VIS Wrong legend when combining multiple plots on the same axes , plotting with legend=False messes up legend

[MarcoGorelli]

• closes BUG: Wrong legend when combining multiple plots on the same axes #39522
• closes BUG: plotting with secondary_y and then plotting another line results in wrong color for (right) line #40044
• tests added / passed
• Ensure all linting tests pass, see here for how to run them
• whatsnew entry

So, in #27808 , leg.legendHandles was replaced with ax.get_legend_handles_labels()[0] in order to preserve marker info.

However, ax.get_legend_handles_labels()[0] may contain extra elements which aren't (yet) visible, which means we may end up at

pandas/pandas/plotting/_matplotlib/core.py

Line 625 in 2724350

ax.legend(handles, labels, loc="best", title=title)

with

(Pdb) handles
[<matplotlib.lines.Line2D object at 0x7f0938a37430>, <ErrorbarContainer object of 3 artists>, <matplotlib.lines.Line2D object at 0x7f0938a37430>]
(Pdb) labels
['orange', 'blue']

This causes the permuting noted in #39522

Ideally, there would be a way to get leg.legendHandles in a way that preserves the marker info. However, I can't find a way to do that - have asked on the matplotlib discourse. Also, the current test doesn't quite work (as it passes on master too). I'm working on finding a satisfactory solution

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On master:

On this branch:

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cc @charlesdong1991 in case you have comments / suggestions

[MarcoGorelli]

closing as I'm not happy with this solution - will get back to it