add dialogs for failed save/load

- failed validation doesn't prevent save/load,
  but the user is now warned about it.
- there is now a warning dialog if fromJSON fails,
  rather than the usual silent failure.

IPython/html/services/contents/filemanager.py

@@ -176,6 +176,7 b' class FileContentsManager(ContentsManager):'
         model['created'] = created
         model['content'] = None
         model['format'] = None
+        model['message'] = None
         return model
 
     def _dir_model(self, name, path='', content=True):
@@ -258,6 +259,7 b' class FileContentsManager(ContentsManager):'
             self.mark_trusted_cells(nb, name, path)
             model['content'] = nb
             model['format'] = 'json'
+            self.validate_notebook_model(model)
         return model
 
     def get_model(self, name, path='', content=True):
@@ -366,7 +368,14 b' class FileContentsManager(ContentsManager):'
         except Exception as e:
             raise web.HTTPError(400, u'Unexpected error while saving file: %s %s' % (os_path, e))
 
+        validation_message = None
+        if model['type'] == 'notebook':
+            self.validate_notebook_model(model)
+            validation_message = model.get('message', None)
+
         model = self.get_model(new_name, new_path, content=False)
+        if validation_message:
+            model['message'] = validation_message
         return model
 
     def update(self, model, name, path=''):

IPython/html/services/contents/manager.py

@@ -5,6 +5,7 b''
 
 from fnmatch import fnmatch
 import itertools
+import json
 import os
 
 from tornado.web import HTTPError
@@ -216,6 +217,16 b' class ContentsManager(LoggingConfigurable):'
                 break
         return name
 
+    def validate_notebook_model(self, model):
+        """Add failed-validation message to model"""
+        try:
+            current.validate(model['content'])
+        except current.ValidationError as e:
+            model['message'] = 'Notebook Validation failed: {}:\n{}'.format(
+                e.message, json.dumps(e.instance, indent=1, default=lambda obj: '<UNKNOWN>'),
+            )
+        return model
+
     def create_file(self, model=None, path='', ext='.ipynb'):
         """Create a new file or directory and return its model with no content."""
         path = path.strip('/')

IPython/html/static/notebook/js/notebook.js

@@ -1826,6 +1826,7 b' define(['
      * @param {Object} data JSON representation of a notebook
      */
     Notebook.prototype.fromJSON = function (data) {
+
         var content = data.content;
         var ncells = this.ncells();
         var i;
@@ -1975,6 +1976,7 b' define(['
             type : "PUT",
             data : JSON.stringify(model),
             headers : {'Content-Type': 'application/json'},
+            dataType : "json",
             success : $.proxy(this.save_notebook_success, this, start),
             error : $.proxy(this.save_notebook_error, this)
         };
@@ -2004,6 +2006,30 b' define(['
      */
     Notebook.prototype.save_notebook_success = function (start, data, status, xhr) {
         this.set_dirty(false);
+        if (data.message) {
+            // save succeeded, but validation failed.
+            var body = $("<div>");
+            var title = "Notebook validation failed";
+
+            body.append($("<p>").text(
+                "The save operation succeeded," +
+                " but the notebook does not appear to be valid." +
+                " The validation error was:"
+            )).append($("<div>").addClass("validation-error").append(
+                $("<pre>").text(data.message)
+            ));
+            dialog.modal({
+                notebook: this,
+                keyboard_manager: this.keyboard_manager,
+                title: title,
+                body: body,
+                buttons : {
+                    OK : {
+                        "class" : "btn-primary"
+                    }
+                }
+            });
+        }
         this.events.trigger('notebook_saved.Notebook');
         this._update_autosave_interval(start);
         if (this._checkpoint_after_save) {
@@ -2278,7 +2304,57 b' define(['
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.load_notebook_success = function (data, status, xhr) {
-        this.fromJSON(data);
+        var failed;
+        try {
+            this.fromJSON(data);
+        } catch (e) {
+            failed = e;
+            console.log("Notebook failed to load from JSON:", e);
+        }
+        if (failed || data.message) {
+            // *either* fromJSON failed or validation failed
+            var body = $("<div>");
+            var title;
+            if (failed) {
+                title = "Notebook failed to load";
+                body.append($("<p>").text(
+                    "The error was: "
+                )).append($("<div>").addClass("js-error").text(
+                    failed.toString()
+                )).append($("<p>").text(
+                    "See the error console for details."
+                ));
+            } else {
+                title = "Notebook validation failed";
+            }
+
+            if (data.message) {
+                var msg;
+                if (failed) {
+                    msg = "The notebook also failed validation:"
+                } else {
+                    msg = "An invalid notebook may not function properly." +
+                    " The validation error was:"
+                }
+                body.append($("<p>").text(
+                    msg
+                )).append($("<div>").addClass("validation-error").append(
+                    $("<pre>").text(data.message)
+                ));
+            }
+
+            dialog.modal({
+                notebook: this,
+                keyboard_manager: this.keyboard_manager,
+                title: title,
+                body: body,
+                buttons : {
+                    OK : {
+                        "class" : "btn-primary"
+                    }
+                }
+            });
+        }
         if (this.ncells() === 0) {
             this.insert_cell_below('code');
             this.edit_mode(0);