理解runBlocking和coroutineScope的行为差异

Question

在Kotlin指南这里中，当解释runBlocking和coroutineScope之间的区别时，它说：

..。主要的区别是runBlocking方法阻塞当前线程等待，而coroutineScope只是挂起，释放底层线程用于其他用途。..。

这是可以理解的但是，在这里列出的示例代码中：

import kotlinx.coroutines.*

fun main() = runBlocking { // this: CoroutineScope
    launch { 
        delay(200L)
        println("Task from runBlocking")
    }
    
    coroutineScope { // Creates a coroutine scope
        launch {
            delay(500L) 
            println("Task from nested launch")
        }
    
        delay(100L)
        println("Task from coroutine scope") // This line will be printed before the nested launch
    }
    
    println("Coroutine scope is over") // This line is not printed until the nested launch completes
}

它产生以下输出：

Task from coroutine scope
Task from runBlocking
Task from nested launch
Coroutine scope is over

将coroutineScope替换为runBlocking：

import kotlinx.coroutines.*

fun main() = runBlocking { // this: CoroutineScope
    launch { 
        delay(200L)
        println("Task from runBlocking")
    }
    
    runBlocking { // instead of coroutineScope, previously
        launch {
            delay(500L) 
            println("Task from nested launch")
        }
    
        delay(100L)
        println("Task from coroutine scope") // This line will be printed before the nested launch
    }
    
    println("Coroutine scope is over") // This line is not printed until the nested launch completes
}

输出中没有任何更改。相反，我期望它生成以下输出，因为嵌套的runBlocking将阻塞直到它的块完成，包括所有子协同：

Task from coroutine scope
Task from nested launch
Task from runBlocking
Coroutine scope is over

有人能解释一下这种行为吗？我在这里监督什么？

Answer 1

在runBlocking中拥有runBlocking是..。不寻常。更常见的是，runBlocking仅仅是一种外在的东西。实际上，runBlocking的实现将使用外部runBlocking的事件循环，而不是创建新的事件循环，因此在这种情况下，它实际上就像coroutineScope一样。

来源：https://github.com/Kotlin/kotlinx.coroutines/blob/dda99e21f45f65eb540ccf4d5e82faf7559bc9e5/kotlinx-coroutines-core/jvm/src/Builders.kt#L46

Answer 2

runBlocking只阻塞当前线程，直到block返回为止。它不影响block的执行方式。