Issue 1520: Propagate feature to child layers of multi-geometries (#2263)

* Propagate feature to child layers of multi-geometries

Leaflet's geometryToLayer returns a FeatureGroup for MultiPoint, and addData assigns `feature` to that group only. Tooltips resolve their source to the layer that fired the event (Tooltip.js:418, v1.9.3), which is a child marker with no `feature`, so GeoJsonTooltip and GeoJsonPopup throw and never render.

Copy the feature onto child layers in onEachFeature, before any user-supplied callback, so both see the same data.

Fixes #1520

* Descend into nested groups when propagating features

A GeometryCollection containing a MultiPoint produces a FeatureGroup inside a FeatureGroup, placing the hovered marker two levels below the layer that owns `feature`. eachLayer only iterates one level, so the propagation now recurses.

* Add regression test for MultiPoint tooltips

Author: nina-mir

folium/features.py

@@ -586,6 +586,13 @@ class GeoJson(Layer):
         {%- endif %}
 
         function {{this.get_name()}}_onEachFeature(feature, layer) {
+            (function propagate(parent){
+                if (typeof parent.eachLayer !== "function") {return;}
+                parent.eachLayer(function (child) {
+                    if (child.feature === undefined) { child.feature = feature; }
+                    propagate(child);
+                })
+            })(layer)
             {%- if this.on_each_feature %}
             ({{this.on_each_feature}})(feature, layer);
             {%- endif %}

tests/selenium/test_multipoints_tooltip_selenium.py

@@ -0,0 +1,65 @@
+import folium
+from folium import GeoJson, GeoJsonTooltip, Map
+from folium.utilities import temp_html_filepath
+
+# Selenium's pointer actions do not reliably reach Leaflet's SVG paths in
+# headless Chrome, so the hover is dispatched as a DOM event instead. It
+# bubbles through Map._handleDOMEvent exactly as a real pointer hover does.
+HOVER = """
+    const el = arguments[0];
+    const rect = el.getBoundingClientRect();
+    const opts = {
+        bubbles: true,
+        clientX: rect.x + rect.width / 2,
+        clientY: rect.y + rect.height / 2,
+    };
+    el.dispatchEvent(new MouseEvent('mouseover', opts));
+    el.dispatchEvent(new MouseEvent('mousemove', opts));
+"""
+
+
+def build() -> Map:
+    data = {
+        "type": "FeatureCollection",
+        "features": [
+            {
+                "type": "Feature",
+                "properties": {"name": "multipoint"},
+                "geometry": {"type": "MultiPoint", "coordinates": [[0.0, 0.0]]},
+            }
+        ],
+    }
+    m = Map((0, 0), zoom_start=10)
+    GeoJson(
+        data,
+        marker=folium.CircleMarker(radius=20),
+        tooltip=GeoJsonTooltip(fields=["name"], labels=False),
+    ).add_to(m)
+    return m
+
+
+def test_geojson_multipoint_tooltip(driver):
+    """A GeoJsonTooltip must render for MultiPoint geometry.
+
+    Leaflet returns a FeatureGroup for MultiPoint and assigns `feature` to
+    that group only, while the tooltip resolves its source to the child
+    layer that fired the event. Without the feature on the children, the
+    tooltip's content function throws and nothing renders.
+
+    https://github.com/python-visualization/folium/issues/1520
+    """
+    html = build().get_root().render()
+    with temp_html_filepath(html) as filepath:
+        driver.get_file(filepath)
+        driver.wait_until(".folium-map")
+
+        marker = driver.wait_until("path.leaflet-interactive")
+        driver.execute_script(HOVER, marker)
+
+        tooltip = driver.wait_until(".leaflet-tooltip.foliumtooltip")
+        assert "multipoint" in tooltip.text
+
+    # No verify_js_logs() here: Leaflet 1.9.3 (our pin) throws
+    # "t.getElement is not a function" from _addFocusListenersOnLayer for any
+    # GeoJSON layer containing a nested FeatureGroup, independent of this fix.
+    # Guarded upstream in 1.9.4.