Improvements in backspace behavior for list items (#8540)

Signed-off-by: Victor Ilyushchenko <alt13ri@gmail.com>

plugins/text-editor-resources/src/components/extension/listkeymap.ts

@@ -13,8 +13,10 @@
 // limitations under the License.
 //
 
-import { type Editor } from '@tiptap/core'
-import ListKeymap, { type ListKeymapOptions, listHelpers } from '@tiptap/extension-list-keymap'
+import { isAtStartOfNode, isNodeActive, type Editor } from '@tiptap/core'
+import ListKeymap, { listHelpers, type ListKeymapOptions } from '@tiptap/extension-list-keymap'
+import { type ResolvedPos, type Node } from '@tiptap/pm/model'
+import { type EditorState } from '@tiptap/pm/state'
 
 /**
  * Workaround for the original ListKeymap extension issue that
@@ -33,7 +35,7 @@ export const ListKeymapExtension = ListKeymap.extend<ListKeymapOptions>({
         if (editor.state.schema.nodes[itemName] === undefined) {
           return
         }
-        if (listHelpers.handleBackspace(editor, itemName, wrapperNames)) {
+        if (handleListItemBackspace(editor, itemName, wrapperNames)) {
           handled = true
         }
       })
@@ -86,3 +88,144 @@ export const ListKeymapExtension = ListKeymap.extend<ListKeymapOptions>({
     }
   }
 })
+
+export const handleListItemBackspace = (editor: Editor, name: string, parentListTypes: string[]): boolean => {
+  // this is required to still handle the undo handling
+  if (editor.commands.undoInputRule()) {
+    return true
+  }
+
+  // if the selection is not collapsed
+  // we can rely on the default backspace behavior
+  if (editor.state.selection.from !== editor.state.selection.to) {
+    return false
+  }
+
+  // if the current item is NOT inside a list item &
+  // the previous item is a list (orderedList or bulletList)
+  // move the cursor into the list and delete the current item
+  if (!isNodeActive(editor.state, name) && listHelpers.hasListBefore(editor.state, name, parentListTypes)) {
+    const { $anchor } = editor.state.selection
+
+    const $listPos = editor.state.doc.resolve($anchor.before() - 1)
+
+    const listDescendants: Array<{ node: Node, pos: number }> = []
+
+    $listPos.node().descendants((node, pos) => {
+      if (node.type.isInGroup('listItems')) {
+        listDescendants.push({ node, pos })
+      }
+    })
+
+    const lastItem = listDescendants.at(-1)
+
+    if (lastItem === undefined) {
+      return false
+    }
+
+    const $lastItemPos = editor.state.doc.resolve($listPos.start() + lastItem.pos + 1)
+
+    return editor
+      .chain()
+      .cut({ from: $anchor.start() - 1, to: $anchor.end() + 1 }, $lastItemPos.end())
+      .joinForward()
+      .run()
+  }
+
+  // if the cursor is not inside the current node type
+  // do nothing and proceed
+  if (!isNodeActive(editor.state, name)) {
+    return false
+  }
+
+  const $from = editor.state.selection.$from
+  const parentOffset = $from.depth > 0 ? $from.index($from.depth - 1) : 0
+
+  // if the cursor is not at the start of a node
+  // do nothing and proceed
+  if (!isAtStartOfNode(editor.state) || parentOffset > 0) {
+    return false
+  }
+
+  const listItemPos = findListItemPos(editor.state)
+  if (listItemPos === null) {
+    return false
+  }
+
+  const $prev = editor.state.doc.resolve(listItemPos.$pos.pos - 2)
+  const prevNode = $prev.node(listItemPos.depth)
+
+  const previousListItemHasSubList = listItemHasSubList(prevNode)
+
+  if (hasListItemBefore(editor.state)) {
+    // if the previous item is a list item and doesn't have a sublist, join the list items
+    if (!previousListItemHasSubList) {
+      return editor.commands.joinItemBackward()
+    } else {
+      return editor.chain().sinkListItem(name).joinItemBackward().run()
+    }
+  }
+
+  // otherwise in the end, a backspace should
+  // always just lift the list item if
+  // joining / merging is not possible
+  return editor.chain().liftListItem(name).run()
+}
+
+const findListItemPos = (state: EditorState): { $pos: ResolvedPos, depth: number } | null => {
+  const { $from } = state.selection
+
+  let currentNode = null
+  let currentDepth = $from.depth
+  let currentPos = $from.pos
+  let targetDepth: number | null = null
+
+  while (currentDepth > 0 && targetDepth === null) {
+    currentNode = $from.node(currentDepth)
+
+    if (currentNode.type.isInGroup('listItems')) {
+      targetDepth = currentDepth
+    } else {
+      currentDepth -= 1
+      currentPos -= 1
+    }
+  }
+
+  if (targetDepth === null) {
+    return null
+  }
+
+  return { $pos: state.doc.resolve(currentPos), depth: targetDepth }
+}
+
+const listItemHasSubList = (node?: Node): boolean => {
+  if (node === undefined) {
+    return false
+  }
+
+  let hasSubList = false
+
+  node.descendants((child) => {
+    if (child.type.isInGroup('listItems')) {
+      hasSubList = true
+    }
+  })
+
+  return hasSubList
+}
+
+const hasListItemBefore = (state: EditorState): boolean => {
+  const { $anchor } = state.selection
+
+  const $targetPos = state.doc.resolve($anchor.pos - 2)
+
+  if ($targetPos.index() === 0) {
+    return false
+  }
+
+  if (!($targetPos.nodeBefore?.type.isInGroup('listItems') ?? false)) {
+    return false
+  }
+
+  return true
+}