I understand the composer-merge-plugin allows the Drupal root composer.json file to load core/composer.json on runtime. I also understand require-dev will only pull dependencies for the root composer.json file (see this link).
How can I force one/all core/composer.json dependencies (including the required-dev ones) to be pulled if I want without hacking the root composer.json file e.g. with a composer require vendor/package?
By default, Composer will install also the development requirements, if you don't use the --no-dev option.
I ran composer create-project drupal/drupal test 8.3.*@dev, and in the output of the command I could see the following:
Installing drupal/drupal (8.3.x-dev 8a84ec5556f354861f1ddc5d7a80081b91ca42df)
- Installing drupal/drupal (8.3.x-dev 8a84ec5)
Cloning 8a84ec5556 from cache
Created project in test
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Package operations: 76 installs, 0 updates, 0 removals[Omissis]
- Installing drupal/coder (8.2.11) Downloading: 100%
- Installing phpunit/phpunit (4.8.28) Downloading: 100%
If you downloaded the archived release for example from https://www.drupal.org/project/drupal/releases/8.2.7, which doesn't include the development requirements, you need to run composer update from the directory containing core and composer.json.
I tested composer update --dev after removing the vendor directory from the test directory created from the previous command, and I got this output:
You are using the deprecated option "dev". Dev packages are installed by default now.
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 76 installs, 0 updates, 0 removals
git clone and installing via drush site-install as there's no way that I know of we can install the tip of 8.4.x (aka chase HEAD) with create-project. But regardless, your answer does provide an interesting workaround to the original issue. Thanks. composer create-project drupal/drupal test 8.4.*@dev for Drupal 8.4.x. composer create-project drupal/drupal test 8.4.*@dev#<commithash> - Filed stackoverflow.com/questions/42872173/… accordingly.