webextension-polyfill/src/browser-polyfill.js

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/* @@package_name - v@@version - @@timestamp */
/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
/* vim: set sts=2 sw=2 et tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
if (typeof browser === "undefined") {
// Wrapping the bulk of this polyfill in a one-time-use function is a minor
// optimization for Firefox. Since Spidermonkey does not fully parse the
// contents of a function until the first time it's called, and since it will
// never actually need to be called, this allows the polyfill to be included
// in Firefox nearly for free.
const wrapAPIs = () => {
// NOTE: apiMetadata is associated to the content of the api-metadata.json file
// at build time by replacing the following "include" with the content of the
// JSON file.
const apiMetadata = {/* include("api-metadata.json") */};
if (Object.keys(apiMetadata).length === 0) {
throw new Error("api-metadata.json has not been included in browser-polyfill");
}
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/**
* A WeakMap subclass which creates and stores a value for any key which does
* not exist when accessed, but behaves exactly as an ordinary WeakMap
* otherwise.
*
* @param {function} createItem
* A function which will be called in order to create the value for any
* key which does not exist, the first time it is accessed. The
* function receives, as its only argument, the key being created.
*/
class DefaultWeakMap extends WeakMap {
constructor(createItem, items = undefined) {
super(items);
this.createItem = createItem;
}
get(key) {
if (!this.has(key)) {
this.set(key, this.createItem(key));
}
return super.get(key);
}
}
/**
* Returns true if the given object is an object with a `then` method, and can
* therefore be assumed to behave as a Promise.
*
* @param {*} value The value to test.
* @returns {boolean} True if the value is thenable.
*/
const isThenable = value => {
return value && typeof value === "object" && typeof value.then === "function";
};
/**
* Creates and returns a function which, when called, will resolve or reject
* the given promise based on how it is called:
*
* - If, when called, `chrome.runtime.lastError` contains a non-null object,
* the promise is rejected with that value.
* - If the function is called with exactly one argument, the promise is
* resolved to that value.
* - Otherwise, the promise is resolved to an array containing all of the
* function's arguments.
*
* @param {object} promise
* An object containing the resolution and rejection functions of a
* promise.
* @param {function} promise.resolve
* The promise's resolution function.
* @param {function} promise.rejection
* The promise's rejection function.
feat: Added devtools.inspectedWindow.eval and devtools.panels.create to wrapped APIs. To be able to wrap the devtools API namespaces, this patch applies the following changes: - fix: Prevent Proxy violation exception on the read-only/non-configurable devtools property by using an empty object with the `chrome` API object as its prototype as the root Proxy target (the Proxy instances returned for the `chrome` API object) and add a related test case. - fix: Added support for a new `singleCallbackArg` metadata property, which prevents devtools.panels.create to resolve an array of parameters (See the related Chromium issue at https://bugs.chromium.org/p/chromium/issues/detail?id=768159) and add the related test cases. - test: Changes to the test case related to proxy getter/setter behavior on non wrapped properties: in the "deletes proxy getter/setter that are not wrapped" test case from the "test-proxied-properties.js" test file, we ensure that when a getter/setter is called for a "non-wrapped" property, the getter/setter is going to affect the original target object, unfortunately this in not true anymore for the root object (the `chrome` API object) because we are using an empty object (which has the `chrome` API object as its prototype and it is not exposed outside of the polyfill sources) as the target of the Proxy instance related to it, this change to the target of the Proxy has been needed to prevent the TypeError exception raised by the Proxy instance when we try to access the "devtools" property (which is non-configurable and read-only on the `chrome` API object).
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* @param {object} metadata
* Metadata about the wrapped method which has created the callback.
* @param {integer} metadata.maxResolvedArgs
* The maximum number of arguments which may be passed to the
* callback created by the wrapped async function.
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*
* @returns {function}
* The generated callback function.
*/
feat: Added devtools.inspectedWindow.eval and devtools.panels.create to wrapped APIs. To be able to wrap the devtools API namespaces, this patch applies the following changes: - fix: Prevent Proxy violation exception on the read-only/non-configurable devtools property by using an empty object with the `chrome` API object as its prototype as the root Proxy target (the Proxy instances returned for the `chrome` API object) and add a related test case. - fix: Added support for a new `singleCallbackArg` metadata property, which prevents devtools.panels.create to resolve an array of parameters (See the related Chromium issue at https://bugs.chromium.org/p/chromium/issues/detail?id=768159) and add the related test cases. - test: Changes to the test case related to proxy getter/setter behavior on non wrapped properties: in the "deletes proxy getter/setter that are not wrapped" test case from the "test-proxied-properties.js" test file, we ensure that when a getter/setter is called for a "non-wrapped" property, the getter/setter is going to affect the original target object, unfortunately this in not true anymore for the root object (the `chrome` API object) because we are using an empty object (which has the `chrome` API object as its prototype and it is not exposed outside of the polyfill sources) as the target of the Proxy instance related to it, this change to the target of the Proxy has been needed to prevent the TypeError exception raised by the Proxy instance when we try to access the "devtools" property (which is non-configurable and read-only on the `chrome` API object).
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const makeCallback = (promise, metadata) => {
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return (...callbackArgs) => {
if (chrome.runtime.lastError) {
promise.reject(chrome.runtime.lastError);
feat: Added devtools.inspectedWindow.eval and devtools.panels.create to wrapped APIs. To be able to wrap the devtools API namespaces, this patch applies the following changes: - fix: Prevent Proxy violation exception on the read-only/non-configurable devtools property by using an empty object with the `chrome` API object as its prototype as the root Proxy target (the Proxy instances returned for the `chrome` API object) and add a related test case. - fix: Added support for a new `singleCallbackArg` metadata property, which prevents devtools.panels.create to resolve an array of parameters (See the related Chromium issue at https://bugs.chromium.org/p/chromium/issues/detail?id=768159) and add the related test cases. - test: Changes to the test case related to proxy getter/setter behavior on non wrapped properties: in the "deletes proxy getter/setter that are not wrapped" test case from the "test-proxied-properties.js" test file, we ensure that when a getter/setter is called for a "non-wrapped" property, the getter/setter is going to affect the original target object, unfortunately this in not true anymore for the root object (the `chrome` API object) because we are using an empty object (which has the `chrome` API object as its prototype and it is not exposed outside of the polyfill sources) as the target of the Proxy instance related to it, this change to the target of the Proxy has been needed to prevent the TypeError exception raised by the Proxy instance when we try to access the "devtools" property (which is non-configurable and read-only on the `chrome` API object).
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} else if (metadata.singleCallbackArg || callbackArgs.length === 1) {
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promise.resolve(callbackArgs[0]);
} else {
promise.resolve(callbackArgs);
}
};
};
/**
* Creates a wrapper function for a method with the given name and metadata.
*
* @param {string} name
* The name of the method which is being wrapped.
* @param {object} metadata
* Metadata about the method being wrapped.
* @param {integer} metadata.minArgs
* The minimum number of arguments which must be passed to the
* function. If called with fewer than this number of arguments, the
* wrapper will raise an exception.
* @param {integer} metadata.maxArgs
* The maximum number of arguments which may be passed to the
* function. If called with more than this number of arguments, the
* wrapper will raise an exception.
feat: Added devtools.inspectedWindow.eval and devtools.panels.create to wrapped APIs. To be able to wrap the devtools API namespaces, this patch applies the following changes: - fix: Prevent Proxy violation exception on the read-only/non-configurable devtools property by using an empty object with the `chrome` API object as its prototype as the root Proxy target (the Proxy instances returned for the `chrome` API object) and add a related test case. - fix: Added support for a new `singleCallbackArg` metadata property, which prevents devtools.panels.create to resolve an array of parameters (See the related Chromium issue at https://bugs.chromium.org/p/chromium/issues/detail?id=768159) and add the related test cases. - test: Changes to the test case related to proxy getter/setter behavior on non wrapped properties: in the "deletes proxy getter/setter that are not wrapped" test case from the "test-proxied-properties.js" test file, we ensure that when a getter/setter is called for a "non-wrapped" property, the getter/setter is going to affect the original target object, unfortunately this in not true anymore for the root object (the `chrome` API object) because we are using an empty object (which has the `chrome` API object as its prototype and it is not exposed outside of the polyfill sources) as the target of the Proxy instance related to it, this change to the target of the Proxy has been needed to prevent the TypeError exception raised by the Proxy instance when we try to access the "devtools" property (which is non-configurable and read-only on the `chrome` API object).
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* @param {integer} metadata.maxResolvedArgs
* The maximum number of arguments which may be passed to the
* callback created by the wrapped async function.
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*
* @returns {function(object, ...*)}
* The generated wrapper function.
*/
const wrapAsyncFunction = (name, metadata) => {
const pluralizeArguments = (numArgs) => numArgs == 1 ? "argument" : "arguments";
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return function asyncFunctionWrapper(target, ...args) {
if (args.length < metadata.minArgs) {
throw new Error(`Expected at least ${metadata.minArgs} ${pluralizeArguments(metadata.minArgs)} for ${name}(), got ${args.length}`);
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}
if (args.length > metadata.maxArgs) {
throw new Error(`Expected at most ${metadata.maxArgs} ${pluralizeArguments(metadata.maxArgs)} for ${name}(), got ${args.length}`);
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}
return new Promise((resolve, reject) => {
feat: Added devtools.inspectedWindow.eval and devtools.panels.create to wrapped APIs. To be able to wrap the devtools API namespaces, this patch applies the following changes: - fix: Prevent Proxy violation exception on the read-only/non-configurable devtools property by using an empty object with the `chrome` API object as its prototype as the root Proxy target (the Proxy instances returned for the `chrome` API object) and add a related test case. - fix: Added support for a new `singleCallbackArg` metadata property, which prevents devtools.panels.create to resolve an array of parameters (See the related Chromium issue at https://bugs.chromium.org/p/chromium/issues/detail?id=768159) and add the related test cases. - test: Changes to the test case related to proxy getter/setter behavior on non wrapped properties: in the "deletes proxy getter/setter that are not wrapped" test case from the "test-proxied-properties.js" test file, we ensure that when a getter/setter is called for a "non-wrapped" property, the getter/setter is going to affect the original target object, unfortunately this in not true anymore for the root object (the `chrome` API object) because we are using an empty object (which has the `chrome` API object as its prototype and it is not exposed outside of the polyfill sources) as the target of the Proxy instance related to it, this change to the target of the Proxy has been needed to prevent the TypeError exception raised by the Proxy instance when we try to access the "devtools" property (which is non-configurable and read-only on the `chrome` API object).
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target[name](...args, makeCallback({resolve, reject}, metadata));
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});
};
};
/**
* Wraps an existing method of the target object, so that calls to it are
* intercepted by the given wrapper function. The wrapper function receives,
* as its first argument, the original `target` object, followed by each of
* the arguments passed to the orginal method.
*
* @param {object} target
* The original target object that the wrapped method belongs to.
* @param {function} method
* The method being wrapped. This is used as the target of the Proxy
* object which is created to wrap the method.
* @param {function} wrapper
* The wrapper function which is called in place of a direct invocation
* of the wrapped method.
*
* @returns {Proxy<function>}
* A Proxy object for the given method, which invokes the given wrapper
* method in its place.
*/
const wrapMethod = (target, method, wrapper) => {
return new Proxy(method, {
apply(targetMethod, thisObj, args) {
return wrapper.call(thisObj, target, ...args);
},
});
};
let hasOwnProperty = Function.call.bind(Object.prototype.hasOwnProperty);
/**
* Wraps an object in a Proxy which intercepts and wraps certain methods
* based on the given `wrappers` and `metadata` objects.
*
* @param {object} target
* The target object to wrap.
*
* @param {object} [wrappers = {}]
* An object tree containing wrapper functions for special cases. Any
* function present in this object tree is called in place of the
* method in the same location in the `target` object tree. These
* wrapper methods are invoked as described in {@see wrapMethod}.
*
* @param {object} [metadata = {}]
* An object tree containing metadata used to automatically generate
* Promise-based wrapper functions for asynchronous. Any function in
* the `target` object tree which has a corresponding metadata object
* in the same location in the `metadata` tree is replaced with an
* automatically-generated wrapper function, as described in
* {@see wrapAsyncFunction}
*
* @returns {Proxy<object>}
*/
const wrapObject = (target, wrappers = {}, metadata = {}) => {
let cache = Object.create(null);
let handlers = {
has(target, prop) {
return prop in target || prop in cache;
},
get(target, prop, receiver) {
if (prop in cache) {
return cache[prop];
}
if (!(prop in target)) {
return undefined;
}
let value = target[prop];
if (typeof value === "function") {
// This is a method on the underlying object. Check if we need to do
// any wrapping.
if (typeof wrappers[prop] === "function") {
// We have a special-case wrapper for this method.
value = wrapMethod(target, target[prop], wrappers[prop]);
} else if (hasOwnProperty(metadata, prop)) {
// This is an async method that we have metadata for. Create a
// Promise wrapper for it.
let wrapper = wrapAsyncFunction(prop, metadata[prop]);
value = wrapMethod(target, target[prop], wrapper);
} else {
// This is a method that we don't know or care about. Return the
// original method, bound to the underlying object.
value = value.bind(target);
}
} else if (typeof value === "object" && value !== null &&
(hasOwnProperty(wrappers, prop) ||
hasOwnProperty(metadata, prop))) {
// This is an object that we need to do some wrapping for the children
// of. Create a sub-object wrapper for it with the appropriate child
// metadata.
value = wrapObject(value, wrappers[prop], metadata[prop]);
} else {
// We don't need to do any wrapping for this property,
// so just forward all access to the underlying object.
Object.defineProperty(cache, prop, {
configurable: true,
enumerable: true,
get() {
return target[prop];
},
set(value) {
target[prop] = value;
},
});
return value;
}
cache[prop] = value;
return value;
},
set(target, prop, value, receiver) {
if (prop in cache) {
cache[prop] = value;
} else {
target[prop] = value;
}
return true;
},
defineProperty(target, prop, desc) {
return Reflect.defineProperty(cache, prop, desc);
},
deleteProperty(target, prop) {
return Reflect.deleteProperty(cache, prop);
},
};
return new Proxy(target, handlers);
};
/**
* Creates a set of wrapper functions for an event object, which handles
* wrapping of listener functions that those messages are passed.
*
* A single wrapper is created for each listener function, and stored in a
* map. Subsequent calls to `addListener`, `hasListener`, or `removeListener`
* retrieve the original wrapper, so that attempts to remove a
* previously-added listener work as expected.
*
* @param {DefaultWeakMap<function, function>} wrapperMap
* A DefaultWeakMap object which will create the appropriate wrapper
* for a given listener function when one does not exist, and retrieve
* an existing one when it does.
*
* @returns {object}
*/
const wrapEvent = wrapperMap => ({
addListener(target, listener, ...args) {
target.addListener(wrapperMap.get(listener), ...args);
},
hasListener(target, listener) {
return target.hasListener(wrapperMap.get(listener));
},
removeListener(target, listener) {
target.removeListener(wrapperMap.get(listener));
},
});
const onMessageWrappers = new DefaultWeakMap(listener => {
if (typeof listener !== "function") {
return listener;
}
/**
* Wraps a message listener function so that it may send responses based on
* its return value, rather than by returning a sentinel value and calling a
* callback. If the listener function returns a Promise, the response is
* sent when the promise either resolves or rejects.
*
* @param {*} message
* The message sent by the other end of the channel.
* @param {object} sender
* Details about the sender of the message.
* @param {function(*)} sendResponse
* A callback which, when called with an arbitrary argument, sends
* that value as a response.
* @returns {boolean}
* True if the wrapped listener returned a Promise, which will later
* yield a response. False otherwise.
*/
return function onMessage(message, sender, sendResponse) {
let result = listener(message, sender);
if (isThenable(result)) {
result.then(sendResponse, error => {
console.error(error);
sendResponse(error);
});
return true;
} else if (result !== undefined) {
sendResponse(result);
}
};
});
const staticWrappers = {
runtime: {
onMessage: wrapEvent(onMessageWrappers),
},
};
// Create a new empty object and copy the properties of the original chrome object
feat: Added devtools.inspectedWindow.eval and devtools.panels.create to wrapped APIs. To be able to wrap the devtools API namespaces, this patch applies the following changes: - fix: Prevent Proxy violation exception on the read-only/non-configurable devtools property by using an empty object with the `chrome` API object as its prototype as the root Proxy target (the Proxy instances returned for the `chrome` API object) and add a related test case. - fix: Added support for a new `singleCallbackArg` metadata property, which prevents devtools.panels.create to resolve an array of parameters (See the related Chromium issue at https://bugs.chromium.org/p/chromium/issues/detail?id=768159) and add the related test cases. - test: Changes to the test case related to proxy getter/setter behavior on non wrapped properties: in the "deletes proxy getter/setter that are not wrapped" test case from the "test-proxied-properties.js" test file, we ensure that when a getter/setter is called for a "non-wrapped" property, the getter/setter is going to affect the original target object, unfortunately this in not true anymore for the root object (the `chrome` API object) because we are using an empty object (which has the `chrome` API object as its prototype and it is not exposed outside of the polyfill sources) as the target of the Proxy instance related to it, this change to the target of the Proxy has been needed to prevent the TypeError exception raised by the Proxy instance when we try to access the "devtools" property (which is non-configurable and read-only on the `chrome` API object).
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// to prevent a Proxy violation exception for the devtools API getter
// (which is a read-only non-configurable property on the original target).
const targetObject = Object.assign({}, chrome);
feat: Added devtools.inspectedWindow.eval and devtools.panels.create to wrapped APIs. To be able to wrap the devtools API namespaces, this patch applies the following changes: - fix: Prevent Proxy violation exception on the read-only/non-configurable devtools property by using an empty object with the `chrome` API object as its prototype as the root Proxy target (the Proxy instances returned for the `chrome` API object) and add a related test case. - fix: Added support for a new `singleCallbackArg` metadata property, which prevents devtools.panels.create to resolve an array of parameters (See the related Chromium issue at https://bugs.chromium.org/p/chromium/issues/detail?id=768159) and add the related test cases. - test: Changes to the test case related to proxy getter/setter behavior on non wrapped properties: in the "deletes proxy getter/setter that are not wrapped" test case from the "test-proxied-properties.js" test file, we ensure that when a getter/setter is called for a "non-wrapped" property, the getter/setter is going to affect the original target object, unfortunately this in not true anymore for the root object (the `chrome` API object) because we are using an empty object (which has the `chrome` API object as its prototype and it is not exposed outside of the polyfill sources) as the target of the Proxy instance related to it, this change to the target of the Proxy has been needed to prevent the TypeError exception raised by the Proxy instance when we try to access the "devtools" property (which is non-configurable and read-only on the `chrome` API object).
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return wrapObject(targetObject, staticWrappers, apiMetadata);
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};
// The build process adds a UMD wrapper around this file, which makes the
// `module` variable available.
module.exports = wrapAPIs(); // eslint-disable-line no-undef
} else {
module.exports = browser; // eslint-disable-line no-undef
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}