Error With Composer 2.2.0@unstable

[XedinUnknown]

Symptoms

When used on GitHub Actions, the following error is produced:

Running composer update to apply merge settings
Loading composer repositories with package information

PHP Fatal error:  Uncaught TypeError: Cannot access offset of type string on string in phar:///usr/local/bin/composer/src/Composer/Util/HttpDownloader.php:484
Stack trace:
#0 phar:///usr/local/bin/composer/src/Composer/Util/Http/CurlDownloader.php(399): Composer\Util\HttpDownloader::outputWarnings()
#1 phar:///usr/local/bin/composer/src/Composer/Util/HttpDownloader.php(404): Composer\Util\Http\CurlDownloader->tick()
#2 phar:///usr/local/bin/composer/src/Composer/Util/Loop.php(96): Composer\Util\HttpDownloader->countActiveJobs()
#3 phar:///usr/local/bin/composer/src/Composer/Repository/ComposerRepository.php(957): Composer\Util\Loop->wait()
#4 phar:///usr/local/bin/composer/src/Composer/Repository/ComposerRepository.php(524): Composer\Repository\ComposerRepository->loadAsyncPackages()
#5 phar:///usr/local/bin/composer/src/Composer/DependencyResolver/PoolBuilder.php(379): Composer\Repository\ComposerRepository->loadPackages()
#6 phar:///usr/local/bin/composer/src/Composer/DependencyResolver/PoolBuilder.php(234): Composer\DependencyResolver\PoolBuilder->loadPackagesMarkedForLoading()
#7 phar:///usr/local/bin/composer/src/Composer/Repository/RepositorySet.php(261): Composer\DependencyResolver\PoolBuilder->buildPool()
#8 phar:///usr/local/bin/composer/src/Composer/Installer.php(435): Composer\Repository\RepositorySet->createPool()
#9 phar:///usr/local/bin/composer/src/Composer/Installer.php(279): Composer\Installer->doUpdate()
#10 /home/runner/work/payoneer-for-woocommerce/payoneer-for-woocommerce/vendor/wikimedia/composer-merge-plugin/src/MergePlugin.php(377): Composer\Installer->run()
#11 [internal function]: Wikimedia\Composer\Merge\V2\MergePlugin->onPostInstallOrUpdate()
#12 phar:///usr/local/bin/composer/src/Composer/EventDispatcher/EventDispatcher.php(192): call_user_func()
#13 phar:///usr/local/bin/composer/src/Composer/EventDispatcher/EventDispatcher.php(119): Composer\EventDispatcher\EventDispatcher->doDispatch()
#14 phar:///usr/local/bin/composer/src/Composer/Installer.php(372): Composer\EventDispatcher\EventDispatcher->dispatchScript()
#15 phar:///usr/local/bin/composer/src/Composer/Command/InstallCommand.php(139): Composer\Installer->run()
#16 phar:///usr/local/bin/composer/vendor/symfony/console/Command/Command.php(245): Composer\Command\InstallCommand->execute()
#17 phar:///usr/local/bin/composer/vendor/symfony/console/Application.php(835): Symfony\Component\Console\Command\Command->run()
#18 phar:///usr/local/bin/composer/vendor/symfony/console/Application.php(185): Symfony\Component\Console\Application->doRunCommand()
#19 phar:///usr/local/bin/composer/src/Composer/Console/Application.php(335): Symfony\Component\Console\Application->doRun()
#20 phar:///usr/local/bin/composer/vendor/symfony/console/Application.php(117): Composer\Console\Application->doRun()
#21 phar:///usr/local/bin/composer/src/Composer/Console/Application.php(130): Symfony\Component\Console\Application->run()
#22 phar:///usr/local/bin/composer/bin/composer(73): Composer\Console\Application->run()
#23 /usr/local/bin/composer(29): require('...')
#24 {main}
  thrown in phar:///usr/local/bin/composer/src/Composer/Util/HttpDownloader.php on line 484

Reproducing

• PHP: 7.4, 8.0;
• Package: v2.0.1.
• Composer: 2.2.1. ⚠️ Cannot reproduce on 2.1.14.

[strangerkir]

More info from the same project

Generating optimized autoload files
composer/package-versions-deprecated: Generating version class...
composer/package-versions-deprecated: ...done generating version class
37 packages you are using are looking for funding.
Use the `composer fund` command to find out more!

Running composer update to apply merge settings
Loading composer repositories with package information
https://repo.packagist.com/inpsyde could not be fully loaded (Illegal string offset 'versions'), package information was loaded from the local cache and may be out of date
Error: Illegal string offset 'versions'

  [ErrorException]                  
  Illegal string offset 'versions'  

Seems like it happens with composer here. From the context, I'm making an assumption the problem is caused by improperly added warning or info that was expected to be an array, but a string was provided.

[XedinUnknown]

Now able to reproduce locally. See updated Reproducing section. The problem appears to manifest with a new version of Composer, 2.2.0. Workaround: switch to 2.1.14.