fix(editor): support more divider markdown shortcut (#10139)

blocksuite/affine/shared/src/utils/string.ts

@@ -76,10 +76,32 @@ export function substringMatchScore(name: string, query: string) {
 
 /**
  * Checks if the prefix is a markdown prefix.
- * Ex. 1. 2. 3. - * [] [ ] [x] # ## ### #### ##### ###### --- *** > ```
+ * Ex. 1. 2. 3. - * [] [ ] [x] # ## ### #### ##### ###### --- *** ___ > ```
  */
 export function isMarkdownPrefix(prefix: string) {
-  return !!prefix.match(
-    /^(\d+\.|-|\*|\[ ?\]|\[x\]|(#){1,6}|(-){3}|(\*){3}|>|```([a-zA-Z0-9]*))$/
+  return (
+    !!prefix.match(
+      /^(\d+\.|-|\*|\[ ?\]|\[x\]|(#){1,6}|>|```([a-zA-Z0-9]*))$/
+    ) || isHorizontalRuleMarkdown(prefix)
   );
 }
+
+/**
+ * Checks if the prefix is a valid markdown horizontal rule - https://www.markdownguide.org/basic-syntax/#horizontal-rules
+ * @param prefix - The string to check for horizontal rule syntax
+ * @returns boolean - True if the string represents a valid horizontal rule
+ *
+ * Valid horizontal rules:
+ * - Three or more consecutive hyphens (e.g., "---", "----")
+ * - Three or more consecutive asterisks (e.g., "***", "****")
+ * - Three or more consecutive underscores (e.g., "___", "____")
+ *
+ * Invalid examples:
+ * - Mixed characters (e.g., "--*", "-*-")
+ * - Less than three characters (e.g., "--", "**")
+ */
+export function isHorizontalRuleMarkdown(prefix: string) {
+  const horizontalRulePattern = /^(-{3,}|\*{3,}|_{3,})$/;
+
+  return !!prefix.match(horizontalRulePattern);
+}