planning

node_modules/mdast-util-to-markdown/lib/util/check-rule.js

@@ -0,0 +1,15 @@
+module.exports = checkRule
+
+function checkRule(context) {
+  var marker = context.options.rule || '*'
+
+  if (marker !== '*' && marker !== '-' && marker !== '_') {
+    throw new Error(
+      'Cannot serialize rules with `' +
+        marker +
+        '` for `options.rule`, expected `*`, `-`, or `_`'
+    )
+  }
+
+  return marker
+}