Merge "Ensure manually adding a fragment to the back stack fails" into androidx-main

Author: Treehugger Robot

navigation/navigation-fragment/src/androidTest/java/androidx/navigation/fragment/FragmentNavigatorTest.kt

@@ -53,6 +53,7 @@ import androidx.testutils.withActivity
 import androidx.testutils.withUse
 import com.google.common.truth.Truth.assertThat
 import com.google.common.truth.Truth.assertWithMessage
+import java.lang.IllegalArgumentException
 import java.util.concurrent.CountDownLatch
 import java.util.concurrent.TimeUnit
 import kotlin.reflect.KClass
@@ -555,7 +556,7 @@ class FragmentNavigatorTest {
 
     @UiThreadTest
     @Test
-    fun testNavigateAndAddIndependentFragment() {
+    fun testNavigationAndAddIndependentFragmentWithoutBackStack() {
         val entry = createBackStackEntry()
 
         fragmentNavigator.navigate(listOf(entry), null, null)
@@ -584,6 +585,42 @@ class FragmentNavigatorTest {
             .isEqualTo(independentFragment)
     }
 
+    @UiThreadTest
+    @Test
+    fun testNavigateAndAddIndependentFragmentWithBackStack() {
+        val entry = createBackStackEntry()
+
+        fragmentNavigator.navigate(listOf(entry), null, null)
+        assertThat(navigatorState.backStack.value)
+            .containsExactly(entry)
+        fragmentManager.executePendingTransactions()
+        val fragment = fragmentManager.findFragmentById(R.id.container)
+        assertWithMessage("Fragment should be added")
+            .that(fragment)
+            .isNotNull()
+        assertWithMessage("Fragment should be the correct type")
+            .that(fragment)
+            .isInstanceOf(EmptyFragment::class.java)
+        assertWithMessage("Fragment should be the primary navigation Fragment")
+            .that(fragmentManager.primaryNavigationFragment)
+            .isSameInstanceAs(fragment)
+
+        val independentFragment = EmptyFragment()
+        fragmentManager.beginTransaction()
+            .replace(R.id.container, independentFragment)
+            .addToBackStack(null)
+            .commit()
+        try {
+            fragmentManager.executePendingTransactions()
+        } catch (e: IllegalArgumentException) {
+            assertWithMessage("adding a fragment to the back stack manually should fail")
+                .that(e.message)
+                .contains("The fragment " + independentFragment + " is unknown to the " +
+                    "FragmentNavigator. Please use the navigate() function to add fragments to " +
+                    "the FragmentNavigator managed FragmentManager.")
+        }
+    }
+
     @LargeTest
     @UiThreadTest
     @Test

navigation/navigation-fragment/src/main/java/androidx/navigation/fragment/FragmentNavigator.kt

@@ -143,6 +143,13 @@ public open class FragmentNavigator(
                 val entry = (state.backStack.value + state.transitionsInProgress.value).lastOrNull {
                     it.id == fragment.tag
                 }
+                if (!pop) {
+                    requireNotNull(entry) {
+                        "The fragment " + fragment + " is unknown to the FragmentNavigator. " +
+                            "Please use the navigate() function to add fragments to the " +
+                            "FragmentNavigator managed FragmentManager."
+                    }
+                }
                 if (entry != null) {
                     // In case we get a fragment that was never attached to the fragment manager,
                     // we need to make sure we still return the entries to their proper final state.