fix: escape markdown characters

Author: mnaoumov

__tests__/file-name-heading.test.ts

@@ -44,5 +44,16 @@ ruleTest({
         fileName: 'Test note',
       },
     },
+    { // accounts for https://github.com/platers/obsidian-linter/issues/1426
+      testName: 'Escapes the markdown special characters in the file name',
+      before: '',
+      after: dedent`
+        # Escape \\[\\_\\]
+        ${''}
+      `,
+      options: {
+        fileName: 'Escape [_]',
+      },
+    },
   ],
 });

src/rules/file-name-heading.ts

@@ -2,7 +2,7 @@ import {Options, rulesDict, RuleType} from '../rules';
 import RuleBuilder, {ExampleBuilder, OptionBuilderBase} from './rule-builder';
 import dedent from 'ts-dedent';
 import {IgnoreTypes} from '../utils/ignore-types';
-import {insert} from '../utils/strings';
+import {escapeMarkdownSpecialCharacters, insert} from '../utils/strings';
 import {App} from 'obsidian';
 import {BooleanOption} from '../option';
 import {ConfirmRuleDisableModal} from '../ui/modals/confirm-rule-disable-modal';
@@ -51,7 +51,7 @@ export default class FileNameHeading extends RuleBuilder<FileNameHeadingOptions>
     yaml_end =
         yaml_end == -1 || !text.startsWith('---\n') ? 0 : yaml_end + 5;
 
-    let header = `# ${fileName}\n`;
+    let header = `# ${escapeMarkdownSpecialCharacters(fileName)}\n`;
     if (text.length < yaml_end) {
       header = '\n' + header;
     }

src/utils/strings.ts

@@ -535,3 +535,18 @@ export function parseCustomReplacements(text: string): Map<string, string> {
 
   return customReplacements;
 }
+
+/**
+ * Escapes the markdown special characters in the provided text.
+ *
+ * @param text The text to escape the markdown special characters in.
+ * @return The text with the markdown special characters escaped.
+ *
+ * @example
+ * ```ts
+ * escapeMarkdownSpecialCharacters('Escape [_]'); // Escape \[\_\]
+ * ```
+ */
+export function escapeMarkdownSpecialCharacters(text: string): string {
+  return text.replace(/[\\[\]<>_*~=`$]/g, '\\$&');
+}