kotlinx-coroutines-core/jvm/test/ThreadContextMutableCopiesTest.kt

/*
 * Copyright 2016-2022 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
 */

package kotlinx.coroutines

import kotlin.coroutines.*
import kotlin.test.*

class ThreadContextMutableCopiesTest : TestBase() {
    companion object {
        val threadLocalData: ThreadLocal<MutableList<String>> = ThreadLocal.withInitial { ArrayList() }
    }

    class MyMutableElement(
        val mutableData: MutableList<String>
    ) : CopyableThreadContextElement<MutableList<String>> {

        companion object Key : CoroutineContext.Key<MyMutableElement>

        override val key: CoroutineContext.Key<*>
            get() = Key

        override fun updateThreadContext(context: CoroutineContext): MutableList<String> {
            val st = threadLocalData.get()
            threadLocalData.set(mutableData)
            return st
        }

        override fun restoreThreadContext(context: CoroutineContext, oldState: MutableList<String>) {
            threadLocalData.set(oldState)
        }

        override fun copyForChild(): MyMutableElement {
            return MyMutableElement(ArrayList(mutableData))
        }

        override fun mergeForChild(overwritingElement: CoroutineContext.Element): MyMutableElement {
            overwritingElement as MyMutableElement // <- app-specific, may be another subtype
            return MyMutableElement((mutableData.toSet() + overwritingElement.mutableData).toMutableList())
        }
    }

    @Test
    fun testDataIsCopied() = runTest {
        val root = MyMutableElement(ArrayList())
        runBlocking(root) {
            val data = threadLocalData.get()
            expect(1)
            launch(root) {
                assertNotSame(data, threadLocalData.get())
                assertEquals(data, threadLocalData.get())
                finish(2)
            }
        }
    }

    @Test
    fun testDataIsNotOverwritten() = runTest {
        val root = MyMutableElement(ArrayList())
        runBlocking(root) {
            expect(1)
            val originalData = threadLocalData.get()
            threadLocalData.get().add("X")
            launch {
                threadLocalData.get().add("Y")
                // Note here, +root overwrites the data
                launch(Dispatchers.Default + root) {
                    assertEquals(listOf("X", "Y"), threadLocalData.get())
                    assertNotSame(originalData, threadLocalData.get())
                    finish(2)
                }
            }
        }
    }

    @Test
    fun testDataIsMerged() = runTest {
        val root = MyMutableElement(ArrayList())
        runBlocking(root) {
            expect(1)
            val originalData = threadLocalData.get()
            threadLocalData.get().add("X")
            launch {
                threadLocalData.get().add("Y")
                // Note here, +root overwrites the data
                launch(Dispatchers.Default + MyMutableElement(mutableListOf("Z"))) {
                    assertEquals(listOf("X", "Y", "Z"), threadLocalData.get())
                    assertNotSame(originalData, threadLocalData.get())
                    finish(2)
                }
            }
        }
    }

    @Test
    fun testDataIsNotOverwrittenWithContext() = runTest {
        val root = MyMutableElement(ArrayList())
        runBlocking(root) {
            val originalData = threadLocalData.get()
            threadLocalData.get().add("X")
            expect(1)
            launch {
                threadLocalData.get().add("Y")
                // Note here, +root overwrites the data
                withContext(Dispatchers.Default + root) {
                    assertEquals(listOf("X", "Y"), threadLocalData.get())
                    assertNotSame(originalData, threadLocalData.get())
                    finish(2)
                }
            }
        }
    }

    @Test
    fun testDataIsCopiedForRunBlocking() = runTest {
        val root = MyMutableElement(ArrayList())
        val originalData = root.mutableData
        runBlocking(root) {
            assertNotSame(originalData, threadLocalData.get())
        }
    }

    @Test
    fun testDataIsCopiedForCoroutine() = runTest {
        val root = MyMutableElement(ArrayList())
        val originalData = root.mutableData
        expect(1)
        launch(root) {
            assertNotSame(originalData, threadLocalData.get())
            finish(2)
        }
    }
}