Fix quadratic time on emphasis

close https://github.com/markdown-it/markdown-it/issues/735

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `[](url (xxx())` is no longer a valid link.
 - Fix performance issues when parsing links, #732, #734.
 - Fix performance issues when parsing backticks, #733.
+- Fix performance issues when parsing emphases, #735.
 
 
 ## [12.0.2] - 2020-10-23

lib/rules_inline/balance_pairs.js

@@ -27,17 +27,15 @@ function processDelimiters(state, delimiters) {
     }
 
     minOpenerIdx = openersBottom[closer.marker][closer.length % 3];
-    newMinOpenerIdx = -1;
 
     openerIdx = closerIdx - closer.jump - 1;
+    newMinOpenerIdx = openerIdx;
 
     for (; openerIdx > minOpenerIdx; openerIdx -= opener.jump + 1) {
       opener = delimiters[openerIdx];
 
       if (opener.marker !== closer.marker) continue;
 
-      if (newMinOpenerIdx === -1) newMinOpenerIdx = openerIdx;
-
       if (opener.open && opener.end < 0) {
 
         isOddMatch = false;

test/pathological.js

@@ -117,4 +117,10 @@ describe('Pathological sequences speed', () => {
       await test_pattern('[a](b'.repeat(30000));
     });
   });
+
+  describe('Markdown-it', () => {
+    it('emphasis **_* pattern', async () => {
+      await test_pattern('**_* '.repeat(50000));
+    });
+  });
 });