electron/lib/renderer/api/remote.js

'use strict';

const v8Util = process.electronBinding('v8_util');

const { CallbacksRegistry } = require('@electron/internal/renderer/callbacks-registry');
const bufferUtils = require('@electron/internal/common/buffer-utils');
const errorUtils = require('@electron/internal/common/error-utils');
const { isPromise } = require('@electron/internal/common/is-promise');
const { ipcRendererInternal } = require('@electron/internal/renderer/ipc-renderer-internal');

const callbacksRegistry = new CallbacksRegistry();
const remoteObjectCache = v8Util.createIDWeakMap();

// An unique ID that can represent current context.
const contextId = v8Util.getHiddenValue(global, 'contextId');

// Notify the main process when current context is going to be released.
// Note that when the renderer process is destroyed, the message may not be
// sent, we also listen to the "render-view-deleted" event in the main process
// to guard that situation.
process.on('exit', () => {
  const command = 'ELECTRON_BROWSER_CONTEXT_RELEASE';
  ipcRendererInternal.send(command, contextId);
});

// Convert the arguments object into an array of meta data.
function wrapArgs (args, visited = new Set()) {
  const valueToMeta = (value) => {
    // Check for circular reference.
    if (visited.has(value)) {
      return {
        type: 'value',
        value: null
      };
    }

    if (Array.isArray(value)) {
      visited.add(value);
      const meta = {
        type: 'array',
        value: wrapArgs(value, visited)
      };
      visited.delete(value);
      return meta;
    } else if (bufferUtils.isBuffer(value)) {
      return {
        type: 'buffer',
        value: bufferUtils.bufferToMeta(value)
      };
    } else if (value instanceof Date) {
      return {
        type: 'date',
        value: value.getTime()
      };
    } else if ((value != null) && typeof value === 'object') {
      if (isPromise(value)) {
        return {
          type: 'promise',
          then: valueToMeta(function (onFulfilled, onRejected) {
            value.then(onFulfilled, onRejected);
          })
        };
      } else if (v8Util.getHiddenValue(value, 'atomId')) {
        return {
          type: 'remote-object',
          id: v8Util.getHiddenValue(value, 'atomId')
        };
      }

      const meta = {
        type: 'object',
        name: value.constructor ? value.constructor.name : '',
        members: []
      };
      visited.add(value);
      for (const prop in value) { // eslint-disable-line guard-for-in
        meta.members.push({
          name: prop,
          value: valueToMeta(value[prop])
        });
      }
      visited.delete(value);
      return meta;
    } else if (typeof value === 'function' && v8Util.getHiddenValue(value, 'returnValue')) {
      return {
        type: 'function-with-return-value',
        value: valueToMeta(value())
      };
    } else if (typeof value === 'function') {
      return {
        type: 'function',
        id: callbacksRegistry.add(value),
        location: v8Util.getHiddenValue(value, 'location'),
        length: value.length
      };
    } else {
      return {
        type: 'value',
        value: value
      };
    }
  };
  return args.map(valueToMeta);
}

// Populate object's members from descriptors.
// The |ref| will be kept referenced by |members|.
// This matches |getObjectMemebers| in rpc-server.
function setObjectMembers (ref, object, metaId, members) {
  if (!Array.isArray(members)) return;

  for (const member of members) {
    if (object.hasOwnProperty(member.name)) continue;

    const descriptor = { enumerable: member.enumerable };
    if (member.type === 'method') {
      const remoteMemberFunction = function (...args) {
        let command;
        if (this && this.constructor === remoteMemberFunction) {
          command = 'ELECTRON_BROWSER_MEMBER_CONSTRUCTOR';
        } else {
          command = 'ELECTRON_BROWSER_MEMBER_CALL';
        }
        const ret = ipcRendererInternal.sendSync(command, contextId, metaId, member.name, wrapArgs(args));
        return metaToValue(ret);
      };

      let descriptorFunction = proxyFunctionProperties(remoteMemberFunction, metaId, member.name);

      descriptor.get = () => {
        descriptorFunction.ref = ref; // The member should reference its object.
        return descriptorFunction;
      };
      // Enable monkey-patch the method
      descriptor.set = (value) => {
        descriptorFunction = value;
        return value;
      };
      descriptor.configurable = true;
    } else if (member.type === 'get') {
      descriptor.get = () => {
        const command = 'ELECTRON_BROWSER_MEMBER_GET';
        const meta = ipcRendererInternal.sendSync(command, contextId, metaId, member.name);
        return metaToValue(meta);
      };

      if (member.writable) {
        descriptor.set = (value) => {
          const args = wrapArgs([value]);
          const command = 'ELECTRON_BROWSER_MEMBER_SET';
          const meta = ipcRendererInternal.sendSync(command, contextId, metaId, member.name, args);
          if (meta != null) metaToValue(meta);
          return value;
        };
      }
    }

    Object.defineProperty(object, member.name, descriptor);
  }
}

// Populate object's prototype from descriptor.
// This matches |getObjectPrototype| in rpc-server.
function setObjectPrototype (ref, object, metaId, descriptor) {
  if (descriptor === null) return;
  const proto = {};
  setObjectMembers(ref, proto, metaId, descriptor.members);
  setObjectPrototype(ref, proto, metaId, descriptor.proto);
  Object.setPrototypeOf(object, proto);
}

// Wrap function in Proxy for accessing remote properties
function proxyFunctionProperties (remoteMemberFunction, metaId, name) {
  let loaded = false;

  // Lazily load function properties
  const loadRemoteProperties = () => {
    if (loaded) return;
    loaded = true;
    const command = 'ELECTRON_BROWSER_MEMBER_GET';
    const meta = ipcRendererInternal.sendSync(command, contextId, metaId, name);
    setObjectMembers(remoteMemberFunction, remoteMemberFunction, meta.id, meta.members);
  };

  return new Proxy(remoteMemberFunction, {
    set: (target, property, value, receiver) => {
      if (property !== 'ref') loadRemoteProperties();
      target[property] = value;
      return true;
    },
    get: (target, property, receiver) => {
      if (!target.hasOwnProperty(property)) loadRemoteProperties();
      const value = target[property];
      if (property === 'toString' && typeof value === 'function') {
        return value.bind(target);
      }
      return value;
    },
    ownKeys: (target) => {
      loadRemoteProperties();
      return Object.getOwnPropertyNames(target);
    },
    getOwnPropertyDescriptor: (target, property) => {
      const descriptor = Object.getOwnPropertyDescriptor(target, property);
      if (descriptor) return descriptor;
      loadRemoteProperties();
      return Object.getOwnPropertyDescriptor(target, property);
    }
  });
}

// Convert meta data from browser into real value.
function metaToValue (meta) {
  const types = {
    value: () => meta.value,
    array: () => meta.members.map((member) => metaToValue(member)),
    buffer: () => bufferUtils.metaToBuffer(meta.value),
    promise: () => Promise.resolve({ then: metaToValue(meta.then) }),
    error: () => metaToPlainObject(meta),
    date: () => new Date(meta.value),
    exception: () => { throw errorUtils.deserialize(meta.value); }
  };

  if (Object.prototype.hasOwnProperty.call(types, meta.type)) {
    return types[meta.type]();
  } else {
    let ret;
    if (remoteObjectCache.has(meta.id)) {
      v8Util.addRemoteObjectRef(contextId, meta.id);
      return remoteObjectCache.get(meta.id);
    }

    // A shadow class to represent the remote function object.
    if (meta.type === 'function') {
      const remoteFunction = function (...args) {
        let command;
        if (this && this.constructor === remoteFunction) {
          command = 'ELECTRON_BROWSER_CONSTRUCTOR';
        } else {
          command = 'ELECTRON_BROWSER_FUNCTION_CALL';
        }
        const obj = ipcRendererInternal.sendSync(command, contextId, meta.id, wrapArgs(args));
        return metaToValue(obj);
      };
      ret = remoteFunction;
    } else {
      ret = {};
    }

    setObjectMembers(ret, ret, meta.id, meta.members);
    setObjectPrototype(ret, ret, meta.id, meta.proto);
    Object.defineProperty(ret.constructor, 'name', { value: meta.name });

    // Track delegate obj's lifetime & tell browser to clean up when object is GCed.
    v8Util.setRemoteObjectFreer(ret, contextId, meta.id);
    v8Util.setHiddenValue(ret, 'atomId', meta.id);
    v8Util.addRemoteObjectRef(contextId, meta.id);
    remoteObjectCache.set(meta.id, ret);
    return ret;
  }
}

// Construct a plain object from the meta.
function metaToPlainObject (meta) {
  const obj = (() => meta.type === 'error' ? new Error() : {})();
  for (let i = 0; i < meta.members.length; i++) {
    const { name, value } = meta.members[i];
    obj[name] = value;
  }
  return obj;
}

function handleMessage (channel, handler) {
  ipcRendererInternal.on(channel, (event, passedContextId, id, ...args) => {
    if (passedContextId === contextId) {
      handler(id, ...args);
    } else {
      // Message sent to an un-exist context, notify the error to main process.
      ipcRendererInternal.send('ELECTRON_BROWSER_WRONG_CONTEXT_ERROR', contextId, passedContextId, id);
    }
  });
}

// Browser calls a callback in renderer.
handleMessage('ELECTRON_RENDERER_CALLBACK', (id, args) => {
  callbacksRegistry.apply(id, metaToValue(args));
});

// A callback in browser is released.
handleMessage('ELECTRON_RENDERER_RELEASE_CALLBACK', (id) => {
  callbacksRegistry.remove(id);
});

exports.require = (module) => {
  const command = 'ELECTRON_BROWSER_REQUIRE';
  const meta = ipcRendererInternal.sendSync(command, contextId, module);
  return metaToValue(meta);
};

// Alias to remote.require('electron').xxx.
exports.getBuiltin = (module) => {
  const command = 'ELECTRON_BROWSER_GET_BUILTIN';
  const meta = ipcRendererInternal.sendSync(command, contextId, module);
  return metaToValue(meta);
};

exports.getCurrentWindow = () => {
  const command = 'ELECTRON_BROWSER_CURRENT_WINDOW';
  const meta = ipcRendererInternal.sendSync(command, contextId);
  return metaToValue(meta);
};

// Get current WebContents object.
exports.getCurrentWebContents = () => {
  const command = 'ELECTRON_BROWSER_CURRENT_WEB_CONTENTS';
  const meta = ipcRendererInternal.sendSync(command, contextId);
  return metaToValue(meta);
};

// Get a global object in browser.
exports.getGlobal = (name) => {
  const command = 'ELECTRON_BROWSER_GLOBAL';
  const meta = ipcRendererInternal.sendSync(command, contextId, name);
  return metaToValue(meta);
};

// Get the process object in browser.
Object.defineProperty(exports, 'process', {
  get: () => exports.getGlobal('process')
});

// Create a function that will return the specified value when called in browser.
exports.createFunctionWithReturnValue = (returnValue) => {
  const func = () => returnValue;
  v8Util.setHiddenValue(func, 'returnValue', true);
  return func;
};

// Get the guest WebContents from guestInstanceId.
exports.getGuestWebContents = (guestInstanceId) => {
  const command = 'ELECTRON_BROWSER_GUEST_WEB_CONTENTS';
  const meta = ipcRendererInternal.sendSync(command, contextId, guestInstanceId);
  return metaToValue(meta);
};

const addBuiltinProperty = (name) => {
  Object.defineProperty(exports, name, {
    get: () => exports.getBuiltin(name)
  });
};

const browserModules =
  require('@electron/internal/common/api/module-list').concat(
    require('@electron/internal/browser/api/module-keys'));

// And add a helper receiver for each one.
browserModules
  .filter((m) => !m.private)
  .map((m) => m.name)
  .forEach(addBuiltinProperty);