fix: unescape H1 markdown

__tests__/yaml-title.test.ts

@@ -374,5 +374,17 @@ ruleTest({
         # Hello world
       `,
     },
+    { // accounts for https://github.com/platers/obsidian-linter/issues/1428
+      testName: 'Unescapes H1 markdown special characters',
+      before: dedent`
+        # Escape \\[\\_\\]
+      `,
+      after: dedent`
+        ---
+        title: Escape [_]
+        ---
+        # Escape \\[\\_\\]
+      `,
+    },
   ],
 });

src/utils/regex.ts

@@ -1,5 +1,5 @@
 import {getAllTablesInText} from './mdast';
-import {makeSureContentHasEmptyLinesAddedBeforeAndAfter} from './strings';
+import {makeSureContentHasEmptyLinesAddedBeforeAndAfter, unescapeMarkdownSpecialCharacters} from './strings';
 
 // Useful regexes
 export const allHeadersRegex = /^([ \t]*)(#+)([ \t]+)([^\n\r]*?)([ \t]+#+)?$/gm;
@@ -123,7 +123,8 @@ export function getFirstHeaderOneText(text: string): string {
       return $2;
     });
 
-    return headerText.replaceAll(genericLinkRegex, '$2');
+    headerText = headerText.replaceAll(genericLinkRegex, '$2');
+    return unescapeMarkdownSpecialCharacters(headerText);
   }
 
   return '';

src/utils/strings.ts

@@ -535,3 +535,22 @@ export function parseCustomReplacements(text: string): Map<string, string> {
 
   return customReplacements;
 }
+
+/**
+ * Unescapes the markdown special characters in the provided text.
+ *
+ * @param {string} text - The text to unescape the markdown special characters in.
+ * @return {string} The text with the markdown special characters unescaped.
+ *
+ * @example
+ * ```ts
+ * unescapeMarkdownSpecialCharacters('Escape \\[\\_\\]'); // Escape [_]
+ * ```
+ */
+export function unescapeMarkdownSpecialCharacters(text: string): string {
+  return text.replace(/(\\+)([!"#$%&'()*+,-./:;<=>?@[\\\]^_`{|}~])/g, (_, backslashes, specialChar) => {
+    const backslashCount = backslashes.length;
+    const keepCount = Math.floor(backslashCount / 2);
+    return '\\'.repeat(keepCount) + specialChar;
+  });
+}