Add system-site-packages setting

closes python-poetry#1393

docs/docs/configuration.md

@@ -112,6 +112,12 @@ Defaults to `true`.
 Create the virtualenv inside the project's root directory.
 Defaults to `false`.
 
+### `virtualenvs.include-system-packages`: boolean
+
+Give the virtual environment access to the system site-packages dir.
+Defaults to `false`.
+
+
 ### `virtualenvs.path`: string
 
 Directory where virtual environments will be created.

poetry/config/config.py

@@ -35,11 +35,18 @@ class Config(object):
         "virtualenvs": {
             "create": True,
             "in-project": False,
+            "include-system-packages": False,
             "path": os.path.join("{cache-dir}", "virtualenvs"),
         },
         "experimental": {"new-installer": True},
     }
 
+    _boolean_settings = (
+        "virtualenvs.create",
+        "virtualenvs.in-project",
+        "virtualenvs.include-system-packages",
+    )
+
     def __init__(
         self, use_environment=True, base_dir=None
     ):  # type: (bool, Optional[Path]) -> None
@@ -131,14 +138,14 @@ def process(self, value):  # type: (Any) -> Any
         return re.sub(r"{(.+?)}", lambda m: self.get(m.group(1)), value)
 
     def _get_validator(self, name):  # type: (str) -> Callable
-        if name in {"virtualenvs.create", "virtualenvs.in-project"}:
+        if name in self._boolean_settings:
             return boolean_validator
 
         if name == "virtualenvs.path":
             return str
 
     def _get_normalizer(self, name):  # type: (str) -> Callable
-        if name in {"virtualenvs.create", "virtualenvs.in-project"}:
+        if name in self._boolean_settings:
             return boolean_normalizer
 
         if name == "virtualenvs.path":

poetry/console/commands/config.py

@@ -52,6 +52,11 @@ def unique_config_values(self):
             ),
             "virtualenvs.create": (boolean_validator, boolean_normalizer, True),
             "virtualenvs.in-project": (boolean_validator, boolean_normalizer, False),
+            "virtualenvs.include-system-packages": (
+                boolean_validator,
+                boolean_normalizer,
+                False,
+            ),
             "virtualenvs.path": (
                 str,
                 lambda val: str(Path(val)),

poetry/utils/env.py

@@ -518,6 +518,9 @@ def create_venv(
 
         create_venv = self._poetry.config.get("virtualenvs.create")
         root_venv = self._poetry.config.get("virtualenvs.in-project")
+        include_system_packages = self._poetry.config.get(
+            "virtualenvs.include-system-packages"
+        )
 
         venv_path = self._poetry.config.get("virtualenvs.path")
         if root_venv:
@@ -627,6 +630,12 @@ def create_venv(
             name = "{}-py{}".format(name, python_minor.strip())
             venv = venv_path / name
 
+        def _build_venv():
+            extra_kwargs = {}
+            if include_system_packages is True:
+                extra_kwargs.update(include_system_packages=True)
+            self.build_venv(str(venv), executable=executable, **extra_kwargs)
+
         if not venv.exists():
             if create_venv is False:
                 io.write_line(
@@ -642,7 +651,7 @@ def create_venv(
                 "Creating virtualenv <c1>{}</> in {}".format(name, str(venv_path))
             )
 
-            self.build_venv(str(venv), executable=executable)
+            _build_venv()
         else:
             if force:
                 if not env.is_sane():
@@ -655,7 +664,7 @@ def create_venv(
                     "Recreating virtualenv <c1>{}</> in {}".format(name, str(venv))
                 )
                 self.remove_venv(str(venv))
-                self.build_venv(str(venv), executable=executable)
+                _build_venv()
             elif io.is_very_verbose():
                 io.write_line("Virtualenv <c1>{}</> already exists.".format(name))
 
@@ -679,19 +688,20 @@ def create_venv(
 
     @classmethod
     def build_venv(
-        cls, path, executable=None
-    ):  # type: (str, Optional[Union[str, Path]]) -> virtualenv.run.session.Session
+        cls, path, executable=None, include_system_packages=False
+    ):  # type: (str, Optional[Union[str, Path]], bool) -> virtualenv.run.session.Session
         if isinstance(executable, Path):
             executable = executable.resolve()
-        return virtualenv.cli_run(
-            [
-                "--no-download",
-                "--no-periodic-update",
-                "--python",
-                executable or sys.executable,
-                path,
-            ]
-        )
+
+        options = [
+            "--no-download",
+            "--no-periodic-update",
+            "--python",
+            executable or sys.executable,
+        ]
+        if include_system_packages:
+            options.extend(["--system-site-packages"])
+        return virtualenv.cli_run([*options, path])
 
     def remove_venv(self, path):  # type: (str) -> None
         shutil.rmtree(path)
@@ -883,7 +893,7 @@ def _run(self, cmd, **kwargs):
                     stderr=subprocess.STDOUT,
                     input=encode(input_),
                     check=True,
-                    **kwargs
+                    **kwargs,
                 ).stdout
             elif call:
                 return subprocess.call(cmd, stderr=subprocess.STDOUT, **kwargs)

tests/console/commands/env/test_use.py

@@ -16,7 +16,7 @@
 CWD = Path(__file__).parent.parent / "fixtures" / "simple_project"
 
 
-def build_venv(path, executable=None):
+def build_venv(path, executable=None, include_system_packages=False):
     os.mkdir(path)
 
 

tests/console/commands/test_config.py

@@ -16,6 +16,7 @@ def test_list_displays_default_value_if_not_set(app, config):
 experimental.new-installer = true
 virtualenvs.create = true
 virtualenvs.in-project = false
+virtualenvs.include-system-packages = false
 virtualenvs.path = {path}  # /foo{sep}virtualenvs
 """.format(
         path=json.dumps(os.path.join("{cache-dir}", "virtualenvs")), sep=os.path.sep
@@ -36,6 +37,7 @@ def test_list_displays_set_get_setting(app, config):
 experimental.new-installer = true
 virtualenvs.create = false
 virtualenvs.in-project = false
+virtualenvs.include-system-packages = false
 virtualenvs.path = {path}  # /foo{sep}virtualenvs
 """.format(
         path=json.dumps(os.path.join("{cache-dir}", "virtualenvs")), sep=os.path.sep
@@ -84,6 +86,7 @@ def test_list_displays_set_get_local_setting(app, config):
 experimental.new-installer = true
 virtualenvs.create = false
 virtualenvs.in-project = false
+virtualenvs.include-system-packages = false
 virtualenvs.path = {path}  # /foo{sep}virtualenvs
 """.format(
         path=json.dumps(os.path.join("{cache-dir}", "virtualenvs")), sep=os.path.sep

tests/test_factory.py

@@ -204,5 +204,6 @@ def test_create_poetry_fails_on_invalid_configuration():
 def test_create_poetry_with_local_config(fixture_dir):
     poetry = Factory().create_poetry(fixture_dir("with_local_config"))
 
-    assert not poetry.config.get("virtualenvs.in-project")
-    assert not poetry.config.get("virtualenvs.create")
+    assert poetry.config.get("virtualenvs.in-project") is False
+    assert poetry.config.get("virtualenvs.create") is False
+    assert poetry.config.get("virtualenvs.include-system-packages") is False

tests/utils/test_env.py

@@ -84,7 +84,7 @@ def test_env_get_in_project_venv(manager, poetry):
     shutil.rmtree(str(venv.path))
 
 
-def build_venv(path, executable=None):
+def build_venv(path, executable=None, include_system_packages=False):
     os.mkdir(path)
 
 
@@ -536,6 +536,18 @@ def test_remove_also_deactivates(tmp_dir, manager, poetry, config, mocker):
     assert venv_name not in envs
 
 
+def test_env_system_packages(tmp_dir, config):
+    venv_path = Path(tmp_dir) / "venv"
+    EnvManager(config).build_venv(str(venv_path), include_system_packages=True)
+    pyvenv_cfg = venv_path / "pyvenv.cfg"
+    if sys.version_info >= (3, 3):
+        assert "include-system-site-packages = true" in pyvenv_cfg.read_text()
+    elif (2, 6) < sys.version_info < (3, 0):
+        assert not venv_path.joinpath(
+            "lib", "python2.7", "no-global-site-packages.txt"
+        ).exists()
+
+
 @pytest.mark.skipif(
     os.name == "nt" or PY2, reason="Symlinks are not support for Windows"
 )