Revamping to matrix style

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

@@ -0,0 +1,21 @@
+/**
+ * @import {Options, State} from 'mdast-util-to-markdown'
+ */
+
+/**
+ * @param {State} state
+ * @returns {Exclude<Options['fence'], null | undefined>}
+ */
+export function checkFence(state) {
+  const marker = state.options.fence || '`'
+
+  if (marker !== '`' && marker !== '~') {
+    throw new Error(
+      'Cannot serialize code with `' +
+        marker +
+        '` for `options.fence`, expected `` ` `` or `~`'
+    )
+  }
+
+  return marker
+}