queue.push({item: child, target: serialized, targetName});
+                    }
+                    break;
+                case "map":
+                    serialized.value = [];
+                    for (let [childKey, childValue] of item.entries()) {
+                        queue.push({item: childKey, target: serialized, targetName: "key"});
+                        queue.push({item: childValue, target: serialized, targetName: "value"});
+                    }
+                    break;
+                default:
+                    throw new TypeError(`Can't serialize value of type ${type}; consider using RemoteObject.from() to wrap the object`);
+                };
+            }
+            if (serialized.objectId === undefined) {
+                objectsSeen.set(item, serialized);
+            }
+
+            if (target === undefined) {
+                if (outValue !== null) {
+                    throw new Error("Tried to create multiple output values");
+                }
+                outValue = serialized;
+            } else {
+                switch (target.type) {
+                case "array":
+                case "set":
+                    target.value.push(serialized);
+                    break;
+                case "object":
+                    target.value[targetName] = serialized;
+                    break;
+                case "map":
+                    // We always serialize key and value as adjacent items in the queue,
+                    // so when we get the key push a new output array and then the value will
+                    // be added on the next iteration.
+                    if (targetName === "key") {
+                        target.value.push([]);
+                    }
+                    target.value[target.value.length - 1].push(serialized);
+                    break;
+                default:
+                    throw new Error(`Unknown collection target type ${target.type}`);
+                }
+            }
+        }
+        return outValue;
+    }
+
+    /**
+     * Deserialize an object from a JSON-compatible representation.
+     *
+     * For details on the serialized representation see serialize().
+     *
+     * @param {Object} obj - The value to be deserialized.
+     * @returns {Any} - The deserialized value.
+     */
+    function deserialize(obj) {
+        let deserialized = null;
+        let queue = [{item: obj, target: null}];
+        let objectMap = new Map();
+
+        /* Instead of making this recursive, use a queue holding the objects to be
+         * deserialized. Each item in the queue has the following properties:
+         *
+         * item - The input item to be deserialised.
+         *
+         * target - For members of a collection, a wrapper around the
+         * output collection. This has a ``type`` field which is the
+         * name of the collection type, and a ``value`` field which is
+         * the actual output collection. For primitives, this is null.
+         *
+         * targetName - For object members, the property name on the
+         * output object. For maps, "key" if the item is a key in the output map,
+         * or "value" if it's a value in the output map.
+         */
+        while (queue.length > 0) {
+            const {item, target, targetName} = queue.shift();
+            const {type, value, objectId} = item;
+            let result;
+            let newTarget;
+            if (objectId !== undefined && value === undefined) {
+                result = objectMap.get(objectId);
+            } else {
+                switch(type) {
+                case "undefined":
+                    result = undefined;
+                    break;
+                case "null":
+                    result = null;
+                    break;
+                case "string":
+                case "boolean":
+                    result = value;
+                    break;
+                case "number":
+                    if (typeof value === "string") {
+                        switch(value) {
+                        case "NaN":
+                            result = NaN;
+                            break;
+                        case "-0":
+                            result = -0;
+                            break;
+                        case "+Infinity":
+                            result = Number.POSITIVE_INFINITY;
+                            break;
+                        case "-Infinity":
+                            result = Number.NEGATIVE_INFINITY;
+                            break;
+                        default:
+                            throw new Error(`Unexpected number value "${value}"`);
+                        }
+                    } else {
+                        result = value;
+                    }
+                    break;
+                case "bigint":
+                    result = BigInt(value);
+                    break;
+                case "function":
+                    result = new Function("...args", `return (${value}).apply(null, args)`);
+                    break;
+                case "remoteobject":
+                    let remote = new RemoteObject(value.type, value.objectId);
+                    let local = remote.toLocal();
+                    if (local !== null) {
+                        result = local;
+                    } else {
+                        result = remote;
+                    }
+                    break;
+                case "sendchannel":
+                    result = new SendChannel(value);
+                    break;
+                case "regexp":
+                    result = new RegExp(value.pattern, value.flags);
+                    break;
+                case "date":
+                    result = new Date(value);
+                    break;
+                case "error":
+                    // The item.value.type property is the name of the error constructor.
+                    // If we have a constructor with the same name in the current realm,
+                    // construct an instance of that type, otherwise use a generic Error
+                    // type.
+                    if (item.value.type in self &&
+                        typeof self[item.value.type] === "function") {
+                        result = new self[item.value.type](item.value.message);
+                    } else {
+                        result = new Error(item.value.message);
+                    }
+                    result.name = item.value.name;
+                    result.lineNumber = item.value.lineNumber;
+                    result.columnNumber = item.value.columnNumber;
+                    result.fileName = item.value.fileName;
+                    result.stack = item.value.stack;
+                    break;
+                case "array":
+                    result = [];
+                    newTarget = {type, value: result};
+                    for (let child of value) {
+                        queue.push({item: child, target: newTarget});
+                    }
+                    break;
+                case "set":
+                    result = new Set();
+                    newTarget = {type, value: result};
+                    for (let child of value) {
+                        queue.push({item: child, target: newTarget});
+                    }
+                    break;
+                case "object":
+                    result = {};
+                    newTarget = {type, value: result};
+                    for (let [targetName, child] of Object.entries(value)) {
+                        queue.push({item: child, target: newTarget, targetName});
+                    }
+                    break;
+                case "map":
+                    result = new Map();
+                    newTarget = {type, value: result};
+                    for (let [key, child] of value) {
+                        queue.push({item: key, target: newTarget, targetName: "key"});
+                        queue.push({item: child, target: newTarget, targetName: "value"});
+                    }
+                    break;
+                default:
+                    throw new TypeError(`Can't deserialize object of type ${type}`);
+                }
+                if (objectId !== undefined) {
+                    objectMap.set(objectId, result);
+                }
+            }
+
+            if (target === null) {
+                if (deserialized !== null) {
+                    throw new Error(`Tried to deserialized a non-root output value without a target`
+                                    ` container object.`);
+                }
+                deserialized = result;
+            } else {
+                switch(target.type) {
+                case "array":
+                    target.value.push(result);
+                    break;
+                case "set":
+                    target.value.add(result);
+                    break;
+                case "object":
+                    target.value[targetName] = result;
+                    break;
+                case "map":
+                    // For maps the same target wrapper is shared between key and value.
+                    // After deserializing the key, set the `key` property on the target
+                    // until we come to the value.
+                    if (targetName === "key") {
+                        target.key = result;
+                    } else {
+                        target.value.set(target.key, result);
+                    }
+                    break;
+                default:
+                    throw new Error(`Unknown target type ${target.type}`);
+                }
+            }
+        }
+        return deserialized;
+    }
+})();