chore: update PHPStan PHP version to 8.1

[kenjis]

Description
PHP 8.1 is the most used version with Composer.

Checklist:

• Securely signed commits
• [] Component(s) with PHPDoc blocks, only if necessary or adds value
• [] Unit testing, with >80% coverage
• [] User guide updated
• [] Conforms to style guide

[MGatner]

Shouldn't we be running PHPStan against each version of PHP we want to support? There doesn't appear to be a command line argument for it but we could have a config file for each that imports the main file.

[kenjis]

Shouldn't we be running PHPStan against each version of PHP we want to support?

Ideally yes, but IIRC we were not able to support PHP 7.4 and 8.0 at the same time.
And PHP 8.1 has new classes like PgSql\Result, so it seems we cannot support 8.0 and 8.1 after all.

Or if we prepare phpstan.neon.dist and phpstan-baseline.neon.dist for each version, we can do it?
But it costs more.

[paulbalandan]

It would be cumbersome to maintain, as shown before. We have code flagged by phpstan in a lower PHP version which we add @phpstan-ignore-line. However, that line is perfectly okay with phpstan when run on a higher PHP version, erroring now at "No error to ignore..."

[kenjis]

It seems to me that rather than increasing the number of PHP versions to check, we should focus on reducing phpstan-baseline.neon.dist and @phpstan-ignore-line and increasing the level (now level: 5).

[MGatner]

I disagree. Baselining is very easy, and if the only hindrance to supporting multiple PHP versions is the error variance then we just baseline them separately. There is nothing special about the baseline config- you can add the same type of error ignores to any. So we can have a single phpstan.neon.dist with whatever we want our "standard" to be, then phpstan-x.x.neon for each PHP version we want to support, including version-specific baselining.

I would be glad to take on this work, I've been doing something similar at my day job. Let's proceed with this change now since it is ready, but please voice any objections in this thread.

[kenjis]

I think if we have phpstan-x.x.neon, we can run PHPStan for all supported PHP versions.
My question is: is it worth doing?

[MGatner]

Is it worth doing?

What other language versioning safety nets do we have? Obviously if a test case tries to use a deprecated or not-yet-available feature that will fail, but that requires test coverage.

I work regularly across 7.4, 8.0, and 8.1 these days and frequently have to look things up. Maybe other people have their heads around that better, but I don't necessarily trust myself to catch a mistake during a code review.

[kenjis]

Okay, it is true that the current code coverage is a bit low.
I'm not sure PHPStan helps us so much, but if you say so, let's try to run in the different PHP versions.

[MGatner]

Let's proceed with this for now. The version of PHP running shouldn't affect the version of analysis.