Merge pull request #137 from zooba/issue-132

Detect when a venv is created from an in-tree build. Fixes #132

distutils/_functools.py

@@ -0,0 +1,20 @@
+import functools
+
+
+# from jaraco.functools 3.5
+def pass_none(func):
+    """
+    Wrap func so it's not called if its first param is None
+
+    >>> print_text = pass_none(print)
+    >>> print_text('text')
+    text
+    >>> print_text(None)
+    """
+
+    @functools.wraps(func)
+    def wrapper(param, *args, **kwargs):
+        if param is not None:
+            return func(param, *args, **kwargs)
+
+    return wrapper

distutils/sysconfig.py

@@ -16,6 +16,7 @@
 
 from .errors import DistutilsPlatformError
 from . import py39compat
+from ._functools import pass_none
 
 IS_PYPY = '__pypy__' in sys.builtin_module_names
 
@@ -51,12 +52,25 @@ def _is_python_source_dir(d):
 
 _sys_home = getattr(sys, '_home', None)
 
+
+def _is_parent(dir_a, dir_b):
+    """
+    Return True if a is a parent of b.
+    """
+    return os.path.normcase(dir_a).startswith(os.path.normcase(dir_b))
+
+
 if os.name == 'nt':
+    @pass_none
     def _fix_pcbuild(d):
-        if d and os.path.normcase(d).startswith(
-                os.path.normcase(os.path.join(PREFIX, "PCbuild"))):
-            return PREFIX
-        return d
+        # In a venv, sys._home will be inside BASE_PREFIX rather than PREFIX.
+        prefixes = PREFIX, BASE_PREFIX
+        matched = (
+            prefix
+            for prefix in prefixes
+            if _is_parent(d, os.path.join(prefix, "PCbuild"))
+        )
+        return next(matched, d)
     project_base = _fix_pcbuild(project_base)
     _sys_home = _fix_pcbuild(_sys_home)
 

distutils/tests/test_sysconfig.py

@@ -7,6 +7,9 @@
 import textwrap
 import unittest
 
+import jaraco.envs
+
+import distutils
 from distutils import sysconfig
 from distutils.ccompiler import get_default_compiler
 from distutils.unixccompiler import UnixCCompiler
@@ -309,6 +312,31 @@ def test_win_ext_suffix(self):
         self.assertTrue(sysconfig.get_config_var("EXT_SUFFIX").endswith(".pyd"))
         self.assertNotEqual(sysconfig.get_config_var("EXT_SUFFIX"), ".pyd")
 
+    @unittest.skipUnless(
+        sys.platform == 'win32',
+        'Testing Windows build layout')
+    @unittest.skipUnless(
+        sys.implementation.name == 'cpython',
+        'Need cpython for this test')
+    @unittest.skipUnless(
+        '\\PCbuild\\'.casefold() in sys.executable.casefold(),
+        'Need sys.executable to be in a source tree')
+    def test_win_build_venv_from_source_tree(self):
+        """Ensure distutils.sysconfig detects venvs from source tree builds."""
+        env = jaraco.envs.VEnv()
+        env.create_opts = env.clean_opts
+        env.root = TESTFN
+        env.ensure_env()
+        cmd = [
+            env.exe(),
+            "-c",
+            "import distutils.sysconfig; print(distutils.sysconfig.python_build)"
+        ]
+        distutils_path = os.path.dirname(os.path.dirname(distutils.__file__))
+        out = subprocess.check_output(cmd, env={**os.environ, "PYTHONPATH": distutils_path})
+        assert out == "True"
+
+
 def test_suite():
     suite = unittest.TestSuite()
     suite.addTest(unittest.TestLoader().loadTestsFromTestCase(SysconfigTestCase))

tox.ini

@@ -4,6 +4,7 @@ minversion = 3.25
 [testenv]
 deps =
 	pytest
+	jaraco.envs>=2.4
 commands =
 	pytest {posargs}
 setenv =