Add test

packages/slate/src/editor/marks.ts

@@ -19,19 +19,26 @@ export const marks: EditorInterface['marks'] = (editor, options = {}) => {
   }
 
   if (Range.isExpanded(selection)) {
+    /**
+     * COMPAT: Make sure hanging ranges (caused by double clicking in Firefox)
+     * do not adversely affect the returned marks.
+     */
     const isEnd = Editor.isEnd(editor, anchor, anchor.path)
     if (isEnd) {
       const after = Editor.after(editor, anchor as Point)
-      // Editor.after() might return undefined
-      anchor = after || anchor
+      if (after) {
+        anchor = after
+      }
     }
+
     const [match] = Editor.nodes(editor, {
       match: Text.isText,
       at: {
         anchor,
         focus,
       },
     })
+
     if (match) {
       const [node] = match as NodeEntry<Text>
       const { text, ...rest } = node

packages/slate/test/interfaces/Editor/marks/firefox-double-click.tsx

@@ -0,0 +1,28 @@
+/** @jsx jsx */
+import { Editor } from 'slate'
+import { jsx } from '../../..'
+
+/**
+ * This test verifies that when double clicking a marked word in Firefox,
+ * Editor.marks for the resulting selection includes the marked word. Double
+ * clicking a marked word in Firefox results in a selection that starts at the
+ * end of the previous text node and ends at the end of the marked text node.
+ */
+
+export const input = (
+  <editor>
+    <block>
+      plain <anchor />
+      <text bold>
+        bold
+        <focus />
+      </text>
+      <text> plain</text>
+    </block>
+    <block>block two</block>
+  </editor>
+)
+export const test = editor => {
+  return Editor.marks(editor)
+}
+export const output = { bold: true }