Talk:Requests for comment/Extension registration

Drawbacks
Besides migration costs, what are the (potential) drawbacks of implementing this proposal? --MZMcBride (talk) 04:38, 24 May 2014 (UTC)
 * Parsing JSON is probably slower than loading a PHP file. We can mitigate this by caching the parsed result.
 * You can't use things like namespace constants in a JSON file. While this doesn't actually break anything (we can just use the actual number), it will hinder readability.
 * There are probably more, but that's what I can think of right now. Legoktm (talk) 04:50, 24 May 2014 (UTC)

It looks like this has been scheduled for discussion soon:

It'll be 1900 UTC http://www.timeanddate.com/worldclock/fixedtime.html?iso=20140530T1900 this Friday 30 May, in #wikimedia-office.

I'd like to see this RFC bolstered with a "Migration costs" (sub)section which would include how many people/hours it would take to do this conversion and other considerations such as the namespace constants mentioned above. You don't need to worry about who would do the migration/conversion work, just estimate about how much work in terms of developer hours are needed to do such a conversion. I guess this might vary between Wikimedia extensions (a hundred or so) and MediaWiki extensions (several thousand). There's still a bit of confusion for me in this area; for example, about whether the old system and the new system can co-exist. I think a section in the RFC for migration costs would be helpful in evaluating this.

I'd also like to see Composer addressed more directly in the RFC itself, particularly if implementing this extension registration RFC will or could impact future work in that direction.

Lastly, I think it's fairly important to figure out what the performance implications of this are and whether they can be mitigated, preferably before discussion and architecture review. My concern is that any discussion of this will immediately get blocked on a discussion of whether this is even feasible to do on huge sites, so it'd be good to get benchmarking about what this would mean for app startup(?) time and any other useful/relevant metrics. Perhaps ping Ori or Chris S. about this? --MZMcBride (talk) 13:51, 25 May 2014 (UTC)

Information conflicts with Composer
Considering we are almost definitely moving in the direction of Composer-managed extensions, it would be a good idea to not duplicate information in the composer.json file. Therefore, the "version", "url", "authors", and "autoload" keys should be removed. Since the composer.json file is also in JSON, it should be trivial to process extensions since it will be in the same folder. Parent5446 (talk) 04:47, 24 May 2014 (UTC)
 * I was under the impression that that RfC was still under discussion and no decision had been made yet. Regardless, I'd like to not have this RfC depend on that one. Aside from autoloading, all of the other keys are trivial and duplicating them really isn't a huge deal. Legoktm (talk) 07:22, 25 May 2014 (UTC)

Btw, the JS library ecosystem already has this issue. Many JS libraries that can run in the browser either support use inside node.js or use node based build tools like Grunt. So many of those projects have both a node/npm package.json and a bower.json for Bower containing the same duplicate information we're talking about. They seem to be doing fine. Daniel Friesen (Dantman) (talk) 07:40, 25 May 2014 (UTC)

As long as the registration is an opt-in and doesn't interfere with the way how Composer works with extensions, I'm more or less indifferent on whether MW needs such functionality. Personally, I can't see the benefit for moving the registration from php to json file but when you argue with "other keys are trivial and duplicating them really isn't a huge deal" where information has to be maintained in two places I find that rather questionable. Using "the same duplicate information ... They seem to be doing fine" as an argument as to why it needs to be this way is also not really satisfactory (DRY comes to mind, which might be fine for WMF supported extensions but I doubt this is entirely true for extensions provided by volunteer developers). --MWJames (talk) 14:53, 25 May 2014 (UTC)

Schema for info.json
I'd recommend writing a JSON schema for the info.json file, so that it is explicit moving forward what type of information will be in it. (It will make approving the RFC a lot easier.) Parent5446 (talk) 04:48, 24 May 2014 (UTC)

Caching of setup information
I would recommend doing some performance testing on this and see what impact this has for a large number of extensions. It may be worthwhile to "cache" the extension information by making a PHP file containing equivalent code. (In other words, have MediaWiki core take all the info.json files and dynamically generate a PHP file that would perform the equivalent configuration.)

Since the cache file will not change often, it can be held in the opcache and will be the equivalent performance of the current situation (maybe even slightly faster since it's including one file rather than one per extension.) Parent5446 (talk) 04:53, 24 May 2014 (UTC)

Some thoughts

 * info.json? That doesn't sound right, too generic and indescriptive. Why not something like extension.json?
 * What about when extensions aren't in $IP/extensions/? We allow extensions to be included from anywhere and we'll probably want to move even further in this direction by fixing extension assets to be per-path.
 * We still support PHP 5.3, "Add Extension name to list" -> "Set config var in LocalSettings.php" -> "Actually load the extension data containing global var info" looks like a register_globals vulnerability.
 * Where is description/descriptionmsg? Also it would be nice if we could physically code in a "If descriptionmsg is used the i18n message must' be defined within the extension itself and it must be using JSON i18n, not .php files". That requirement would allow a web based extension manager to display information about an extension without actually loading the extension or running any PHP from it.
 * The extension type is also missing.
 * The MassMessage/ in the module's remoteExtPath is redundant and also means the extension dirname is still restricted. Since this is now part of a context sensitive file it would be nice if the path settings were implicit/optional and the base path to the extension was automatically handled.
 * There should be a way to declare the minimum version of MediaWiki needed.

When I played around with ideas like these I went for something along the lines of this instead:

Of course I never picked specific names, MWExtension, load, loadFromPath, etc... are kind of just pulled out of a hat. But the method call meant the config load order and not being able to specify path issue never showed up. Daniel Friesen (Dantman) (talk) 07:54, 24 May 2014 (UTC)


 * I don't really care about the name, I just picked something simple. extension.json would also work.
 * Part of this RfC would be making that a requirement (it's mentioned in the "Loading extensions" section).
 * Sigh. It might be. I'll look into it more.
 * I didn't include all the keys, but this would also be in the JSON file. Given that all extensions were already migrated to JSON messages, I'd expect that if they support this new method of loading, they would also have converted their messages.
 * Same as above.
 * You're right, it is. I just copied that part from the PHP file, but I think we can simplify that now.
 * I didn't really want to address dependency management in this RfC, but it should be doable.


 * The method call works if you're using a LocalSettings.php, but what if your settings are stored in a database? How would you specify the call then? I think just requiring extensions to be in one place simplifies a lot of things - the web extension manager shouldn't need to look through a bunch of different directories to find extensions, they should just be in one place. Legoktm (talk) 07:41, 25 May 2014 (UTC)


 * The examples I gave were just for when extensions "are" installed using LocalSettings.php. The assets path for an extension is managed by the extension loading system in it so the assetsPath there is not an extension setting but a statement to the extension loading system when an extension is loaded from a custom path that doesn't have an implied asset path. If you activated extensions using an extension manager (web or cli) neither the settings nor the method call would be in LocalSettings.php.
 * I don't like the idea of requiring all extensions to always be in $IP/extensions/. The web extension manager isn't relevant – making it only install into and manage stuff in $IP/extensions/ is fine. But we have an assortment of wiki farms of various sizes and complex installations. These will stick with LocalSettings.php and we shouldn't force them to load things from $IP/extensions/ if they have a reason to load them from somewhere else. This requirement may also run counter to the attempts we've been trying to make to support package based installations of MediaWiki a bit better.
 * Daniel Friesen (Dantman) (talk) 09:08, 25 May 2014 (UTC)