[FIX] [RUMS-5852] Android JS long task detection

packages/core/android/src/main/kotlin/com/datadog/reactnative/DdSdkImplementation.kt

@@ -30,7 +30,8 @@ class DdSdkImplementation(
     private val reactContext: ReactApplicationContext,
     private val datadog: DatadogWrapper = DatadogSDKWrapper(),
     private val ddTelemetry: DdTelemetry = DdTelemetry(),
-    private val uiThreadExecutor: UiThreadExecutor = ReactUiThreadExecutor()
+    private val uiThreadExecutor: UiThreadExecutor = ReactUiThreadExecutor(),
+    private val jsThreadExecutor: JsThreadExecutor = ReactJsThreadExecutor(reactContext)
 ) {
     internal val appContext: Context = reactContext.applicationContext
     internal val initialized = AtomicBoolean(false)
@@ -327,10 +328,8 @@ class DdSdkImplementation(
         ddSdkConfiguration: DdSdkConfiguration
     ): FrameRateProvider? {
         val frameTimeCallback = buildFrameTimeCallback(ddSdkConfiguration) ?: return null
-        val frameRateProvider = FrameRateProvider(frameTimeCallback, uiThreadExecutor)
-        reactContext.runOnJSQueueThread {
-            frameRateProvider.start()
-        }
+        val frameRateProvider = FrameRateProvider(frameTimeCallback, jsThreadExecutor)
+        frameRateProvider.start()
 
         return frameRateProvider
     }

packages/core/android/src/main/kotlin/com/datadog/reactnative/FrameRateProvider.kt

@@ -10,11 +10,11 @@ import android.view.Choreographer
 
 internal class FrameRateProvider(
     reactFrameRateCallback: ((Double) -> Unit),
-    uiThreadExecutor: UiThreadExecutor
+    jsThreadExecutor: JsThreadExecutor
 ) {
     private val frameCallback: FpsFrameCallback = FpsFrameCallback(
         reactFrameRateCallback,
-        uiThreadExecutor
+        jsThreadExecutor
     )
 
     fun start() {
@@ -29,7 +29,7 @@ internal class FrameRateProvider(
 
 internal class FpsFrameCallback(
     private val reactFrameRateCallback: ((Double) -> Unit),
-    private val uiThreadExecutor: UiThreadExecutor
+    private val jsThreadExecutor: JsThreadExecutor
 ) : Choreographer.FrameCallback {
 
     private var choreographer: Choreographer? = null
@@ -43,16 +43,24 @@ internal class FpsFrameCallback(
         choreographer?.postFrameCallback(this)
     }
 
+    @Suppress("SwallowedException")
     fun start() {
-        uiThreadExecutor.runOnUiThread {
-            choreographer = Choreographer.getInstance()
-            choreographer?.postFrameCallback(this@FpsFrameCallback)
+        // Choreographer is thread-local: we register on the JS thread so frame callbacks
+        // measure JS frame timings, matching the iOS CADisplayLink-on-JS-RunLoop approach.
+        jsThreadExecutor.runOnJsThread {
+            try {
+                val instance = Choreographer.getInstance()
+                instance.removeFrameCallback(this@FpsFrameCallback)
+                choreographer = instance
+                instance.postFrameCallback(this@FpsFrameCallback)
+            } catch (e: IllegalStateException) {
+                // Choreographer requires a Looper; guard defensively in case the JS thread lacks one.
+            }
         }
     }
 
     fun stop() {
-        uiThreadExecutor.runOnUiThread {
-            choreographer = Choreographer.getInstance()
+        jsThreadExecutor.runOnJsThread {
             choreographer?.removeFrameCallback(this@FpsFrameCallback)
         }
     }

packages/core/android/src/main/kotlin/com/datadog/reactnative/JsThreadExecutor.kt

@@ -0,0 +1,27 @@
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2016-Present Datadog, Inc.
+ */
+
+package com.datadog.reactnative
+
+import com.facebook.react.bridge.ReactApplicationContext
+
+/**
+ * Simple JS Thread Executor. By default it is based on [ReactApplicationContext.runOnJSQueueThread].
+ */
+interface JsThreadExecutor {
+    /**
+     * Runs the given runnable on the JS Thread.
+     */
+    fun runOnJsThread(runnable: Runnable)
+}
+
+internal class ReactJsThreadExecutor(
+    private val reactContext: ReactApplicationContext
+) : JsThreadExecutor {
+    override fun runOnJsThread(runnable: Runnable) {
+        reactContext.runOnJSQueueThread(runnable)
+    }
+}

packages/core/android/src/test/kotlin/com/datadog/reactnative/DdSdkTest.kt

@@ -37,6 +37,7 @@ import com.datadog.android.trace.TraceConfiguration
 import com.datadog.android.trace.TracingHeaderType
 import com.datadog.tools.unit.GenericAssert.Companion.assertThat
 import com.datadog.tools.unit.MockRumMonitor
+import com.datadog.tools.unit.TestJsThreadExecutor
 import com.datadog.tools.unit.TestUiThreadExecutor
 import com.datadog.tools.unit.forge.BaseConfigurator
 import com.datadog.tools.unit.setStaticValue
@@ -165,15 +166,12 @@ internal class DdSdkTest {
                 0
             )
         ) doReturn mockPackageInfo
-        whenever(mockReactContext.runOnJSQueueThread(any())).thenAnswer { answer ->
-            answer.getArgument<Runnable>(0).run()
-            true
-        }
         testedBridgeSdk = DdSdkImplementation(
             mockReactContext,
             mockDatadog,
             mockDdTelemetry,
-            TestUiThreadExecutor()
+            TestUiThreadExecutor(),
+            TestJsThreadExecutor()
         )
 
         DatadogSDKWrapperStorage.onInitializedListeners.clear()

packages/core/android/src/test/kotlin/com/datadog/tools/unit/TestJsThreadExecutor.kt

@@ -0,0 +1,16 @@
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2016-Present Datadog, Inc.
+ */
+
+package com.datadog.tools.unit
+
+import com.datadog.reactnative.JsThreadExecutor
+
+internal class TestJsThreadExecutor : JsThreadExecutor {
+    override fun runOnJsThread(runnable: Runnable) {
+        // Run immediately in the same thread for tests
+        runnable.run()
+    }
+}