Fix absolute paths for Cygwin (#1970)

* Fix absolute paths for Cygwin

Absolute paths on Windows take the form "c:\somePath" -- these need to be mapped to the form "/cygdrive/c/somePath" on Cygwin. Otherwise, the virtualenv path gets garbled when activated on Cygwin, which can cause the wrong Python environment to be used.

* Remove Cygwin from the list, rely on the shell script for that

* Improved formatting

* Update tests to handle mingw + msys explicitly

* Add changelog entry

* lint errors

* Add msys support to the activation script

* Fix script error & linting

4 files changed, 5 insertions, 58 deletions

diff --git a/docs/changelog/1969.bugfix.rst b/docs/changelog/1969.bugfix.rst
new file mode 100644
index 0000000..6e6e706
--- /dev/null
+++ b/docs/changelog/1969.bugfix.rst
@@ -0,0 +1 @@
+Handle Cygwin path conversion in the activation script - by :user:`davidcoghlan`.
diff --git a/src/virtualenv/activation/bash/activate.sh b/src/virtualenv/activation/bash/activate.sh
index 19bf552..222d982 100644
--- a/src/virtualenv/activation/bash/activate.sh
+++ b/src/virtualenv/activation/bash/activate.sh
@@ -47,6 +47,9 @@ deactivate () {
 deactivate nondestructive
 
 VIRTUAL_ENV='__VIRTUAL_ENV__'
+if ([ "$OSTYPE" = "cygwin" ] || [ "$OSTYPE" = "msys" ]) && $(command -v cygpath &> /dev/null) ; then
+    VIRTUAL_ENV=$(cygpath -u "$VIRTUAL_ENV")
+fi
 export VIRTUAL_ENV
 
 _OLD_VIRTUAL_PATH="$PATH"
diff --git a/src/virtualenv/activation/via_template.py b/src/virtualenv/activation/via_template.py
index 6839f05..14f0979 100644
--- a/src/virtualenv/activation/via_template.py
+++ b/src/virtualenv/activation/via_template.py
@@ -1,9 +1,7 @@
 from __future__ import absolute_import, unicode_literals
 
 import os
-import re
 import sys
-import sysconfig
 from abc import ABCMeta, abstractmethod
 
 from six import add_metaclass
@@ -33,20 +31,9 @@ class ViaTemplateActivator(Activator):
         return generated
 
     def replacements(self, creator, dest_folder):
-        current_platform = sysconfig.get_platform()
-        platforms = ["mingw", "cygwin", "msys"]
-        if any(platform in current_platform for platform in platforms):
-            pattern = re.compile("^([A-Za-z]):(.*)")
-            match = pattern.match(str(creator.dest))
-            if match:
-                virtual_env = "/" + match.group(1).lower() + match.group(2)
-            else:
-                virtual_env = str(creator.dest)
-        else:
-            virtual_env = str(creator.dest)
         return {
             "__VIRTUAL_PROMPT__": "" if self.flag_prompt is None else self.flag_prompt,
-            "__VIRTUAL_ENV__": ensure_text(virtual_env),
+            "__VIRTUAL_ENV__": ensure_text(str(creator.dest)),
             "__VIRTUAL_NAME__": creator.env_name,
             "__BIN_NAME__": ensure_text(str(creator.bin_dir.relative_to(creator.dest))),
             "__PATH_SEP__": ensure_text(os.pathsep),
diff --git a/tests/unit/activation/test_activation_support.py b/tests/unit/activation/test_activation_support.py
index 5a234f9..d493c23 100644
--- a/tests/unit/activation/test_activation_support.py
+++ b/tests/unit/activation/test_activation_support.py
@@ -13,8 +13,6 @@ from virtualenv.activation import (
     PythonActivator,
 )
 from virtualenv.discovery.py_info import PythonInfo
-from virtualenv.info import IS_WIN
-from virtualenv.util.path import Path
 
 
 @pytest.mark.parametrize(
@@ -55,45 +53,3 @@ def test_activator_no_support_posix(mocker, activator_class):
     interpreter = mocker.Mock(spec=PythonInfo)
     interpreter.os = "posix"
     assert not activator.supports(interpreter)
-
-
-class Creator:
-    def __init__(self):
-        self.dest = "C:/tools/msys64/home"
-        self.env_name = "venv"
-        self.bin_dir = Path("C:/tools/msys64/home/bin")
-
-
-@pytest.mark.skipif(IS_WIN, reason="Github Actions ships with WSL bash")
-@pytest.mark.parametrize("activator_class", [BashActivator])
-def test_cygwin_msys2_path_conversion(mocker, activator_class):
-    mocker.patch("sysconfig.get_platform", return_value="mingw")
-    activator = activator_class(Namespace(prompt=None))
-    creator = Creator()
-    mocker.stub(creator.bin_dir.relative_to)
-    resource = activator.replacements(creator, "")
-    assert resource["__VIRTUAL_ENV__"] == "/c/tools/msys64/home"
-
-
-@pytest.mark.skipif(IS_WIN, reason="Github Actions ships with WSL bash")
-@pytest.mark.parametrize("activator_class", [BashActivator])
-def test_win_path_no_conversion(mocker, activator_class):
-    mocker.patch("sysconfig.get_platform", return_value="win-amd64")
-    activator = activator_class(Namespace(prompt=None))
-    creator = Creator()
-    mocker.stub(creator.bin_dir.relative_to)
-    resource = activator.replacements(creator, "")
-    assert resource["__VIRTUAL_ENV__"] == "C:/tools/msys64/home"
-
-
-@pytest.mark.skipif(IS_WIN, reason="Github Actions ships with WSL bash")
-@pytest.mark.parametrize("activator_class", [BashActivator])
-def test_cygwin_path_no_conversion(mocker, activator_class):
-    mocker.patch("sysconfig.get_platform", return_value="cygwin")
-    activator = activator_class(Namespace(prompt=None))
-    creator = Creator()
-    creator.dest = "/c/tools/msys64/home"
-    creator.bin_dir = Path("/c/tools/msys64/home/bin")
-    mocker.stub(creator.bin_dir.relative_to)
-    resource = activator.replacements(creator, "")
-    assert resource["__VIRTUAL_ENV__"] == "/c/tools/msys64/home"