Handle Decimal in Kaleido JSON serialization

src/py/kaleido/_kaleido_tab/_tab.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import base64
+from decimal import Decimal
 from typing import TYPE_CHECKING
 
 import logistro
@@ -27,6 +28,8 @@
 
 def _orjson_default(obj):
     """Fallback for types orjson can't handle natively (e.g. NumPy string arrays)."""
+    if isinstance(obj, Decimal):
+        return float(obj)
     if hasattr(obj, "tolist"):
         return obj.tolist()
     raise TypeError(f"Type is not JSON serializable: {type(obj).__name__}")

src/py/tests/test_kaleido_tab.py

@@ -0,0 +1,16 @@
+from decimal import Decimal
+
+import orjson
+import plotly.graph_objects as go
+
+from kaleido._kaleido_tab._tab import _orjson_default
+from kaleido._utils import fig_tools
+
+
+def test_orjson_default_handles_decimal():
+    fig = go.Figure(data=[go.Bar(y=[Decimal("10.5"), Decimal(20), Decimal("-3.25")])])
+    spec = fig_tools.coerce_for_js(fig, None, {"format": "json"})
+
+    encoded = orjson.dumps(spec, default=_orjson_default)
+
+    assert b'"y":[10.5,20.0,-3.25]' in encoded