Cherry Pick: [SuperEditor] Fix crashing when deleting all content whi…

…ch contains a non-deletable node at an edge (Resolves #2393) (#2405)

super_editor/lib/src/default_editor/common_editor_operations.dart

@@ -2,6 +2,7 @@ import 'dart:math';
 import 'dart:ui';
 
 import 'package:attributed_text/attributed_text.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:linkify/linkify.dart';
@@ -1381,13 +1382,15 @@ class CommonEditorOperations {
   /// Returns the [DocumentPosition] where the caret should sit after deleting
   /// the given [selection] from the given [document].
   ///
+  /// Returns `null` if there are no deletable nodes within the [selection].
+  ///
   /// This method doesn't delete any content. Instead, it determines what would
   /// be deleted if a delete operation was run for the given [selection]. Based
   /// on the shared understanding of content deletion rules, the resulting caret
   /// position is returned.
   // TODO: Move this method to an appropriate place. It was made public and static
   //       because document_keyboard_actions.dart also uses this behavior.
-  static DocumentPosition getDocumentPositionAfterExpandedDeletion({
+  static DocumentPosition? getDocumentPositionAfterExpandedDeletion({
     required Document document,
     required DocumentSelection selection,
   }) {
@@ -1419,15 +1422,32 @@ class CommonEditorOperations {
     final bottomNodePosition =
         baseNodeIndex < extentNodeIndex ? extentPosition.nodePosition : basePosition.nodePosition;
 
+    final normalizedRange = selection.normalize(document);
+    final nodes = document.getNodesInside(normalizedRange.start, normalizedRange.end);
+    final firstDeletableNodeId = nodes.firstWhereOrNull((node) => node.isDeletable)?.id;
+
     DocumentPosition newSelectionPosition;
 
     if (baseNodeIndex != extentNodeIndex) {
       if (topNodePosition == topNode.beginningPosition && bottomNodePosition == bottomNode.endPosition) {
-        // All nodes in the selection will be deleted. Assume that the start
-        // node will be retained and converted into a paragraph, if it's not
+        // All deletable nodes in the selection will be deleted. Assume that one of the
+        // nodes will be retained and converted into a paragraph, if it's not
         // already a paragraph.
+
+        final emptyParagraphId = topNode.isDeletable
+            ? topNode.id
+            : bottomNode.isDeletable
+                ? bottomNode.id
+                : firstDeletableNodeId;
+
+        if (emptyParagraphId == null) {
+          // There are no deletable nodes in the selection. Fizzle.
+          // We don't expect this method to be called if there are no deletable nodes.
+          return null;
+        }
+
         newSelectionPosition = DocumentPosition(
-          nodeId: topNode.id,
+          nodeId: emptyParagraphId,
           nodePosition: const TextNodePosition(offset: 0),
         );
       } else if (topNodePosition == topNode.beginningPosition) {
@@ -2277,7 +2297,7 @@ class CommonEditorOperations {
   /// moves the caret, it's possible that the clipboard content will be pasted
   /// at the wrong spot.
   void paste() {
-    DocumentPosition pastePosition = composer.selection!.extent;
+    DocumentPosition? pastePosition = composer.selection!.extent;
 
     // Start a transaction so that we can capture both the initial deletion behavior,
     // and the clipboard content insertion, all as one transaction.
@@ -2290,6 +2310,11 @@ class CommonEditorOperations {
         selection: composer.selection!,
       );
 
+      if (pastePosition == null) {
+        // There are no deletable nodes in the selection. Do nothing.
+        return;
+      }
+
       // Delete the selected content.
       editor.execute([
         DeleteContentRequest(documentRange: composer.selection!),

super_editor/lib/src/default_editor/multi_node_editing.dart

@@ -753,7 +753,10 @@ class DeleteContentCommand extends EditCommand {
     if (endNode == null) {
       throw Exception('Could not locate end node for DeleteSelectionCommand: ${normalizedRange.end}');
     }
-    final endNodeIndex = document.getNodeIndexById(endNode.id);
+
+    // We expect that this command will only be called when the delete range
+    // contains at least one deletable node.
+    final firstDeletableNodeId = nodes.firstWhere((node) => node.isDeletable).id;
 
     executor.logChanges(
       _deleteNodesBetweenFirstAndLast(
@@ -786,19 +789,40 @@ class DeleteContentCommand extends EditCommand {
       );
     }
 
+    final wereAllDeletableNodesInRangeDeleted = nodes.every(
+      (node) => document.getNodeById(node.id) == null || !node.isDeletable,
+    );
+    final hasNonDeletableNodesInRange = nodes.any((node) => !node.isDeletable);
+
     // If all selected nodes were deleted, e.g., the user selected from
     // the beginning of the first node to the end of the last node, then
     // we need insert an empty paragraph node so that there's a place
     // to position the caret.
-    if (document.getNodeById(startNode.id) == null && document.getNodeById(endNode.id) == null) {
-      final insertIndex = min(startNodeIndex, endNodeIndex);
+    if (wereAllDeletableNodesInRangeDeleted) {
+      // If there are any non-deletable nodes in the range, insert the new node
+      // after the last non-deletable node. Otherwise, insert the new node at
+      // the position where the first selected node was.
+      final insertIndex = hasNonDeletableNodesInRange //
+          ? document.getNodeIndexById(nodes.lastWhere((node) => !node.isDeletable).id) + 1
+          : startNodeIndex;
+
+      // If one of the edge nodes is deletable, we can use it as the ID for the
+      // new empty paragraph. Otherwise, use the ID of the first deletable node in the range.
+      // We expect that this method is never called when there are no deletable nodes
+      // in the range.
+      final emptyParagraphId = startNode.isDeletable
+          ? startNode.id
+          : endNode.isDeletable
+              ? endNode.id
+              : firstDeletableNodeId;
+
       document.insertNodeAt(
         insertIndex,
-        ParagraphNode(id: startNode.id, text: AttributedText()),
+        ParagraphNode(id: emptyParagraphId, text: AttributedText()),
       );
       executor.logChanges([
         DocumentEdit(
-          NodeChangeEvent(startNode.id),
+          NodeChangeEvent(emptyParagraphId),
         )
       ]);
     }
@@ -1144,12 +1168,12 @@ class DeleteSelectionCommand extends EditCommand {
       }
     }
 
-    final newSelectionPosition = CommonEditorOperations.getDocumentPositionAfterExpandedDeletion(
-      document: document,
-      selection: selection,
-    );
-
     final nodes = document.getNodesInside(selection.start, selection.end);
+    if (nodes.every((node) => !node.isDeletable)) {
+      // All selected nodes are non-deletable. Do nothing.
+      return;
+    }
+
     if (nodes.length == 2) {
       final normalizedSelection = selection.normalize(document);
       final nodeAbove = document.getNode(normalizedSelection.start)!;
@@ -1197,19 +1221,26 @@ class DeleteSelectionCommand extends EditCommand {
       }
     }
 
-    executor
-      ..executeCommand(
-        DeleteContentCommand(
-          documentRange: selection,
-        ),
-      )
-      ..executeCommand(
+    final newSelectionPosition = CommonEditorOperations.getDocumentPositionAfterExpandedDeletion(
+      document: document,
+      selection: selection,
+    );
+
+    executor.executeCommand(
+      DeleteContentCommand(
+        documentRange: selection,
+      ),
+    );
+
+    if (newSelectionPosition != null) {
+      executor.executeCommand(
         ChangeSelectionCommand(
           DocumentSelection.collapsed(position: newSelectionPosition),
           SelectionChangeType.deleteContent,
           SelectionReason.userInteraction,
         ),
       );
+    }
   }
 }