Fix streamlit-folium incompatibility (add layer to map with new class) (

#1834)

* Add Layer to map with MacroElement class

* run ruff

* add ElementAddToElement only once

* Fix marker cluster test

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

folium/elements.py

@@ -1,6 +1,7 @@
 from typing import List, Tuple
 
-from branca.element import CssLink, Element, Figure, JavascriptLink
+from branca.element import CssLink, Element, Figure, JavascriptLink, MacroElement
+from jinja2 import Template
 
 
 class JSCSSMixin(Element):
@@ -22,3 +23,20 @@ def render(self, **kwargs) -> None:
             figure.header.add_child(CssLink(url), name=name)
 
         super().render(**kwargs)
+
+
+class ElementAddToElement(MacroElement):
+    """Abstract class to add an element to another element."""
+
+    _template = Template(
+        """
+        {% macro script(this, kwargs) %}
+            {{ this.element_name }}.addTo({{ this.element_parent_name }});
+        {% endmacro %}
+    """
+    )
+
+    def __init__(self, element_name: str, element_parent_name: str):
+        super().__init__()
+        self.element_name = element_name
+        self.element_parent_name = element_parent_name

folium/map.py

@@ -9,12 +9,12 @@
 from branca.element import Element, Figure, Html, MacroElement
 from jinja2 import Template
 
+from folium.elements import ElementAddToElement
 from folium.utilities import (
     TypeBounds,
     TypeJsonValue,
     camelize,
     escape_backticks,
-    get_and_assert_figure_root,
     parse_options,
     validate_location,
 )
@@ -51,24 +51,15 @@ def __init__(
         self.show = show
 
     def render(self, **kwargs):
-        super().render(**kwargs)
         if self.show:
-            self._add_layer_to_map()
-
-    def _add_layer_to_map(self, **kwargs):
-        """Show the layer on the map by adding it to its parent in JS."""
-        template = Template(
-            """
-            {%- macro script(this, kwargs) %}
-                {{ this.get_name() }}.addTo({{ this._parent.get_name() }});
-            {%- endmacro %}
-            """
-        )
-        script = template.module.__dict__["script"]
-        figure = get_and_assert_figure_root(self)
-        figure.script.add_child(
-            Element(script(self, kwargs)), name=self.get_name() + "_add"
-        )
+            self.add_child(
+                ElementAddToElement(
+                    element_name=self.get_name(),
+                    element_parent_name=self._parent.get_name(),
+                ),
+                name=self.get_name() + "_add",
+            )
+        super().render(**kwargs)
 
 
 class FeatureGroup(Layer):

tests/plugins/test_marker_cluster.py

@@ -23,24 +23,7 @@ def test_marker_cluster():
     m = folium.Map([45.0, 3.0], zoom_start=4)
     mc = plugins.MarkerCluster(data).add_to(m)
 
-    out = normalize(m._parent.render())
-
-    # We verify that imports
-    assert (
-        '<script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet.markercluster/1.1.0/leaflet.markercluster.js"></script>'  # noqa
-        in out
-    )  # noqa
-    assert (
-        '<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet.markercluster/1.1.0/MarkerCluster.css"/>'  # noqa
-        in out
-    )  # noqa
-    assert (
-        '<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet.markercluster/1.1.0/MarkerCluster.Default.css"/>'  # noqa
-        in out
-    )  # noqa
-
-    # Verify the script part is okay.
-    tmpl = Template(
+    tmpl_for_expected = Template(
         """
         var {{this.get_name()}} = L.markerClusterGroup(
             {{ this.options|tojson }}
@@ -60,7 +43,24 @@ def test_marker_cluster():
         {{ this.get_name() }}.addTo({{ this._parent.get_name() }});
     """
     )
-    expected = normalize(tmpl.render(this=mc))
+    expected = normalize(tmpl_for_expected.render(this=mc))
+
+    out = normalize(m._parent.render())
+
+    # We verify that imports
+    assert (
+        '<script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet.markercluster/1.1.0/leaflet.markercluster.js"></script>'  # noqa
+        in out
+    )  # noqa
+    assert (
+        '<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet.markercluster/1.1.0/MarkerCluster.css"/>'  # noqa
+        in out
+    )  # noqa
+    assert (
+        '<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet.markercluster/1.1.0/MarkerCluster.Default.css"/>'  # noqa
+        in out
+    )  # noqa
+
     assert expected in out
 
     bounds = m.get_bounds()