Config defaults using ServiceLoader

leakcanary/leakcanary-android-core/src/main/java/leakcanary/LeakCanary.kt

@@ -1,6 +1,7 @@
 package leakcanary
 
 import android.content.Intent
+import java.util.ServiceLoader
 import leakcanary.LeakCanary.config
 import leakcanary.internal.HeapDumpControl
 import leakcanary.internal.InternalLeakCanary
@@ -88,9 +89,13 @@ object LeakCanary {
      * heap. You can create your own [ObjectInspector] implementations, and also add
      * a [shark.AppSingletonInspector] instance created with the list of internal singletons.
      *
-     * Defaults to [AndroidObjectInspectors.appDefaults]
+     * Defaults to [AndroidObjectInspectors.appDefaults] and any discoverable [ObjectInspector]
+     * through the classpath at `META-INF/services/shark.ObjectInspector`.
+     *
+     * @see [ServiceLoader]
      */
-    val objectInspectors: List<ObjectInspector> = AndroidObjectInspectors.appDefaults,
+    val objectInspectors: List<ObjectInspector> =
+      AndroidObjectInspectors.appDefaults + ServiceLoader.load(ObjectInspector::class.java),
 
     /**
      * Extracts metadata from a hprof to be reported in [HeapAnalysisSuccess.metadata].
@@ -182,6 +187,11 @@ object LeakCanary {
      *   )
      * }
      * ```
+     *
+     * Any [EventListener] discoverable through the classpath at
+     * `META-INF/services/leakcanary.EventListener` will be automatically loaded.
+     *
+     * @see [ServiceLoader]
      */
     val eventListeners: List<EventListener> = listOf(
       LogcatEventListener,
@@ -194,8 +204,8 @@ object LeakCanary {
             RemoteWorkManagerHeapAnalyzer
           WorkManagerHeapAnalyzer.validWorkManagerInClasspath -> WorkManagerHeapAnalyzer
           else -> BackgroundThreadHeapAnalyzer
-      }
-    ),
+      },
+    ) + ServiceLoader.load(EventListener::class.java),
 
     /**
      * Whether to show LeakCanary notifications. When [showNotifications] is true, LeakCanary

leakcanary/leakcanary-android-core/src/test/java/leakcanary/LeakCanaryConfigTest.kt

@@ -4,6 +4,8 @@ import org.assertj.core.api.Assertions.assertThat
 import org.junit.Test
 import kotlin.reflect.full.memberFunctions
 import kotlin.reflect.full.memberProperties
+import shark.ObjectInspector
+import shark.ObjectReporter
 
 class LeakCanaryConfigTest {
 
@@ -22,4 +24,22 @@ class LeakCanaryConfigTest {
 
   private fun configProperties() = LeakCanary.Config::class.memberProperties
     .map { it.name }
+
+  @Test fun `LeakCanary Config loads extensions from classpath`() {
+    val config = LeakCanary.Config()
+
+    assertThat(config.objectInspectors.filterIsInstance<TestObjectInspector>()).size().isEqualTo(1)
+    assertThat(config.eventListeners.filterIsInstance<TestEventListener>()).size().isEqualTo(1)
+  }
+
+  class TestObjectInspector : ObjectInspector {
+    override fun inspect(reporter: ObjectReporter) {
+    }
+  }
+
+  class TestEventListener : EventListener {
+    override fun onEvent(event: EventListener.Event) {
+    }
+  }
+
 }

leakcanary/leakcanary-android-core/src/test/resources/META-INF/services/leakcanary.EventListener

@@ -0,0 +1 @@
+leakcanary.LeakCanaryConfigTest$TestEventListener

leakcanary/leakcanary-android-core/src/test/resources/META-INF/services/shark.ObjectInspector

@@ -0,0 +1 @@
+leakcanary.LeakCanaryConfigTest$TestObjectInspector

leakcanary/leakcanary-android-instrumentation/src/main/java/leakcanary/DetectLeaksAssert.kt

@@ -1,18 +1,23 @@
 package leakcanary
 
+import java.util.ServiceLoader
+
 /**
  * The interface for the implementation that [LeakAssertions.assertNoLeaks] delegates to.
  * You can call [DetectLeaksAssert.update] to provide your own implementation.
  *
- * The default implementation is [AndroidDetectLeaksAssert].
+ * The default implementation is [AndroidDetectLeaksAssert] or to a discoverable [DetectLeaksAssert]
+ * through the classpath at `META-INF/services/leakcanary.DetectLeaksAssert`.
  */
 fun interface DetectLeaksAssert {
 
   fun assertNoLeaks(tag: String)
 
   companion object {
     @Volatile
-    internal var delegate: DetectLeaksAssert = AndroidDetectLeaksAssert()
+    internal var delegate: DetectLeaksAssert =
+      ServiceLoader.load(DetectLeaksAssert::class.java).singleOrNull()
+        ?: AndroidDetectLeaksAssert()
 
     fun update(delegate: DetectLeaksAssert) {
       DetectLeaksAssert.delegate = delegate