configuration: don't use canon_path()

Rely on pathlib instead, which handles canonicalization on Windows in
a much better way.

Start using os.fspath(pathlike) instead of str(pathlike). After
studying some CPython sources that deal with path-like objects, this
seems to be the recommended thing to do.

The reason why is that not all os.PathLike objects are going to return
their file system path representations when str() is called on them;
even though the pathlib ones do.

I therefore want to use os.fspath() everywhere instead of str(), even
if it's sometimes safe to use str(). That way, when we inevitably
start copy/pasting code around, it will still do the right thing when
we're dealing with the general case os.PathLike behavior, e.g. from a
user-supplied argument to an API function, which may do something
different in its __str__ than its __fspath__ method.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

src/west/configuration.py

@@ -37,13 +37,13 @@ lowest.
 
 import configparser
 import os
-import pathlib
+from pathlib import PureWindowsPath, Path
 import platform
 from enum import Enum
 
 import configobj
 
-from west.util import west_dir, WestNotFound, canon_path
+from west.util import west_dir, WestNotFound
 
 def _configparser():            # for internal use
     return configparser.ConfigParser(allow_no_value=True)
@@ -198,6 +198,11 @@ def _location(cfg, topdir=None):
     # Its existence is also relied on in the test cases, to ensure
     # that the WEST_CONFIG_xyz variables are respected and we're not about
     # to clobber the user's own configuration files.
+    #
+    # Make sure to use pathlib's / operator override to join paths in
+    # any cases which might run on Windows, then call fspath() on the
+    # final result. This lets the standard library do the work of
+    # producing a canonical string name.
     env = os.environ
 
     if cfg == ConfigFile.ALL:
@@ -223,8 +228,8 @@ def _location(cfg, topdir=None):
             #
             # See https://github.com/zephyrproject-rtos/west/issues/300
             # for details.
-            pd = pathlib.PureWindowsPath(os.environ['ProgramData'])
-            return str(pd / 'west' / 'config')
+            pd = PureWindowsPath(os.environ['ProgramData'])
+            return os.fspath(pd / 'west' / 'config')
         else:
             raise ValueError('unsupported platform ' + plat)
     elif cfg == ConfigFile.GLOBAL:
@@ -233,16 +238,15 @@ def _location(cfg, topdir=None):
         elif platform.system() == 'Linux' and 'XDG_CONFIG_HOME' in env:
             return os.path.join(env['XDG_CONFIG_HOME'], 'west', 'config')
         else:
-            return canon_path(
-                os.path.join(os.path.expanduser('~'), '.westconfig'))
+            return os.fspath(Path.home() / '.westconfig')
     elif cfg == ConfigFile.LOCAL:
         if topdir:
-            return os.path.join(topdir, '.west', 'config')
+            return os.fspath(Path(topdir) / '.west' / 'config')
         elif 'WEST_CONFIG_LOCAL' in env:
             return env['WEST_CONFIG_LOCAL']
         else:
             # Might raise WestNotFound!
-            return os.path.join(west_dir(), 'config')
+            return os.fspath(Path(west_dir()) / 'config')
     else:
         raise ValueError(f'invalid configuration file {cfg}')
 
@@ -267,11 +271,11 @@ def _ensure_config(configfile, topdir):
     # Ensure the given configfile exists, returning its path. May
     # raise permissions errors, WestNotFound, etc.
     loc = _location(configfile, topdir=topdir)
-    path = pathlib.Path(loc)
+    path = Path(loc)
 
     if path.is_file():
         return loc
 
     path.parent.mkdir(parents=True, exist_ok=True)
     path.touch(exist_ok=True)
-    return canon_path(str(path))
+    return os.fspath(path)