Continuous integration/Tutorials/Add phan to a MediaWiki extension

This is a tutorial to set up phan for a MediaWiki extension. We'll look at the ParserMigration extension specifically.

Setup
You'll need to install PHP 7+, and the ast extension. On Debian/Ubuntu  should do it. phan has some other advice for this part too.

Preparing your extension
Your extension must follow the best practices file structure, since the default phan configuration will only look in those directories for PHP code.

Adding phan configuration
I'm going to assume that you installed MediaWiki core to  and ParserMigration to. Make sure you've fully set up MediaWiki core and installed all the composer dependencies.

First, let's set up the default configuration:

We're now ready to try to run phan:

If MediaWiki core isn't two levels above your current directory, you can explicitly declare the install path:

You should see a progress bar, and it might take a minute to finish running. It looks like we have some errors:

includes/Hooks.php:11 PhanUndeclaredTypeParameter Parameter of undeclared type \MediaWiki\ParserMigration\User includes/MigrationEditPage.php:31 PhanDeprecatedProperty Reference to deprecated property \MediaWiki\ParserMigration\MigrationEditPage::mTitle defined at ./../../includes/EditPage.php:230 includes/MigrationEditPage.php:34 PhanDeprecatedProperty Reference to deprecated property \MediaWiki\ParserMigration\MigrationEditPage::mTitle defined at ./../../includes/EditPage.php:230

Looking at the first one, the namespace for User on the  documentation comment is wrong. Let's fix it (example).

For the second one,  is marked as deprecated for public use, to it's OK that we're using it in MigrationEditPage. You can suppress that warning on each particular line (phan docs) or you can suppress it throughout the extension. Let's suppress that warning for now by adding it to  in config.php.

We can do something like:

Note that you'll usually want to suppress issues on particular lines, as suppressing them for the whole extension may hide bugs.

For whatever extension you're working on, there will likely be other errors. You'll have to use some judgement on whether the issue needs fixing or can be suppressed.

Let's run phan again with the same command, and there should be no errors left! You can commit your work and submit it to Gerrit.

On your Gerrit patch, comment  and it'll run phan as part of the CI system to make sure it will pass when enabled for all patches.

You can then send a patch to the  repository to run phan for the repository on a per-commit basis. See r606940 for an example.

Advanced
If your extension depends upon other extensions, you can add those extensions to  and. Here's an example:

Stubs
If you don't want to require having the dependency checked out while running phan, you can also use stubs. Stubs are a copy of the class/function structure, with any necessary documentation blocks, but none of the implementation code. You can see an example of this in the MassMessage extension. The downside to using stubs is that if the dependency changes, you also need to update the stub for phan to know of the change.

Stub files should be placed in.

The upstream documentation about stubs may also be useful.