Forbid nested reference links

lib/rules_inline/links.js

@@ -95,6 +95,9 @@ function links(state) {
     // Link reference
     //
 
+    // do not allow nested reference links
+    if (state.linkLevel > 0) { return false; }
+
     // [foo]  [bar]
     //      ^^ optional whitespace (can include newlines)
     for (; pos < max; pos++) {
@@ -147,7 +150,9 @@ function links(state) {
       title: title,
       level: state.level++
     });
+    state.linkLevel++;
     state.parser.tokenize(state);
+    state.linkLevel--;
     state.push({ type: 'link_close', level: --state.level });
   }
 

lib/rules_inline/state_inline.js

@@ -14,6 +14,7 @@ function StateInline(src, parser, options, env) {
   this.posMax = this.src.length;
   this.validateInsideEm = false;
   this.validateInsideLink = false;
+  this.linkLevel = 0;
   this.level = 0;
   this.link_content = '';
   this.pendingLevel = 0;

test/fixtures/stmd/bad.txt

@@ -1,20 +1,3 @@
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-src line: 5169
-
-.
-[[[foo]]]
-
-[[[foo]]]: /url1
-[foo]: /url2
-.
-<p><a href="/url1">[[foo]]</a></p>
-.
-
-error:
-
-<p><a href="/url1">[<a href="/url2">foo</a>]</a></p>
-
-
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 src line: 5248
 

test/fixtures/stmd/good.txt

@@ -4561,6 +4561,18 @@ src line: 5161
 <p><a href="/url">[[foo]]</a></p>
 .
 
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+src line: 5169
+
+.
+[[[foo]]]
+
+[[[foo]]]: /url1
+[foo]: /url2
+.
+<p><a href="/url1">[[foo]]</a></p>
+.
+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 src line: 5180