Smarter redirect on slice creation

After ea8a7ec creating a slice
started redirecting to druid datasource from sqlalchemy tables.
That's quite painful for sqlalchemy tables users.
Instead of hardcoding a choice just query the db, if we don't
have any druid datasource fallback to sqlalchemy tables.
Bonus points we remove hacky javascript and make the message
translatable.

While at it fix druid client test to not hardcode datasource id.

caravel/views.py

@@ -520,7 +520,6 @@ class DruidClusterModelView(CaravelModelView, DeleteMixin):  # noqa
 
 class SliceModelView(CaravelModelView, DeleteMixin):  # noqa
     datamodel = SQLAInterface(models.Slice)
-    add_template = "caravel/add_slice.html"
     can_add = False
     label_columns = {
         'datasource_link': 'Datasource',
@@ -568,6 +567,28 @@ def pre_update(self, obj):
     def pre_delete(self, obj):
         check_ownership(obj)
 
+    @expose('/add', methods=['GET', 'POST'])
+    @has_access
+    def add(self):
+        widget = self._add()
+        if not widget:
+            return redirect(self.get_redirect())
+
+        a_druid_datasource = db.session.query(models.DruidDatasource).first()
+        if a_druid_datasource is not None:
+            url = "/druiddatasourcemodelview/list/"
+            msg = _(
+                "Click on a datasource link to create a Slice, "
+                "or click on a table link <a href='/tablemodelview/list/'>here</a> "
+                "to create a Slice for a table"
+            )
+        else:
+            url = "/tablemodelview/list/"
+            msg = _("Click on a table link to create a Slice")
+
+        redirect_url = "/r/msg/?url={}&msg={}".format(url, msg)
+        return redirect(redirect_url)
+
 appbuilder.add_view(
     SliceModelView,
     "Slices",

tests/core_tests.py

@@ -17,7 +17,7 @@
 
 import caravel
 from caravel import app, db, models, utils, appbuilder
-from caravel.models import DruidCluster
+from caravel.models import DruidCluster, DruidDatasource
 
 os.environ['CARAVEL_CONFIG'] = 'tests.caravel_test_config'
 
@@ -218,6 +218,27 @@ def test_add_slices(self, username='admin'):
         assert new_slice in dash.slices
         assert len(set(dash.slices)) == len(dash.slices)
 
+    def test_add_slice_redirect_to_sqla(self, username='admin'):
+        self.login(username=username)
+        url = '/slicemodelview/add'
+        resp = self.client.get(url, follow_redirects=True)
+        assert "Click on a table link to create a Slice" in resp.data.decode('utf-8')
+
+    def test_add_slice_redirect_to_druid(self, username='admin'):
+        datasource = DruidDatasource(
+            datasource_name="datasource_name",
+        )
+        db.session.add(datasource)
+        db.session.commit()
+
+        self.login(username=username)
+        url = '/slicemodelview/add'
+        resp = self.client.get(url, follow_redirects=True)
+        assert "Click on a datasource link to create a Slice" in resp.data.decode('utf-8')
+
+        db.session.delete(datasource)
+        db.session.commit()
+
     def test_gamma(self):
         self.login(username='gamma')
         resp = self.client.get('/slicemodelview/list/')
@@ -409,7 +430,7 @@ def test_client(self, PyDruid):
         instance.export_pandas.return_value = df
         instance.query_dict = {}
         instance.query_builder.last_query.query_dict = {}
-        resp = self.client.get('/caravel/explore/druid/1/?viz_type=table&granularity=one+day&druid_time_origin=&since=7+days+ago&until=now&row_limit=5000&include_search=false&metrics=count&groupby=name&flt_col_0=dim1&flt_op_0=in&flt_eq_0=&slice_id=&slice_name=&collapsed_fieldsets=&action=&datasource_name=test_datasource&datasource_id=1&datasource_type=druid&previous_viz_type=table&json=true&force=true')
+        resp = self.client.get('/caravel/explore/druid/{}/?viz_type=table&granularity=one+day&druid_time_origin=&since=7+days+ago&until=now&row_limit=5000&include_search=false&metrics=count&groupby=name&flt_col_0=dim1&flt_op_0=in&flt_eq_0=&slice_id=&slice_name=&collapsed_fieldsets=&action=&datasource_name=test_datasource&datasource_id={}&datasource_type=druid&previous_viz_type=table&json=true&force=true'.format(datasource_id, datasource_id))
         assert "Canada" in resp.data.decode('utf-8')