bpo-41282: (PEP 632) Load install schemes from sysconfig

Lib/distutils/command/install.py

@@ -3,7 +3,9 @@
 Implements the Distutils 'install' command."""
 
 import sys
+import sysconfig
 import os
+import re
 
 from distutils import log
 from distutils.core import Command
@@ -20,33 +22,45 @@
 
 HAS_USER_SITE = (USER_SITE is not None)
 
-WINDOWS_SCHEME = {
-    'purelib': '$base/Lib/site-packages',
-    'platlib': '$base/Lib/site-packages',
-    'headers': '$base/Include/$dist_name',
-    'scripts': '$base/Scripts',
-    'data'   : '$base',
-}
-
-INSTALL_SCHEMES = {
-    'unix_prefix': {
-        'purelib': '$base/lib/python$py_version_short/site-packages',
-        'platlib': '$platbase/$platlibdir/python$py_version_short/site-packages',
-        'headers': '$base/include/python$py_version_short$abiflags/$dist_name',
-        'scripts': '$base/bin',
-        'data'   : '$base',
-        },
-    'unix_home': {
-        'purelib': '$base/lib/python',
-        'platlib': '$base/$platlibdir/python',
-        'headers': '$base/include/python/$dist_name',
-        'scripts': '$base/bin',
-        'data'   : '$base',
-        },
-    'nt': WINDOWS_SCHEME,
-    }
-
-# user site schemes
+# The keys to an installation scheme; if any new types of files are to be
+# installed, be sure to add an entry to every installation scheme above,
+# and to SCHEME_KEYS here.
+SCHEME_KEYS = ('purelib', 'platlib', 'headers', 'scripts', 'data')
+
+# The following code provides backward-compatible INSTALL_SCHEMES
+# while making the sysconfig module the single point of truth.
+# This makes it easier for OS distributions where they need to
+# alter locations for packages installations on single place.
+# This module is depracated anyway (PEP 632) so if anything
+# doesn't work for you, take a look at sysconfig.
+INSTALL_SCHEMES = {"unix_prefix": {}, "unix_home": {}, "nt": {}}
+
+# Copy from sysconfig._INSTALL_SCHEMES
+for key in SCHEME_KEYS:
+    sys_key = key
+    if key == "headers":
+        sys_key = "include"
+    INSTALL_SCHEMES["unix_prefix"][key] = sysconfig._INSTALL_SCHEMES["posix_prefix"][sys_key]
+    INSTALL_SCHEMES["unix_home"][key] = sysconfig._INSTALL_SCHEMES["posix_home"][sys_key]
+    INSTALL_SCHEMES["nt"][key] = sysconfig._INSTALL_SCHEMES["nt"][sys_key]
+
+# Transformation to different template format
+for main_key in INSTALL_SCHEMES:
+    for key, value in INSTALL_SCHEMES[main_key].items():
+        # Change all ocurences of {variable} to $variable
+        value = re.sub(r"\{(.+?)\}", r"$\g<1>", value)
+        value = value.replace("$installed_base", "$base")
+        value = value.replace("$py_version_nodot_plat", "$py_version_nodot")
+        if key == "headers":
+            value += "/$dist_name"
+        if sys.version_info >= (3, 9) and key == "platlib":
+            # platlibdir is available since 3.9: bpo-1294959
+            value = value.replace("/lib/", "/$platlibdir/")
+        INSTALL_SCHEMES[main_key][key] = value
+
+# The following part of INSTALL_SCHEMES has different definition
+# that the one in sysconfig but because both depends on site module
+# the outcomes should be the same.
 if HAS_USER_SITE:
     INSTALL_SCHEMES['nt_user'] = {
         'purelib': '$usersite',
@@ -65,11 +79,6 @@
         'data'   : '$userbase',
         }
 
-# The keys to an installation scheme; if any new types of files are to be
-# installed, be sure to add an entry to every installation scheme above,
-# and to SCHEME_KEYS here.
-SCHEME_KEYS = ('purelib', 'platlib', 'headers', 'scripts', 'data')
-
 
 class install(Command):
 

Lib/sysconfig.py

@@ -176,12 +176,6 @@ def is_python_build(check_home=False):
 
 _PYTHON_BUILD = is_python_build(True)
 
-if _PYTHON_BUILD:
-    for scheme in ('posix_prefix', 'posix_home'):
-        _INSTALL_SCHEMES[scheme]['include'] = '{srcdir}/Include'
-        _INSTALL_SCHEMES[scheme]['platinclude'] = '{projectbase}/.'
-
-
 def _subst_vars(s, local_vars):
     try:
         return s.format(**local_vars)

Misc/NEWS.d/next/Library/2021-02-16-13-18-38.bpo-41282.GK9a0l.rst

@@ -0,0 +1,2 @@
+Install schemes in :mod:`distutils.command.install` are now loaded from
+:mod:`sysconfig`.