Optimize the size of the coroutines library in Android projects (WIP)

* Android module readme file include a number of recommended R8
  configuration settings that give ~68Kb reduction in the size of
  non-obfuscated dex file.

TODO: Need to write a test for these settings to make sure they all
actually have the desired effect (it would fail if any of the
"checkdiscard" assertions fail).

Author: elizarov

README.md

@@ -165,9 +165,15 @@ threads are handled by Android runtime.
 
 For R8 no actions required, it will take obfuscation rules from the jar.
 
-For Proguard  you need to add options from [coroutines.pro](kotlinx-coroutines-core/jvm/resources/META-INF/proguard/coroutines.pro) to your rules manually.
+For Proguard  you need to add options from 
+[coroutines.pro](kotlinx-coroutines-core/jvm/resources/META-INF/proguard/coroutines.pro) to your rules manually.
 
-R8 is a replacement for ProGuard in Android ecosystem, it is enabled by default since Android gradle plugin 3.4.0 (3.3.0-beta also had it enabled).
+R8 is a replacement for ProGuard in Android ecosystem, it is enabled by default since Android gradle plugin 3.4.0 
+(3.3.0-beta also had it enabled).
+
+You can optimize the size of the coroutines library in Android projects by statically removing 
+debugging and other advanced features using R8. 
+See [Optimization section in Android readme](ui/kotlinx-coroutines-android/README.md#Optimization) for details. 
 
 ### JS
 

binary-compatibility-validator/reference-public-api/kotlinx-coroutines-core.txt

@@ -4,11 +4,15 @@ public abstract class kotlinx/coroutines/AbstractCoroutine : kotlinx/coroutines/
 	public synthetic fun <init> (Lkotlin/coroutines/CoroutineContext;ZILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public final fun getContext ()Lkotlin/coroutines/CoroutineContext;
 	public fun getCoroutineContext ()Lkotlin/coroutines/CoroutineContext;
+	public fun getDefaultResumeMode ()I
+	public final fun handleOnCompletionException (Ljava/lang/Throwable;)V
 	public fun isActive ()Z
+	public fun nameString ()Ljava/lang/String;
 	protected fun onCancelled (Ljava/lang/Throwable;Z)V
 	protected fun onCompleted (Ljava/lang/Object;)V
 	protected final fun onCompletionInternal (Ljava/lang/Object;)V
 	protected fun onStart ()V
+	public final fun onStartInternal ()V
 	public final fun resumeWith (Ljava/lang/Object;)V
 	public final fun start (Lkotlinx/coroutines/CoroutineStart;Ljava/lang/Object;Lkotlin/jvm/functions/Function2;)V
 	public final fun start (Lkotlinx/coroutines/CoroutineStart;Lkotlin/jvm/functions/Function1;)V
@@ -55,12 +59,15 @@ public final class kotlinx/coroutines/CancellableContinuation$DefaultImpls {
 public class kotlinx/coroutines/CancellableContinuationImpl : kotlin/coroutines/jvm/internal/CoroutineStackFrame, kotlinx/coroutines/CancellableContinuation {
 	public fun <init> (Lkotlin/coroutines/Continuation;I)V
 	public fun cancel (Ljava/lang/Throwable;)Z
+	public fun cancelResult (Ljava/lang/Object;Ljava/lang/Throwable;)V
 	public fun completeResume (Ljava/lang/Object;)V
 	public fun getCallerFrame ()Lkotlin/coroutines/jvm/internal/CoroutineStackFrame;
 	public fun getContext ()Lkotlin/coroutines/CoroutineContext;
 	public fun getContinuationCancellationCause (Lkotlinx/coroutines/Job;)Ljava/lang/Throwable;
+	public final fun getDelegate ()Lkotlin/coroutines/Continuation;
 	public final fun getResult ()Ljava/lang/Object;
 	public fun getStackTraceElement ()Ljava/lang/StackTraceElement;
+	public fun getSuccessfulResult (Ljava/lang/Object;)Ljava/lang/Object;
 	public synthetic fun initCancellability ()V
 	public fun invokeOnCancellation (Lkotlin/jvm/functions/Function1;)V
 	public fun isActive ()Z
@@ -71,6 +78,7 @@ public class kotlinx/coroutines/CancellableContinuationImpl : kotlin/coroutines/
 	public fun resumeUndispatched (Lkotlinx/coroutines/CoroutineDispatcher;Ljava/lang/Object;)V
 	public fun resumeUndispatchedWithException (Lkotlinx/coroutines/CoroutineDispatcher;Ljava/lang/Throwable;)V
 	public fun resumeWith (Ljava/lang/Object;)V
+	public fun takeState ()Ljava/lang/Object;
 	public fun toString ()Ljava/lang/String;
 	public fun tryResume (Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
 	public fun tryResumeWithException (Ljava/lang/Throwable;)Ljava/lang/Object;
@@ -380,6 +388,7 @@ public class kotlinx/coroutines/JobSupport : kotlinx/coroutines/ChildJob, kotlin
 	public synthetic fun cancel (Ljava/lang/Throwable;)Z
 	public fun cancel (Ljava/util/concurrent/CancellationException;)V
 	public final fun cancelCoroutine (Ljava/lang/Throwable;)Z
+	public final fun cancelImpl (Ljava/lang/Object;)Z
 	public fun cancelInternal (Ljava/lang/Throwable;)Z
 	public fun childCancelled (Ljava/lang/Throwable;)Z
 	public fun fold (Ljava/lang/Object;Lkotlin/jvm/functions/Function2;)Ljava/lang/Object;
@@ -390,9 +399,14 @@ public class kotlinx/coroutines/JobSupport : kotlinx/coroutines/ChildJob, kotlin
 	protected final fun getCompletionCause ()Ljava/lang/Throwable;
 	protected final fun getCompletionCauseHandled ()Z
 	public final fun getCompletionExceptionOrNull ()Ljava/lang/Throwable;
+	public fun getHandlesException ()Z
 	public final fun getKey ()Lkotlin/coroutines/CoroutineContext$Key;
+	public fun getOnCancelComplete ()Z
 	public final fun getOnJoin ()Lkotlinx/coroutines/selects/SelectClause0;
+	public final fun getState ()Ljava/lang/Object;
 	protected fun handleJobException (Ljava/lang/Throwable;)Z
+	public fun handleOnCompletionException (Ljava/lang/Throwable;)V
+	public final fun initParentJobInternal (Lkotlinx/coroutines/Job;)V
 	public final fun invokeOnCompletion (Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/DisposableHandle;
 	public final fun invokeOnCompletion (ZZLkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/DisposableHandle;
 	public fun isActive ()Z
@@ -401,9 +415,12 @@ public class kotlinx/coroutines/JobSupport : kotlinx/coroutines/ChildJob, kotlin
 	public final fun isCompletedExceptionally ()Z
 	protected fun isScopedCoroutine ()Z
 	public final fun join (Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+	public final fun makeCompletingOnce (Ljava/lang/Object;I)Z
 	public fun minusKey (Lkotlin/coroutines/CoroutineContext$Key;)Lkotlin/coroutines/CoroutineContext;
+	public fun nameString ()Ljava/lang/String;
 	protected fun onCancelling (Ljava/lang/Throwable;)V
 	protected fun onCompletionInternal (Ljava/lang/Object;)V
+	public fun onStartInternal ()V
 	public final fun parentCancelled (Lkotlinx/coroutines/ParentJob;)V
 	public fun plus (Lkotlin/coroutines/CoroutineContext;)Lkotlin/coroutines/CoroutineContext;
 	public fun plus (Lkotlinx/coroutines/Job;)Lkotlinx/coroutines/Job;

build.gradle

@@ -137,6 +137,8 @@ allprojects {
         kotlinOptions.freeCompilerArgs += "-progressive"
         // Binary compatibility support
         kotlinOptions.freeCompilerArgs += ["-Xdump-declarations-to=${buildDir}/visibilities.json"]
+        // Remove null assertions to get smaller bytecode on Android
+        kotlinOptions.freeCompilerArgs += ["-Xno-param-assertions", "-Xno-receiver-assertions", "-Xno-call-assertions"]
     }
 }
 

knit/src/Knit.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 import java.io.*
@@ -228,7 +228,7 @@ fun knit(markdownFile: File): Boolean {
                     }
                 }
                 for (code in codeLines) {
-                    outLines += code.replace("System.currentTimeMillis()", "timeSource.currentTimeMillis()")
+                    outLines += code.replace("System.currentTimeMillis()", "currentTimeMillis()")
                 }
                 codeLines.clear()
                 writeLinesIfNeeded(file, outLines)

kotlinx-coroutines-core/common/src/AbstractCoroutine.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 @file:Suppress("DEPRECATION_ERROR")
 
@@ -71,7 +71,7 @@ public abstract class AbstractCoroutine<in T>(
      */
     protected open fun onStart() {}
 
-    internal final override fun onStartInternal() {
+    final override fun onStartInternal() {
         onStart()
     }
 
@@ -102,7 +102,7 @@ public abstract class AbstractCoroutine<in T>(
             onCompleted(state as T)
     }
 
-    internal open val defaultResumeMode: Int get() = MODE_ATOMIC_DEFAULT
+    open val defaultResumeMode: Int get() = MODE_ATOMIC_DEFAULT
 
     /**
      * Completes execution of this with coroutine with the specified result.
@@ -111,11 +111,11 @@ public abstract class AbstractCoroutine<in T>(
         makeCompletingOnce(result.toState(), defaultResumeMode)
     }
 
-    internal final override fun handleOnCompletionException(exception: Throwable) {
+    final override fun handleOnCompletionException(exception: Throwable) {
         handleCoroutineException(context, exception)
     }
 
-    internal override fun nameString(): String {
+    override fun nameString(): String {
         val coroutineName = context.coroutineName ?: return super.nameString()
         return "\"$coroutineName\":${super.nameString()}"
     }

kotlinx-coroutines-core/common/src/CancellableContinuationImpl.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.coroutines
@@ -297,7 +297,7 @@ internal open class CancellableContinuationImpl<in T>(
                 }
                 is CompletedIdempotentResult -> {
                     return if (state.idempotentResume === idempotent) {
-                        check(state.result === value) { "Non-idempotent resume" }
+                        assert { state.result === value } // "Non-idempotent resume"
                         state.token
                     } else {
                         null

kotlinx-coroutines-core/common/src/Debug.common.kt

@@ -1,8 +1,10 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.coroutines
 
+internal expect val DEBUG: Boolean
 internal expect val Any.hexAddress: String
 internal expect val Any.classSimpleName: String
+internal expect fun assert(value: () -> Boolean)

kotlinx-coroutines-core/common/src/Dispatched.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.coroutines
@@ -8,9 +8,9 @@ import kotlinx.coroutines.internal.*
 import kotlin.coroutines.*
 import kotlin.jvm.*
 
-@Suppress("PrivatePropertyName")
 @SharedImmutable
-private val UNDEFINED = Symbol("UNDEFINED")
+@JvmField // JvmField + internal avoids generation of accessors
+internal val UNKNOWN = Symbol("UNDEFINED")
 
 /**
  * Executes given [block] as part of current event loop, updating current continuation
@@ -79,16 +79,16 @@ internal class DispatchedContinuation<in T>(
 ) : DispatchedTask<T>(MODE_ATOMIC_DEFAULT), CoroutineStackFrame, Continuation<T> by continuation {
     @JvmField
     @Suppress("PropertyName")
-    internal var _state: Any? = UNDEFINED
+    internal var _state: Any? = UNKNOWN
     override val callerFrame: CoroutineStackFrame? = continuation as? CoroutineStackFrame
     override fun getStackTraceElement(): StackTraceElement? = null
     @JvmField // pre-cached value to avoid ctx.fold on every resumption
     internal val countOrElement = threadContextElements(context)
 
     override fun takeState(): Any? {
         val state = _state
-        check(state !== UNDEFINED) // fail-fast if repeatedly invoked
-        _state = UNDEFINED
+        assert { state !== UNKNOWN } // fail-fast if repeatedly invoked
+        _state = UNKNOWN
         return state
     }
 
@@ -203,17 +203,17 @@ internal fun <T> Continuation<T>.resumeDirectWithException(exception: Throwable)
 internal abstract class DispatchedTask<in T>(
     @JvmField public var resumeMode: Int
 ) : SchedulerTask() {
-    internal abstract val delegate: Continuation<T>
+    abstract val delegate: Continuation<T>
 
-    internal abstract fun takeState(): Any?
+    abstract fun takeState(): Any?
 
-    internal open fun cancelResult(state: Any?, cause: Throwable) {}
+    open fun cancelResult(state: Any?, cause: Throwable) {}
 
     @Suppress("UNCHECKED_CAST")
-    internal open fun <T> getSuccessfulResult(state: Any?): T =
+    open fun <T> getSuccessfulResult(state: Any?): T =
         state as T
 
-    internal fun getExceptionalResult(state: Any?): Throwable? =
+    fun getExceptionalResult(state: Any?): Throwable? =
         (state as? CompletedExceptionally)?.cause
 
     public final override fun run() {
@@ -268,7 +268,7 @@ internal abstract class DispatchedTask<in T>(
      * Fatal exception handling can be intercepted with [CoroutineExceptionHandler] element in the context of
      * a failed coroutine, but such exceptions should be reported anyway.
      */
-    internal fun handleFatalException(exception: Throwable?, finallyException: Throwable?) {
+    fun handleFatalException(exception: Throwable?, finallyException: Throwable?) {
         if (exception === null && finallyException === null) return
         if (exception !== null && finallyException !== null) {
             exception.addSuppressedThrowable(finallyException)

kotlinx-coroutines-core/common/src/EventLoop.common.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.coroutines
@@ -104,7 +104,7 @@ internal abstract class EventLoop : CoroutineDispatcher() {
     fun decrementUseCount(unconfined: Boolean = false) {
         useCount -= delta(unconfined)
         if (useCount > 0) return
-        check(useCount == 0L) { "Extra decrementUseCount" }
+        assert { useCount == 0L } // "Extra decrementUseCount"
         if (shared) {
             // shut it down and remove from ThreadLocalEventLoop
             shutdown()
@@ -118,17 +118,17 @@ internal abstract class EventLoop : CoroutineDispatcher() {
 internal object ThreadLocalEventLoop {
     private val ref = CommonThreadLocal<EventLoop?>()
 
-    internal val eventLoop: EventLoop
+    val eventLoop: EventLoop
         get() = ref.get() ?: createEventLoop().also { ref.set(it) }
 
-    internal fun currentOrNull(): EventLoop? =
+    fun currentOrNull(): EventLoop? =
         ref.get()
 
-    internal fun resetEventLoop() {
+    fun resetEventLoop() {
         ref.set(null)
     }
 
-    internal fun setEventLoop(eventLoop: EventLoop) {
+    fun setEventLoop(eventLoop: EventLoop) {
         ref.set(eventLoop)
     }
 }