[lexical][lexical-clipboard] Bug Fix: Preserve alignment when pasting selected text

packages/lexical-clipboard/src/clipboard.ts

@@ -29,6 +29,7 @@ import {
   $getTextPointCaret,
   $isElementNode,
   $isRangeSelection,
+  $isRootNode,
   $isTextNode,
   $isTextPointCaret,
   $parseSerializedNode,
@@ -480,6 +481,40 @@ function exportNodeToJSON<T extends LexicalNode>(node: T): BaseSerializedNode {
   return serializedNode;
 }
 
+function $shouldIncludeElementWithSelectedChildren(
+  node: LexicalNode,
+  selection: BaseSelection | null,
+): boolean {
+  if (
+    !$isRangeSelection(selection) ||
+    !$isElementNode(node) ||
+    $isRootNode(node) ||
+    node.isInline()
+  ) {
+    return false;
+  }
+  const selectedNodes = selection.getNodes();
+  if (selectedNodes.length === 0) {
+    return false;
+  }
+  const selectedTextContent = selectedNodes
+    .filter(selectedNode => node.isParentOf(selectedNode))
+    .map(selectedNode => {
+      if ($isTextNode(selectedNode)) {
+        return $sliceSelectedTextNodeContent(
+          selection,
+          selectedNode,
+          'clone',
+        ).getTextContent();
+      }
+      return selectedNode.getTextContent();
+    })
+    .join('');
+  return (
+    selectedTextContent !== '' && selectedTextContent === node.getTextContent()
+  );
+}
+
 function $appendNodesToJSON(
   editor: LexicalEditor,
   selection: BaseSelection | null,
@@ -526,6 +561,11 @@ function $appendNodesToJSON(
 
   if (shouldInclude && !shouldExclude) {
     targetArray.push(serializedNode);
+  } else if (
+    !shouldExclude &&
+    $shouldIncludeElementWithSelectedChildren(currentNode, selection)
+  ) {
+    targetArray.push(serializedNode);
   } else if (Array.isArray(serializedNode.children)) {
     for (let i = 0; i < serializedNode.children.length; i++) {
       const serializedChildNode = serializedNode.children[i];

packages/lexical/src/__tests__/unit/HTMLCopyAndPaste.test.ts

@@ -6,10 +6,15 @@
  *
  */
 
-import {$insertDataTransferForRichText} from '@lexical/clipboard';
+import {
+  $getClipboardDataFromSelection,
+  $insertDataTransferForRichText,
+  setLexicalClipboardDataTransfer,
+} from '@lexical/clipboard';
 import {$patchStyleText} from '@lexical/selection';
 import {
   $createParagraphNode,
+  $createTextNode,
   $getRoot,
   $getSelection,
   $isRangeSelection,
@@ -143,6 +148,43 @@ describe('HTMLCopyAndPaste tests', () => {
         });
       });
 
+      test('preserves paragraph alignment when pasting into an unformatted paragraph', async () => {
+        const {editor} = testEnv;
+        const dataTransfer = new DataTransfer();
+
+        await editor.update(() => {
+          const root = $getRoot();
+          root.clear();
+          const text = $createTextNode('Centered');
+          const source = $createParagraphNode()
+            .setFormat('center')
+            .append(text);
+          const target = $createParagraphNode().append(
+            $createTextNode('Target'),
+          );
+          root.append(source, target);
+          text.select(0, text.getTextContentSize());
+
+          setLexicalClipboardDataTransfer(
+            dataTransfer,
+            $getClipboardDataFromSelection(),
+          );
+
+          target.select(0, target.getChildrenSize());
+
+          const selection = $getSelection();
+          invariant(
+            $isRangeSelection(selection),
+            'isRangeSelection(selection)',
+          );
+          $insertDataTransferForRichText(dataTransfer, selection, editor);
+        });
+
+        expect(testEnv.innerHTML).toBe(
+          '<p dir="auto" style="text-align: center;"><span data-lexical-text="true">Centered</span></p><p dir="auto" style="text-align: center;"><span data-lexical-text="true">Centered</span></p>',
+        );
+      });
+
       test('iOS fix: Word predictions should be handled as plain text to maintain selection formatting', async () => {
         const {editor} = testEnv;