Components

Components are parts of a snap that can be built and uploaded in conjunction with a snap and later optionally installed beside it. Components are defined with a top-level components key in the project file.

Components are useful for distributing optional resources alongside a snap. For example, debug symbols are useful for the developer of an application and are closely linked to a particular build of an application. Debug symbols are not useful for the users. Including debug symbols in a snap package would waste user’s network bandwidth and disk space. If an application packages debug symbols as a component alongside the snap, then the developers who require debug symbols can download and install them as a component.

Note

Components are under development and not production ready.

Components and Partitions

Components utilize a Craft Parts feature called partitions. This feature is enabled only when the component key is defined in the project file.

Each component has a namespaced partition component/<component-name> where component is the partition’s namespace and <component-name> is the name of the component from the project file.

The partition for the snap itself is known as the default partition.

Component lifecycle directories

When a part is built, the output is the default partition’s install directory for that part.

Each component has a partition. This means each component has its own install, stage, and prime directories. When a file is organized into a component’s partition, it is moved to the part’s install directory for that component’s partition.

For example, consider a part with the organize key:

snapcraft.yaml

parts:
  my-part:
    plugin: nil
    override-build: |
      touch $CRAFT_PART_INSTALL/hello
    organize:
      hello: (component/translations)/hello-world

This part’s build creates a file called hello in my-part’s default install directory. If no organize key was used, this file would be included in the snap itself.

However this example uses the organize key to move the file hello from my-part’s default install directory to my-parts’s install directory for the translations component. It also renames the file from hello to hello-world.

The packed snap will contain nothing from this part and the translations component will contain the hello-world file.