Merge pull request matplotlib#20128 from meeseeksmachine/auto-backport-of-pr-20123-on-v3.4.x

Backport PR matplotlib#20123 on branch v3.4.x (Ensure that Matplotlib is importable even if there's no HOME.)

Author: jklymak

lib/matplotlib/__init__.py

@@ -408,12 +408,14 @@ def _get_xdg_cache_dir():
     return os.environ.get('XDG_CACHE_HOME') or str(Path.home() / ".cache")
 
 
-def _get_config_or_cache_dir(xdg_base):
+def _get_config_or_cache_dir(xdg_base_getter):
     configdir = os.environ.get('MPLCONFIGDIR')
     if configdir:
         configdir = Path(configdir).resolve()
-    elif sys.platform.startswith(('linux', 'freebsd')) and xdg_base:
-        configdir = Path(xdg_base, "matplotlib")
+    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")
     else:
         configdir = Path.home() / ".matplotlib"
     try:
@@ -454,7 +456,7 @@ def get_configdir():
     4. Else, create a temporary directory, and use it as the configuration
        directory.
     """
-    return _get_config_or_cache_dir(_get_xdg_config_dir())
+    return _get_config_or_cache_dir(_get_xdg_config_dir)
 
 
 @_logged_cached('CACHEDIR=%s')
@@ -465,7 +467,7 @@ def get_cachedir():
     The procedure used to find the directory is the same as for
     _get_config_dir, except using ``$XDG_CACHE_HOME``/``$HOME/.cache`` instead.
     """
-    return _get_config_or_cache_dir(_get_xdg_cache_dir())
+    return _get_config_or_cache_dir(_get_xdg_cache_dir)
 
 
 @_logged_cached('matplotlib data path: %s')

lib/matplotlib/font_manager.py

@@ -129,14 +129,18 @@
 
 
 # OS Font paths
+try:
+    _HOME = Path.home()
+except Exception:  # Exceptions thrown by home() are not specified...
+    _HOME = Path(os.devnull)  # Just an arbitrary path with no children.
 MSFolders = \
     r'Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders'
 MSFontDirectories = [
     r'SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts',
     r'SOFTWARE\Microsoft\Windows\CurrentVersion\Fonts']
 MSUserFontDirectories = [
-    str(Path.home() / 'AppData/Local/Microsoft/Windows/Fonts'),
-    str(Path.home() / 'AppData/Roaming/Microsoft/Windows/Fonts'),
+    str(_HOME / 'AppData/Local/Microsoft/Windows/Fonts'),
+    str(_HOME / 'AppData/Roaming/Microsoft/Windows/Fonts'),
 ]
 X11FontDirectories = [
     # an old standard installation point
@@ -149,9 +153,9 @@
     # common application, not really useful
     "/usr/lib/openoffice/share/fonts/truetype/",
     # user fonts
-    str((Path(os.environ.get('XDG_DATA_HOME') or Path.home() / ".local/share"))
+    str((Path(os.environ.get('XDG_DATA_HOME') or _HOME / ".local/share"))
         / "fonts"),
-    str(Path.home() / ".fonts"),
+    str(_HOME / ".fonts"),
 ]
 OSXFontDirectories = [
     "/Library/Fonts/",
@@ -160,7 +164,7 @@
     # fonts installed via MacPorts
     "/opt/local/share/fonts",
     # user fonts
-    str(Path.home() / "Library/Fonts"),
+    str(_HOME / "Library/Fonts"),
 ]
 
 

lib/matplotlib/tests/test_matplotlib.py

@@ -25,6 +25,14 @@ def test_tmpconfigdir_warning(tmpdir):
         os.chmod(tmpdir, mode)
 
 
+def test_importable_with_no_home(tmpdir):
+    subprocess.run(
+        [sys.executable, "-c",
+         "import pathlib; pathlib.Path.home = lambda *args: 1/0; "
+         "import matplotlib.pyplot"],
+        env={**os.environ, "MPLCONFIGDIR": str(tmpdir)}, check=True)
+
+
 def test_use_doc_standard_backends():
     """
     Test that the standard backends mentioned in the docstring of