sdk/fidl/fuchsia.component.sandbox/availability.fidl

// Copyright 2024 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.component.sandbox;

// TODO(b/337248133): This type was copied from fuchsia.component.decl.
// When the sandbox library is exposed in the SDK, delete the decl Availiability
// in favor of this one.
/// Describes the expected availability of the capability.
///
/// Some capabilities may not be present on all system configurations. In those
/// cases, the availability will be declared as `OPTIONAL` along the chains of
/// exposes/offers/uses, and the capability would be routed from `void` on
/// system configurations where it does not make sense to route or provide a
/// particular capability (e.g. graphical capabilities on a headless system).
@available(added=HEAD)
type Availability = strict enum {
    /// The capability must be available. Failure to route the capability is an
    /// error.
    REQUIRED = 1;

    /// Inside a use declaration: the component can function if it fails to
    /// obtain the capability.
    ///
    /// Inside an offer/expose declaration: the capability may not be available
    /// in some system configurations. As a corollary, the target component must
    /// not have a required dependency on the capability.
    OPTIONAL = 2;

    /// If the target of the corresponding offer or expose declaration requires
    /// the capability, then the behavior is equivalent to required. If the
    /// target has an optional dependency on the capability, then the behavior
    /// is equivalent to optional. This is useful for container components that
    /// would like to change their routing availability based on ones inside.
    ///
    /// This value is not allowed inside a use declaration.
    SAME_AS_TARGET = 3;

    /// The source may omit the route completely without even having to route
    /// from `void`.
    ///
    /// [`TRANSITIONAL`] is used for soft transitions that introduce new
    /// capabilities.
    TRANSITIONAL = 4;
};