Fix python 2 activator from python 3 invalid (#1794)

docs/changelog/1776.bugfix.rst

@@ -0,0 +1 @@
+Fix generating a Python 2 environment from Python 3 creates invalid python activator - by :user:`gaborbernat`.

src/virtualenv/activation/python/__init__.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import, unicode_literals
 
 import os
+import sys
 from collections import OrderedDict
 
 from virtualenv.util.path import Path
@@ -29,5 +30,5 @@ def replacements(self, creator, dest_folder):
     def _repr_unicode(creator, value):
         py2 = creator.interpreter.version_info.major == 2
         if py2:  # on Python 2 we need to encode this into explicit utf-8, py3 supports unicode literals
-            value = ensure_text(repr(value.encode("utf-8"))[1:-1])
+            value = ensure_text(repr(value.encode("utf-8"))[2 if sys.version_info[0] == 3 else 1 : -1])
         return value

src/virtualenv/activation/via_template.py

@@ -25,9 +25,10 @@ def templates(self):
     def generate(self, creator):
         dest_folder = creator.bin_dir
         replacements = self.replacements(creator, dest_folder)
-        self._generate(replacements, self.templates(), dest_folder, creator)
+        at_path = self._generate(replacements, self.templates(), dest_folder, creator)
         if self.flag_prompt is not None:
             creator.pyenv_cfg["prompt"] = self.flag_prompt
+        return at_path
 
     def replacements(self, creator, dest_folder):
         return {
@@ -43,6 +44,7 @@ def _generate(self, replacements, templates, to_folder, creator):
             text = self.instantiate_template(replacements, template, creator)
             dest = to_folder / self.as_name(template)
             dest.write_text(text, encoding="utf-8")
+            return dest
 
     def as_name(self, template):
         return template.name

tests/conftest.py

@@ -12,6 +12,7 @@
 import pytest
 import six
 
+from virtualenv.discovery.builtin import get_interpreter
 from virtualenv.discovery.py_info import PythonInfo
 from virtualenv.info import IS_PYPY, IS_WIN, fs_supports_symlink
 from virtualenv.report import LOGGER
@@ -318,3 +319,16 @@ def temp_app_data(monkeypatch, tmp_path):
     app_data = tmp_path / "app-data"
     monkeypatch.setenv(str("VIRTUALENV_OVERRIDE_APP_DATA"), str(app_data))
     return app_data
+
+
+@pytest.fixture(scope="session")
+def cross_python(is_inside_ci, session_app_data):
+    current = PythonInfo.current(session_app_data)
+    spec = "{}{}".format(current.implementation, 2 if current.version_info.major == 3 else 3)
+    interpreter = get_interpreter(spec, session_app_data)
+    if interpreter is None:
+        msg = "could not find {}".format(spec)
+        if is_inside_ci:
+            raise RuntimeError(msg)
+        pytest.skip(msg=msg)
+    yield interpreter

tests/unit/activation/test_activate_this.py

@@ -0,0 +1,23 @@
+from virtualenv.activation import PythonActivator
+from virtualenv.config.cli.parser import VirtualEnvOptions
+from virtualenv.run import session_via_cli
+
+
+def test_from_py3_to_py2(session_app_data, cross_python, special_name_dir):
+    options = VirtualEnvOptions()
+    cli_args = [
+        str(special_name_dir),
+        "-p",
+        str(cross_python.executable),
+        "--app-data",
+        str(session_app_data.path),
+        "--without-pip",
+        "--activators",
+        "",
+    ]
+    session = session_via_cli(cli_args, options)
+    activator = PythonActivator(options)
+    session.creator.bin_dir.mkdir(parents=True)
+    result = activator.generate(session.creator)
+    content = result.read_text()
+    assert "\"'" not in content

tests/unit/create/test_creator.py

@@ -23,7 +23,6 @@
 from virtualenv.create.via_global_ref.builtin.cpython.cpython2 import CPython2PosixBase
 from virtualenv.create.via_global_ref.builtin.cpython.cpython3 import CPython3Posix
 from virtualenv.create.via_global_ref.builtin.python2.python2 import Python2
-from virtualenv.discovery.builtin import get_interpreter
 from virtualenv.discovery.py_info import PythonInfo
 from virtualenv.info import IS_PYPY, IS_WIN, PY2, PY3, fs_is_case_sensitive
 from virtualenv.pyenv_cfg import PyEnvCfg
@@ -315,18 +314,6 @@ def test_prompt_set(tmp_path, creator, prompt):
             assert cfg["prompt"] == actual_prompt
 
 
-@pytest.fixture(scope="session")
-def cross_python(is_inside_ci, session_app_data):
-    spec = "{}{}".format(CURRENT.implementation, 2 if CURRENT.version_info.major == 3 else 3)
-    interpreter = get_interpreter(spec, session_app_data)
-    if interpreter is None:
-        msg = "could not find {}".format(spec)
-        if is_inside_ci:
-            raise RuntimeError(msg)
-        pytest.skip(msg=msg)
-    yield interpreter
-
-
 @pytest.mark.slow
 def test_cross_major(cross_python, coverage_env, tmp_path, session_app_data, current_fastest):
     cmd = [