fix: Improve patch merging of links in table cells (#12614)

* fix: Improve merging of links in table cells through patch

* PR feedback

server/commands/documentUpdater.test.ts

@@ -3,6 +3,7 @@ import * as Y from "yjs";
 import { TextEditMode } from "@shared/types";
 import { APIUpdateExtension } from "@server/collaboration/APIUpdateExtension";
 import { Event } from "@server/models";
+import { parser } from "@server/editor";
 import { DocumentHelper } from "@server/models/helpers/DocumentHelper";
 import { ProsemirrorHelper } from "@server/models/helpers/ProsemirrorHelper";
 import { buildDocument, buildUser } from "@server/test/factories";
@@ -1481,5 +1482,82 @@ describe("documentUpdater", () => {
         "Second item"
       );
     });
+
+    it("should apply a link when wrapping existing table cell text", async () => {
+      const user = await buildUser();
+      const document = await buildDocument({ teamId: user.teamId });
+
+      document.content = parser
+        .parse("| Name | Notes |\n|------|-------|\n| Alpha | see |\n")
+        .toJSON();
+      await document.save();
+
+      const result = DocumentHelper.applyMarkdownToDocument(
+        document,
+        "[see](https://example.com/docs)",
+        TextEditMode.Patch,
+        "see"
+      );
+
+      // The cell text is unchanged but should now carry a link mark — it must
+      // not be silently dropped during the merge.
+      const cellText =
+        result.content!.content![0].content![1].content![1].content![0]
+          .content![0];
+      expect(cellText.text).toEqual("see");
+      expect(cellText.marks).toEqual([
+        expect.objectContaining({
+          type: "link",
+          attrs: expect.objectContaining({ href: "https://example.com/docs" }),
+        }),
+      ]);
+    });
+
+    it("should preserve other table cells when adding a link to one cell", async () => {
+      const user = await buildUser();
+      const document = await buildDocument({ teamId: user.teamId });
+
+      document.content = parser
+        .parse(
+          "| Name | Notes |\n|------|-------|\n| Alpha | see |\n| Beta | other |\n"
+        )
+        .toJSON();
+      await document.save();
+
+      // Capture the untouched (Beta) row BEFORE patching so we can assert its
+      // structure and attrs are preserved exactly, not just its text.
+      const beforeDoc = DocumentHelper.toProsemirror(document).toJSON();
+      const untouchedRow = beforeDoc.content[0].content[2];
+
+      const result = DocumentHelper.applyMarkdownToDocument(
+        document,
+        "see [docs](https://example.com/d)",
+        TextEditMode.Patch,
+        "see"
+      );
+
+      // The patched cell gained the link
+      expect(result.text).toContain("[docs](https://example.com/d)");
+      // The untouched row node must remain identical
+      expect(result.content!.content![0].content![2]).toEqual(untouchedRow);
+    });
+
+    it("should apply a mark when wrapping existing list item text", async () => {
+      const user = await buildUser();
+      const document = await buildDocument({ teamId: user.teamId });
+
+      document.content = parser.parse("- clickme\n- other\n").toJSON();
+      await document.save();
+
+      const result = DocumentHelper.applyMarkdownToDocument(
+        document,
+        "[clickme](https://example.com)",
+        TextEditMode.Patch,
+        "clickme"
+      );
+
+      expect(result.text).toContain("[clickme](https://example.com)");
+      expect(result.text).toContain("other");
+    });
   });
 });

server/models/helpers/DocumentHelper.tsx

@@ -817,8 +817,18 @@ export class DocumentHelper {
       const textSame = oldChild.textContent === newChild.textContent;
 
       if (textSame && oldChild.sameMarkup(newChild)) {
-        // Fully unchanged — keep original with its rich content
-        merged.push(oldChild);
+        // Compare against the round-tripped baseline: when the
+        // updated child is identical to a plain round-trip of the original,
+        // the patch did not touch it
+        if (!rtChild || newChild.eq(rtChild)) {
+          merged.push(oldChild);
+        } else if (!oldChild.isTextblock && !oldChild.isLeaf) {
+          // Container child changed deeper down — recurse to preserve rich
+          // content in the parts that did not change.
+          merged.push(DocumentHelper.mergeNodes(oldChild, newChild, rtChild));
+        } else {
+          merged.push(newChild);
+        }
       } else if (textSame) {
         // Attrs changed (e.g. checked state) but content same — merge attrs
         // so that non-markdown-representable values (colwidth, highlight