Issue #3563: Introduce StoreException for errors caught in Store/Reducer

components/browser/state/src/test/java/mozilla/components/browser/state/store/BrowserStoreExceptionTest.kt

@@ -7,11 +7,11 @@ package mozilla.components.browser.state.store
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import mozilla.components.browser.state.action.TabListAction
 import mozilla.components.browser.state.state.createTab
+import mozilla.components.lib.state.StoreException
 import mozilla.components.support.test.ext.joinBlocking
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.shadows.ShadowLooper
-import java.lang.IllegalStateException
 
 // These tests are in a separate class because they needs to run with
 // Robolectric (different runner, slower) while all other tests only
@@ -30,7 +30,7 @@ class BrowserStoreExceptionTest {
 
             // Wait for the main looper to process the re-thrown exception.
             ShadowLooper.idleMainLooper()
-        } catch (e: IllegalStateException) {
+        } catch (e: StoreException) {
             val cause = e.cause
             if (cause != null) {
                 throw cause

components/lib/state/src/main/java/mozilla/components/lib/state/Store.kt

@@ -48,7 +48,7 @@ open class Store<S : State, A : Action>(
         // We want exceptions in the reducer to crash the app and not get silently ignored. Therefore we rethrow the
         // exception on the main thread.
         Handler(Looper.getMainLooper()).postAtFrontOfQueue {
-            throw IllegalStateException("Exception while reducing state", throwable)
+            throw StoreException("Exception while reducing state", throwable)
         }
 
         // Once an exception happened we do not want to accept any further actions. So let's cancel the scope which
@@ -141,3 +141,9 @@ open class Store<S : State, A : Action>(
         }
     }
 }
+
+/**
+ * Exception for otherwise unhandled errors caught while reducing state or
+ * while managing/notifying observers.
+ */
+class StoreException(val msg: String, val e: Throwable? = null) : Exception(msg, e)

components/lib/state/src/test/java/mozilla/components/lib/state/StoreExceptionTest.kt

@@ -15,7 +15,7 @@ import org.robolectric.shadows.ShadowLooper
 class StoreExceptionTest {
     // This test is in a separate class because it needs to run with Robolectric (different runner, slower) while all
     // other tests only need a Java VM (fast).
-    @Test(expected = java.lang.IllegalStateException::class)
+    @Test(expected = StoreException::class)
     fun `Exception in reducer will be rethrown on main thread`() {
         val throwingReducer: (TestState, TestAction) -> TestState = { _, _ ->
             throw IllegalStateException("Not reducing today")