René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: colorbar with unattached mappables can't steal space","articleBody":"### Bug summary\r\n\r\nThis is something I noticed downstream in networkx: https://github.com/networkx/networkx/pull/5937#issuecomment-1223097369\r\n\r\nFormerly, space for a `Colorbar` was stolen from the current `Axes`; that was deprecated and now in 3.6, it is stolen from the mappable's `Axes`. But if the mappable is not added to an `Axes`, it fails with a somewhat unrelated-looking error.\r\n\r\n### Code for reproduction\r\n\r\n```python\r\nimport matplotlib as mpl\r\nimport matplotlib.pyplot as plt\r\n\r\ncmap = plt.get_cmap('viridis')\r\n\r\npc = mpl.collections.PatchCollection([], cmap=cmap)\r\npc.set_array([])\r\n\r\nplt.colorbar(pc)\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\n```pytb\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/home/elliott/code/matplotlib/lib/matplotlib/pyplot.py\", line 2053, in colorbar\r\n    ret = gcf().colorbar(mappable, cax=cax, ax=ax, **kwargs)\r\n  File \"/home/elliott/code/matplotlib/lib/matplotlib/figure.py\", line 1260, in colorbar\r\n    cax, kwargs = cbar.make_axes(ax, **kwargs)\r\n  File \"/home/elliott/code/matplotlib/lib/matplotlib/colorbar.py\", line 1396, in make_axes\r\n    fig = parents[0].get_figure()\r\nAttributeError: 'NoneType' object has no attribute 'get_figure'\r\n```\r\n\r\n### Expected outcome\r\n\r\nEither we should switch to the current Axes if the mappable doesn't have one (probably not desired given the previous change), or raise a clearer error message when this happens.\r\n\r\n### Additional information\r\n\r\n_No response_\r\n\r\n### Operating system\r\n\r\n_No response_\r\n\r\n### Matplotlib Version\r\n\r\n3.6.0rc1\r\n\r\n### Matplotlib Backend\r\n\r\n_No response_\r\n\r\n### Python version\r\n\r\n_No response_\r\n\r\n### Jupyter version\r\n\r\n_No response_\r\n\r\n### Installation\r\n\r\npip","author":{"url":"https://github.com/QuLogic","@type":"Person","name":"QuLogic"},"datePublished":"2022-08-23T00:15:01.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/23709/matplotlib/issues/23709"}