Some more error handling when rendering the explore view (#361)

caravel/forms.py

@@ -112,11 +112,13 @@ class FormFactory(object):
         from caravel.viz import viz_types
         viz = self.viz
         datasource = viz.datasource
+        if not datasource.metrics_combo:
+            raise Exception("Please define at least one metric for your table")
         default_metric = datasource.metrics_combo[0][0]
 
         gb_cols = datasource.groupby_column_names
         default_groupby = gb_cols[0] if gb_cols else None
-        group_by_choices = [(s, s) for s in datasource.groupby_column_names]
+        group_by_choices = self.choicify(gb_cols)
         # Pool of all the fields that can be used in Caravel
         self.field_dict = {
             'viz_type': SelectField(

caravel/views.py

@@ -490,10 +490,14 @@ class Caravel(BaseView):
             return redirect(datasource.default_endpoint)
         if not viz_type:
             viz_type = "table"
-        obj = viz.viz_types[viz_type](
-            datasource,
-            form_data=request.args,
-            slice_=slc)
+        try:
+            obj = viz.viz_types[viz_type](
+                datasource,
+                form_data=request.args,
+                slice_=slc)
+        except Exception as e:
+            flash(str(e), "danger")
+            return redirect(error_redirect)
         if request.args.get("json") == "true":
             status = 200
             try: