Throw errors when too many 'cursor' found in doc (#13339)

src/document/printer.js

@@ -294,6 +294,7 @@ function printDocToString(doc, options) {
   let shouldRemeasure = false;
   /** @type Command[] */
   const lineSuffix = [];
+  let printedCursorCount = 0;
 
   while (cmds.length > 0) {
     const { ind, mode, doc } = cmds.pop();
@@ -313,7 +314,11 @@ function printDocToString(doc, options) {
       }
 
       case DOC_TYPE_CURSOR:
+        if (printedCursorCount >= 2) {
+          throw new Error("There are too many 'cursor' in doc.");
+        }
         out.push(CURSOR_PLACEHOLDER);
+        printedCursorCount++;
         break;
 
       case DOC_TYPE_INDENT:

tests/unit/print-doc-to-string.js

@@ -0,0 +1,8 @@
+import { cursor } from "../../src/document/builders.js";
+import { printDocToString } from "../../src/document/printer.js";
+
+test("Should reject if too many cursor in doc", () => {
+  expect(() => {
+    printDocToString([cursor, cursor, cursor], { printWidth: 80, tabWidth: 2 });
+  }).toThrow({ message: "There are too many 'cursor' in doc." });
+});