Merge one or more additional composer.json files at Composer runtime.

Composer Merge Plugin is intended to allow easier dependency management for applications which ship a composer.json file and expect some deployments to install additional Composer managed libraries. It does this by allowing the application's top level composer.json file to provide a list of optional additional configuration files. When Composer is run it will parse these files and merge their configuration into the base configuration. This combined configuration will allow downloading additional libraries and generating the autoloader. It was specifically created to help with installation of MediaWiki which has core Composer managed library requirements and optional libraries and extensions which may also be managed via Composer.

$ composer require wikimedia/composer-merge-plugin

{
    "require": {
        "wikimedia/composer-merge-plugin": "dev-master"
    },
    "extra": {
        "merge-plugin": {
            "include": [
                "composer.local.json",
                "extensions/*/composer.json"
            ],
            "recurse": false,
            "replace": false,
            "merge-extra": false
        }
    }
}

The include key can specify either a single value or an array of values. Each value is treated as a glob() pattern identifying additional composer.json style configuration files to merge into the configuration for the current Composer execution. By default the merge plugin is recursive, if an included file also has a "merge-plugin" section it will also be processed. This functionality can be disabled by setting "recurse": false inside the "merge-plugin" section.

The "require", "require-dev", "repositories" and "suggest" sections of the found configuration files will be merged into the root package configuration as though they were directly included in the top-level composer.json file.

The "merge-extra": true setting enables the merging of the "extra" section. The normal merge mode for the extra section is to accept the first version of any key found (e.g. a key in the master config wins over the version found in an imported config). If replace mode is active (see below) then this behaviour changes and the last found key will win (the key in the master config is replaced by the key in the imported config). Note that the merge-plugin key itself is excluded from this merge process. Your mileage with merging the extra section will vary depending on the plugins being used and the order in which they are processed by Composer.

By default, Composer's normal conflict resolution engine is used to determine which version of a package should be installed if multiple files specify the same package. A "replace": true setting can be provided inside the "merge-plugin" section to change to a "last version specified wins" conflict resolution strategy. In this mode, duplicate package declarations in merged files will overwrite the declarations made in earlier files. Files are loaded in the order specified in the include section with globbed files being loaded in alphabetical order.

$ composer install
$ composer test

Bug, feature requests and other issues should be reported to the GitHub project. We accept code and documentation contributions via Pull Requests on GitHub as well.

• PSR-2 Coding Standard is used by the project. The included test configuration uses PHP Code Sniffer to validate the conventions.
• Tests are encouraged. Our test coverage isn't perfect but we'd like it to get better rather than worse, so please try to include tests with your changes.
• Keep the documentation up to date. Make sure README.md and other relevant documentation is kept up to date with your changes.
• One pull request per feature. Try to keep your changes focused on solving a single problem. This will make it easier for us to review the change and easier for you to make sure you have updated the necessary tests and documentation.

Composer Merge plugin is licensed under the MIT license. See the LICENSE file for more details.