undomodule: disallow undoing "clear authorship colors"

Clearing the authorship colors of a document with at least two authors, and then
undoing that action caused a disconnect from the pad.
This change disallows undoing clearing authorship colors in order to prevent
the problem from affecting users, and adds the relative test coverage.

This is a change of behaviour, and is documented in the changelog.

Fixes #2802 (sidestepping it).

src/locales/en.json

@@ -154,7 +154,7 @@
   "pad.userlist.guest": "Guest",
   "pad.userlist.deny": "Deny",
   "pad.userlist.approve": "Approve",
-  "pad.editbar.clearcolors": "Clear authorship colors on entire document?",
+  "pad.editbar.clearcolors": "Clear authorship colors on entire document? This cannot be undone",
 
   "pad.impexp.importbutton": "Import Now",
   "pad.impexp.importing": "Importing...",

src/locales/qqq.json

@@ -113,7 +113,7 @@
 	"pad.userlist.guest": "Preceded by the link text which is labeled {{msg-etherpadlite|Pad.userlist.approve}}.\n{{Identical|Guest}}",
 	"pad.userlist.deny": "Used as link text.\n\nFollowed by the link which is labeled {{msg-etherpadlite|Pad.userlist.approve}}.",
 	"pad.userlist.approve": "Used as link text.\n\nPreceded by the link which is labeled {{msg-etherpadlite|Pad.userlist.deny}}.\n\nFollowed by the message {{msg-etherpadlite|Pad.userlist.guest}}.\n{{Identical|Approve}}",
-	"pad.editbar.clearcolors": "Used as confirmation message (JavaScript <code>confirm()</code> function).\n\nThis message means \"Are you sure you want to clear authorship colors on entire document?\".",
+	"pad.editbar.clearcolors": "Used as confirmation message (JavaScript <code>confirm()</code> function).\n\nThis message means \"Are you sure you want to clear authorship colors on entire document? This cannot be undone\".",
 	"pad.impexp.importbutton": "Used as label for the Submit button.",
 	"pad.impexp.importing": "Used to indicate that the file is being imported.\n{{Identical|Importing}}",
 	"pad.impexp.confirmimport": "Used as confirmation message (JavaScript <code>confirm()</code> function).",

src/node/handler/PadMessageHandler.js

@@ -932,7 +932,7 @@ async function handleClientReady(client, message)
   await Promise.all(authors.map(authorId => {
     return authorManager.getAuthor(authorId).then(author => {
       if (!author) {
-        messageLogger.error("There is no author for authorId:", authorId);
+        messageLogger.error("There is no author for authorId: ", authorId, ". This is possibly related to https://github.com/ether/etherpad-lite/issues/2802");
       } else {
         historicalAuthorData[authorId] = { name: author.name, colorId: author.colorId }; // Filter author attribs (e.g. don't send author's pads to all clients)
       }

src/static/js/Changeset.js

@@ -791,6 +791,9 @@ exports.textLinesMutator = function (lines) {
         }
       } else {
         var sline = putCurLineInSplice();
+        if (!curSplice[sline]) {
+          console.error("curSplice[sline] not populated, actual curSplice contents is ", curSplice, ". Possibly related to https://github.com/ether/etherpad-lite/issues/2802");
+        }
         curSplice[sline] = curSplice[sline].substring(0, curCol) + text + curSplice[sline].substring(curCol);
         curCol += text.length;
       }

src/static/js/ace2_inner.js

@@ -292,6 +292,7 @@ function Ace2Inner(){
   {
     if ((typeof author) != "string")
     {
+      top.console.error("Going to throw new error, potentially caused by: https://github.com/ether/etherpad-lite/issues/2802");
       throw new Error("setAuthorInfo: author (" + author + ") is not a string");
     }
     if (!info)

src/static/js/undomodule.js

@@ -253,7 +253,15 @@ var undoModule = (function()
       }
       if (!merged)
       {
-        stack.pushEvent(event);
+        /*
+         * Push the event on the undo stack only if it exists, and if it's
+         * not a "clearauthorship". This disallows undoing the removal of the
+         * authorship colors, but is a necessary stopgap measure against
+         * https://github.com/ether/etherpad-lite/issues/2802
+         */
+        if (event && (event.eventType !== "clearauthorship")) {
+          stack.pushEvent(event);
+        }
       }
       undoPtr = 0;
     }