fix: Prevent duplicate of comment marks through copy/paste. closes #6263

shared/editor/marks/Comment.ts

@@ -1,5 +1,5 @@
 import { toggleMark } from "prosemirror-commands";
-import { MarkSpec, MarkType, Schema } from "prosemirror-model";
+import { MarkSpec, MarkType, Schema, Mark as PMMark } from "prosemirror-model";
 import { Command, Plugin } from "prosemirror-state";
 import { v4 as uuidv4 } from "uuid";
 import collapseSelection from "../commands/collapseSelection";
@@ -106,6 +106,45 @@ export default class Comment extends Mark {
   get plugins(): Plugin[] {
     return [
       new Plugin({
+        appendTransaction(transactions, oldState, newState) {
+          if (
+            !transactions.some(
+              (transaction) => transaction.getMeta("uiEvent") === "paste"
+            )
+          ) {
+            return;
+          }
+
+          // Record existing comment marks
+          const existingComments: PMMark[] = [];
+          oldState.doc.descendants((node) => {
+            node.marks.forEach((mark) => {
+              if (mark.type.name === "comment") {
+                existingComments.push(mark);
+              }
+            });
+            return true;
+          });
+
+          // Remove comment marks that are new duplicates of existing ones. This allows us to cut
+          // and paste a comment mark, but not copy and paste.
+          let tr = newState.tr;
+          newState.doc.descendants((node, pos) => {
+            node.marks.forEach((mark) => {
+              if (
+                mark.type.name === "comment" &&
+                existingComments.find((m) => m.attrs.id === mark.attrs.id) &&
+                !existingComments.find((m) => m === mark)
+              ) {
+                tr = tr.removeMark(pos, pos + node.nodeSize, mark.type);
+              }
+            });
+
+            return true;
+          });
+
+          return tr;
+        },
         props: {
           handleDOMEvents: {
             mouseup: (_view, event: MouseEvent) => {