Plotting not interacting well with Altair schema wrappers (x=alt.X(...))

[AdrienDart]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import polars as pl
import altair as alt
import numpy as np

np.random.seed (42) 

df =pl.DataFrame({
"value": np.random.normal(0,1,1000)
})

df.plot.bar(x=alt.X("value", bin=alt.BinParams(step=1)), y="count()") # bad behavior

alt.Chart(df).mark_bar().encode(x=alt.X("value", bin=alt.BinParams(step=1)), y="count()") # good behavior (similar to hvplot.hist)

Log output

No response

Issue description

Polars plot not using the altair wrapper the right way.

Expected behavior

We should get a usual histogram plot.

Installed versions

Polars 1.9.0
Python 3.9.13

[MarcoGorelli]

Thanks for the report, will take a look

[dangotbanned]

Following up as promised in vega/altair#3635 (comment)

The issue is stemming from #18625 (comment)

Retrospective read

@joelostblom flagged _add_tooltip(), providing link as an alternative.
However, that appears to be pointing to the wrong place, it should be api.py#L3994-L3999

Applying that change would have looked like:

Expected diff

def _add_tooltip(chart: alt.Chart, /) -> alt.Chart:
-    chart.mark = {"type": chart.mark, "tooltip": True}
+    if isinstance(chart.mark, str):
+        chart.mark = {"type": chart.mark, "tooltip": True}
+    else:
+        chart.mark.tooltip = True
     return chart

In the same thread, I was focusing on the testing aspect in (#18625 (comment)) and (#18625 (review))

I definitely overlooked the change from alt.Chart.mark -> alt.Chart.encoding, really dropped the ball on that one.
Sorry @MarcoGorelli

Suggestion

As mentioned in vega/altair#3635 (comment), simply pass in tooltip=True for calls like

self._chart.mark_...(tooltip=True).encode(**encodings, **kwargs).interactive()

I don't think the consideration of alt.Chart.mark's type is relevant for you; since you're simply calling the alt.Chart.mark_... method(s) directly.

You would only need to handle that case if you parameterized this:

polars/py-polars/polars/dataframe/plotting.py

Lines 48 to 52 in 44439d9

	class DataFramePlot:
	"""DataFrame.plot namespace."""
	def __init__(self, df: DataFrame) -> None:
	self._chart = alt.Chart(df)

Like:

alt.Chart(df, mark="bar")

[MarcoGorelli]

thanks so much @dangotbanned ! can confirm this works well

[AdrienDart]

Thank you @MarcoGorelli @dangotbanned for looking into this!