Command to get composer to self-update to the latest sub-sub-version - composer-php

Question

I'm trying to write an alias to run something like composer self-update x.y.z where the command installs the composer specified version of x.y (say, 2.2 or 2.3 or 2.4) but where z is automatically determined to be the highest stable number found. The purpose is to switch easily between compatible composer versions of different major PHP versions (like 5 or 8) for the projects I have to work with.
The command right now makes me specify the specific z version (which could be 0, 11, 18, whatever), otherwise errors (like '2.2 not found' or '2.3 not found' etc).
Example of output causing me cognitive dissonance:
% composer self-update 2.2
Warning: You forced the install of 2.2.18 via --2.2, but 2.4.2 is the latest stable version. Updating to it via composer self-update --stable is recommended.
Upgrading to version 2.2 (2.2.x channel).
[InvalidArgumentException]
Version "2.2" could not be found.
It's strange that it says I "forced the install of 2.2.18" but then tries to use specific version 2.2 (not 2.2.0) then tells me it doesn't exist :facepalm:. To me this is just weird counter-intuitive behavior, so I'd like to find a smart way I don't have to look up which sub-sub-version is the latest (since 2.2 is LTS, and any sub-version could have sub-sub-version updates anyway that could be useful).

Answer 1

You're using the wrong command if you'd like to stay on the 2.2 LTS channel (it covers your different PHP versions), the correct one is with --2.2, you don't provide the major/minor version verbatim, but the channel:
$ php composer.phar self-update --2.2
Warning: You forced the install of 2.2.18 via --2.2, but 2.4.2 is the latest stable version. Updating to it via composer self-update --stable is recommended.
You are already using the latest available Composer version 2.2.18 (2.2.x channel).
It still gives the hint how to update to the latest actually, but as you can further on see, it looks up the latest in 2.2.x and sees it is the same so quits without downloading and exit status 0 (which is fine/OK/success).
You can find the same command-line option (--2.2) with the installer btw.:
$ curl -sS https://getcomposer.org/installer | php -- --2.2
All settings correct for using Composer
Downloading...
Composer (version 2.2.18) successfully installed to: /home/user/project/composer.phar
Use it: php composer.phar
Just keep in mind to use --help if things are happening you were not expecting, especially with utilities you learn about their invocation still that is.
(and yes, the warning message can not be fully understood when the expectation is to provide major/minor verbatim and getting another error for that. it showed a hint about --2.2 already thought.)