Improve UX when maxUploadSize is reached in sheets

www/common/onlyoffice/inner.js

@@ -356,10 +356,32 @@ define([
             }
         };
 
+        Messages.oo_cantMigrate = "This sheet exceeds the maximum upload size and is too large to be migrated."; // XXX
         var onUploaded = function (ev, data, err) {
             content.saveLock = undefined;
             if (err) {
                 console.error(err);
+                if (content.saveLock === myOOId) { delete content.saveLock; } // Unlock checkpoints
+                if (APP.migrateModal) {
+                    try { getEditor().asc_setRestriction(true); } catch (e) {}
+                    setEditable(true);
+                    delete content.migration;
+                    APP.migrateModal.closeModal();
+                    APP.onLocal();
+                }
+                if (isLockedModal.modal && err === "TOO_LARGE") {
+                    if (APP.migrate) {
+                        UI.warn(Messages.oo_cantMigrate);
+                    }
+                    APP.cantCheckpoint = true;
+                    isLockedModal.modal.closeModal();
+                    delete isLockedModal.modal;
+                    if (content.saveLock === myOOId) {
+                        delete content.saveLock;
+                    }
+                    APP.onLocal();
+                    return;
+                }
                 return void UI.alert(Messages.oo_saveError);
             }
             // Get the last cp idx
@@ -453,6 +475,7 @@ define([
         };
 
         var saveToServer = function () {
+            if (APP.cantCheckpoint) { return; } // TOO_LARGE
             var text = getContent();
             var blob = new Blob([text], {type: 'plain/text'});
             var file = getFileType();
@@ -479,6 +502,8 @@ define([
         var noLogin = false;
 
         var makeCheckpoint = function (force) {
+            if (APP.cantCheckpoint) { return; } // TOO_LARGE
+
             var locked = content.saveLock;
             var lastCp = getLastCp();
 
@@ -1388,7 +1413,7 @@ define([
                                 h('span.fa.fa-spin.fa-spinner'),
                                 h('span', Messages.oo_sheetMigration_loading)
                             ]);
-                            UI.openCustomModal(UI.dialog.customModal(div, {buttons: []}));
+                            APP.migrateModal = UI.openCustomModal(UI.dialog.customModal(div, {buttons: []}));
                             makeCheckpoint(true);
                         });
                         // DEPRECATED: from version 3, the queue is sent again during init

www/common/sframe-common-file.js

@@ -133,6 +133,7 @@ define([
                 $pv.text(Messages.error);
                 queue.inProgress = false;
                 queue.next();
+                if (config.onError) { config.onError("TOO_LARGE"); }
                 return void UI.alert(Messages._getKey('upload_tooLargeBrief', [maxSizeStr]));
             }