Get Composer to suggest dev packages to require-dev

Composer 2.4 added a feature that the composer require command prompts to install the package with --dev flag if the package being installed is meant to be used as a developer tool.

When the --dev flag is passed, the package is installed under require-dev section in the composer.json file, and other Composer commands (such as composer update, install, dump-autoload, etc can optionally skip require-dev dependencies.

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Composer inspects the keywords section of the composer.json file being installed, and if it contains dev, testing, or static analysis as keywords, Composer prompts the user to install it with --dev flag if it is not passed.

The prompt contains the reason why the package was determined to be a dev dependency:

The package you required is recommended to be placed in require-dev (because it is tagged as "testing") but you did not use --dev.

This feature is skipped if Composer is run in a non-interactive environment (such as CI builds or when --no-interaction flag is passed).

How to make Composer prompt --dev flag on your packages

If you publish a developer tool (such as testing tools, data fixture tools, debugging tools, etc.), you can make use of this feature so Composer interactively prompts the user to install them under require-dev section in case the user forgets to use the --dev flag.

To do this, add one of the following keywords to the keywords section of the package's composer.json file.

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Keywords Composer uses to recommend a package as a dev dependency:

• dev
• testing
• static analysis

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Update the composer.json file, and add one of the keywords above to the keywords section:

  "name": "you/your-dev-tool",
+ "keywords": ["dev"],
  "type": "library",

The keyword only needs to be present in the default branch, and not necessarily in all branches and tags.