uBlock/platform/chromium/vapi.js
Rob Wu b27f23d520 Clear return value of vapi.js content script (#3721)
Upon start-up, uBlock runs all content scripts in manifest.json using
`chrome.tabs.executeScript`. When this API is used, the value of the
last expression is automatically cloned and transferred to the
callback of `chrome.tabs.executeScript`. This is convenient if needed,
and a performance burden otherwise (the latter is the case for uBlock).

There are three content scripts that need to be checked:

- vapi.js
  The last expression is often the vAPI object, and it is relatively
  expensive to clone this object. This commit sets the value of the
  last expression to `void 0` to solve this inefficiency.

- vapi-client.js
  No action needed yet; The last expression is `vAPI.shutdown.add(...)`,
  which has a void return value.

- contentscript.js
  No action needed yet; The last expression is an immediately-invoked
  function expression without return value.
2018-05-01 07:28:21 -04:00

60 lines
2.2 KiB
JavaScript

/*******************************************************************************
uBlock Origin - a browser extension to block requests.
Copyright (C) 2017 The uBlock Origin authors
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see {http://www.gnu.org/licenses/}.
Home: https://github.com/gorhill/uBlock
*/
'use strict';
/* global HTMLDocument, XMLDocument */
// For background page, auxiliary pages, and content scripts.
/******************************************************************************/
// https://bugzilla.mozilla.org/show_bug.cgi?id=1408996#c9
var vAPI = window.vAPI; // jshint ignore:line
// https://github.com/chrisaljoudi/uBlock/issues/464
// https://github.com/chrisaljoudi/uBlock/issues/1528
// A XMLDocument can be a valid HTML document.
// https://github.com/gorhill/uBlock/issues/1124
// Looks like `contentType` is on track to be standardized:
// https://dom.spec.whatwg.org/#concept-document-content-type
// https://forums.lanik.us/viewtopic.php?f=64&t=31522
// Skip text/plain documents.
if (
(document instanceof HTMLDocument ||
document instanceof XMLDocument &&
document.createElement('div') instanceof HTMLDivElement
) &&
(/^image\/|^text\/plain/.test(document.contentType || '') === false)
) {
vAPI = window.vAPI = vAPI instanceof Object && vAPI.uBO === true
? vAPI
: { uBO: true };
}
// Set the value of the last expression to undefined to avoid serializing the
// vAPI object when the content script is run using chrome.tabs.executeScript.
void 0;
/******************************************************************************/