Add support for composer 2

[jderusse]

This PR add compatibility with composer-plugin-api: ^2.0 and fixes #661

Maintaining compatibility with both 1.x and 2.0 was too complex.
I think we need to release a version 2.0 of flex compatible with composer 2.

• remove ParallelDownloader (no more needed with composer 2)
• replace TruncateRepository by eventListener on PluginEvents::PRE_POOL_CREATE

note: I didn't change the way commands are added to the application, current plugin's contract expect a class name, while we currently inject command instances (with config and flex itself injected inside) in the application.

[maxhelias]

@jderusse for the command instances, I think we can declare the flex class itself as the command provider. This would allow us to keep the injection of the configuration and flex

[jderusse]

That's a good idea @maxhelias , I totally missed that feature I implemented ^^

Unfortunaly, it does not works for some command (require, install, update). Composer prevent overriding internal methods (https://github.com/composer/composer/blob/master/src/Composer/Console/Application.php#L180)

One solution could be to declare the command with name "symfony:require" and alias "require" (aliases are not (yet) checked, and will override the composer's command)
WDYT @nicolas-grekas

side note: Composer improved a lots dependencies resolution. TruncatedPackage is maybe not needed anymore? Do you have good project to benchmark?

[nicolas-grekas]

Unfortunaly, it does not works for some command (require, install, update)

yep, that's why we used this technic. Then, better have the same strategy for all commands.

TruncatedPackage is maybe not needed anymore? Do you have good project to benchmark?

it's not only for performance, but to enforce the version of nested dependencies. So yes, it's needed.

[k0d3r1s]

hey, what's happening with this one? any eta?

[stof]

Well, as I discussed in the issue, enforcing constraints should be doable with a listener on the pool building in Composer 2. This would remove the need for TruncatedPackageRepository.

And for commands, adding support for aliases in require, update and remove should be doable by manipulating the arguments using the symmfony/console console.command event instead.

[jderusse]

Well, as I discussed in the issue, enforcing constraints should be doable with a listener on the pool building in Composer 2. This would remove the need for TruncatedPackageRepository.

The TruncatedPackageRepositoryis already removed, and replaced by a listener on PluginEvents::PRE_POOL_CREATE

And for commands, adding support for aliases in require, update and remove should be doable by manipulating the arguments using the symmfony/console console.command event instead

Hmm composer does not inject the EventDispatcher in BaseApplication, (bu can be doable in the backtrace hack). And command override is not only about alias (ie. adding option unpack in require). I afraid we still have to replace original's commandes and keep the hack.

PR rebased

[vasilvestre]

This is needed for PHP 8 on Symfony Flex (and so in all other versions of Symfony). #624

[vasilvestre]

@jderusse could you please rebase ?

[nicolas-grekas]

This PR is now compatible with composer 1 and 2.
I think it's ready to merge: the code for composer 1 didn't change, and the one for composer 2 is experimental anyway as long as composer 2 also is.

[fabpot]

Thank you @jderusse.