From 80994eaeac7e2079325c8f6cba2e3bd4e84d9324 Mon Sep 17 00:00:00 2001
From: Logan Pageler <pagelerlogan@gmail.com>
Date: Thu, 21 Aug 2025 20:24:58 -0700
Subject: [PATCH 1/2] Added handleing for undetermined home directory

---
 lib/matplotlib/__init__.py | 39 ++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
index dc3555fd7969..95e422b4fa74 100644
--- a/lib/matplotlib/__init__.py
+++ b/lib/matplotlib/__init__.py
@@ -532,19 +532,30 @@ def _get_config_or_cache_dir(xdg_base_getter):
     elif sys.platform.startswith(('linux', 'freebsd')):
         # Only call _xdg_base_getter here so that MPLCONFIGDIR is tried first,
         # as _xdg_base_getter can throw.
-        configdir = Path(xdg_base_getter(), "matplotlib")
+        try:
+            configdir = Path(xdg_base_getter(), "matplotlib")
+        except RuntimeError:
+            pass
     else:
-        configdir = Path.home() / ".matplotlib"
-    # Resolve the path to handle potential issues with inaccessible symlinks.
-    configdir = configdir.resolve()
-    try:
-        configdir.mkdir(parents=True, exist_ok=True)
-    except OSError as exc:
-        _log.warning("mkdir -p failed for path %s: %s", configdir, exc)
+        try:
+            configdir = Path.home() / ".matplotlib"
+        except RuntimeError:
+            pass
+
+    if configdir:
+        # Resolve the path to handle potential issues with inaccessible symlinks.
+        configdir = configdir.resolve()
+        try:
+            configdir.mkdir(parents=True, exist_ok=True)
+        except OSError as exc:
+            _log.warning("mkdir -p failed for path %s: %s", configdir, exc)
+        else:
+            if os.access(str(configdir), os.W_OK) and configdir.is_dir():
+                return str(configdir)
+            _log.warning("%s is not a writable directory", configdir)
+        issue_msg = "the default path ({configdir})"
     else:
-        if os.access(str(configdir), os.W_OK) and configdir.is_dir():
-            return str(configdir)
-        _log.warning("%s is not a writable directory", configdir)
+        issue_msg = "resolving the home directory"
     # If the config or cache directory cannot be created or is not a writable
     # directory, create a temporary one.
     try:
@@ -552,17 +563,17 @@ def _get_config_or_cache_dir(xdg_base_getter):
     except OSError as exc:
         raise OSError(
             f"Matplotlib requires access to a writable cache directory, but there "
-            f"was an issue with the default path ({configdir}), and a temporary "
+            f"was an issue with {issue_msg}, and a temporary "
             f"directory could not be created; set the MPLCONFIGDIR environment "
             f"variable to a writable directory") from exc
     os.environ["MPLCONFIGDIR"] = tmpdir
     atexit.register(shutil.rmtree, tmpdir)
     _log.warning(
         "Matplotlib created a temporary cache directory at %s because there was "
-        "an issue with the default path (%s); it is highly recommended to set the "
+        "an issue with %s; it is highly recommended to set the "
         "MPLCONFIGDIR environment variable to a writable directory, in particular to "
         "speed up the import of Matplotlib and to better support multiprocessing.",
-        tmpdir, configdir)
+        tmpdir, issue_msg)
     return tmpdir
 
 

From 01e1163d78efb3ef4d192f93483baad0e907bfdd Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Fri, 22 Aug 2025 11:27:27 +0200
Subject: [PATCH 2/2] Add comment on the cause of the RuntimeError

---
 lib/matplotlib/__init__.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
index 95e422b4fa74..d1e575107f49 100644
--- a/lib/matplotlib/__init__.py
+++ b/lib/matplotlib/__init__.py
@@ -534,12 +534,12 @@ def _get_config_or_cache_dir(xdg_base_getter):
         # as _xdg_base_getter can throw.
         try:
             configdir = Path(xdg_base_getter(), "matplotlib")
-        except RuntimeError:
+        except RuntimeError:  # raised if Path.home() is not available
             pass
     else:
         try:
             configdir = Path.home() / ".matplotlib"
-        except RuntimeError:
+        except RuntimeError:  # raised if Path.home() is not available
             pass
 
     if configdir: