Return nulls from MultibindingWorkerFactory for non-existent Worker c…

…lasses instead of throwing exceptions (#96)

whetstone-worker/src/main/java/com/deliveryhero/whetstone/worker/MultibindingWorkerFactory.kt

@@ -1,6 +1,7 @@
 package com.deliveryhero.whetstone.worker
 
 import android.content.Context
+import androidx.annotation.RestrictTo
 import androidx.work.ListenableWorker
 import androidx.work.WorkerFactory
 import androidx.work.WorkerParameters
@@ -21,22 +22,32 @@ public class MultibindingWorkerFactory @Inject constructor(
         workerParameters: WorkerParameters
     ): ListenableWorker? {
         val workerComponent = workerComponentFactory.create(appContext, workerParameters)
-        val workerClass = loadClass(appContext.classLoader, workerClassName)
+        val workerClass = loadClass(appContext.classLoader, workerClassName) ?: return null
 
         return workerComponent.workerMap[workerClass]?.get()
     }
 
-    private companion object {
+    internal companion object {
 
         // Implementation adapted from androidx.fragment.app.FragmentFactory#loadClass
-        private val classCache: MutableMap<ClassLoader, MutableMap<String, Class<out ListenableWorker>>> = hashMapOf()
+        private val classCache: MutableMap<ClassLoader, MutableMap<String, Class<out ListenableWorker>>> =
+            hashMapOf()
 
-        @Throws(ClassNotFoundException::class)
-        private fun loadClass(classLoader: ClassLoader, className: String): Class<out ListenableWorker> {
+        @RestrictTo(RestrictTo.Scope.LIBRARY)
+        internal fun loadClass(
+            classLoader: ClassLoader,
+            className: String,
+        ): Class<out ListenableWorker>? {
             val classMap = classCache.getOrPut(classLoader) { hashMapOf() }
             return classMap.getOrPut(className) {
-                val rawClass = Class.forName(className, false, classLoader)
-                rawClass.asSubclass(ListenableWorker::class.java)
+                try {
+                    Class.forName(className, false, classLoader)
+                        .asSubclass(ListenableWorker::class.java)
+                } catch (e: ClassNotFoundException) {
+                    return null
+                } catch (e: ClassCastException) {
+                    return null
+                }
             }
         }
     }

whetstone-worker/src/test/java/com/deliveryhero/whetstone/worker/LoadClassTest.kt

@@ -0,0 +1,49 @@
+package com.deliveryhero.whetstone.worker
+
+import android.content.Context
+import androidx.work.Worker
+import androidx.work.WorkerParameters
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+internal class LoadClassTest {
+    @Test
+    fun `loadClass returns null for non-existing class`() {
+        val result = MultibindingWorkerFactory.loadClass(
+            this.javaClass.classLoader!!,
+            "non.existent.worker.Class"
+        )
+        assertNull(result)
+    }
+
+    @Test
+    fun `loadClass returns null for class which is not ListenableWorker subclass`() {
+        val result = MultibindingWorkerFactory.loadClass(
+            this.javaClass.classLoader!!,
+            "com.deliveryhero.whetstone.worker.LoadClassTest\$TestClass"
+        )
+        assertNull(result)
+    }
+
+    @Test
+    fun `loadClass returns class for existing classname`() {
+        val result = MultibindingWorkerFactory.loadClass(
+            this.javaClass.classLoader!!,
+            "com.deliveryhero.whetstone.worker.LoadClassTest\$TestWorker"
+        )
+        assertEquals(TestWorker::class.java, result)
+    }
+
+    private class TestWorker(
+        context: Context,
+        workerParams: WorkerParameters,
+    ) : Worker(context, workerParams) {
+        override fun doWork(): Result {
+            TODO("Not implemented")
+        }
+    }
+
+    @Suppress("unused")
+    private class TestClass
+}