Not yet fully-tested, but move(), copy(), remove() work properly. These changes allow for

archives themselves to be handled. Without these changes, an archive would be automatically
mounted, once mounted, operations on the archive file itself would fail. 

Also added a max_size parameter to ArchiveMountFS, to avoid mounting really large archives.

fs/contrib/archivefs.py

@@ -157,46 +157,30 @@ class ArchiveFS(FS):
         if not self.exists(path):
             raise ResourceNotFoundError(path)
         path = normpath(path).lstrip('/')
-        if path == '':
-            # We are being asked about root (the archive itself)
-            if self.root_path:
-                st = os.stat(self.root_path)
-            elif hasattr(self.fileobj, 'fileno'):
-                st = os.fstat(self.fileobj.fileno())
+        info = { 'size': 0 }
+        entry = self.contents.get(path)
+        for attr in dir(entry):
+            if attr.startswith('_'):
+                continue
+            elif attr == 'mtime':
+                info['modified_time'] = datetime.datetime.fromtimestamp(entry.mtime)
+            elif attr == 'mode':
+                info['st_mode'] = entry.mode
             else:
-                raise Exception('Could not stat archive.')
-            info = dict((k, getattr(st, k)) for k in dir(st) if k.startswith('st_'))
-            for name, longname in (
-                    ('st_ctime', 'created_time'), ('st_atime', 'accessed_time'),
-                    ('st_mtime', 'modified_time'),
-                ):
-                if name in info:
-                    t = info.pop(name)
-                    if t:
-                        info[longname] = datetime.datetime.fromtimestamp(t)
-            info['size'] = info.pop('st_size')
-            # Masquerade as a directory.
-            info['st_mode'] = info.get('st_mode', 0) | stat.S_IFDIR
-        else:
-            info = { 'size': 0 }
-            entry = self.contents.get(path)
-            for attr in dir(entry):
-                if attr.startswith('_'):
-                    continue
-                elif attr == 'mtime':
-                    info['modified_time'] = datetime.datetime.fromtimestamp(entry.mtime)
-                elif attr == 'mode':
-                    info['st_mode'] = entry.mode
-                else:
-                    info[attr] = getattr(entry, attr)
+                info[attr] = getattr(entry, attr)
         return info
 
+    def getsize(self, path):
+        return self.getinfo(path)['st_size']
+
 
 class ArchiveMountFS(mountfs.MountFS):
     '''A subclass of MountFS that automatically identifies archives. Once identified
     archives are mounted in place of the archive file.'''
-    def __init__(self, rootfs, auto_mount=True):
+
+    def __init__(self, rootfs, auto_mount=True, max_size=None):
         self.auto_mount = auto_mount
+        self.max_size = max_size
         super(ArchiveMountFS, self).__init__(auto_close=True)
         self.rootfs = rootfs
         self.mountdir('/', rootfs)
@@ -213,39 +197,66 @@ class ArchiveMountFS(mountfs.MountFS):
         return type(object) is mountfs.MountFS.DirMount
 
     def _delegate(self, path):
-        if self.auto_mount:
+        if self.auto_mount and auto_mount:
             for ppath in recursepath(path)[1:]:
-                # Don't mount again...
                 if self.ismount(ppath):
+                    # If something is already mounted here, no need to continue.
                     break
                 if libarchive.is_archive_name(ppath):
-                    # It looks like an archive, try mounting it.
+                    # It looks like an archive, we might mount it.
+                    # First check that the size is acceptable.
+                    if self.max_size:
+                        if self.rootfs.exists(ppath) and \
+                           self.rootfs.getsize(ppath) > self.max_size:
+                            break
+                    # Looks good, the proof is in the pudding, so let's try to
+                    # mount this *supposed* archive...
                     full_path = self.rootfs.getsyspath(ppath)
                     try:
+                        # TODO: it would be really nice if we could open the path using
+                        # self.rootfs.open(), that way we could support archives on a file
+                        # system other than osfs (even nested archives). However, the libarchive
+                        # wrapper is not sophisticated enough to handle a Python file-like object,
+                        # it uses an actual fd.
                         self.mountdir(ppath, ArchiveFS(full_path, 'r'))
+                        # That worked!! Stop recursing path, we support just one archive per path!
+                        break
                     except:
-                        pass # Must NOT have been an archive after all
-                    # Stop recursing path, we support just one archive per path!
-                    # No nested archives yet!
-                    break
+                        # Must NOT have been an archive after all, but maybe
+                        # there is one deeper in the directory...
+                        continue
         return super(ArchiveMountFS, self)._delegate(path)
 
-    # TODO: probably need to override move(), movedir() and any other methods
-    # that modify files (and therefore archives). See remove() below to see
-    # why.
-
     def getsyspath(self, path):
-        # Optimized getsyspath() that avoids calling _delegate() and thus
-        # mounting an archive.
+        """Optimized getsyspath() that avoids calling _delegate() and thus
+        mounting an archive."""
         return self.rootfs.getsyspath(path)
 
+    def getinfo(self, path):
+        "Optimized getinfo() that skips mounting an archive to get it's info."
+        path = normpath(path).lstrip('/')
+        if libarchive.is_archive_name(path):
+            # Skip trying to mount the archive and just get it's info.
+            info = self.rootfs.getinfo(path)
+            # Masquerade as a directory.
+            info['st_mode'] = info.get('st_mode', 0) | stat.S_IFDIR
+            return info
+        return super(ArchiveMountFS, self).getinfo(path)
+
+    def getsize(self, path):
+        "Optimized getsize() that skips mounting an archive to get is' size."
+        path = normpath(path).lstrip('/')
+        if libarchive.is_archive_name(path):
+            return self.rootfs.getsize(path)
+        return super(ArchiveMountFS, self).getsize(path)
+
     def remove(self, path):
-        # In case one of our mounted file systems backing archive is being
-        # deleted, unmout it before continuing. Once unmounted, the archive
-        # can be deleted by root fs, otherwise, the ArchiveFS will be asked
-        # to remove itself, which it cannot do.
+        "Optimized remove() that deletes an archive directly."
+        path = normpath(path).lstrip('/')
         if self.ismount(path) and libarchive.is_archive_name(path):
+            # Ensure a mount archive is unmounted before it is deleted.
             self.unmount(path)
+        if libarchive.is_archive_name(path):
             # Send the delete directoy to the root filesystem. This avoids
             # being delegated, and the fs we just unmounted being remounted.
             return self.rootfs.remove(path)
@@ -257,9 +268,54 @@ class ArchiveMountFS(mountfs.MountFS):
         # we should raise an error. In the case when allow_recreate=True, this
         # call would succeed without the check below.
         if self.rootfs.isfile(path):
-            raise ResourceInvalidError(path,msg="Cannot create directory, there's already a file of that name: %(path)s")
+            raise ResourceInvalidError(path, msg="Cannot create directory, there's "
+                                       "already a file of that name: %(path)s")
         return super(ArchiveMountFS, self).makedir(path, *args, **kwargs)
 
+    def copy(self, src, dst, **kwargs):
+        """An optimized copy() that will skip mounting an archive if one is involved
+        as either the src or dst. It tries to be smart and delegate as much work as
+        possible."""
+        src = normpath(src).lstrip('/')
+        dst = normpath(dst).lstrip('/')
+        # If src or dst are an archive unmount them. Then delegate their path and allow mounting
+        # only if the path itself does not point at an archive.
+        src_is_archive = libarchive.is_archive_name(src)
+        if src_is_archive and self.ismount(src):
+            self.unmount(src)
+        fs1, _mount_path1, delegate_path1 = self._delegate(src, auto_mount=(not src_is_archive))
+        dst_is_archive = libarchive.is_archive_name(dst)
+        if dst_is_archive and self.ismount(dst):
+            self.unmount(dst)
+        fs2, _mount_path2, delegate_path2 = self._delegate(dst, auto_mount=(not dst_is_archive))
+        # Use the same logic that appears in MountFS:
+        if fs1 is fs2 and fs1 is not self:
+            fs1.copy(delegate_path1, delegate_path2, **kwargs)
+        else:
+            super(ArchiveMountFS, self).copy(src, dst, **kwargs)
+
+    def move(self, src, dst, **kwargs):
+        """An optimized move() that does not bother mounting an archive to perform a move.
+        It actually uses copy() then remove() to do it's work, since both of those are
+        already "safe"."""
+        src = normpath(src).lstrip('/')
+        dst = normpath(dst).lstrip('/')
+        # If src or dst are an archive unmount them. Then delegate their path and allow mounting
+        # only if the path itself does not point at an archive.
+        src_is_archive = libarchive.is_archive_name(src)
+        if src_is_archive and self.ismount(src):
+            self.unmount(src)
+        fs1, _mount_path1, delegate_path1 = self._delegate(src, auto_mount=(not src_is_archive))
+        dst_is_archive = libarchive.is_archive_name(dst)
+        if dst_is_archive and self.ismount(dst):
+            self.unmount(dst)
+        fs2, _mount_path2, delegate_path2 = self._delegate(dst, auto_mount=(not dst_is_archive))
+        # Use the same logic that appears in MountFS:
+        if fs1 is fs2 and fs1 is not self:
+            fs1.move(delegate_path1, delegate_path2, **kwargs)
+        else:
+            super(ArchiveMountFS, self).move(src, dst, **kwargs)
+
 
 def main():
     ArchiveFS()