[2.1.0] module:uninstall can remove code it uses itself

[hostep]

Preconditions

1. Figure out a way to travel back and forth in time (I added some hints)
2. We use composer version 1.1.3 by adding this to our composer.json file: "composer/composer": "1.1.3 as 1.0.0-beta1",, due to another bug, but I think it won't really matter which version is being used
3. PHP 7.0.9
4. Magento 2.1.0

Steps to reproduce

1. Travel back in time to when symfony/process version 2.8.8 wasn't released yet (hint: try to downgrade to version 2.8.7 of the module after step 2)
2. Install Magento 2.1.0 using composer
3. Install a third party module using composer (composer require, bin/magento setup:upgrade, ...)
4. Travel back to the current time when symfony/process version 2.8.8 was released (hint: don't do anything in this step)
5. Uninstall the module you installed in step 3 by using bin/magento module:uninstall

Expected result

1. Module is uninstalled without a problem

Actual result

1. When Magento tries to uninstall the module using composer, it also at the same time tries to update symfony/process from version 2.8.7 to 2.8.8 for some strange reason. And since symfony/process is being used by the module:uninstall command, the command stops running.
2. Console output:

➜ php bin/magento module:uninstall Vendor_MyModule
You are about to remove code and/or database tables. Are you sure?[y/N]y
Enabling maintenance mode
You are about to remove a module(s) that might have database data. Do you want to remove the data from database?[y/N]N
Removing Vendor_MyModule from module registry in database
Removing Vendor_MyModule from module list in deployment configuration
Removing code from Magento codebase:
Command "remove" failed: Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Removing vendor/my-module (v1.0.11)
Removing Vendor/MyModule
  - Removing symfony/process (v2.8.7)

Removal failed, reverting ./composer.json to its original content.



  [ErrorException]
  include(/Users/me/Projects/my-project/vendor/composer/../symfony/process/ExecutableFinder.php): failed to open stream: No such file or directory



remove [--dev] [--no-progress] [--no-update] [--update-no-dev] [--update-with-dependencies] [--no-update-with-dependencies] [--ignore-platform-reqs] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [packages1] ... [packagesN]



Please disable maintenance mode after you resolved above issues

Bit of debugging

It turns out at the step when the composer remove step is executed, this happens:

➜ composer remove --working-dir=/Users/me/Projects/my-project vendor/my-module
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Removing vendor/my-module (v1.0.11)
Removing Vendor/MyModule
  - Removing symfony/process (v2.8.7)
  - Installing symfony/process (v2.8.8)
    Loading from cache

Package fabpot/php-cs-fixer is abandoned, you should avoid using it. Use friendsofphp/php-cs-fixer instead.
Writing lock file
Generating optimized autoload files

So for some reason symfony/process gets updated to the latest version while removing another module which has no direct dependencies on symfony/process. But this particular module has some dependencies on some magento modules which in itself will probably have dependencies on symfony/process module.

I think you can work around this if you add the --no-update-with-dependencies switch, since that won't update symfony/process:

➜ composer remove --no-update-with-dependencies --working-dir=/Users/me/Projects/my-project vendor/my-module
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Removing vendor/my-module (v1.0.11)
Removing Vendor/MyModule
Package fabpot/php-cs-fixer is abandoned, you should avoid using it. Use friendsofphp/php-cs-fixer instead.
Writing lock file
Generating optimized autoload files

Please review thoroughly, because this seems to be something which can turn out to be quite complicated!
Also: I haven't tested my solution with that --no-update-with-dependencies flag yet.

For other people running into this problem: first update all your dependencies to the latest version by just running composer update (hint you can run composer update --dry-run to preview what it will do first) and only after your dependencies are updated, run the module:uninstall command.

[hostep]

Possible related issue: #3544

[shiftedreality]

Hi @hostep

Thank you for deep investigation and reporting.
We've create internal ticket MAGETWO-58132 to fix this issue.

[mattcoz]

I'm unable to upgrade from 2.1.3 to 2.1.6 because of this error. It removes symfony/process and then immediately throws the error. It happens during the "composer update" command, so that doesn't help me.