Stop the empty login error box leaving a gap above the fields

app/src/androidTest/java/dev/wander/android/opentagviewer/AppleLoginFlowTest.java

@@ -9,6 +9,7 @@
 import static androidx.test.espresso.intent.Intents.intending;
 import static androidx.test.espresso.intent.matcher.IntentMatchers.hasComponent;
 import static androidx.test.espresso.matcher.ViewMatchers.isDisplayed;
+import static androidx.test.espresso.matcher.ViewMatchers.withEffectiveVisibility;
 import static androidx.test.espresso.matcher.ViewMatchers.withId;
 import static androidx.test.espresso.matcher.ViewMatchers.withText;
 import static androidx.test.platform.app.InstrumentationRegistry.getInstrumentation;
@@ -28,6 +29,7 @@
 import static androidx.test.espresso.intent.matcher.IntentMatchers.hasExtra;
 import static org.hamcrest.Matchers.allOf;
 import androidx.test.espresso.intent.Intents;
+import androidx.test.espresso.matcher.ViewMatchers;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import androidx.test.filters.LargeTest;
 
@@ -389,6 +391,26 @@ public void thelogButtonIsNotOfferedBeforeAnythingHasFailed() {
         onView(withId(R.id.login_error_export_logs)).check(matches(not(isDisplayed())));
     }
 
+    /**
+     * <b>The empty error box takes no room.</b>
+     *
+     * <p>It started as {@code invisible}, which hides a view but keeps its height, so before any
+     * failure there was a blank band between the title and the fields - one that grew when the
+     * Export logs button went inside the box, which is when somebody noticed. Asserted as
+     * {@code GONE} specifically, because {@code not(isDisplayed())} is equally true of an
+     * invisible view and would have passed against the gap.
+     */
+    @Test
+    public void theemptyErrorBoxTakesNoRoomBeforeAnythingHasFailed() {
+        this.apple = FakeAppleAuthService.rejectsTheSignIn("Bad password");
+        AppDependencies.replaceAuthService(this.apple);
+
+        launch();
+
+        onView(withId(R.id.login_error_container))
+                .check(matches(withEffectiveVisibility(ViewMatchers.Visibility.GONE)));
+    }
+
     /** A rejected code says so, and gives the boxes back rather than stranding them. */
     @Test
     public void aWrongCodeIsReportedAndTheBoxesComeBack() {

app/src/main/res/layout/activity_apple_login.xml

@@ -120,15 +120,22 @@
                 android:visibility="gone"
                 tools:visibility="gone">
 
+                <!--
+                    **`gone` until something fails, never `invisible`.** An invisible view still
+                    takes its full height, so the empty box sat between the title and the fields
+                    as a blank band - and grew when the Export logs button went inside it. The code
+                    only ever sets VISIBLE on a failure and GONE on success, so gone is also the
+                    state it was always meant to start in.
+                -->
                 <FrameLayout
                     android:id="@+id/login_error_container"
                     android:layout_width="match_parent"
-                    android:layout_height="match_parent"
+                    android:layout_height="wrap_content"
                     android:layout_marginTop="8dp"
                     android:layout_marginBottom="8dp"
                     android:background="@drawable/layout_rounded_less"
                     android:backgroundTint="?attr/colorErrorContainer"
-                    android:visibility="invisible"
+                    android:visibility="gone"
                     tools:visibility="visible">
 
                     <LinearLayout