no-empty-url: check urls from definitions

Closes GH-299.

Reviewed-by: Titus Wormer <tituswormer@gmail.com>

Author: Xunnamius

packages/remark-lint-no-empty-url/index.js

@@ -26,18 +26,27 @@
  *
  *   ![charlie](http://delta.com/echo.png "foxtrot").
  *
+ *   [zulu][yankee].
+ *
+ *   [yankee]: http://xray.com
+ *
  * @example
  *   {"name": "not-ok.md", "label": "input"}
  *
  *   [golf]().
  *
  *   ![hotel]().
  *
+ *   [zulu][yankee].
+ *
+ *   [yankee]: <>
+ *
  * @example
  *   {"name": "not-ok.md", "label": "output"}
  *
  *   1:1-1:9: Don’t use links without URL
  *   3:1-3:11: Don’t use images without URL
+ *   7:1-7:13: Don’t use definitions without URL
  */
 
 /**
@@ -57,7 +66,9 @@ const remarkLintNoEmptyUrl = lintRule(
   (tree, file) => {
     visit(tree, (node) => {
       if (
-        (node.type === 'link' || node.type === 'image') &&
+        (node.type === 'link' ||
+          node.type === 'image' ||
+          node.type === 'definition') &&
         !generated(node) &&
         !node.url
       ) {

packages/remark-lint-no-empty-url/readme.md

@@ -136,6 +136,10 @@ It’s recommended to fill them out.
 [alpha](http://bravo.com).
 
 ![charlie](http://delta.com/echo.png "foxtrot").
+
+[zulu][yankee].
+
+[yankee]: http://xray.com
 ```
 
 ###### Out
@@ -150,13 +154,18 @@ No messages.
 [golf]().
 
 ![hotel]().
+
+[zulu][yankee].
+
+[yankee]: <>
 ```
 
 ###### Out
 
 ```text
 1:1-1:9: Don’t use links without URL
 3:1-3:11: Don’t use images without URL
+7:1-7:13: Don’t use definitions without URL
 ```
 
 ## Compatibility