René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Config directory location finder doesn't account for the home directory being undetermined.","articleBody":"### Bug summary\n\nIf the `home` directory cannot be created/written to, matplotlib defaults to creating a temporary folder for its caching/config. However, if the `home` directory cannot be determined a `RunTimeError` will be raised.\n\n### Code for reproduction\n\n```Python\n# This will fail on windows\nimport os\nos.environ.pop('HOMEPATH', None)\nos.environ.pop('USERPROFILE', None)\nimport matplotlib\n\n# For linux the following will fail only if the user doesn't exist in the password database\nimport os\nos.environ.pop('HOME', None)\nimport matplotlib\n```\n\n### Actual outcome\n\nYou will get the following error:\n```\nFile ~\\Documents\\programming\\testing\\.venv\\Lib\\site-packages\\matplotlib\\__init__.py:1010\n   1008 rcParams = RcParams()  # The global instance.\n   1009 rcParams._update_raw(rcParamsDefault)\n-\u003e 1010 rcParams._update_raw(_rc_params_in_file(matplotlib_fname()))\n   1011 rcParamsOrig = rcParams.copy()\n   1012 with _api.suppress_matplotlib_deprecation_warning():\n   1013     # This also checks that all rcParams are indeed listed in the template.\n   1014     # Assigning to rcsetup.defaultParams is left only for backcompat.\n\nFile ~\\Documents\\programming\\testing\\.venv\\Lib\\site-packages\\matplotlib\\__init__.py:636, in matplotlib_fname()\n    633     yield os.path.join(get_configdir(), 'matplotlibrc')\n    634     yield os.path.join(get_data_path(), 'matplotlibrc')\n--\u003e 636 for fname in gen_candidates():\n    637     if os.path.exists(fname) and not os.path.isdir(fname):\n    638         return fname\n\nFile ~\\Documents\\programming\\testing\\.venv\\Lib\\site-packages\\matplotlib\\__init__.py:633, in matplotlib_fname.\u003clocals\u003e.gen_candidates()\n    631     yield matplotlibrc\n    632     yield os.path.join(matplotlibrc, 'matplotlibrc')\n--\u003e 633 yield os.path.join(get_configdir(), 'matplotlibrc')\n    634 yield os.path.join(get_data_path(), 'matplotlibrc')\n\nFile ~\\Documents\\programming\\testing\\.venv\\Lib\\site-packages\\matplotlib\\__init__.py:340, in _logged_cached.\u003clocals\u003e.wrapper(**kwargs)\n    338 nonlocal called, ret\n    339 if not called:\n--\u003e 340     ret = func(**kwargs)\n    341     called = True\n    342     _log.debug(fmt, ret)\n\nFile ~\\Documents\\programming\\testing\\.venv\\Lib\\site-packages\\matplotlib\\__init__.py:579, in get_configdir()\n    563 @_logged_cached('CONFIGDIR=%s')\n    564 def get_configdir():\n    565     \"\"\"\n    566     Return the string path of the configuration directory.\n    567 \n   (...)    577        directory.\n    578     \"\"\"\n--\u003e 579     return _get_config_or_cache_dir(_get_xdg_config_dir)\n\nFile ~\\Documents\\programming\\testing\\.venv\\Lib\\site-packages\\matplotlib\\__init__.py:531, in _get_config_or_cache_dir(xdg_base_getter)\n    529     configdir = Path(xdg_base_getter(), \"matplotlib\")\n    530 else:\n--\u003e 531     configdir = Path.home() / \".matplotlib\"\n    532 # Resolve the path to handle potential issues with inaccessible symlinks.\n    533 configdir = configdir.resolve()\n\nFile ~\\AppData\\Roaming\\uv\\python\\cpython-3.13.7-windows-x86_64-none\\Lib\\pathlib\\_abc.py:758, in PathBase.home(cls)\n    754 @classmethod\n    755 def home(cls):\n    756     \"\"\"Return a new path pointing to expanduser('~').\n    757     \"\"\"\n--\u003e 758     return cls(\"~\").expanduser()\n\nFile ~\\AppData\\Roaming\\uv\\python\\cpython-3.13.7-windows-x86_64-none\\Lib\\pathlib\\_local.py:808, in Path.expanduser(self)\n    806 homedir = os.path.expanduser(self._tail[0])\n    807 if homedir[:1] == \"~\":\n--\u003e 808     raise RuntimeError(\"Could not determine home directory.\")\n    809 drv, root, tail = self._parse_path(homedir)\n    810 return self._from_parsed_parts(drv, root, tail + self._tail[1:])\n\nRuntimeError: Could not determine home directory.\n```\n\n\n\n### Expected outcome\n\nI would expect it to default to creating a temporary directory for the caching and config directories, using them instead.\n\n### Additional information\n\nThe issue is caused by some calls to `Path.home()` in `_get_config_or_cache_dir`.\n\nhttps://github.com/matplotlib/matplotlib/blob/e775274d7f1412bdb75414b1085f2cd7990490ad/lib/matplotlib/__init__.py#L532C1-L537C48\n\nThe simple solution would be to handle the potential `RunTimeErrors` from the `Path.home()` calls.\n\nAdditionally [#12549](https://github.com/matplotlib/matplotlib/issues/12549) would probably also resolve this, bit that seems like a bigger push.\n\n### Operating system\n\nWindows\n\n### Matplotlib Version\n\n3.10.5\n\n### Matplotlib Backend\n\nmodule://matplotlib_inline.backend_inline\n\n### Python version\n\n3.13.7\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\npip","author":{"url":"https://github.com/Logan-Pageler","@type":"Person","name":"Logan-Pageler"},"datePublished":"2025-08-21T05:36:14.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/30449/matplotlib/issues/30449"}