interface compatibility with before rewrite (#1479)

Ensure that what ran with virtualenv 17 will continue running in a post
rewrite world minus the deprecated flags, plus the relocatable feature.

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

1 files changed, 50 insertions, 0 deletions

diff --git a/src/virtualenv/util/path/_sync.py b/src/virtualenv/util/path/_sync.py
new file mode 100644
index 0000000..c3d6111
--- /dev/null
+++ b/src/virtualenv/util/path/_sync.py
@@ -0,0 +1,50 @@
+from __future__ import absolute_import, unicode_literals
+
+import logging
+import os
+import shutil
+from functools import partial
+
+import six
+
+HAS_SYMLINK = hasattr(os, "symlink")
+
+
+def ensure_dir(path):
+    if not path.exists():
+        logging.debug("created %s", six.ensure_text(str(path)))
+        os.makedirs(six.ensure_text(str(path)))
+
+
+def symlink_or_copy(do_copy, src, dst, relative_symlinks_ok=False):
+    """
+    Try symlinking a target, and if that fails, fall back to copying.
+    """
+    if do_copy is False and HAS_SYMLINK is False:  # if no symlink, always use copy
+        do_copy = True
+    if not do_copy:
+        try:
+            if not dst.is_symlink():  # can't link to itself!
+                if relative_symlinks_ok:
+                    assert src.parent == dst.parent
+                    os.symlink(six.ensure_text(src.name), six.ensure_text(str(dst)))
+                else:
+                    os.symlink(six.ensure_text(str(src)), six.ensure_text(str(dst)))
+        except OSError as exception:
+            logging.warning(
+                "symlink failed %r, for %s to %s, will try copy",
+                exception,
+                six.ensure_text(str(src)),
+                six.ensure_text(str(dst)),
+            )
+            do_copy = True
+    if do_copy:
+        copier = shutil.copy2 if src.is_file() else shutil.copytree
+        copier(six.ensure_text(str(src)), six.ensure_text(str(dst)))
+    logging.debug("%s %s to %s", "copy" if do_copy else "symlink", six.ensure_text(str(src)), six.ensure_text(str(dst)))
+
+
+symlink = partial(symlink_or_copy, False)
+copy = partial(symlink_or_copy, True)
+
+__all__ = ("ensure_dir", "symlink", "copy", "symlink_or_copy")