Improved paste handling (#4474)

* Improved paste handling

* Remove file

shared/editor/lib/isMarkdown.ts

@@ -19,7 +19,7 @@ export default function isMarkdown(text: string): boolean {
   }
 
   // list-ish
-  const listItems = text.match(/^[\d-*].?\s\S+/gm);
+  const listItems = text.match(/^([-*]|\d+.)\s\S+/gm);
   if (listItems && listItems.length > 1) {
     return true;
   }

shared/editor/lib/markdown/normalize.ts

@@ -0,0 +1,22 @@
+/**
+ * Add support for additional syntax that users paste even though it isn't
+ * supported by the markdown parser directly by massaging the text content.
+ *
+ * @param text The incoming pasted plain text
+ */
+export default function normalizePastedMarkdown(text: string): string {
+  const CHECKBOX_REGEX = /^\s?(\[(X|\s|_|-)\]\s(.*)?)/gim;
+
+  // find checkboxes not contained in a list and wrap them in list items
+  while (text.match(CHECKBOX_REGEX)) {
+    text = text.replace(CHECKBOX_REGEX, (match) => `- ${match.trim()}`);
+  }
+
+  // find multiple newlines and insert a hard break to ensure they are respected
+  text = text.replace(/\n{3,}/g, "\n\n\\\n");
+
+  // find single newlines and insert an extra to ensure they are treated as paragraphs
+  text = text.replace(/\b\n\b/g, "\n\n");
+
+  return text;
+}