CustomIcon Marker fails when used in GeoJson

[sgrefen]

Describe the bug
When applying a Marker with a CustomIcon to a GeoJson the generate HTML fails in the browser with 'Uncaught TypeError: iconRootAlias.CustomIcon is not a constructor'.

To Reproduce

import folium

m = folium.Map(location=[45.3288, -121.6625], zoom_start=12)

url = "https://leafletjs.com/examples/custom-icons/{}".format
icon_image = url("leaf-red.png")
shadow_image = url("leaf-shadow.png")

icon = folium.CustomIcon(
    icon_image,
    icon_size=(38, 95),
    icon_anchor=(22, 94),
)

icon2 = folium.CustomIcon(
    icon_image='https://leafletjs.com/examples/custom-icons/leaf-green.png',
    icon_size=(38, 95),
    icon_anchor=(22, 94),
    popup_anchor=(-3, -76)
)


# this works
folium.Marker(
    location=[45.3288, -121.6625], icon=icon, popup="Mt. Hood Meadows",
).add_to(m)

#this fails
rt = folium.GeoJson(
    "b.geojson",
    marker=folium.Marker(icon=icon2)
).add_to(m)


with open("test.html","w") as f:
    f.write(m.get_root().render())
================
b.geojson:
[ {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [
		-121.6625,
		45.3288 
        ]
      }
    }
  ]
}]

Expected behavior
a green Icon overlay a red Icon on the map and no JS errors

Environment (please complete the following information):

• Browser Chrome & Firefoc
• Python version (3.13.3)
• folium version (0.19.6`
• branca version (0.8.1)

Additional context
Add any other context about the problem here.

Possible solutions
The following fix it for CustomIcon with Icon, but I'm not sure whether it impacts other Markers (eg. AwesomeIcons) in the GeoJson Macro.

--- old/folium/features.py	2025-05-31 23:56:47.789211663 +0200
+++ new/folium/features.py	2025-05-31 23:55:55.852144161 +0200
@@ -1940,7 +1940,7 @@
         popup_anchor: Optional[Tuple[int, int]] = None,
     ):
         super(Icon, self).__init__()
-        self._name = "CustomIcon"
+        self._name = "icon"
         self.options = remove_empty(
             icon_url=image_to_url(icon_image),
             icon_size=icon_size,

folium is maintained by volunteers. Can you help making a fix for this issue?

[sgrefen]

As a quick workaround until it is resolved:

import folium

v=[int(i) for i in folium.__version__.split('.')]
if v[0]<1 and v[1]<20 and v[2]<7:
    def helper(**args):
        r=folium.CustomIcon(**args)
        r._name='icon'
        return r
    CustomIcon=helper

else:
    CustomIcon=folium.CustomIcon

icon2 = CustomIcon(
    icon_image='https://leafletjs.com/examples/custom-icons/leaf-green.png',
    icon_size=(38, 95),
    icon_anchor=(22, 94),
    popup_anchor=(-3, -76)

[hansthen]

I managed to reproduce the error.

[hansthen]

@sgrefen

Your proposed change does not seem to break any tests so far. Would you care to make a Pull Request for it?

[sgrefen]

@sgrefen

Your proposed change does not seem to break any tests so far. Would you care to make a Pull Request for it?

Pushed.

[hansthen]

I don't see it yet. Perhaps you pushed it only to your own fork of the code? If so, you need to go to the python-visualization repo. Then select "Pull Requests" and "New Pull Request". You should see a link "compare across forks". When you click that you should be able to select your own repo and branch to make a Pull Request.