Fixup some failing tests

redwood-layout-shared-test/src/jvmMain/kotlin/app/cash/redwood/layout/AbstractFlexContainerTest.kt

@@ -52,6 +52,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     val flexDirection = flexDirectionEnum.value
     val container = flexContainer(flexDirection)
     container.crossAxisAlignment(CrossAxisAlignment.Start)
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -68,6 +69,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     container.width(width)
     container.height(height)
     container.add(widget(movies.first()))
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -81,6 +83,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     movies.take(5).forEach { movie ->
       container.add(widget(movie))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -94,6 +97,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     movies.forEach { movie ->
       container.add(widget(movie))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -115,6 +119,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
       }
       container.add(widget(movie, modifier))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -132,6 +137,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     movies.forEach { movie ->
       container.add(widget(movie))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -144,6 +150,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     movies.forEach { movie ->
       container.add(widget(movie))
     }
+    container.onEndChanges()
     verifySnapshot(container, "Center")
     container.crossAxisAlignment(CrossAxisAlignment.End)
     container.onEndChanges()
@@ -163,6 +170,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     movies.forEach { movie ->
       container.add(widget(movie))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -174,6 +182,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     repeat(10) { index ->
       container.add(widget("$index", WidthImpl(50.dp)))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -185,6 +194,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     repeat(10) { index ->
       container.add(widget("$index", HeightImpl(50.dp)))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -196,6 +206,7 @@ abstract class AbstractFlexContainerTest<T : Any> {
     repeat(10) { index ->
       container.add(widget("$index", SizeImpl(50.dp, 50.dp)))
     }
+    container.onEndChanges()
     verifySnapshot(container)
   }
 
@@ -206,8 +217,10 @@ abstract class AbstractFlexContainerTest<T : Any> {
     container.crossAxisAlignment(CrossAxisAlignment.Start)
     val widget = widget("")
     container.add(widget)
+    container.onEndChanges()
     verifySnapshot(container, "initial")
     widget.text(movies.first())
+    container.onEndChanges()
     verifySnapshot(container, "updated")
   }
 }

redwood-lazylayout-view/src/main/kotlin/app/cash/redwood/lazylayout/view/ViewLazyList.kt

@@ -138,7 +138,12 @@ internal open class ViewLazyList private constructor(
 
   override fun crossAxisAlignment(crossAxisAlignment: CrossAxisAlignment) {
     this.crossAxisAlignment = crossAxisAlignment
-    adapter.notifyItemRangeChanged(0, processor.size)
+
+    // Layout params are invalid when crossAxisAlignment changes.
+    for (binding in processor.bindings) {
+      val view = binding.view ?: continue
+      view.content?.value?.layoutParams = createLayoutParams()
+    }
   }
 
   override fun onViewportChanged(onViewportChanged: (Int, Int) -> Unit) {

redwood-lazylayout-view/src/test/kotlin/app/cash/redwood/lazylayout/view/ViewLazyListTest.kt

@@ -28,6 +28,7 @@ import app.cash.redwood.layout.TestFlexContainer
 import app.cash.redwood.layout.Text
 import app.cash.redwood.layout.api.MainAxisAlignment
 import app.cash.redwood.lazylayout.widget.LazyList
+import app.cash.redwood.widget.ChangeListener
 import app.cash.redwood.widget.Widget
 import app.cash.redwood.yoga.FlexDirection
 import com.android.resources.LayoutDirection
@@ -70,7 +71,7 @@ class ViewLazyListTest(
 
   class ViewTestFlexContainer private constructor(
     private val delegate: ViewLazyList,
-  ) : TestFlexContainer<View>, LazyList<View> by delegate {
+  ) : TestFlexContainer<View>, LazyList<View> by delegate, ChangeListener {
     private var childCount = 0
 
     constructor(context: Context, direction: FlexDirection) : this(
@@ -88,6 +89,7 @@ class ViewLazyListTest(
     }
 
     override fun onEndChanges() {
+      delegate.onEndChanges()
     }
   }
 }

redwood-lazylayout-widget/src/commonMain/kotlin/app/cash/redwood/lazylayout/widget/LazyListUpdateProcessor.kt

@@ -38,6 +38,9 @@ import app.cash.redwood.widget.Widget
  */
 public abstract class LazyListUpdateProcessor<V : BoundView<W>, W : Any> {
 
+  public val bindings: List<Binding<V, W>>
+    get() = itemsBefore.nonNullElements + loadedItems + itemsAfter.nonNullElements
+
   /** Pool of placeholder widgets. */
   private val placeholdersQueue = ArrayDeque<Widget<W>>()
 
@@ -342,9 +345,14 @@ public abstract class LazyListUpdateProcessor<V : BoundView<W>, W : Any> {
     internal val processor: LazyListUpdateProcessor<V, W>,
     internal var isPlaceholder: Boolean = false,
   ) {
-    internal var view: V? = null
+    /** The currently-bound view. Null if this is not on-screen. */
+    public var view: V? = null
       private set
 
+    /**
+     * The currently-bound content. This should be `lateinit`, but it can't be because of the
+     * side-effect in set().
+     */
     internal var content: Widget<W>? = null
       set(value) {
         field = value

redwood-lazylayout-widget/src/commonMain/kotlin/app/cash/redwood/lazylayout/widget/SparseList.kt

@@ -17,7 +17,7 @@ package app.cash.redwood.lazylayout.widget
 
 internal class SparseList<T> : AbstractList<T?>() {
   /** The non-null elements of this sparse list. */
-  private val elements = mutableListOf<T>()
+  private val elements = mutableListOf<T & Any>()
 
   /**
    * This contains the external indexes of the values in [elements]. The last element is the size of
@@ -37,6 +37,10 @@ internal class SparseList<T> : AbstractList<T?>() {
   override val size: Int
     get() = externalIndexes.last()
 
+  /** Returns a snapshot of the non-null elements in this list. */
+  val nonNullElements: List<T & Any>
+    get() = elements.toList()
+
   override fun get(index: Int): T? {
     require(index in 0 until size)
     val internalIndex = externalIndexes.binarySearch(index)

redwood-lazylayout-widget/src/commonTest/kotlin/app/cash/redwood/lazylayout/widget/SparseListTest.kt

@@ -17,6 +17,7 @@ package app.cash.redwood.lazylayout.widget
 
 import assertk.assertThat
 import assertk.assertions.containsExactly
+import assertk.assertions.isEmpty
 import assertk.assertions.isEqualTo
 import kotlin.test.Test
 
@@ -291,4 +292,41 @@ class SparseListTest {
     assertThat(list.size).isEqualTo(2)
     assertThat(list.toList()).containsExactly(null, "C")
   }
+
+  @Test
+  fun nonNullElements() {
+    val list = SparseList<String?>()
+    assertThat(list.nonNullElements).isEmpty()
+
+    list.add(null)
+    assertThat(list.nonNullElements).isEmpty()
+
+    list.add("A")
+    val a = list.nonNullElements
+    assertThat(a).containsExactly("A")
+
+    list.add(null)
+    assertThat(list.nonNullElements).containsExactly("A")
+
+    list.add("B")
+    assertThat(list.nonNullElements).containsExactly("A", "B")
+    assertThat(a).containsExactly("A") // Confirm each access returns a snapshot.
+  }
+
+  @Test
+  fun getOrCreateCreates() {
+    val list = SparseList<String?>()
+    list.addNulls(0, 10)
+
+    assertThat(list.getOrCreate(3) { "A" }).isEqualTo("A")
+    assertThat(list[3]).isEqualTo("A")
+  }
+
+  @Test
+  fun getOrCreateGets() {
+    val list = SparseList<String?>()
+    list.addNulls(0, 10)
+    list.set(3, "A")
+    assertThat(list.getOrCreate(3) { error("boom") }).isEqualTo("A")
+  }
 }