Add PHP static analysis via PHPStan

[westonruter]

Feature description

I've only recently become aware of PHPStan, but it seems like it could help with catching subtle bugs. See GoogleForCreators/web-stories-wp#334 and GoogleChromeLabs/pwa-wp#243.

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[schlessera]

Yes, PHPStan is great. It will only make sense with clean and strongly typed code of course, but we're having more and more of this, so we'll probably start reaping benefits from it by now.

I've been using it with a WordPress stubs file for WP plugins: https://github.com/mwpd/basic-scaffold/blob/master/phpstan.neon.dist

[schlessera]

This will need a bit of a work-around, as PHP-Stan requires PHP 7.1.

[szepeviktor]

There is a WordPress Extension for PHPStan.

[swissspidy]

Thanks for opening this, @westonruter! I was about to do it after my experience with the Web Stories plugin but you beat me to it. 🙂

The extension @szepeviktor maintains is indeed super helpful to get off the ground quickly.

@schlessera In the Web Stories plugin we run PHPStan only on 7.1 in a separate job, installing it via composer require --no-interaction --dev szepeviktor/phpstan-wordpress --ignore-platform-reqs. That means you cannot easily use it locally though, but it works fine for us so far. LMK if you come up with a better solution.

[schlessera]

I've done a bit of a more manual approach, as @szepeviktor's extension requires PHP 7.1+.

PHPStan is downloaded as a Phar instead, and the needed stubs are provided in the tests/ folder (some copied from the above extension, some written as needed).

This now works so that you can run composer analyse on your local installation as well, without any extra effort. We could also add this to a precommit then.

[swissspidy]

Pretty cool! I also like how you snuck autoloading through Composer in there 🎉

[schlessera]

Composer was already a requirement in the plugin because of the CSS Parser library.

[swissspidy]

But we still had AMP_Autoloader 🙂

[szepeviktor]

as @szepeviktor's extension requires PHP 7.1+.

It is PHPStan's requirement :)

[schlessera]

To run it, yes. But the codebase that you want to check does not need to be PHP 7.1+. The plugin is currently at PHP 5.6+, and it makes perfect sense to check the code with PHPStan. But we can't install it directly via Composer because of its requirement. That's why I'm downloading it as a Phar instead.

[schlessera]

But we still had AMP_Autoloader

Yes, presumably because it is "extensible" for plugins wanting to extend the AMP support. However, this was broken from 2017 onwards and never fixed.

So all it does is provide a class map we need to maintain manually and that is less optimized than the one that Composer generates.