env/run: ensure all args are quoted as required

Resolves: python-poetry#3013

poetry/utils/_compat.py

@@ -46,15 +46,11 @@
 
 WINDOWS = sys.platform == "win32"
 
-if PY2:
-    import pipes
-
-    shell_quote = pipes.quote
-else:
-    import shlex
-
-    shell_quote = shlex.quote
-
+try:
+    from shlex import quote
+except ImportError:
+    # PY2
+    from pipes import quote  # noqa
 
 if PY34:
     from importlib.machinery import EXTENSION_SUFFIXES
@@ -288,10 +284,7 @@ def to_str(string):
 
 
 def list_to_shell_command(cmd):
-    executable = cmd[0]
-
-    if " " in executable:
-        executable = '"{}"'.format(executable)
-        cmd[0] = executable
-
-    return " ".join(cmd)
+    return " ".join(
+        '"{}"'.format(token) if " " in token and token[0] not in {"'", '"'} else token
+        for token in cmd
+    )

tests/utils/test_env.py

@@ -15,6 +15,7 @@
 from poetry.factory import Factory
 from poetry.utils._compat import PY2
 from poetry.utils._compat import Path
+from poetry.utils.env import GET_BASE_PREFIX
 from poetry.utils.env import EnvCommandError
 from poetry.utils.env import EnvManager
 from poetry.utils.env import NoCompatiblePythonVersionFound
@@ -74,6 +75,26 @@ def test_virtualenvs_with_spaces_in_their_path_work_as_expected(tmp_dir, manager
     assert venv.run("python", "-V", shell=True).startswith("Python")
 
 
+def test_env_commands_with_spaces_in_their_arg_work_as_expected(tmp_dir, manager):
+    venv_path = Path(tmp_dir) / "Virtual Env"
+    manager.build_venv(str(venv_path))
+    venv = VirtualEnv(venv_path)
+    assert venv.run("python", venv.pip, "--version", shell=True).startswith(
+        "pip {} from ".format(venv.pip_version)
+    )
+
+
+def test_env_shell_commands_with_stdinput_in_their_arg_work_as_expected(
+    tmp_dir, manager
+):
+    venv_path = Path(tmp_dir) / "Virtual Env"
+    manager.build_venv(str(venv_path))
+    venv = VirtualEnv(venv_path)
+    assert venv.run("python", "-", input_=GET_BASE_PREFIX, shell=True).strip() == str(
+        venv.get_base_prefix()
+    )
+
+
 @pytest.fixture
 def in_project_venv_dir(poetry):
     os.environ.pop("VIRTUAL_ENV", None)