Use ServiceLoader to find instances of CoroutineExceptionHandler;

Use Thread.getUncaughtExceptionPreHandler on Android to make sure
that exceptions are logged before crash.

Also update versions for Android example app.
Fixes #148

Author: elizarov

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

@@ -16,6 +16,7 @@
 
 package kotlinx.coroutines.experimental
 
+import java.util.*
 import kotlin.coroutines.experimental.AbstractCoroutineContextElement
 import kotlin.coroutines.experimental.CoroutineContext
 
@@ -29,7 +30,8 @@ import kotlin.coroutines.experimental.CoroutineContext
  *   (because that is the supposed mechanism to cancel the running coroutine)
  * * Otherwise:
  *     * if there is a [Job] in the context, then [Job.cancel] is invoked;
- *     * and current thread's [Thread.uncaughtExceptionHandler] is invoked.
+ *     * all instances of [CoroutineExceptionHandler] found via [ServiceLoader] are invoked;
+ *     * current thread's [Thread.uncaughtExceptionHandler] is invoked.
  */
 fun handleCoroutineException(context: CoroutineContext, exception: Throwable) {
     context[CoroutineExceptionHandler]?.let {
@@ -40,6 +42,10 @@ fun handleCoroutineException(context: CoroutineContext, exception: Throwable) {
     if (exception is CancellationException) return
     // try cancel job in the context
     context[Job]?.cancel(exception)
+    // use additional extension handlers
+    ServiceLoader.load(CoroutineExceptionHandler::class.java).forEach { handler ->
+        handler.handleException(context, exception)
+    }
     // use thread's handler
     val currentThread = Thread.currentThread()
     currentThread.uncaughtExceptionHandler.uncaughtException(currentThread, exception)

ui/kotlinx-coroutines-android/example-app/app/build.gradle

@@ -4,7 +4,7 @@ apply plugin: 'kotlin-android-extensions'
 
 android {
     compileSdkVersion 25
-    buildToolsVersion "25.0.2"
+    buildToolsVersion '26.0.2'
     defaultConfig {
         applicationId "com.example.app"
         minSdkVersion 9
@@ -22,18 +22,18 @@ android {
 }
 
 repositories {
-    mavenLocal()
-    mavenCentral()
+    jcenter()
+    google()
 }
 
 dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
     androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
         exclude group: 'com.android.support', module: 'support-annotations'
     })
-    compile 'com.android.support:appcompat-v7:25.2.0'
-    compile 'com.android.support.constraint:constraint-layout:1.0.1'
-    compile 'com.android.support:design:25.2.0'
+    compile 'com.android.support:appcompat-v7:25.4.0'
+    compile 'com.android.support.constraint:constraint-layout:1.0.2'
+    compile 'com.android.support:design:25.4.0'
     testCompile 'junit:junit:4.12'
     compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
     compile "org.jetbrains.kotlinx:kotlinx-coroutines-android:0.19.3"

ui/kotlinx-coroutines-android/example-app/build.gradle

@@ -4,9 +4,10 @@ buildscript {
     ext.kotlin_version = '1.1.51'
     repositories {
         jcenter()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.0'
+        classpath 'com.android.tools.build:gradle:3.0.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong

ui/kotlinx-coroutines-android/example-app/gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Mon Dec 28 10:00:20 PST 2015
+#Sun Nov 05 23:56:59 MSK 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.1-all.zip

ui/kotlinx-coroutines-android/src/main/kotlin/kotlinx/coroutines/experimental/android/AndroidExceptionPreHandler.kt

@@ -0,0 +1,30 @@
+package kotlinx.coroutines.experimental.android
+
+import kotlinx.coroutines.experimental.CoroutineExceptionHandler
+import java.lang.reflect.Modifier
+import kotlin.coroutines.experimental.AbstractCoroutineContextElement
+import kotlin.coroutines.experimental.CoroutineContext
+
+private val getter =
+    try {
+        Thread::class.java.getDeclaredMethod("getUncaughtExceptionPreHandler").takeIf {
+            Modifier.isPublic(it.modifiers) && Modifier.isStatic(it.modifiers)
+        }
+    }
+    catch (e: Throwable) { null /* not found */ }
+
+/**
+ * Uses Android's `Thread.getUncaughtExceptionPreHandler()` whose default behavior is to log exception.
+ * See
+ * [here](https://github.com/aosp-mirror/platform_frameworks_base/blob/2efbc7239f419c931784acf98960ed6abc38c3f2/core/java/com/android/internal/os/RuntimeInit.java#L142)
+ *
+ * @suppress This is an internal impl class.
+ */
+class AndroidExceptionPreHandler :
+    AbstractCoroutineContextElement(CoroutineExceptionHandler), CoroutineExceptionHandler
+{
+    override fun handleException(context: CoroutineContext, exception: Throwable) {
+        (getter?.invoke(null) as? Thread.UncaughtExceptionHandler)
+            ?.uncaughtException(Thread.currentThread(), exception)
+    }
+}

ui/kotlinx-coroutines-android/src/main/resources/META-INF/services/kotlinx.coroutines.experimental.CoroutineExceptionHandler

@@ -0,0 +1 @@
+kotlinx.coroutines.experimental.android.AndroidExceptionPreHandler