Say which views the sheet moved, so a mounting crash can be attributed

android/src/main/java/com/sheet2/AppFittedSheet.kt

@@ -211,6 +211,12 @@ open class AppFittedSheet(context: Context) : ViewGroup(context), LifecycleEvent
         isSystemUILight = isSystemUILight
       ) { dismissAll ->
         val parent = mHostView.parent as? ViewGroup
+        SheetTreeLog.log(
+          context,
+          "sheet.detachHost",
+          "host=${SheetTreeLog.tag(mHostView)} parent=${SheetTreeLog.tag(parent)}" +
+            " parentChildren=${SheetTreeLog.childTags(parent)}",
+        )
         parent?.removeViewAt(0)
         onSheetDismiss()
         if (dismissAll) {
@@ -262,6 +268,16 @@ open class AppFittedSheet(context: Context) : ViewGroup(context), LifecycleEvent
 
   override fun addView(child: View, index: Int) {
     UiThreadUtil.assertOnUiThread()
+    // An overlay child is kept out of mHostView while getChildCount keeps
+    // counting it, so from here on this view's children and React Native's idea
+    // of them are two different lists.
+    SheetTreeLog.log(
+      context,
+      "sheet.addView",
+      "child=${SheetTreeLog.tag(child)} index=$index self=${SheetTreeLog.tag(this)}" +
+        " hostChildren=${SheetTreeLog.childTags(mHostView)}" +
+        " inline=$useInlinePresentation",
+    )
     if (useInlinePresentation && index > 0) {
       inlineOverlayView = child
       inlinePresenter.setOverlayView(child)
@@ -289,6 +305,12 @@ open class AppFittedSheet(context: Context) : ViewGroup(context), LifecycleEvent
 
   override fun removeView(child: View) {
     UiThreadUtil.assertOnUiThread()
+    SheetTreeLog.log(
+      context,
+      "sheet.removeView",
+      "child=${SheetTreeLog.tag(child)} self=${SheetTreeLog.tag(this)}" +
+        " hostChildren=${SheetTreeLog.childTags(mHostView)}",
+    )
     if (child == inlineOverlayView) {
       inlineOverlayView = null
       inlinePresenter.setOverlayView(null)
@@ -304,6 +326,12 @@ open class AppFittedSheet(context: Context) : ViewGroup(context), LifecycleEvent
 
   override fun removeViewAt(index: Int) {
     UiThreadUtil.assertOnUiThread()
+    SheetTreeLog.log(
+      context,
+      "sheet.removeViewAt",
+      "index=$index self=${SheetTreeLog.tag(this)}" +
+        " hostChildren=${SheetTreeLog.childTags(mHostView)}",
+    )
     if (useInlinePresentation && index >= mHostView.childCount && inlineOverlayView != null) {
       inlineOverlayView = null
       inlinePresenter.setOverlayView(null)

android/src/main/java/com/sheet2/DialogRootViewGroup.kt

@@ -6,7 +6,6 @@ import android.graphics.Outline
 import android.os.Looper
 import android.view.View
 import android.view.ViewOutlineProvider
-import com.facebook.react.uimanager.PixelUtil.pxToDp
 import kotlin.math.max
 import kotlin.math.min
 
@@ -86,7 +85,6 @@ class DialogRootViewGroup(context: Context) : BaseRNView(context) {
     if (sheetMaxHeightSize == Float.MAX_VALUE) return
     val newHeight = allowedHeight
     val newWidth = allowedWidth
-    println("😀 DialogRootViewGroup.setVirtualHeight ${newHeight.pxToDp()} :${newWidth.pxToDp()}")
     ensureLayoutParams()
     layoutParams?.height = newHeight
     translationX = centeringTranslationX(newWidth)
@@ -105,19 +103,39 @@ class DialogRootViewGroup(context: Context) : BaseRNView(context) {
   }
 
   override fun addView(child: View, index: Int, params: LayoutParams) {
-    println("😀 DialogRootViewGroup.addView ${child.id}")
-    if (reactView != null) removeView(reactView)
+    // Dropping the previous child here is a removal React Native never hears
+    // about: it goes on counting that child, and its next insert lands at an
+    // index the group no longer has.
+    val replaced = reactView
+    SheetTreeLog.log(
+      context,
+      "host.addView",
+      "child=${SheetTreeLog.tag(child)} index=$index children=${SheetTreeLog.childTags(this)}" +
+        " replaces=${SheetTreeLog.tag(replaced)}",
+    )
+    if (replaced != null) removeView(replaced)
     super.addView(child, index, params)
     reactView = child
     setVirtualHeight(sheetMaxHeightSize)
   }
 
   override fun removeView(view: View?) {
+    SheetTreeLog.log(
+      context,
+      "host.removeView",
+      "child=${SheetTreeLog.tag(view)} children=${SheetTreeLog.childTags(this)}",
+    )
     if (view == reactView) releaseReactView()
     super.removeView(view)
   }
 
   override fun removeViewAt(index: Int) {
+    SheetTreeLog.log(
+      context,
+      "host.removeViewAt",
+      "index=$index child=${SheetTreeLog.tag(getChildAt(index))}" +
+        " children=${SheetTreeLog.childTags(this)}",
+    )
     if (getChildAt(index) === reactView) releaseReactView()
     super.removeViewAt(index)
   }

android/src/main/java/com/sheet2/FragmentModalBottomSheet.kt

@@ -84,7 +84,16 @@ class FragmentModalBottomSheet() : BottomSheetDialogFragment() {
     val view = overlayView ?: return
     val decorView = dialog?.window?.decorView as? ViewGroup ?: return
     detachOverlayHost()
-    (view.parent as? ViewGroup)?.removeView(view)
+    // Same as the inline presenter: the overlay is taken out of whatever parent
+    // React Native gave it and put into the dialog's own host.
+    val previousParent = view.parent as? ViewGroup
+    SheetTreeLog.log(
+      view.context,
+      "dialog.attachOverlay",
+      "overlay=${SheetTreeLog.tag(view)} from=${SheetTreeLog.tag(previousParent)}" +
+        " fromChildren=${SheetTreeLog.childTags(previousParent)}",
+    )
+    previousParent?.removeView(view)
 
     val host = DialogPassThroughFrameLayout(decorView.context).apply {
       layoutParams = ViewGroup.LayoutParams(

android/src/main/java/com/sheet2/InlineSheetPresenter.kt

@@ -169,7 +169,16 @@ internal class InlineSheetPresenter(
   private fun attachOverlayView() {
     val host = overlayHost ?: return
     val view = overlayView ?: return
-    (view.parent as? ViewGroup)?.removeView(view)
+    // Re-parenting a view React Native mounted somewhere else: its old parent
+    // loses a child without React Native being told.
+    val previousParent = view.parent as? ViewGroup
+    SheetTreeLog.log(
+      view.context,
+      "inline.attachOverlay",
+      "overlay=${SheetTreeLog.tag(view)} from=${SheetTreeLog.tag(previousParent)}" +
+        " fromChildren=${SheetTreeLog.childTags(previousParent)} to=${SheetTreeLog.tag(host)}",
+    )
+    previousParent?.removeView(view)
     view.layoutParams = FrameLayout.LayoutParams(
       FrameLayout.LayoutParams.MATCH_PARENT,
       FrameLayout.LayoutParams.MATCH_PARENT,

android/src/main/java/com/sheet2/SheetModule.kt

@@ -4,6 +4,7 @@ import android.view.ViewGroup
 import androidx.appcompat.app.AppCompatActivity
 import com.facebook.react.bridge.Arguments
 import com.facebook.react.bridge.ReactApplicationContext
+import com.facebook.react.bridge.WritableArray
 import com.facebook.react.bridge.WritableMap
 
 class SheetModule(reactContext: ReactApplicationContext) : NativeSheetSpec(reactContext) {
@@ -23,6 +24,12 @@ class SheetModule(reactContext: ReactApplicationContext) : NativeSheetSpec(react
     return Arguments.createMap()
   }
 
+  override fun getTreeLog(): WritableArray {
+    val entries = Arguments.createArray()
+    SheetTreeLog.snapshot().forEach { entries.pushString(it) }
+    return entries
+  }
+
   override fun dismissAll() {
     reactApplicationContext.runOnUiQueueThread {
       reactApplicationContext.currentActivity?.let { AppFittedSheet.Companion.dismissAll(it as AppCompatActivity) }

android/src/main/java/com/sheet2/SheetTreeLog.kt

@@ -0,0 +1,71 @@
+package com.sheet2
+
+import android.content.Context
+import android.util.Log
+import android.view.View
+import android.view.ViewGroup
+import com.facebook.react.bridge.ReactContext
+import com.facebook.react.modules.core.DeviceEventManagerModule
+
+/**
+ * Every place where this library moves a view React Native believes it owns.
+ *
+ * The mounting crashes worth chasing carry no frame of ours: on Android the
+ * stack between `ViewGroupManager.addView` and `ViewGroup.addInArray` is React
+ * Native and the framework only ("addViewAt: failed to insert view [child] into
+ * parent [parent] at index N", caused by "IndexOutOfBoundsException: index=N
+ * count=0"). So the only way to tell afterwards whether a sheet was involved is
+ * to say so ourselves, naming the views by the id React Native uses as the tag —
+ * which is exactly what that message carries.
+ *
+ * Entries go to logcat, to a small in-memory ring for a local session, and — when
+ * a listener is registered from JS — to the app, which is expected to turn them
+ * into breadcrumbs. Breadcrumbs are what survives into a native crash report.
+ */
+object SheetTreeLog {
+  private const val TAG = "Sheet2Tree"
+  private const val EVENT = "sheet2:tree"
+  private const val CAPACITY = 32
+
+  private val entries = ArrayDeque<String>()
+
+  fun log(context: Context?, op: String, details: String) {
+    val entry = "$op $details"
+
+    synchronized(entries) {
+      if (entries.size == CAPACITY) entries.removeFirst()
+      entries.addLast(entry)
+    }
+
+    Log.d(TAG, entry)
+    emit(context, entry)
+  }
+
+  /** The tag React Native knows the view by, or "-" when there is no view. */
+  fun tag(view: View?): String = view?.let { "${it.id}" } ?: "-"
+
+  fun childTags(parent: ViewGroup?): String {
+    if (parent == null) return "-"
+    val count = parent.childCount
+    if (count == 0) return "none"
+
+    return (0 until count).joinToString(",") { "${parent.getChildAt(it).id}" }
+  }
+
+  fun snapshot(): List<String> = synchronized(entries) { entries.toList() }
+
+  private fun emit(context: Context?, entry: String) {
+    val reactContext = context as? ReactContext ?: return
+    if (!reactContext.hasActiveReactInstance()) return
+
+    try {
+      reactContext
+        .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter::class.java)
+        .emit(EVENT, entry)
+    } catch (error: Throwable) {
+      // A sheet can be torn down while the instance is going away; diagnostics
+      // must never be the reason something crashes.
+      Log.d(TAG, "emit failed: ${error.message}")
+    }
+  }
+}

ios/HostFittedSheet.swift

@@ -133,7 +133,14 @@ public final class HostFittedSheet: UIView {
   }
 
   public override func insertReactSubview(_ subview: UIView!, at atIndex: Int) {
+    SheetTreeLog.log(
+      "sheet.insertReactSubview",
+      details: "child=\(SheetTreeLog.name(subview)) index=\(atIndex) self=\(SheetTreeLog.name(self))"
+        + " presented=\(_isPresented)"
+    )
     if atIndex > 0 {
+      // The overlay never becomes a subview of the content view React Native
+      // mounted it into.
       _overlaySubview = subview
       subview.isUserInteractionEnabled = false
       attachOverlaySubview()
@@ -148,6 +155,11 @@ public final class HostFittedSheet: UIView {
   }
 
   public override func removeReactSubview(_ subview: UIView!) {
+    SheetTreeLog.log(
+      "sheet.removeReactSubview",
+      details: "child=\(SheetTreeLog.name(subview)) self=\(SheetTreeLog.name(self))"
+        + " presented=\(_isPresented)"
+    )
     if let overlaySubview = _overlaySubview, subview === overlaySubview {
       _overlaySubview?.removeFromSuperview()
       _overlaySubview = nil
@@ -166,6 +178,12 @@ public final class HostFittedSheet: UIView {
     guard let overlaySubview = _overlaySubview,
           let sheetView = _modalViewController?.view else { return }
 
+    SheetTreeLog.log(
+      "sheet.attachOverlay",
+      details: "overlay=\(SheetTreeLog.name(overlaySubview))"
+        + " from=\(SheetTreeLog.name(overlaySubview.superview))"
+        + " to=\(SheetTreeLog.name(sheetView))"
+    )
     overlaySubview.removeFromSuperview()
     overlaySubview.frame = sheetView.bounds
     overlaySubview.autoresizingMask = [.flexibleWidth, .flexibleHeight]
@@ -416,6 +434,11 @@ public final class HostFittedSheet: UIView {
 
   @objc
   public func destroy() {
+    SheetTreeLog.log(
+      "sheet.destroy",
+      details: "self=\(SheetTreeLog.name(self)) content=\(SheetTreeLog.name(_reactSubview))"
+        + " overlay=\(SheetTreeLog.name(_overlaySubview)) presented=\(_isPresented)"
+    )
     if !_isPresented && _modalViewController == nil {
       return
     }

ios/SheetModule.mm

@@ -37,6 +37,10 @@ - (NSDictionary *)viewportSize {
   return dict;
 }
 
+- (NSArray<NSString *> *)getTreeLog {
+  return [SheetTreeLog snapshot];
+}
+
 - (void)dismiss:(NSInteger)tag {
   NSLog(@"😀 dismissModule %d", [[NSNumber alloc] initWithInt:tag].intValue);
 }

ios/SheetTreeLog.swift

@@ -0,0 +1,49 @@
+import Foundation
+import UIKit
+import os
+
+/**
+ Every place where this library moves a view React Native believes it owns —
+ the iOS half of the Android `SheetTreeLog`.
+
+ On iOS the crashes do carry our symbols (`HostFittedSheet.setFittedSheetParams`,
+ `dismissSheet` inside `RCTMountingManager.performTransaction`), so what is
+ missing there is not the name but the state: which subview was mounted, which
+ one was taken away, and whether the sheet was already being destroyed. That is
+ what these entries carry.
+
+ The trail lives in memory and in the unified log under the `com.sheet2`
+ subsystem; `getTreeLog()` on the Sheet module hands the last entries to JS.
+ */
+@objc public class SheetTreeLog: NSObject {
+  private static let capacity = 32
+  private static let lock = NSLock()
+  private static var entries: [String] = []
+  private static let osLog = OSLog(subsystem: "com.sheet2", category: "tree")
+
+  @objc public static func log(_ op: String, details: String) {
+    let entry = "\(op) \(details)"
+
+    lock.lock()
+    entries.append(entry)
+    if entries.count > capacity {
+      entries.removeFirst(entries.count - capacity)
+    }
+    lock.unlock()
+
+    os_log("%{public}@", log: osLog, type: .debug, entry)
+  }
+
+  @objc public static func snapshot() -> [String] {
+    lock.lock()
+    defer { lock.unlock() }
+    return entries
+  }
+
+  /// A view named the way a crash report names it: the React tag when the view
+  /// carries one, and the address, which is what an EXC_BAD_ACCESS points at.
+  @objc public static func name(_ view: UIView?) -> String {
+    guard let view else { return "-" }
+    return "tag=\(view.tag)/\(Unmanaged.passUnretained(view).toOpaque())"
+  }
+}

ios/SheetView.mm

@@ -135,6 +135,10 @@ - (void)updateProps:(Props::Shared const &)props oldProps:(Props::Shared const &
 }
 
 - (void)mountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index {
+  [SheetTreeLog log:@"host.mountChild"
+              details:[NSString stringWithFormat:@"child=%@ index=%ld host=%@",
+                                        [SheetTreeLog name:childComponentView], (long)index,
+                                        [SheetTreeLog name:_view2]]];
   [_view2 insertReactSubview:childComponentView atIndex:index];
 
   __weak SheetView *weakSelf = self;
@@ -150,10 +154,18 @@ - (void)mountChildComponentView:(UIView<RCTComponentViewProtocol> *)childCompone
 }
 
 - (void)unmountChildComponentView:(UIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index {
+  [SheetTreeLog log:@"host.unmountChild"
+              details:[NSString stringWithFormat:@"child=%@ index=%ld host=%@",
+                                        [SheetTreeLog name:childComponentView], (long)index,
+                                        [SheetTreeLog name:_view2]]];
   [_view2 removeReactSubview:childComponentView];
 }
 
 - (void)prepareForRecycle {
+  // The HostFittedSheet is thrown away and rebuilt here, so anything the
+  // mounting layer still holds from before this point is stale.
+  [SheetTreeLog log:@"host.prepareForRecycle"
+              details:[NSString stringWithFormat:@"host=%@", [SheetTreeLog name:_view2]]];
   [_view2 destroy];
   _view2.onSheetDismiss = nil;
 

package.json

@@ -4,7 +4,7 @@
     "example"
   ],
   "private": "true",
-  "version": "7.10.2",
+  "version": "7.11.0",
   "description": "Native implementation of Bottom sheet",
   "main": "src/index.tsx",
   "module": "src/index",