Merge pull request #4319 from pypa/bugfix/4315

Correctly populate the system python path

news/4315.bugfix.rst

@@ -0,0 +1 @@
+Fix a bug that incorrect Python path will be used when ``--system`` flag is on.

pipenv/core.py

@@ -1946,6 +1946,8 @@ def do_install(
     # Automatically use an activated virtualenv.
     if PIPENV_USE_SYSTEM:
         system = True
+    if system:
+        os.environ["PIPENV_USE_SYSTEM"] = "1"
     # Check if the file is remote or not
     if remote:
         click.echo(

pipenv/environment.py

@@ -41,6 +41,7 @@ class Environment(object):
     def __init__(
         self,
         prefix=None,  # type: Optional[str]
+        python=None,  # type: Optional[str]
         is_venv=False,  # type: bool
         base_working_set=None,  # type: pkg_resources.WorkingSet
         pipfile=None,  # type: Optional[Union[tomlkit.toml_document.TOMLDocument, TPipfile]]
@@ -51,6 +52,9 @@ def __init__(
         self._modules = {'pkg_resources': pkg_resources, 'pipenv': pipenv}
         self.base_working_set = base_working_set if base_working_set else BASE_WORKING_SET
         prefix = normalize_path(prefix)
+        self._python = None
+        if python is not None:
+            self._python = vistir.compat.Path(python).absolute().as_posix()
         self.is_venv = is_venv or prefix != normalize_path(sys.prefix)
         if not sources:
             sources = []
@@ -267,9 +271,15 @@ def script_basedir(self):
     def python(self):
         # type: () -> str
         """Path to the environment python"""
-        py = vistir.compat.Path(self.script_basedir).joinpath("python").absolute().as_posix()
+        if self._python is not None:
+            return self._python
+        if os.name == "nt" and not self.is_venv:
+            py = vistir.compat.Path(self.prefix).joinpath("python").absolute().as_posix()
+        else:
+            py = vistir.compat.Path(self.script_basedir).joinpath("python").absolute().as_posix()
         if not py:
-            return vistir.compat.Path(sys.executable).as_posix()
+            py = vistir.compat.Path(sys.executable).as_posix()
+        self._python = py
         return py
 
     @cached_property

pipenv/project.py

@@ -352,12 +352,14 @@ def get_environment(self, allow_global=False):
         is_venv = is_in_virtualenv()
         if allow_global and not is_venv:
             prefix = sys.prefix
+            python = sys.executable
         else:
             prefix = self.virtualenv_location
+            python = None
         sources = self.sources if self.sources else [DEFAULT_SOURCE]
         environment = Environment(
-            prefix=prefix, is_venv=is_venv, sources=sources, pipfile=self.parsed_pipfile,
-            project=self
+            prefix=prefix, python=python, is_venv=is_venv, sources=sources,
+            pipfile=self.parsed_pipfile, project=self
         )
         pipenv_dist = get_pipenv_dist(pkg="pipenv")
         if pipenv_dist: