Handle invalid snippets

src/config.ts

@@ -66,6 +66,11 @@ interface ResolvedConfig extends BaseConfig {
      * new object.
      */
     cache?: Cache;
+
+    /**
+     * A callback for internal warnings or errors (for example, when parsing invalid abbreviation)
+     */
+    warn?: (message: string, err?: Error) => void
 }
 
 export type Config = ResolvedConfig & { options: Options };

src/markup/snippets.ts

@@ -15,6 +15,7 @@ import type { Config } from '../config.js';
 export default function resolveSnippets(abbr: Abbreviation, config: Config): Abbreviation {
     const stack: string[] = [];
     const reversed = config.options['output.reverseAttributes'];
+    const { warn } = config;
 
     const resolve = (child: AbbreviationNode): Abbreviation | null => {
         const snippet = child.name && config.snippets[child.name];
@@ -26,7 +27,15 @@ export default function resolveSnippets(abbr: Abbreviation, config: Config): Abb
             return null;
         }
 
-        const snippetAbbr = parse(snippet, config);
+        let snippetAbbr: Abbreviation;
+        try {
+            // User may add invlid snippet. In this case, silently bail out
+            snippetAbbr = parse(snippet, config);
+        } catch (err) {
+            warn?.(`Unable to parse "${snippet}" snippet`, err);
+            return null;
+        }
+
         stack.push(snippet);
         walkResolve(snippetAbbr, resolve, config);
         stack.pop();

test/snippets.ts

@@ -14,4 +14,14 @@ describe('Snippets', () => {
     it('XSL', () => {
         Object.keys(xsl).forEach(k => ok(markup(xsl[k]), k));
     });
+
+    it('Invalid snippets', () => {
+        const snippets = {
+            invalid: 'invalid snippet',
+            valid: 'button'
+        }
+
+        const result = expand('invalid+valid', { snippets })
+        equal(result, '<invalid></invalid>\n<button></button>')
+    });
 });