This is more a question for which I couldn't find if this had been discussed before.

Code to reproduce can be found here: https://github.com/jrfnl/composer-install-action-bug/tree/testing/composer-reinstall
Test run output: https://github.com/jrfnl/composer-install-action-bug/actions/runs/1790724084

My composer.json:

{
    "name": "jrfnl/composer-reinstall",
    "description": "Testing",
    "license": "MIT",
    "require-dev": {
        "php": ">=5.4",
        "phpcsstandards/phpcsextra": "^1.0.0"
    },
    "minimum-stability": "dev",
    "prefer-stable": true,
    "config": {
        "allow-plugins": {
            "dealerdirect/phpcodesniffer-composer-installer": true
        }
    }
}

When I run this command:

composer reinstall phpcsstandards/phpcsextra

I get the following output:

Run composer reinstall phpcsstandards/phpcsextra -v
  - Removing phpcsstandards/phpcsextra (1.0.0-alpha3)
  - Installing phpcsstandards/phpcsextra (1.0.0-alpha3): Extracting archive

And I expected this to happen:

That the Dealerdirect PHPCS Composer plugin, which is installed as as part of the package would run, but it didn't.

Plugin also doesn't run when installed as a root requirement.

As there is no separate "reinstall" event, I would expect post-install events to run on reinstall as well.