Use synchronous ajax to load data in GeoJson (#1353)

* Use synchronous ajax in GeoJson

* Add test case

Author: Conengmo

folium/features.py

@@ -428,17 +428,20 @@ class GeoJson(Layer):
             {% if this.style %}
                 style: {{ this.get_name() }}_styler,
             {%- endif %}
-        }).addTo({{ this._parent.get_name() }});
+        });
 
         function {{ this.get_name() }}_add (data) {
-            {{ this.get_name() }}.addData(data);
+            {{ this.get_name() }}
+                .addData(data)
+                .addTo({{ this._parent.get_name() }});
         }
         {%- if this.embed %}
             {{ this.get_name() }}_add({{ this.data|tojson }});
         {%- else %}
-            $.ajax({{ this.embed_link|tojson }}, {dataType: 'json'})
+            $.ajax({{ this.embed_link|tojson }}, {dataType: 'json', async: false})
                 .done({{ this.get_name() }}_add);
         {%- endif %}
+
         {% endmacro %}
         """)  # noqa
 

tests/selenium/test_geojson_selenium.py

@@ -0,0 +1,36 @@
+import folium
+import folium.plugins
+from folium.utilities import temp_html_filepath
+
+
+def test_geojson(driver):
+    """Verify that loading data in GeoJson works well for different use cases.
+
+    Prevent two regressions:
+    - https://github.com/python-visualization/folium/pull/1190
+    - https://github.com/python-visualization/folium/pull/1289
+
+    """
+    data_url = 'https://cdn.jsdelivr.net/gh/python-visualization/folium@master/examples/data/search_bars_rome.json'
+
+    m = folium.Map((41.9, 12.5), zoom_start=10, tiles='cartodbpositron')
+    marker_cluster = folium.plugins.MarkerCluster(name='cluster').add_to(m)
+    folium.GeoJson(data_url, embed=False).add_to(marker_cluster)
+    folium.GeoJson(data_url, embed=False, show=False, name='geojson').add_to(m)
+    folium.LayerControl(collapsed=False).add_to(m)
+
+    html = m.get_root().render()
+    with temp_html_filepath(html) as filepath:
+        driver.get_file(filepath)
+        assert driver.wait_until('.folium-map')
+        driver.verify_js_logs()
+    # Verify the marker cluster is shown, it's a yellow icon with '18' in it.
+    icon = driver.wait_until('.leaflet-marker-icon.marker-cluster > div > span')
+    assert icon.text == '18'
+    # Verify the second GeoJson layer is not shown, because we used show=False.
+    control_label = driver.wait_until(
+        '.leaflet-control-layers-overlays > label:nth-of-type(2)'
+    )
+    assert control_label.text == 'geojson'
+    control_input = control_label.find_element_by_css_selector('input')
+    assert control_input.get_attribute('checked') is None