Close #1359

Add an include statement, that will allow users to override
specific methods at Leaflet level. This allows users to customize
the "createTile" method using a JsCode object.

Author: hansthen

folium/elements.py

@@ -155,15 +155,15 @@ class IncludeStatement(MacroElement):
 
     _template = Template(
         """
-        L.{{ this.class_name }}.include(
+        {{ this.leaflet_class_name }}.include(
             {{ this.options | tojavascript }}
         )
     """
     )
 
-    def __init__(self, class_name: str, **kwargs):
+    def __init__(self, leaflet_class_name: str, **kwargs):
         super().__init__()
-        self.class_name = class_name
+        self.leaflet_class_name = leaflet_class_name
         self.options = kwargs
 
     def render(self, *args, **kwargs):

folium/map.py

@@ -48,15 +48,26 @@ def include(cls, **kwargs):
     def includes(cls):
         return cls._includes[cls]
 
+    @property
+    def leaflet_class_name(self):
+        # TODO: I did not check all Folium classes to see if
+        # this holds up. This breaks at least for CustomIcon.
+        return f"L.{self._name}"
+
     def render(self, **kwargs):
         figure = self.get_root()
         assert isinstance(
             figure, Figure
         ), "You cannot render this Element if it is not in a Figure."
         if self.includes:
-            stmt = IncludeStatement(self._name, **self.includes)
+            stmt = IncludeStatement(self.leaflet_class_name, **self.includes)
+            # A bit weird. I tried adding IncludeStatement directly to both
+            # figure and script, but failed. So we render this ourself.
             figure.script.add_child(
                 Element(stmt._template.render(this=stmt, kwargs=self.includes)),
+                # make sure each class include gets rendered only once
+                name=self._name + "_includes",
+                # make sure this renders before the element itself
                 index=-1,
             )
         super().render(**kwargs)

tests/test_map.py

@@ -10,7 +10,7 @@
 import pytest
 
 from folium import GeoJson, Map, TileLayer
-from folium.map import CustomPane, Icon, LayerControl, Marker, Popup
+from folium.map import Class, CustomPane, Icon, LayerControl, Marker, Popup
 from folium.utilities import JsCode, normalize
 
 tmpl = """
@@ -173,11 +173,11 @@ def test_include():
         tiles=tiles,
     )
     rendered = m.get_root().render()
+    Class._includes.clear()
     expected = """
     L.TileLayer.include({
       "createTile":
         function(coords, done) {
-            console.log("creating tile");
             const url = this.getTileUrl(coords);
             const img = document.createElement('img');
             fetch(url, {
@@ -193,10 +193,32 @@ def test_include():
         },
     })
     """
+    print(expected)
+    print("-----")
+    print(rendered)
 
     assert normalize(expected) in normalize(rendered)
 
 
+def test_include_once():
+    abc = "MY BEAUTIFUL SENTINEL"
+    TileLayer.include(abc=abc)
+    tiles = TileLayer(
+        tiles="OpenStreetMap",
+    )
+    m = Map(
+        tiles=tiles,
+    )
+    TileLayer(
+        tiles="OpenStreetMap",
+    ).add_to(m)
+
+    rendered = m.get_root().render()
+    Class._includes.clear()
+
+    assert rendered.count(abc) == 1, "Includes should happen only once per class"
+
+
 def test_popup_backticks():
     m = Map()
     popup = Popup("back`tick`tick").add_to(m)