kotlinx-coroutines-core/src/main/kotlin/kotlinx/coroutines/experimental/NonCancellable.kt

/*
 * Copyright 2016-2017 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package kotlinx.coroutines.experimental

import kotlinx.coroutines.experimental.NonCancellable.isActive
import kotlin.coroutines.experimental.AbstractCoroutineContextElement

/**
 * A non-cancelable job that is always [active][isActive]. It is designed to be used with [run] builder
 * to prevent cancellation of code blocks that need to run without cancellation.
 *
 * Use it like this:
 * ```
 * run(NonCancellable) {
 *     // this code will not be cancelled
 * }
 * ```
 */
object NonCancellable : AbstractCoroutineContextElement(Job), Job {
    override val isActive: Boolean  get() = true
    override fun getCompletionException(): CancellationException = throw IllegalStateException("This job is always active")
    override fun onCompletion(handler: CompletionHandler): Job.Registration = EmptyRegistration
    override fun cancel(cause: Throwable?): Boolean = false
}