Wednesday, September 20, 2017

Greasemonkey 4 Announcement

Greasemonkey has been a Firefox extension for well over a decade, with version 0.3.5 dating from 2005.  We've grown and changed a lot over that time.  With the upcoming Firefox 57 release, we need to change even more.  Mozilla is completely replacing the extension system in Firefox, to align with the budding Browser Extension standard, based on/shared with Google Chrome.

As a result, version 4 of Greasemonkey is a nearly complete re-write.  Its interface and feature set have been rebuilt in order to best to work with coming Firefox versions.  A variety of compromises have been made.  We've elected to make a rare backwards incompatible change.

If you are a regular user, please continue reading Greasemonkey 4 For Users.

If you are a developer, please continue reading Greasemonkey 4 For Script Authors.

Greasemonkey 4 For Script Authors

As mentioned in the main post, Greasemonkey 4 is changing to be compatible with the Browser Extension API.  At its core, this set of APIs is completely asynchronous.  Greasemonkey's old "GM_" APIs are typically synchronous.


There exist other user script engines which have already done the work of bridging the gap.  Greasemonkey has elected to move exclusively towards a more performant asynchronous model.  Eventually in the future, such scripts will be faster.


The Greasespot Wiki will be updated to explain Greasemonkey 4 in detail.  Until then, here's a quick summary.

First, there is only an embedded editor.  Browser Extensions have no access to the file system, so you can no longer author user scripts in your familiar text editor.

There is only one object provided to user scripts now, named GM.  It has several properties.  One of them is info – the equivalent of the old GM_info.  There are also several methods of this object: getResourceUrl, deleteValue/getValue/listValues/setValue, xmlHttpRequest.

To use these methods you still need @grant, and use the new name, e.g.:
// @grant GM.setValue
The new form has a dot, where the old form has an underscore.  You may specify both @grants, if you'd like to be compatible with Greasemonkey 4 and other user script engines at the same time.  As of today, there is no support for: GM_log (use console.log), GM_addStyle, GM_registerMenuCommand, nor GM_getResourceText.

In general these methods work like their old counterparts, but their return values are Promises. The async and await keywords make asynchronous promises easy to work with.  For example:
// ==UserScript==
// @name     GM set/get demo
// @grant    GM.getValue
// @grant    GM.setValue
// ==/UserScript==

(async function() {
console.log('Starting the get/set demo ...');
let i = await GM.getValue('i', 0);
console.log(`This time, i was ${i}.`);
GM.setValue('i', i+1);
Here the GM.getValue() method actually returns a promise, but the await keyword transparently converts that to its resolved value, allowing us to write code just as if the value was directly returned – with neither callbacks nor promise resolution.  See the documentation on async and await.

If you'd like your script to be compatible with Greasemonkey 4 and also Greasemonkey 3 (or other user script engines), we have provided a polyfill, which makes new-style API calls work on top of older engines.  To use it: 1) keep your old-API @grant line, 2) add a new-API @grant line, 4) require the polyfill script, 4) switch your code to use new-API style (and probably async/await).  So the above example might look like:
// ==UserScript==
// @name     GM set/get demo
// @require
// @grant    GM.getValue// @grant    GM_getValue// @grant    GM.setValue// @grant    GM_setValue// ==/UserScript==

With the exact same new-API style code as above.  Such a script can be installed in either Greasemonkey 4 or Greasemonkey 3 (or TamperMonkey, or ViolentMonkey, etc.) and work as intended.


Do note that new style APIs have slightly different names.  In short, a consistent naming style has been adopted: all words and acronyms get a consistent case.  So what was before GM_getResourceURL is now GM.getResourceUrl.  What was GM_xmlhttpRequest is now GM_xmlHttpRequest.  In the near future the Greasespot Wiki will be updated with all details of the new APIs, including exact names with case.


We welcome feedback, reach out via the greasemonkey-users discussion group.  Please also keep in mind the volunteer nature of this open source project when doing so!

Greasemonkey 4 For Users

As mentioned in the main post, Greasemonkey 4 is changing how it runs user scripts.  Many user scripts will continue to run as expected, but this will break some scripts.

If you rely on such scripts, you might want to install Violentmonkey or Tampermonkey, both of which provide compatibility for existing scripts.

If you'd prefer to stick with Greasemonkey, you'll need to wait for the script to be updated to be compatible.  Find the original author of your script, and ask them to update for Greasemonkey 4 compatibility.  Referencing this post may help.

We welcome feedback, reach out via the greasemonkey-users discussion group.  Please also keep in mind the volunteer nature of this open source project when doing so!

Tuesday, September 19, 2017

Greasemonkey 3.12 Release

The entire list of bugs handled in this release is also available via the 3.12 milestone on GitHub. Note that as always it takes some time for Mozilla to review the new version.  If you're interested in staying on the bleeding edge, try installing the development channel beta release.  If you are using this version and notice problems, it's best to log an issue or let us know at greasemonkey-dev (and be clear that it's with this version).

Fixed bugs:
  • Repair rare breakage in GM_getValue/GM_setValue. (#2506
New features:
  • Migrate existing scripts to a WebExtension (for Firefox 57+) compatible data storage location.  (#2551)