Don’t try to install something when running from uninstalled source (#12246).

Original patch by Tshepang Lekhonkhobe.

1 files changed, 14 insertions, 3 deletions

diff --git a/Lib/packaging/install.py b/Lib/packaging/install.py
index 2317645..c5bda45 100644
--- a/Lib/packaging/install.py
+++ b/Lib/packaging/install.py
@@ -13,7 +13,7 @@ import errno
 import shutil
 import logging
 import tempfile
-from sysconfig import get_config_var, get_path
+from sysconfig import get_config_var, get_path, is_python_build
 
 from packaging import logger
 from packaging.dist import Distribution
@@ -488,20 +488,31 @@ def install(project):
 
     Returns True on success, False on failure
     """
+    if is_python_build():
+        # Python would try to install into the site-packages directory under
+        # $PREFIX, but when running from an uninstalled code checkout we don't
+        # want to create directories under the installation root
+        message = ('installing third-party projects from an uninstalled '
+                   'Python is not supported')
+        logger.error(message)
+        return False
+
     logger.info('Checking the installation location...')
     purelib_path = get_path('purelib')
+
     # trying to write a file there
     try:
         with tempfile.NamedTemporaryFile(suffix=project,
                                          dir=purelib_path) as testfile:
             testfile.write(b'test')
     except OSError:
-        # was unable to write a file
+        # FIXME this should check the errno, or be removed altogether (race
+        # condition: the directory permissions could be changed between here
+        # and the actual install)
         logger.info('Unable to write in "%s". Do you have the permissions ?'
                     % purelib_path)
         return False
 
-
     logger.info('Getting information about %r...', project)
     try:
         info = get_infos(project)