[test262] Strip codeframes from Forget errors so results are grouped

correctly

compiler/forget/scripts/test262-preprocessor.js

@@ -13,6 +13,7 @@ module.exports = (test) => {
     message = message.replace(/^\/.*?:\s/, ""); // babel seems to output filenames
     message = message.split(/\(\d+:\d+\)/)[0]; // some errors report line numbers and codeframes
     message = message.trim();
+    message = formatReactForgetErrorMessage(message);
 
     // For unknown reasons I don't have the energy to dig into some Babel error instances can't be
     // written to, so we construct a psedudo object here so the correctly formatted error messages
@@ -26,3 +27,12 @@ module.exports = (test) => {
 
   return test;
 };
+
+function formatReactForgetErrorMessage(message) {
+  // Strip codeframes so we can group errors
+  const matches = message.match(/^\[ReactForget\].*\n?/);
+  if (Array.isArray(matches) && matches.length > 0) {
+    return matches[0].replace("\n", "");
+  }
+  return message;
+}