It seems like composer 2.0 is right around the corner. Downloading https://getcomposer.org/composer.phar already gives you a 2.0 build.
Our deployments just started to fail because of this. It seems like there is an issue with the composer-merge-plugin, as it explicitly requires composer 1.1:
https://github.com/wikimedia/composer-merge-plugin/blob/master/composer.json#L15
I have opened an issue on the plugins' GitHub page:
https://github.com/wikimedia/composer-merge-plugin/issues/184
I guess this needs a bump of the wikimedia/composer-merge-plugin dependency in October once a new version has been released.
Your requirements could not be resolved to an installable set of packages.
Problem 1
- Root composer.json requires wikimedia/composer-merge-plugin 1.4.1 -> satisfiable by wikimedia/composer-merge-plugin[v1.4.1].
- wikimedia/composer-merge-plugin v1.4.1 requires composer-plugin-api ^1.0 -> found composer-plugin-api[2.0.0] but it does not match your constraint.
It has been happening everywhere for a few days now, happens to everyone in our team.
TEMPORARY solution:
composer create october/october .
composer i --ignore-platform-reqs
I'm getting a similar issue which I believe is related to this. Surprising that the error message makes no sense because I'm using php 7.2 when the minimal requirement is 7.0 as per the platform.

@SaifurRahmanMohsin The issue is we use the config key in composer.json to lock the version of PHP to 7.0. @daftspunk's reasoning for the change can be found here. If this issue occurs for you, you can either remove the config key in composer.json, use @idpsycho's suggestion above, or use the wip/laravel-6 branch.
@bennothommo using the L6 branch in @SaifurRahmanMohsin's case isn't the problem, he needs to update his composer.json to pull in 1.4.1 of the merge plugin instead of using dev-master. It's unfortunate that we were using dev-master in the first place, every project that's ever been pulled down before the recent fix will still have the broken version in their composer.json.
Downgrade to 1.9.2 works for me, but in different project.
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Marking this as In Progress as Wikimedia are working on it, and just so this doesn't get archived again.
Hello, I tested it on the branch dev-composer20 (https://github.com/wikimedia/composer-merge-plugin/tree/composer20) and presented the error below. We will probably have to wait for a stable release from them before we update.

Hello, I tested it on the branch
dev-composer20(https://github.com/wikimedia/composer-merge-plugin/tree/composer20) and presented the error below. We will probably have to wait for a stable release from them before we update.
I made an adjustment for them that corrects this problem, let's see if they approve, I tested here with my fork and october, and ran the tests well on a large project with more than 40 plugins and with october developer branch and everything went well.
@prhost please test https://github.com/wikimedia/composer-merge-plugin/pull/189#issuecomment-719514950 against October, that's the PR that adds full 2.0 support to the merge plugin.
I tested it here, my project ran fine with laravel 6. but I ran phpunit and presented the error below:
PHPUnit 8.5.8 by Sebastian Bergmann and contributors.
............................................................... 63 / 505 ( 12%)
............................................................... 126 / 505 ( 24%)
............................................................... 189 / 505 ( 37%)
............................................................... 252 / 505 ( 49%)
............................................................... 315 / 505 ( 62%)
...........................................................S... 378 / 505 ( 74%)
............................................................... 441 / 505 ( 87%)
............................................EEEEEE............. 504 / 505 ( 99%)
. 505 / 505 (100%)
Time: 1.92 minutes, Memory: 92.50 MB
There were 6 errors:
1) HelpersTest::testConfigPath
Error: Class 'Mockery' not found
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:116
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:100
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:88
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/october/rain/tests/Support/HelpersTest.php:18
2) HelpersTest::testPluginsPath
Error: Class 'Mockery' not found
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:116
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:100
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:88
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/october/rain/tests/Support/HelpersTest.php:18
3) HelpersTest::testThemesPath
Error: Class 'Mockery' not found
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:116
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:100
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:88
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/october/rain/tests/Support/HelpersTest.php:18
4) HelpersTest::testTempPath
Error: Class 'Mockery' not found
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:116
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:100
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:88
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/october/rain/tests/Support/HelpersTest.php:18
5) HelpersTest::testUploadsPath
Error: Class 'Mockery' not found
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:116
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:100
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:88
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/october/rain/tests/Support/HelpersTest.php:18
6) HelpersTest::testMediaPath
Error: Class 'Mockery' not found
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:116
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:100
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:88
/Users/kallef/PhpstormProjects/orbital/october-develop/vendor/october/rain/tests/Support/HelpersTest.php:18
ERRORS!
Tests: 505, Assertions: 2890, Errors: 6, Skipped: 1.
➜ october-develop git:(develop) ✗
@bennothommo ^
@LukeTowers fixed: fffa6db8d8b9dddd6b8fca79ffed26753029d59f
Thanks @bennothommo, it worked. However @LukeTowers I believe that this version of the composer-merge-plugin did not work for us, what we really should do is to merge the vendor autoload of a plugin with the main autoload did not work.
I tested it by installing October.Drivers and creating an instance of Aws, one of the packages installed by him.

@prhost how did you install the package?
@prhost how did you install the package?
php artisan plugin:install Orctober.Drivers
Within this plugin is the vendor folder plugins/october/drivers/vendor, in theory composer-plugin-merge should recognize that vendor and merge with the main vendor.
I remember that there was a native october class that did this job, I don't know why @daftspunk left the previous class to use composer-plugin-merge. Maybe save maintenance. I know 🤷🏻♂️
@prhost that native class still exists, it handles marketplace plugins, which if you run plugin:install is what you have. The composer-merge-plugin has nothing to do with marketplace plugins or plugins with vendor directories in the plugin folder. It simply merges the project composer.json with any composer.json files present in the plugins so that all project dependencies are loaded in the main project vendor folder.
Your requirements could not be resolved to an installable set of packages.
Problem 1
- Root composer.json requires wikimedia/composer-merge-plugin dev-master -> satisfiable by wikimedia/composer-merge-plugin[dev-master].
- wikimedia/composer-merge-plugin dev-master requires composer-plugin-api ^1.1 -> found composer-plugin-api[2.0.0] but it does not match the constraint.
Help unable to update or install composer
@anilloutombam We are aware of the error message - you do not need to re-paste the same error message, nor create another issue with the exact same message.
What is the solution for now @bennothommo
@anilloutombam Download Composer 1.10.17 locally into your October CMS folder and run that directly.
If you happen to run into this problem when your build pipeline throws errors with composer v2, while it worked on v1. This might work:
composer self-update --1
This workaround makes sure that your pipeline runs Composer v1.x instead of v2
Suggestion found in the release notes:
https://github.com/composer/composer/releases/tag/2.0.0-RC2
Worth noting that if you manually add the repository from here: https://github.com/wikimedia/composer-merge-plugin/pull/189#issuecomment-719514950 and switch to the 2.0 patch branch in your project's composer.json it seems to work fine with 2.0. Using it on all my projects right now.
Thanks @bennothommo, it worked. However @LukeTowers I believe that this version of the composer-merge-plugin did not work for us, what we really should do is to merge the vendor autoload of a plugin with the main autoload did not work.
I tested it by installing October.Drivers and creating an instance of Aws, one of the packages installed by him.
@prhost I meet this problem too, do you have any workaround for this?
@prhost that native class still exists, it handles marketplace plugins, which if you run
plugin:installis what you have. The composer-merge-plugin has nothing to do with marketplace plugins or plugins with vendor directories in the plugin folder. It simply merges the project composer.json with any composer.json files present in the plugins so that all project dependencies are loaded in the main project vendor folder.
@LukeTowers looks like the plugins' composer.json not loaded in the main project vendor folder in v1.1.1, how can I get this wokr?
@everyx what makes you think that's the case? Did you remove any vendor directory from the plugin folder itself and run composer update from the project root?
@everyx what makes you think that's the case? Did you remove any vendor directory from the plugin folder itself and run composer update from the project root?
@LukeTowers thanks your reply, and I have solved this problem by
# disable scripts
composer create-project --no-scripts october/october . 1.1.1;
# and run discover manually
php artisan package:discover;
Most helpful comment
If you happen to run into this problem when your build pipeline throws errors with composer v2, while it worked on v1. This might work:
composer self-update --1This workaround makes sure that your pipeline runs Composer v1.x instead of v2
Suggestion found in the release notes:
https://github.com/composer/composer/releases/tag/2.0.0-RC2