Composer does not respect installer-paths - php

Question

Here is the scenario:
I have two projects driven by composer. The first one looks like this:
{
"name": "myusername/composer_test",
"description": "Composer project for CircleK Drupal 8",
"type": "project",
"license": "GPL-2.0-or-later",
"authors": [
{
"name": "Name Surname",
"role": "webdeveloper"
}
],
"repositories": [
{
"type": "composer",
"url": "https://packages.drupal.org/8"
}
],
"require": {
"php": ">=5.6",
"composer/installers": "^1.2",
"drupal-composer/drupal-scaffold": "^2.5",
"drupal/core": "^8.7.0",
"vlucas/phpdotenv": "^2.4",
"webflo/drupal-finder": "^1.0.0",
"webmozart/path-util": "^2.3",
"zaporylie/composer-drupal-optimizations": "^1.0"
},
"minimum-stability": "dev",
"prefer-stable": true,
"extra": {
"installer-paths": {
"web/core": ["type:drupal-core"]
}
}
}
Second one requires the first one and it's pretty straight forward:
{
"name": "user/site",
"description": "Composer for Site",
"type": "project",
"license": "GPL-2.0-or-later",
"authors": [
{
"name": "Name Surname",
"role": "webdeveloper"
}
],
"repositories": [
{
"type": "git",
"url": "git#github.com:myusername/composer_test.git"
},
{
"type": "composer",
"url": "https://packages.drupal.org/8"
}
],
"require": {
"myusername/composer_test": "dev-drupal_only"
},
"minimum-stability": "dev",
"prefer-stable": true
}
As you can see the first one defines where drupal core should be placed at by defining installer-paths. It turns out that when I run composer install just for the first composer.json file drupal core ends up in ./web directory as should, however when I run composer install for second file it does download every package from first composer.json just fine, but drupal core ends up in main directory instead of ./web. I know I can put installer-paths into the last composer file and overwrite it, but that's not the point. I want first file to define where stuff should be place at.

Answer 1

The extra settings only work for the root package. Consider user/site requiring 2 different packages that both specifiy different installer paths. Which one should composer use and how should it know? By ignoring those settings, unless they are specified in your root composer.json, composer circumvents any surprises/problems.
There is a way around this, you can create a post-install script that determines the correct path for you, e.g. by checking if myusername/composer_test is installed and the variable is set. This is a bit similar to how Symfony's Install-Script in the SensioDistributionBundle used to do it. It provides a fallback to determine the right directory to use based on configs and folder structure (due to changes in how the default directory structure looks at ~2.8, e.g. moving app/console to bin/console).
You could write your own install script that inspects the installed composer packages. The downside is, that just like you now have to specify the extra config in your second composer.json, you will have to specify the install scripts, plus you have to write the install script itself. So it might be a lot of extra work without gaining a lot from it.