Update MD051/link-fragments to support indexing of repated headings.

demo/markdownlint-browser.js

@@ -4421,10 +4421,15 @@ module.exports = {
     "description": "Link fragments should be valid",
     "tags": ["links"],
     "function": function MD051(params, onError) {
-        var fragments = new Set();
+        var fragments = new Map();
         // Process headings
         forEachHeading(params, function (heading, content, inline) {
-            fragments.add(convertHeadingToHTMLFragment(inline));
+            var fragment = convertHeadingToHTMLFragment(inline);
+            var count = fragments.get(fragment) || 0;
+            if (count) {
+                fragments.set("".concat(fragment, "-").concat(count), 0);
+            }
+            fragments.set(fragment, count + 1);
         });
         // Process HTML anchors
         var processHtmlToken = function (token) {
@@ -4434,7 +4439,7 @@ module.exports = {
                 if (element.toLowerCase() === "a") {
                     var idMatch = identifierRe.exec(tag);
                     if (idMatch) {
-                        fragments.add("#".concat(idMatch[1]));
+                        fragments.set("#".concat(idMatch[1]), 0);
                     }
                 }
             }

lib/md051.js

@@ -37,10 +37,15 @@ module.exports = {
   "description": "Link fragments should be valid",
   "tags": [ "links" ],
   "function": function MD051(params, onError) {
-    const fragments = new Set();
+    const fragments = new Map();
     // Process headings
     forEachHeading(params, (heading, content, inline) => {
-      fragments.add(convertHeadingToHTMLFragment(inline));
+      const fragment = convertHeadingToHTMLFragment(inline);
+      const count = fragments.get(fragment) || 0;
+      if (count) {
+        fragments.set(`${fragment}-${count}`, 0);
+      }
+      fragments.set(fragment, count + 1);
     });
     // Process HTML anchors
     const processHtmlToken = (token) => {
@@ -50,7 +55,7 @@ module.exports = {
         if (element.toLowerCase() === "a") {
           const idMatch = identifierRe.exec(tag);
           if (idMatch) {
-            fragments.add(`#${idMatch[1]}`);
+            fragments.set(`#${idMatch[1]}`, 0);
           }
         }
       }

test/link-fragments.md

@@ -26,6 +26,12 @@
 
 [Valid](#valid-setext-heading)
 
+[Valid](#valid-repeated-heading)
+
+[Valid](#valid-repeated-heading-1)
+
+[Valid](#valid-repeated-heading-2)
+
 [Valid](#namedlink)
 
 [Valid](#idlink)
@@ -77,6 +83,16 @@ Valid Setext Heading
 
 Text
 
+### Valid Repeated Heading
+
+Text
+
+### Valid Repeated Heading
+
+Text
+
+### Valid Repeated Heading
+
 <a name="namedlink"></a>
 
 <a id = idlink></a>
@@ -89,7 +105,9 @@ Text
 
 ## Invalid Fragments
 
-[Inalid](#valid-heading-2004-) {MD051}
+[Invalid](#valid-heading-2004-) {MD051}
+
+[Invalid](#valid-repeated-heading-3) {MD051}
 
 [Invalid](#invalid-fragment) {MD051}
 
@@ -104,5 +122,6 @@ Text
 <!-- markdownlint-configure-file {
   "emphasis-style": false,
   "heading-style": false,
+  "no-duplicate-heading": false,
   "no-inline-html": false
 } -->