With Ceylon we try our best to make every developer’s life easier. We do this with a great language, a powerful IDE, a wonderful online module repository, but also with an amazing command-line interface (CLI).

Our command line is built around the idea of discoverability where you get a single executable called ceylon and lots of subcommands that you can discover via --help or completion. We have a number of predefined subcommands, but every so often, we want to be able to write new subcommands.

For example, I want to be able to invoke both Java and JavaScript compilers and generate the API documentation in a single command ceylon all, or I want to be able to invoke the ceylon.formatter module with ceylon format instead of ceylon run ceylon.formatter.

Well, with Ceylon 1.1 we now support custom subcommands, fashioned after the git plugin system. They’re easy to write: just place them in script/your/module/ceylon-foo and package them with ceylon plugin pack your.module, and you can publish them to Herd.

Now every one can install your CLI plugin with ceylon plugin install your.module/1.0 and call them with ceylon foo.

What’s even better is that they will be listed in the ceylon --help and even work with autocompletion.

ceylon.formatter uses one, and I encourage you to install them with ceylon plugin install ceylon.formatter/1.1.0 and format your code at will with ceylon format :)

ceylon.build.engine also defines one and it just feels great being able to build your Ceylon project with ceylon build compile, I have to say. Although, unfortunately that particular module has not yet been published to Herd yet, but hopefully it will be pushed soon.

You can find out all about them in our reference.