Support built-in “venv”

.travis.yml

@@ -21,16 +21,40 @@ matrix:
         - pip install -e . --upgrade
         - pip install pytest
       script: py.test -rws tests/ --ignore=tests/test_install.py
+    - language: python
+      sudo: false
+      python: "3.4"
+      env: PEW_USE_VIRTUALENV=1
+      install:
+        - pip install -e . --upgrade
+        - pip install pytest
+      script: py.test -rws tests/ --ignore=tests/test_install.py
     - language: python
       sudo: false
       python: "3.5"
       install:
         - pip install -e . --upgrade
         - pip install pytest
       script: py.test -rws tests/ --ignore=tests/test_install.py
+    - language: python
+      sudo: false
+      python: "3.5"
+      env: PEW_USE_VIRTUALENV=1
+      install:
+        - pip install -e . --upgrade
+        - pip install pytest
+      script: py.test -rws tests/ --ignore=tests/test_install.py
+    - language: python
+      sudo: false
+      python: "3.6"
+      install:
+        - pip install -e .[pythonz] --upgrade
+        - pip install pytest
+      script: py.test -rws tests/
     - language: python
       sudo: false
       python: "3.6"
+      env: PEW_USE_VIRTUALENV=1
       install:
         - pip install -e .[pythonz] --upgrade
         - pip install pytest
@@ -42,4 +66,4 @@ matrix:
         - pip install -e .[pythonz] --upgrade
         - pip install pytest
       script: py.test -rws tests/
-    - language: nix
+    - language: nix

appveyor.yml

@@ -1,7 +1,7 @@
 install:
-  - SET PATH=C:\\Python34;C:\\Python34\\Scripts;%PATH%
-  - pip install tox
+  - SET PATH=C:\\Python36;C:\\Python35;C:\\Python34;C:\\Python33;C:\\Python27;C:\\Python26;%PATH%
+  - C:\\Python36\\Scripts\\pip.exe install tox
 
 build: false
 
-test_script: tox -e "py27,py34"
+test_script: C:\\Python36\\Scripts\\tox.exe

pew/__main__.py

@@ -0,0 +1,3 @@
+if __name__ == '__main__':
+    from . import pew
+    pew.pew()

pew/_cfg.py

@@ -0,0 +1,32 @@
+import collections
+import pathlib
+
+
+class Cfg(object):
+    """Minimal parser for pyvenv.cfg.
+    """
+    def __init__(self, path):
+        self._path = path
+        self._data = collections.OrderedDict()
+        with path.open(encoding='utf-8') as f:
+            for line in f:
+                key, _, value = line.partition('=')
+                self._data[key.strip().lower()] = value.strip()
+
+    @property
+    def bindir(self):
+        return pathlib.Path(self._data['home'])
+
+    @property
+    def include_system_sitepackages(self):
+        return self._data['include-system-site-packages'] == 'true'
+
+    @include_system_sitepackages.setter
+    def include_system_sitepackages(self, value):
+        value = {True: 'true', False: 'false'}[value]
+        self._data['include-system-site-packages'] = value
+
+    def save(self):
+        with self._path.open('w', encoding='utf-8') as f:
+            for k, v in self._data.items():
+                f.write('{} = {}\n'.format(k, v))

pew/_utils.py

@@ -64,13 +64,22 @@ def invoke(*args, **kwargs):
 
 env_bin_dir = 'bin' if sys.platform != 'win32' else 'Scripts'
 
+if windows:
+    default_home = '~/.virtualenvs'
+else:
+    default_home = os.path.join(
+        os.environ.get('XDG_DATA_HOME', '~/.local/share'), 'virtualenvs')
+
 
 def expandpath(path):
     return Path(os.path.expanduser(os.path.expandvars(path)))
 
 
+workon_home = expandpath(os.environ.get('WORKON_HOME', default_home))
+
+
 def own(path):
-    if sys.platform == 'win32':
+    if windows:
         # Even if run by an administrator, the permissions will be set
         # correctly on Windows, no need to check
         return True
@@ -87,3 +96,7 @@ def temp_environ():
     finally:
         os.environ.clear()
         os.environ.update(environ)
+
+
+def uses_venv():
+    return sys.version_info >= (3, 4) and not os.environ.get('PEW_USE_VIRTUALENV')

pew/_venv.py

@@ -0,0 +1,160 @@
+__all__ = ['choose_backend', 'guess_backend']
+
+import os
+import pathlib
+import subprocess
+import sys
+import warnings
+
+from ._cfg import Cfg
+from ._utils import env_bin_dir, invoke, uses_venv, windows
+
+
+class Backend(object):
+
+    def __init__(self, root):
+        super(Backend, self).__init__()
+        self.root = root.absolute()
+
+    def get_python(self):
+        return self.root.joinpath(env_bin_dir, 'python.exe' if windows else 'python')
+
+    def get_sitepackages_dir(self):
+        result = invoke(
+            str(self.get_python()), '-c',
+            'import distutils.sysconfig; '
+            'print(distutils.sysconfig.get_python_lib())',
+        )
+        if result.returncode != 0:
+            raise RuntimeError(
+                'could not get site-packages location.\n%s' % result.err,
+            )
+        return pathlib.Path(result.out)
+
+
+class VirtualenvBackend(Backend):
+    """Functionality provided by virtualenv.
+    """
+    def create_env(self, py, args):
+        if py:
+            args = ["--python=%s" % py] + args
+        subprocess.check_call(
+            [sys.executable, '-m', 'virtualenv', str(self.root)] + args,
+        )
+
+    def restore_env(self):
+        subprocess.check_call([
+            sys.executable, "-m", 'virtualenv', str(self.root),
+            "--python=%s" % self.get_python().name,
+        ])
+
+    def toggle_global_sitepackages(self):
+        ngsp = self.get_sitepackages_dir().with_name(
+            'no-global-site-packages.txt',
+        )
+        should_enable = not ngsp.exists()
+        if should_enable:
+            with ngsp.open('w'):
+                pass
+        else:
+            ngsp.unlink()
+        return should_enable
+
+
+class BrokenEnvironmentError(RuntimeError):
+    pass
+
+
+def find_real_python():
+    # We need to run venv on the Python we want to use. sys.executable is not
+    # enough because it might come from a venv itself. venv can be easily
+    # confused if it is nested inside another venv.
+    # https://bugs.python.org/issue30811
+    python = ('python.exe' if windows else 'python')
+
+    # If we're in a venv, excellent! The config file has this information.
+    pyvenv_cfg = pathlib.Path(sys.prefix, 'pyvenv.cfg')
+    if pyvenv_cfg.exists():
+        return Cfg(pyvenv_cfg).bindir.joinpath(python)
+
+    # Or we can try looking this up from the build configuration. This is
+    # usually good enough, unless we're in a virtualenv (i.e. sys.real_prefix
+    # is set), and sysconfig reports the wrong Python (i.e. in the virtualenv).
+    import sysconfig
+    bindir = sysconfig.get_config_var('BINDIR')
+    try:
+        real_prefix = sys.real_prefix
+    except AttributeError:
+        return pathlib.Path(bindir, python)
+    if not os.path.realpath(bindir).startswith(real_prefix):
+        return pathlib.Path(bindir, python)
+
+    # OK, so we're in a virtualenv, and sysconfig lied. At this point there's
+    # no definitive way to tell where the real Python is, so let's make an
+    # educated guess. This works if the user isn't using a very exotic build.
+    for rel in ['', os.path.relpath(str(bindir), real_prefix), env_bin_dir]:
+        try:
+            path = pathlib.Path(real_prefix, rel, python).resolve()
+        except FileNotFoundError:
+            continue
+        if path.exists():   # On 3.6+ resolve() doesn't check for existence.
+            return path
+
+    # We've tried everything. Sorry.
+    raise BrokenEnvironmentError
+
+
+class VenvBackend(Backend):
+    """Functionality provided by venv, built-in since Python 3.4.
+    """
+    module_name = 'venv'
+
+    def create_env(self, py, args):
+        if not py:
+            py = find_real_python()
+        subprocess.check_call([str(py), '-m', 'venv', str(self.root)] + args)
+
+    def restore_env(self):
+        cfg = Cfg(self.root.joinpath('pyvenv.cfg'))
+        py = cfg.bindir.joinpath('python.exe' if windows else 'python')
+        subprocess.check_call([str(py), "-m", 'venv', str(self.root)])
+
+    def toggle_global_sitepackages(self):
+        cfg = Cfg(self.root.joinpath('pyvenv.cfg'))
+        should_enable = not cfg.include_system_sitepackages
+        cfg.include_system_sitepackages = should_enable
+        cfg.save()
+        return should_enable
+
+
+def choose_backend(root):
+    """Choose a preferred virtual environment backend to use.
+    """
+    if not uses_venv():
+        return VirtualenvBackend(root)
+
+    # Without ensurepip the venv can can't bootstrap Setuptools and Pip.
+    # The venv would not be useful for us without them.
+    for module_name in ['ensurepip', 'venv']:
+        try:
+            __import__(module_name)
+        except ImportError:
+            warnings.warn(
+                'Module "%s" unavailable, falling back to virtualenv...\n'
+                'Set PEW_USE_VIRTUALENV environment variable to '
+                'suppress this.' % module_name,
+                FutureWarning,
+            )
+            return VirtualenvBackend(root)
+    return VenvBackend(root)
+
+
+def guess_backend(root):
+    """Guess what backend a virtual environment backend uses.
+
+    The built-in venv writes a pyvenv.cfg file; check if it exists.
+    """
+    pyvenv_cfg = root / 'pyvenv.cfg'
+    if pyvenv_cfg.exists():
+        return VenvBackend(root)
+    return VirtualenvBackend(root)