Fix duplicate HTML when map.save() is called repeatedly (#2239)

* Fix duplicate HTML when map.save() is called repeatedly

Repeated save() calls appended duplicate JavaScript because SetIcon and
ElementAddToElement created new render children with unique IDs on each
pass. Use stable script names so repeated renders replace instead of
append. Do not clear figure.html in render(); geopandas adds legend HTML
directly there.

Fixes #2237

* Remove unrelated changes from repeated save fix

Keep only ElementAddToElement.render() and Marker.SetIcon.render()
per review feedback.

Author: vraj2131

folium/elements.py

@@ -149,6 +149,18 @@ def __init__(self, element_name: str, element_parent_name: str):
         self.element_name = element_name
         self.element_parent_name = element_parent_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."
+        script = self._template.module.__dict__.get("script", None)
+        if script is not None:
+            figure.script.add_child(
+                Element(script(self, kwargs)),
+                name=f"{self.element_name}_add_to_{self.element_parent_name}",
+            )
+
 
 class IncludeStatement(MacroElement):
     """Generate an include statement on a class."""

folium/map.py

@@ -517,6 +517,18 @@ def __init__(
             self.marker = marker
             self.icon = icon
 
+        def render(self, **kwargs):
+            figure = self.get_root()
+            assert isinstance(
+                figure, Figure
+            ), "You cannot render this Element if it is not in a Figure."
+            script = self._template.module.__dict__.get("script", None)
+            if script is not None:
+                figure.script.add_child(
+                    Element(script(self, kwargs)),
+                    name=f"{self.marker.get_name()}_set_icon",
+                )
+
     def __init__(
         self,
         location: Optional[Sequence[float]] = None,

tests/test_map.py

@@ -290,3 +290,27 @@ def test_icon_invalid_marker_colors():
     pytest.warns(UserWarning, Icon, color="lila")
     pytest.warns(UserWarning, Icon, color=42)
     pytest.warns(UserWarning, Icon, color=None)
+
+
+def test_repeated_save_produces_identical_html(tmp_path):
+    """Regression test for https://github.com/python-visualization/folium/issues/2237"""
+    m = Map(location=[40.75, -73.98], zoom_start=13)
+    locations = [
+        [40.7829, -73.9654],
+        [40.7484, -73.9857],
+        [40.7580, -73.9855],
+    ]
+    for lat, lon in locations:
+        Marker([lat, lon], icon=Icon(color="blue", icon="info-sign")).add_to(m)
+
+    path1 = tmp_path / "1.html"
+    path2 = tmp_path / "2.html"
+    path3 = tmp_path / "3.html"
+    m.save(path1)
+    m.save(path2)
+    m.save(path3)
+
+    html1 = path1.read_text()
+    html2 = path2.read_text()
+    html3 = path3.read_text()
+    assert html1 == html2 == html3