Closes issue python#17732: ignore install-directory specific options in

distutils.cfg when a venv is active.

Doc/install/index.rst

@@ -645,6 +645,11 @@ environment variables, such as Mac OS 9, the configuration variables supplied by
 the Distutils are the only ones you can use.) See section :ref:`inst-config-files`
 for details.
 
+.. note:: When a :ref:`virtual environment <venv-def>` is activated, any options
+   that change the installation path will be ignored from all distutils configuration
+   files to prevent inadvertently installing projects outside of the virtual
+   environment.
+
 .. XXX need some Windows examples---when would custom installation schemes be
    needed on those platforms?
 

Doc/library/venv.rst

@@ -57,6 +57,10 @@ Creating virtual environments
    :attr:`sys.exec_prefix` is the same as :attr:`sys.base_exec_prefix` (they
    all point to a non-venv Python installation).
 
+   When a venv is active, any options that change the installation path will be
+   ignored from all distutils configuration files to prevent projects being
+   inadvertently installed outside of the virtual environment.
+
 
 API
 ---

Lib/distutils/dist.py

@@ -343,6 +343,18 @@ def find_config_files(self):
     def parse_config_files(self, filenames=None):
         from configparser import ConfigParser
 
+        # Ignore install directory options if we have a venv
+        if sys.prefix != sys.base_prefix:
+            ignore_options = [
+                'install-base', 'install-platbase', 'install-lib',
+                'install-platlib', 'install-purelib', 'install-headers',
+                'install-scripts', 'install-data', 'prefix', 'exec-prefix',
+                'home', 'user', 'root']
+        else:
+            ignore_options = []
+
+        ignore_options = frozenset(ignore_options)
+
         if filenames is None:
             filenames = self.find_config_files()
 
@@ -359,7 +371,7 @@ def parse_config_files(self, filenames=None):
                 opt_dict = self.get_option_dict(section)
 
                 for opt in options:
-                    if opt != '__name__':
+                    if opt != '__name__' and opt not in ignore_options:
                         val = parser.get(section,opt)
                         opt = opt.replace('-', '_')
                         opt_dict[opt] = (filename, val)

Lib/distutils/tests/test_dist.py

@@ -6,6 +6,8 @@
 import warnings
 import textwrap
 
+from unittest import mock
+
 from distutils.dist import Distribution, fix_help_options
 from distutils.cmd import Command
 
@@ -18,7 +20,7 @@ class test_dist(Command):
 
     user_options = [
         ("sample-option=", "S", "help text"),
-        ]
+    ]
 
     def initialize_options(self):
         self.sample_option = None
@@ -77,6 +79,64 @@ def test_command_packages_cmdline(self):
         self.assertIsInstance(cmd, test_dist)
         self.assertEqual(cmd.sample_option, "sometext")
 
+    def test_venv_install_options(self):
+        sys.argv.append("install")
+        self.addCleanup(os.unlink, TESTFN)
+
+        fakepath = '/somedir'
+
+        with open(TESTFN, "w") as f:
+            print(("[install]\n"
+                   "install-base = {0}\n"
+                   "install-platbase = {0}\n"
+                   "install-lib = {0}\n"
+                   "install-platlib = {0}\n"
+                   "install-purelib = {0}\n"
+                   "install-headers = {0}\n"
+                   "install-scripts = {0}\n"
+                   "install-data = {0}\n"
+                   "prefix = {0}\n"
+                   "exec-prefix = {0}\n"
+                   "home = {0}\n"
+                   "user = {0}\n"
+                   "root = {0}").format(fakepath), file=f)
+
+        # Base case: Not in a Virtual Environment
+        with mock.patch.multiple(sys, prefix='/a', base_prefix='/a') as values:
+            d = self.create_distribution([TESTFN])
+
+        option_tuple = (TESTFN, fakepath)
+
+        result_dict = {
+            'install_base': option_tuple,
+            'install_platbase': option_tuple,
+            'install_lib': option_tuple,
+            'install_platlib': option_tuple,
+            'install_purelib': option_tuple,
+            'install_headers': option_tuple,
+            'install_scripts': option_tuple,
+            'install_data': option_tuple,
+            'prefix': option_tuple,
+            'exec_prefix': option_tuple,
+            'home': option_tuple,
+            'user': option_tuple,
+            'root': option_tuple,
+        }
+
+        self.assertEqual(
+            sorted(d.command_options.get('install').keys()),
+            sorted(result_dict.keys()))
+
+        for (key, value) in d.command_options.get('install').items():
+            self.assertEqual(value, result_dict[key])
+
+        # Test case: In a Virtual Environment
+        with mock.patch.multiple(sys, prefix='/a', base_prefix='/b') as values:
+            d = self.create_distribution([TESTFN])
+
+        for key in result_dict.keys():
+            self.assertNotIn(key, d.command_options.get('install', {}))
+
     def test_command_packages_configfile(self):
         sys.argv.append("build")
         self.addCleanup(os.unlink, TESTFN)
@@ -304,7 +364,7 @@ def test_custom_pydistutils(self):
                 os.environ['HOME'] = temp_dir
                 files = dist.find_config_files()
                 self.assertIn(user_filename, files,
-                             '%r not found in %r' % (user_filename, files))
+                              '%r not found in %r' % (user_filename, files))
         finally:
             os.remove(user_filename)
 

Misc/NEWS

@@ -49,6 +49,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #17732: Ignore distutils.cfg options pertaining to install paths if a
+  virtual environment is active.
+
 - Issue #1159051: Back out a fix for handling corrupted gzip files that
   broke backwards compatibility.