Composer Merge Plugin

Merge multiple 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 settings into the base configuration. This
combined configuration will then be used when downloading additional libraries
and generating the autoloader.

Composer Merge Plugin was created to help with installation of MediaWiki
which has core library requirements as well as optional libraries and
extensions which may be managed via Composer.

Installation

Composer Merge Plugin requires Composer 1.0.0 or
newer.

$ composer require wikimedia/composer-merge-plugin

Usage

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

Updating sub-levels composer.json files

In order for composer-merge-plugin to install dependencies from updated or newly created sub-level composer.json files in your project you need to run the command:

$ composer update --lock

This will instruct Composer to recalculate the file hash for the top-level composer.json thus triggering composer-merge-plugin to look for the sub-level configuration files and update your dependencies.

Plugin configuration

The plugin reads its configuration from the merge-plugin section of your
composer.json's extra section. An include setting is required to tell
Composer Merge Plugin which file(s) to merge.

include

The include setting can specify either a single value or an array of values.
Each value is treated as a PHP glob() pattern identifying additional
composer.json style configuration files to merge into the root package
configuration for the current Composer execution.

The following sections of the found configuration files will be merged into
the Composer root package configuration as though they were directly included
in the top-level composer.json file:

• autoload
• autoload-dev
  (optional, see merge-dev below)
• conflict
• provide
• replace
• repositories
• require
• require-dev
  (optional, see merge-dev below)
• suggest
• extra
  (optional, see merge-extra below)
• scripts
  (optional, see merge-scripts below)

require

The require setting is identical to include except when
a pattern fails to match at least one file then it will cause an error.

recurse

By default the merge plugin is recursive; if an included file has
a merge-plugin section it will also be processed. This functionality can be
disabled by adding a "recurse": false setting.

replace

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

ignore-duplicates

By default, Composer's conflict resolution engine is used to determine which
version of a package should be installed when multiple files specify the same
package. An "ignore-duplicates": true setting can be provided to change to
a "first version specified wins" conflict resolution strategy. In this mode,
duplicate package declarations found in merged files will be ignored in favor
of the declarations made by earlier files. Files are loaded in the order
specified by the include setting with globbed files being processed in
alphabetical order.

Note: "replace": true and "ignore-duplicates": true modes are mutually
exclusive. If both are set, "ignore-duplicates": true will be used.

merge-dev

By default, autoload-dev and require-dev sections of included files are
merged. A "merge-dev": false setting will disable this behavior.

merge-extra

A "merge-extra": true setting enables the merging the contents of the
extra section of included files as well. 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 any imported config). If
replace mode is active (see above) then this behavior changes
and the last key found will win (e.g. the key in the master config is replaced
by the key in the imported config). If "merge-extra-deep": true is specified
then, the sections are merged similar to array_merge_recursive() - however
duplicate string array keys are replaced instead of merged, while numeric
array keys are merged as usual. The usefulness of merging the extra section
will vary depending on the Composer plugins being used and the order in which
they are processed by Composer.

Note that merge-plugin sections are excluded from the merge process, but are
always processed by the plugin unless recursion is disabled.

merge-scripts

A "merge-scripts": true setting enables merging the contents of the
scripts section of included files as well. The normal merge mode for the
scripts 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 any imported config). If
replace mode is active (see above) then this behavior changes
and the last key found will win (e.g. the key in the master config is replaced
by the key in the imported config).

Note: custom commands added by merged configuration will work when invoked
as composer run-script my-cool-command but will not be available using the
normal composer my-cool-command shortcut.

Running tests

$ composer install
$ composer test

Contributing

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.

License

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