GeoJsonTooltip warn for GeometryCollection

folium/features.py

@@ -8,6 +8,7 @@
 from __future__ import (absolute_import, division, print_function)
 
 import json
+import warnings
 
 from branca.colormap import LinearColormap
 from branca.element import (Element, Figure, JavascriptLink, MacroElement)
@@ -704,10 +705,24 @@ def __init__(self, fields, aliases=None, labels=True,
             # noqa outside of type checking.
             self.style = style
 
+    def warn_for_geometry_collections(self):
+        """Checks for GeoJson GeometryCollection features to warn user about incompatibility."""
+        geom_collections = [
+            feature.get('properties') if feature.get('properties') is not None else key
+            for key, feature in enumerate(self._parent.data['features'])
+            if feature['geometry']['type'] == 'GeometryCollection'
+        ]
+        if any(geom_collections):
+            warnings.warn(
+                "GeoJsonTooltip is not configured to render tooltips for GeoJson GeometryCollection geometries. "
+                "Please consider reworking these features: {} to MultiPolygon for full functionality.\n"
+                "https://tools.ietf.org/html/rfc7946#page-9".format(geom_collections), UserWarning)
+
     def render(self, **kwargs):
         """Renders the HTML representation of the element."""
         if isinstance(self._parent, GeoJson):
             keys = tuple(self._parent.data['features'][0]['properties'].keys())
+            self.warn_for_geometry_collections()
         elif isinstance(self._parent, TopoJson):
             obj_name = self._parent.object_path.split('.')[-1]
             keys = tuple(self._parent.data['objects'][obj_name][

tests/test_features.py

@@ -10,6 +10,8 @@
 
 import os
 
+import warnings
+
 from branca.element import Element
 from branca.six import text_type
 
@@ -104,3 +106,14 @@ def test_color_line():
         opacity=1)
     m.add_child(color_line)
     m._repr_html_()
+
+def test_geojson_tooltip():
+    m = folium.Map([30.5, -97.5], zoom_start=10)
+    geojson = folium.GeoJson("./kuntarajat.geojson",
+                             tooltip=folium.GeoJsonTooltip(
+                                 fields=['code','name']
+                             )).add_to(m)
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter('always')
+        m._repr_html_()
+        assert isinstance(w[-1].category, UserWarning), "GeoJsonTooltip GeometryCollection test failed."