Make components always truthy

dash/development/base_component.py

@@ -433,6 +433,11 @@ def __iter__(self):
         for t in self._traverse_ids():
             yield t.id  # type: ignore[reportAttributeAccessIssue]
 
+    def __bool__(self):
+        # Without this, truthiness falls back to __len__, so a component
+        # with no children (or no children prop, like DataTable) is falsy.
+        return True
+
     def __len__(self):
         """Return the number of items in the tree."""
         # TODO - Should we return the number of items that have IDs

tests/unit/development/test_base_component.py

@@ -6,7 +6,7 @@
 from dash import __version__, Dash
 from dash import html
 from dash.development.base_component import Component
-from dash import dcc, Input, Output
+from dash import dcc, dash_table, Input, Output
 
 Component._prop_names = ("id", "a", "children", "style")
 Component._type = "TestComponent"
@@ -539,3 +539,11 @@ def update2(v):
 def test_debc030_invalid_children_args():
     with pytest.raises(TypeError):
         dcc.Input(children="invalid children")
+
+
+def test_debc031_bool_is_always_true():
+    assert bool(Component())
+    assert bool(Component(children=[]))
+    assert bool(html.Div())
+    assert bool(dash_table.DataTable(data=[{"a": 1}]))
+    assert (html.Div() or None) is not None