Unstable CML features

Oftentimes when a new CML feature is being developed (e.g. a new capability type), the Component Framework team wants to experiment with the API or implementation before committing to supporting the new feature.

For this reason, the CML compiler cmc will only allow the use of unstable features in your CML if you’ve opted-in to them.

Opting-in

In order to use an unstable feature, you need to add the unstable_features property to your component build rule.

fuchsia_component("my-component") {
  manifest = "meta/my-component.cml"
  unstable_features = [ "services" ]  # This component opts-in to the unstable "services" feature.
  deps = [ ... ]
}

Use of unstable features are restricted to an allowlist. You must add your component to the allowlist for the feature at //tools/cmc/build/unstable_features/BUILD.gn.