Composer 2.6.5 failing to install due to symfony7 release

[matthiaz]

When you try to install composer it will fail with the following error:

Fatal error: Declaration of Composer\Command\InitCommand::execute(Symfony\Component\Console\Input\InputInterface $input, Symfony\Component\Console\Output\OutputInterface $output) must be compatible with Symfony\Component\Console\Command\Command::execute(Symfony\Component\Console\Input\InputInterface $input, Symfony\Component\Console\Output\OutputInterface $output): int in /app/.global/composer/composer/vendor/composer/composer/src/Composer/Command/InitCommand.php on line 85
          W: PHP Fatal error:  Declaration of Composer\Command\InitCommand::execute(Symfony\Component\Console\Input\InputInterface $input, Symfony\Component\Console\Output\OutputInterface $output) must be compatible with Symfony\Component\Console\Command\Command::execute(Symfony\Component\Console\Input\InputInterface $input, Symfony\Component\Console\Output\OutputInterface $output): int in /app/.global/composer/composer/vendor/composer/composer/src/Composer/Command/InitCommand.php on line 85
        
        E: Error building project: `composer` could not be run.

There is a bug fix in composer 2.7 and even in 2.6 but neither has been released:
Please release the bug fix: 23be508

The only work around is to pin composer to 2.5, which is far from ideal because it's a step back and potentially breaks other things.

Also mentioned in #11736

[Seldaek]

I tagged 2.6.6 which fixes this by removing the symfony/console requirement. It will not allow using symfony 7 though as it locks you to symfony/console 5.4 or 6.x.

I'm not sure what your environment is but I assume you are running Composer within a project that has Symfony 7 installed, so I don't know if this will help..

Proper symfony 7 support will have to wait for Composer 2.7.

[apfelbox]

I had the same error on deploying to Platform.sh: when building, they recommend installing the most recent composer via their outdated preinstalled composer and there I ran into this issue.

Composer 2.6.5 allowed to install Symfony 7 components but failed instantly, as it isn't yet compatible with it yet.

[matthiaz]

This has been resolved in 2.6.6 👍