Removing the packagist.com repository fixes the issue but prevents us from using packagist.com :(

        {
            "type": "composer",
            "url": "https://repo.packagist.com/yproximite/"
        },
        {
            "packagist.org": false
        },

@tristanbes has a symfony fork in the Private Packagist repo causing this freakout in Flex, not a composer bug.

Thanks @Seldaek. Will remove all forks to prevent this kind of issues again and try to fork the packages under personal space when sending patches.

this should probably still be reported to Flex though

We started to have same problem, but we don't use custom symfony fork, or this drupal plugin. What helped in our case was

Index: composer.json
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- composer.json	(revision c0719fbceabff1d1acc856412a73b8588a930fcc)
+++ composer.json	(date 1601982579444)
@@ -157,8 +157,7 @@
         "symfony-tests-dir": "tests",
         "symfony-assets-install": "relative",
         "symfony": {
-            "allow-contrib": false,
-            "require": "4.3.*"
+            "allow-contrib": false
         }
     }
 }

I would like to know what is the trigger of this problem though, since this worked fine till now.

I am having the same problem today as well without custom forks

For me it happens in plugin I use - exactly in this line https://github.com/rubenrua/symfony-clean-tags-composer-plugin/blob/master/src/Cache.php#L61

so i guess it is not composer related... but still strange it started today.

I looks like some change done recently in symfony/symfony

@ostrolucky I think this commit in symfony released today broke it

symfony/symfony@5f1c3a7#diff-b5d0ee8c97c7abd7e3fa29b9a27d1780

Same problem here, a couple of days ago everything works fine, now when i try to install a Drupal module with composer i get an error.

[ErrorException]
Undefined index: extra

Exception trace: () at /usr/share/nginx/html/yoursite/vendor/zaporylie/composer-drupal-optimizations/src/Cache.php:76 Composer\Util\ErrorHandler::handle() at /usr/share/nginx/html/yoursite/vendor/zaporylie/composer-drupal-optimizations/src/Cache.php:76 zaporylie\ComposerDrupalOptimizations\Cache->removeLegacyTags() at /usr/share/nginx/html/yoursite/vendor/zaporylie/composer-drupal-optimizations/src/TruncatedComposerRepository.php:21 zaporylie\ComposerDrupalOptimizations\TruncatedComposerRepository->fetchFile() at phar:///usr/local/bin/composer/src/Composer/Repository/ComposerRepository.php:366 Composer\Repository\ComposerRepository->whatProvides() at phar:///usr/local/bin/composer/src/Composer/DependencyResolver/Pool.php:213 Composer\DependencyResolver\Pool->computeWhatProvides() at phar:///usr/local/bin/composer/src/Composer/DependencyResolver/Pool.php:202 Composer\DependencyResolver\Pool->whatProvides() at phar:///usr/local/bin/composer/src/Composer/DependencyResolver/RuleSetGenerator.php:173 Composer\DependencyResolver\RuleSetGenerator->whitelistFromPackage() at phar:///usr/local/bin/composer/src/Composer/DependencyResolver/RuleSetGenerator.php:153 Composer\DependencyResolver\RuleSetGenerator->allowListFromPackage() at phar:///usr/local/bin/composer/src/Composer/DependencyResolver/RuleSetGenerator.php:371 Composer\DependencyResolver\RuleSetGenerator->getRulesFor() at phar:///usr/local/bin/composer/src/Composer/DependencyResolver/Solver.php:217 Composer\DependencyResolver\Solver->solve() at phar:///usr/local/bin/composer/src/Composer/Installer.php:489 Composer\Installer->doInstall() at phar:///usr/local/bin/composer/src/Composer/Installer.php:232 Composer\Installer->run() at phar:///usr/local/bin/composer/src/Composer/Command/UpdateCommand.php:163 Composer\Command\UpdateCommand->execute() at phar:///usr/local/bin/composer/vendor/symfony/console/Command/Command.php:245 Symfony\Component\Console\Command\Command->run() at phar:///usr/local/bin/composer/vendor/symfony/console/Application.php:835 Symfony\Component\Console\Application->doRunCommand() at phar:///usr/local/bin/composer/vendor/symfony/console/Application.php:185 Symfony\Component\Console\Application->doRun() at phar:///usr/local/bin/composer/src/Composer/Console/Application.php:281 Composer\Console\Application->doRun() at phar:///usr/local/bin/composer/vendor/symfony/console/Application.php:117 Symfony\Component\Console\Application->run() at phar:///usr/local/bin/composer/src/Composer/Console/Application.php:113 Composer\Console\Application->run() at phar:///usr/local/bin/composer/bin/composer:61 require() at /usr/local/bin/composer:24

@denisp1993

there is discussion about it on drupal zaporylie/composer-drupal-optimizations#22

still it is not composer/compser fault so not topic for this repo :)

the issue is that composer-drupal-optimizations assumes that a master branch always has a branch-alias, while there is no such guarantee in composer. And when symfony removed the branch-alias, drupal projects using that plugin became affected by the wrong assumption.

Yes, drupal and also symfony-clean-tags-composer-plugin which was my case today.

Funny thing, this error just started to happen today to me, and it fails when using composer 1.x but upgrading to composer 2.x solves the problem.

Error started to happen today for me too.

Since i'm not using the drupal plugin neither symfony-clean-tags-composer-plugin and i'd like to avoid jumping on the 2.x version of composer what can i do to solve that Undefined index: extra situation ?

Tried the @ostrolucky change but no success :/

@Skape252 please check at the stack trace of your exception to identify which place in your project is wrongly assuming that a dev-master alias exists (which is absolutely not a guarantee in Composer)

@Skape252
You could change this line in vendor/symfony/flex/src/Cache.php as in screenshot temporarily

from
https://files.slack.com/files-pri/T38L468JV-F01C4754L1G/image.png

to

After that composer update should work. After package update, it should solve the problem and you don't need to change this line again.

@shahidnafridi your patch still does not account for missing branch-alias, if there are other extra field

No other extra field for me so @shahidnafridi solution works fine, thanks

If your problem is with Drupal, a quick solution is to edit composer.lock to update zaporylie/composer-drupal-optimizations. the relevant sections below are version and reference to update.

            "name": "zaporylie/composer-drupal-optimizations",
            "version": "1.1.2",

and

            "source": {
                "type": "git",
                "url": "https://github.com/zaporylie/composer-drupal-optimizations.git",
                "reference": "0d6ebd8bc03679d312f99a1e4e950685dbf0ff18"
            },
            "dist": {
                "type": "zip",
                "url": "https://api.github.com/repos/zaporylie/composer-drupal-optimizations/zipball/0d6ebd8bc03679d312f99a1e4e950685dbf0ff18",
                "reference": "0d6ebd8bc03679d312f99a1e4e950685dbf0ff18",
                "shasum": ""
            },

then run composer install and composer update --lock

Or, you know, rm -rf vendor/zaporylie/composer-drupal-optimizations && composer update zaporylie/composer-drupal-optimizations is also quick.

I understand that upgrading to Composer 2.0 RC1 might not be easy (or acceptable in some cases), and I always advise caution on such kind of actions, especially when a serious app or environment is involved.

However, I can say that Composer 2 has given me successful results so far (for the vague test that I have done on small projects), and I don't see a reason not to use it if it solves the problem.

Anyway, I still find concerning that yesterday everything was working and today started to fail after getting the latest version of Composer 1 (when booting up my Docker containers) but works with Composer 2.

Issue is using old symfony/flex version. All that updating composer to 2.0 does is that you are forced to update symfony/flex version with it. Also, tricky part is updating symfony/flex while it crashes because you have old version.

@DavidGarciaCat it is not composer issue. It is change in symfony/symfony and some other symfony libraries which was done yesterday and broke some other libraries/vendors like older versions of flex (but not only).

For me it happened without any update of conposer itself.