Hi,
I'm proposing a fix to an edge case where conversion from matplotlib to plotly would break when converting a "lines+markers" plot with a legend. The issue happens because go.layout.Shape is not expecting "symbol" or "size" properties. My proposed fix is to ignore those two properties for "lines" type legend shapes. Please let me know if another fix would be more appropriate.

Thanks

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I have read through thecontributing notes and understand the structure of the package. In particular, if my PR modifies code ofplotly.graph_objects, my modifications concern thecodegen files and not generated files.
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gvwilson self-requested a review

June 20, 2025 13:41

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Jun 20, 2025

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fixfixes something broken labels

Jun 20, 2025

robertoffmoura force-pushed therm/fix-line+markers-plot branch 2 times, most recently frombf91f93 toda37239Compare

August 12, 2025 09:31

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emilykl commentedOct 1, 2025

Hi@robertoffmoura, could you explain the issue in a little more detail and provide an example of a plot that fails currently (expected output vs. actual output)? That will help me evaluate this fix.

Thank you for the contribution!

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robertoffmoura commentedOct 9, 2025

Hi@emilykl,
Please see below the error we get if we run the tests I added in this commit without the changes I made torenderer.py:

=========================================================================================== test session starts ===========================================================================================platform linux -- Python 3.12.0, pytest-8.4.0, pluggy-1.6.0configfile: pyproject.tomlplugins: anyio-4.3.0collected 1 item                                                                                                                                                                                          plotly/matplotlylib/tests/test_renderer.py F                                                                                                                                                        [100%]================================================================================================ FAILURES =================================================================================================_____________________________________________________________________________________ test_lines_markers_legend_plot ______________________________________________________________________________________    def test_lines_markers_legend_plot():        x = [0, 1]        y = [0, 1]        label = "label"        plt.figure()        plt.plot(x, y, "o-", label=label)        plt.legend()    >       plotly_fig = tls.mpl_to_plotly(plt.gcf())                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^plotly/matplotlylib/tests/test_renderer.py:14: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _plotly/tools.py:104: in mpl_to_plotly    matplotlylib.Exporter(renderer).run(fig)plotly/matplotlylib/mplexporter/exporter.py:54: in run    self.crawl_fig(fig)plotly/matplotlylib/mplexporter/exporter.py:125: in crawl_fig    self.crawl_ax(ax)plotly/matplotlylib/mplexporter/exporter.py:156: in crawl_ax    self.crawl_legend(ax, legend)plotly/matplotlylib/mplexporter/exporter.py:182: in crawl_legend    self.draw_line(ax, child, force_trans=ax.transAxes)plotly/matplotlylib/mplexporter/exporter.py:206: in draw_line    self.renderer.draw_marked_line(plotly/matplotlylib/renderer.py:504: in draw_marked_line    self.draw_legend_shapes(mode=mode, shape=shape, **props)plotly/matplotlylib/renderer.py:373: in draw_legend_shapes    legend_shape = go.layout.Shape(plotly/graph_objs/layout/_shape.py:1286: in __init__    self._process_kwargs(**dict(arg, **kwargs))_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _self = layout.Shape({    'fillcolor': '#1F77B4',    'line': {'color': '#1F77B4', 'width': 1.0},    'opacity': 1,    'type...f': 'paper',    'y0': np.float64(0.9695701058201058),    'y1': np.float64(0.9695701058201058),    'yref': 'paper'})kwargs = {'size': 6.0, 'symbol': 'circle'}, k = 'symbol', v = 'circle'err = ValueError('Invalid property specified for object of type plotly.graph_objs.layout.Shape: \'symbol\'\n\nDid you mean "...elative to data or plot\n            fraction.\n        \nDid you mean "label"?\n\nBad property path:\nsymbol\n^^^^^^')    def _process_kwargs(self, **kwargs):        """        Process any extra kwargs that are not predefined as constructor params        """        for k, v in kwargs.items():            err = _check_path_in_prop_tree(self, k, error_cast=ValueError)            if err is None:                # e.g. underscore kwargs like marker_line_color                self[k] = v            elif not self._validate:                # Set extra property as-is                self[k] = v            elif not self._skip_invalid:>               raise errE               ValueError: Invalid property specified for object of type plotly.graph_objs.layout.Shape: 'symbol'E               [...]E               Did you mean "label"?E               E               Bad property path:E               symbolE               ^^^^^^plotly/basedatatypes.py:4451: ValueError============================================================================================ warnings summary =============================================================================================plotly/conftest.py:4  /plotly.py/plotly/conftest.py:4: PytestRemovedIn9Warning: The (path: py.path.local) argument is deprecated, please use (collection_path: pathlib.Path)  see https://docs.pytest.org/en/latest/deprecations.html#py-path-local-arguments-for-hooks-replaced-with-pathlib-path    def pytest_ignore_collect(path):plotly/matplotlylib/tests/test_renderer.py::test_lines_markers_legend_plotplotly/matplotlylib/tests/test_renderer.py::test_lines_markers_legend_plot  /plotly.py/plotly/matplotlylib/mplexporter/utils.py:293: MatplotlibDeprecationWarning:    The converter attribute was deprecated in Matplotlib 3.10 and will be removed in 3.12. Use get_converter and set_converter methods instead.-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html========================================================================================= short test summary info =========================================================================================FAILED plotly/matplotlylib/tests/test_renderer.py::test_lines_markers_legend_plot - ValueError: Invalid property specified for object of type plotly.graph_objs.layout.Shape: 'symbol'====================================================================================== 1 failed, 3 warnings in 1.09s ======================================================================================

robertoffmoura added2 commits

October 9, 2025 16:37

Fix issue when converting matplotlib lines+markers legend to plotly

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robertoffmoura force-pushed therm/fix-line+markers-plot branch fromda37239 to719248aCompare

October 9, 2025 15:42

robertoffmoura changed the title~~Fix issue when converting matplotlib lines+markers legend to plotly~~Add matplotlib lines+markers plot conversion test

Oct 9, 2025

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robertoffmoura commentedOct 9, 2025

Hi@emilykl,
You're right, after rebasing this branch on top ofthis, the issue is no longer there. I still think we should add a test for the lines+markers plot, so I renamed this PR.