tests: Add regression tests for character composition race

See: https://github.com/ether/etherpad-lite/issues/4978

src/tests/frontend/helper/multipleUsers.js

@@ -0,0 +1,147 @@
+'use strict';
+
+helper.multipleUsers = {
+  thisUser: null,
+  otherUser: null,
+
+  // open the same pad on different frames (allows concurrent editions to pad)
+  async init() {
+    // do some cleanup, in case any of the tests failed on the previous run
+    const currentToken = _createTokenForCurrentUser();
+    const otherToken = _createTokenForAnotherUser();
+    _removeExistingTokensFromCookie();
+
+    this.thisUser = {
+      $frame: $('#iframe-container iframe'),
+      token: currentToken,
+      // we'll switch between pads, need to store current values of helper.pad*
+      // to be able to restore those values later
+      padChrome$: helper.padChrome$,
+      padOuter$: helper.padOuter$,
+      padInner$: helper.padInner$,
+    };
+
+    this.otherUser = {
+      token: otherToken,
+    };
+
+    // need to perform as the other user, otherwise we'll get the userdup error message
+    await this.performAsOtherUser(this._createFrameForOtherUser.bind(this));
+  },
+
+  async performAsOtherUser(action) {
+    _startActingLike(this.otherUser);
+    await action();
+    // go back to initial state when we're done
+    _startActingLike(this.thisUser);
+  },
+
+  close() {
+    this.thisUser.$frame.attr('style', ''); // make the default ocopy the full height
+    this.otherUser.$frame.remove();
+  },
+
+  async _loadJQueryCodeForOtherFrame() {
+    const code = await $.get('/static/js/jquery.js');
+
+    // make sure we don't override existing jquery
+    const jQueryCode = `if(typeof $ === "undefined") {\n${code}\n}`;
+    const sendkeysCode = await $.get('/tests/frontend/lib/sendkeys.js');
+    const codesToLoad = [jQueryCode, sendkeysCode];
+
+    this.otherUser.padChrome$ = _getFrameJQuery(codesToLoad, this.otherUser.$frame);
+    this.otherUser.padOuter$ =
+        _getFrameJQuery(codesToLoad, this.otherUser.padChrome$('iframe[name="ace_outer"]'));
+    this.otherUser.padInner$ =
+        _getFrameJQuery(codesToLoad, this.otherUser.padOuter$('iframe[name="ace_inner"]'));
+
+    // update helper vars now that they are available
+    helper.padChrome$ = this.otherUser.padChrome$;
+    helper.padOuter$ = this.otherUser.padOuter$;
+    helper.padInner$ = this.otherUser.padInner$;
+  },
+
+  async _createFrameForOtherUser() {
+    // create the iframe
+    const padUrl = this.thisUser.$frame.attr('src');
+    this.otherUser.$frame = $(`<iframe id="other_pad" src="${padUrl}"></iframe>`);
+
+    // place one iframe (visually) below the other
+    this.thisUser.$frame.attr('style', 'height: 50%');
+    this.otherUser.$frame.attr('style', 'height: 50%; top: 50%');
+    this.otherUser.$frame.insertAfter(this.thisUser.$frame);
+
+    // wait for other pad to load
+    await new Promise((resolve) => this.otherUser.$frame.one('load', resolve));
+
+    const $editorLoadingMessage = this.otherUser.$frame.contents().find('#editorloadingbox');
+    const $errorMessageModal = this.thisUser.$frame.contents().find('#connectivity .userdup');
+
+    await helper.waitForPromise(() => {
+      const finishedLoadingOtherFrame = !$editorLoadingMessage.is(':visible');
+      // make sure we don't get the userdup by mistake
+      const didNotDetectUserDup = !$errorMessageModal.is(':visible');
+
+      return finishedLoadingOtherFrame && didNotDetectUserDup;
+    }, 50000);
+
+    // need to get values for this.otherUser.pad* vars
+    await this._loadJQueryCodeForOtherFrame();
+  },
+};
+
+// adapted form helper.js on Etherpad code
+const _getFrameJQuery = (codesToLoad, $iframe) => {
+  const win = $iframe[0].contentWindow;
+  const doc = win.document;
+
+  for (let i = 0; i < codesToLoad.length; i++) {
+    win.eval(codesToLoad[i]);
+  }
+
+  win.$.window = win;
+  win.$.document = doc;
+
+  return win.$;
+};
+
+const _getDocumentWithCookie = () => (
+  helper.padChrome$
+    ? helper.padChrome$.document
+    : helper.multipleUsers.thisUser.$frame.get(0).contentDocument
+);
+
+const _setTokenOnCookie = (token) => {
+  _getDocumentWithCookie().cookie = `token=${token};secure`;
+};
+
+const _getTokenFromCookie = () => {
+  const fullCookie = _getDocumentWithCookie().cookie;
+  return fullCookie.replace(/.*token=([^;]*).*/, '$1').trim();
+};
+
+const _createTokenForCurrentUser = () => (
+  _getTokenFromCookie().replace(/-other_user.*/g, '')
+);
+
+const _createTokenForAnotherUser = () => {
+  const currentToken = _createTokenForCurrentUser();
+  return `${currentToken}-other_user${helper.randomString(4)}`;
+};
+
+const _startActingLike = (user) => {
+  // update helper references, so other methods will act as if the main frame
+  // was the one we're using from now on
+  helper.padChrome$ = user.padChrome$;
+  helper.padOuter$ = user.padOuter$;
+  helper.padInner$ = user.padInner$;
+
+  _setTokenOnCookie(user.token);
+};
+
+const _removeExistingTokensFromCookie = () => {
+  // Expire cookie, to make sure it is removed by the browser.
+  // See https://developer.mozilla.org/en-US/docs/Web/API/Document/cookie#Example_4_Reset_the_previous_cookie
+  _getDocumentWithCookie().cookie = 'token=foo;expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/p';
+  _getDocumentWithCookie().cookie = 'token=foo;expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/';
+};