Deterministic sort order for plotly express modes

Author: alev000

packages/python/plotly/plotly/express/_core.py

@@ -1929,7 +1929,7 @@ def infer_config(args, constructor, trace_patch, layout_patch):
             modes.add("text")
         if len(modes) == 0:
             modes.add("lines")
-        trace_patch["mode"] = "+".join(modes)
+        trace_patch["mode"] = "+".join(sorted(modes))
     elif constructor != go.Splom and (
         "symbol" in args or constructor == go.Scattermapbox
     ):

packages/python/plotly/plotly/tests/test_optional/test_px/test_px.py

@@ -80,6 +80,26 @@ def test_labels():
     assert fig.layout.annotations[4].text.startswith("TIME")
 
 
+@pytest.mark.parametrize(
+    ["extra_kwargs", "expected_mode"],
+    [
+        ({}, "lines"),
+        ({"markers": True}, "lines+markers"),
+        ({"text": "continent"}, "lines+markers+text"),
+    ],
+)
+def test_line_mode(extra_kwargs, expected_mode):
+    gapminder = px.data.gapminder()
+    fig = px.line(
+        gapminder,
+        x="year",
+        y="pop",
+        color="country",
+        **extra_kwargs,
+    )
+    assert fig.data[0].mode == expected_mode
+
+
 def test_px_templates():
     try:
         import plotly.graph_objects as go