separate describe/create - check upfront if can create (#1502)

* start

Signed-off-by: Bernat Gabor <bgabor8@bloomberg.net>

* test for Windows

Signed-off-by: Bernat Gabor <bgabor8@bloomberg.net>

* test for Windows

Signed-off-by: Bernat Gabor <bgabor8@bloomberg.net>

* fix Windows symlink cache

1 files changed, 193 insertions, 0 deletions

diff --git a/src/virtualenv/create/creator.py b/src/virtualenv/create/creator.py
new file mode 100644
index 0000000..2ec19ae
--- /dev/null
+++ b/src/virtualenv/create/creator.py
@@ -0,0 +1,193 @@
+from __future__ import absolute_import, print_function, unicode_literals
+
+import json
+import logging
+import os
+import shutil
+import sys
+from abc import ABCMeta, abstractmethod
+from argparse import ArgumentTypeError
+from ast import literal_eval
+from collections import OrderedDict
+from stat import S_IWUSR
+
+import six
+from six import add_metaclass
+
+from virtualenv.discovery.py_info import Cmd
+from virtualenv.info import IS_ZIPAPP
+from virtualenv.pyenv_cfg import PyEnvCfg
+from virtualenv.util.path import Path
+from virtualenv.util.subprocess import run_cmd
+from virtualenv.util.zipapp import extract_to_app_data
+from virtualenv.version import __version__
+
+HERE = Path(__file__).absolute().parent
+DEBUG_SCRIPT = HERE / "debug.py"
+
+
+@add_metaclass(ABCMeta)
+class Creator(object):
+    def __init__(self, options, interpreter):
+        self.interpreter = interpreter
+        self._debug = None
+        self.dest = Path(options.dest)
+        self.enable_system_site_package = options.system_site
+        self.clear = options.clear
+        self.pyenv_cfg = PyEnvCfg.from_folder(self.dest)
+
+    def __repr__(self):
+        return six.ensure_str(self.__unicode__())
+
+    def __unicode__(self):
+        return "{}({})".format(self.__class__.__name__, ", ".join("{}={}".format(k, v) for k, v in self._args()))
+
+    def _args(self):
+        return [
+            ("dest", six.ensure_text(str(self.dest))),
+            ("global", self.enable_system_site_package),
+            ("clear", self.clear),
+        ]
+
+    @classmethod
+    def add_parser_arguments(cls, parser, interpreter, meta):
+        parser.add_argument(
+            "dest", help="directory to create virtualenv at", type=cls.validate_dest, default="venv", nargs="?",
+        )
+        parser.add_argument(
+            "--clear",
+            dest="clear",
+            action="store_true",
+            help="clear out the non-root install and start from scratch",
+            default=False,
+        )
+        parser.add_argument(
+            "--system-site-packages",
+            default=False,
+            action="store_true",
+            dest="system_site",
+            help="give the virtual environment access to the system site-packages dir",
+        )
+
+    @classmethod
+    def validate_dest(cls, raw_value):
+        """No path separator in the path, valid chars and must be write-able"""
+
+        def non_write_able(dest, value):
+            common = Path(*os.path.commonprefix([value.parts, dest.parts]))
+            raise ArgumentTypeError(
+                "the destination {} is not write-able at {}".format(dest.relative_to(common), common)
+            )
+
+        # the file system must be able to encode
+        # note in newer CPython this is always utf-8 https://www.python.org/dev/peps/pep-0529/
+        encoding = sys.getfilesystemencoding()
+        refused = OrderedDict()
+        kwargs = {"errors": "ignore"} if encoding != "mbcs" else {}
+        for char in six.ensure_text(raw_value):
+            try:
+                trip = char.encode(encoding, **kwargs).decode(encoding)
+                if trip == char:
+                    continue
+                raise ValueError(trip)
+            except ValueError:
+                refused[char] = None
+        if refused:
+            raise ArgumentTypeError(
+                "the file system codec ({}) cannot handle characters {!r} within {!r}".format(
+                    encoding, "".join(refused.keys()), raw_value
+                )
+            )
+        for char in (i for i in (os.pathsep, os.altsep) if i is not None):
+            if char in raw_value:
+                raise ArgumentTypeError(
+                    "destination {!r} must not contain the path separator ({}) as this would break "
+                    "the activation scripts".format(raw_value, char)
+                )
+
+        value = Path(raw_value)
+        if value.exists() and value.is_file():
+            raise ArgumentTypeError("the destination {} already exists and is a file".format(value))
+        if (3, 3) <= sys.version_info <= (3, 6):
+            # pre 3.6 resolve is always strict, aka must exists, sidestep by using os.path operation
+            dest = Path(os.path.realpath(raw_value))
+        else:
+            dest = value.resolve()
+        value = dest
+        while dest:
+            if dest.exists():
+                if os.access(six.ensure_text(str(dest)), os.W_OK):
+                    break
+                else:
+                    non_write_able(dest, value)
+            base, _ = dest.parent, dest.name
+            if base == dest:
+                non_write_able(dest, value)  # pragma: no cover
+            dest = base
+        return str(value)
+
+    def run(self):
+        if self.dest.exists() and self.clear:
+            logging.debug("delete %s", self.dest)
+
+            def onerror(func, path, exc_info):
+                if not os.access(path, os.W_OK):
+                    os.chmod(path, S_IWUSR)
+                    func(path)
+                else:
+                    raise
+
+            shutil.rmtree(str(self.dest), ignore_errors=True, onerror=onerror)
+        self.create()
+        self.set_pyenv_cfg()
+
+    @abstractmethod
+    def create(self):
+        raise NotImplementedError
+
+    @classmethod
+    def can_create(cls, interpreter):
+        """Default is that we can"""
+        return True
+
+    def set_pyenv_cfg(self):
+        self.pyenv_cfg.content = {
+            "home": self.interpreter.system_exec_prefix,
+            "include-system-site-packages": "true" if self.enable_system_site_package else "false",
+            "implementation": self.interpreter.implementation,
+            "version_info": ".".join(str(i) for i in self.interpreter.version_info),
+            "virtualenv": __version__,
+        }
+
+    @property
+    def debug(self):
+        if self._debug is None and self.exe is not None:
+            self._debug = get_env_debug_info(self.exe, self.debug_script())
+        return self._debug
+
+    # noinspection PyMethodMayBeStatic
+    def debug_script(self):
+        return DEBUG_SCRIPT
+
+
+def get_env_debug_info(env_exe, debug_script):
+    if IS_ZIPAPP:
+        debug_script = extract_to_app_data(debug_script)
+    cmd = [six.ensure_text(str(env_exe)), six.ensure_text(str(debug_script))]
+    logging.debug("debug via %r", Cmd(cmd))
+    env = os.environ.copy()
+    env.pop(str("PYTHONPATH"), None)
+    code, out, err = run_cmd(cmd)
+    # noinspection PyBroadException
+    try:
+        if code != 0:
+            result = literal_eval(out)
+        else:
+            result = json.loads(out)
+        if err:
+            result["err"] = err
+    except Exception as exception:
+        return {"out": out, "err": err, "returncode": code, "exception": repr(exception)}
+    if "sys" in result and "path" in result["sys"]:
+        del result["sys"]["path"][0]
+    return result