Remove static analysis with psalm

INFO

This document represents an architecture decision record (ADR) and has been mirrored from the ADR section in our Shopware 6 repository. You can find the original version here

Context

Currently, we are running static analysis over the php code with both phpstan and psalm. This slows down our pipeline and may lead to weird effects where phpstan and psalm report errors that are incompatible with each other.

Decision

There is not much need anymore to run both tools, as they pretty much converged to a common feature set. This was different when we started with shopware 6 where both tools had some different features, but most of the differences are gone by now. Therefore, we won't run both tools anymore in the CI.

We decided to stick with phpstan and remove psalm because:

• It's easier to write custom phpstan rules than to extend psalm
• We already have custom phpstan rules
• There are more extension for phpstan, e.g. for symfony or phpunit

Consequences

psalm will be completely removed from the repository and the CI.