def test_layer_errors():
toplevel_chart = alt.Chart("data.txt").mark_point().configure_legend(
columns=2)
facet_chart1 = alt.Chart("data.txt").mark_point().encode(facet="row:Q")
facet_chart2 = alt.Chart("data.txt").mark_point().facet("row:Q")
repeat_chart = alt.Chart("data.txt").mark_point().repeat(["A", "B", "C"])
simple_chart = alt.Chart("data.txt").mark_point()
with pytest.raises(ValueError) as err:
toplevel_chart + simple_chart
assert str(err.value).startswith(
'Objects with "config" attribute cannot be used within LayerChart.')
with pytest.raises(ValueError) as err:
repeat_chart + simple_chart
assert str(err.value) == "Repeat charts cannot be layered."
with pytest.raises(ValueError) as err:
facet_chart1 + simple_chart
assert str(err.value) == "Faceted charts cannot be layered."
with pytest.raises(ValueError) as err:
alt.layer(simple_chart) + facet_chart2
assert str(err.value) == "Faceted charts cannot be layered."
def test_layer_add_selection():
base = alt.Chart("data.csv").mark_point()
selection = alt.selection_single()
chart1 = alt.layer(base.add_selection(selection), base)
chart2 = alt.layer(base, base).add_selection(selection)
assert chart1.to_dict() == chart2.to_dict()
