How to update composer in project to > 2.*?

Question

PHP

Good afternoon, I have a question about composer.
My project (php site) uses composer 1.9.3 (locally).
There is a need to update it to the latest version (as well as libraries) without loss of project performance.
When using version > 2.*, autoloader errors and so on occur.

Can you tell me what is the algorithm for this operation? :)
Perhaps there are some nuances in the transition from 1.* to 2.*

Answer 1

first upgrade the composer itself, then the packages.
There shouldn't be any problems (all actual packages have already been rewritten for composer changes).
but it's better to pre-roll back on a copy, not a working project.
the second version is fire. and you need to switch to it.
but there may be problems with old (unsupported) packages. then either look for a modern replacement for this package, or use the old composer specifically for this project.