Is it possible to make a patch that modifies a module's composer.json?

Question

I want to confirm some behavior of Composer to see if this is a limitation of Composer or something I did wrong.

This is based on an issue in the Markdown module queue.

Basically, here's the issue.

1. The Markdown module requires ^0.15 of a library.
2. I wrote a patch to require ~0.15 of the library. (to allow 0.16, 0.17, etc.)

But, when I apply this patch via Composer, and then try to update the library, I still get a drupal/markdown 1.2.0 requires league/commonmark (^0.15.0) even though the module's (patched) code on my site requires ~0.15.

So, is there no way to "patch" a composer.json so that it will be picked up for composer update? Am I reliant on the module maintainer to commit the patch?

Answer 1

This issue is actually addressed in the composer-patches documentation:

Because patching occurs after Composer calculates dependencies and installs packages, changes to an underlying dependency's composer.json file introduced in a patch will have no effect on installed packages.

If you need to modify a dependency's composer.json or its underlying dependencies, you cannot use this plugin. Instead, you must do one of the following:

• Work to get the underlying issue resolved in the upstream package.
• Fork the package and specify your fork as the package repository in your root composer.json
• Specify compatible package version requirements in your root composer.json

If you want to follow option #2, you can fork the project's git repo, modify it, and add the forked repo to your project's repositories property:

    {
        "type":"git",
        "url": "https://github.com/vendor/module"
    }

So you can reference that dependency until the upstream has resolved the issue.