use better mechanism for enums in gs_utils.py

py/utils/gs_utils.py

 #!/usr/bin/python
 
 # pylint: disable=C0301
 """
 Copyright 2014 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 
 Utilities for accessing Google Cloud Storage, using the boto library (wrapper
 for the XML API).
 
 API/library references:
 - https://developers.google.com/storage/docs/reference-guide
 - http://googlecloudstorage.blogspot.com/2012/09/google-cloud-storage-tutorial-using-boto.html
 """
 # pylint: enable=C0301
 
 # System-level imports
 import errno
 import os
 import posixpath
-import random
 import re
-import shutil
 import sys
-import tempfile
 
 # Imports from third-party code
 TRUNK_DIRECTORY = os.path.abspath(os.path.join(
     os.path.dirname(__file__), os.pardir, os.pardir))
 for import_subdir in ['boto']:
   import_dirpath = os.path.join(
       TRUNK_DIRECTORY, 'third_party', 'externals', import_subdir)
   if import_dirpath not in sys.path:
     # We need to insert at the beginning of the path, to make sure that our
     # imported versions are favored over others that might be in the path.
     sys.path.insert(0, import_dirpath)
 from boto.exception import BotoServerError
 from boto.gs import acl
 from boto.gs.bucket import Bucket
 from boto.gs.connection import GSConnection
 from boto.gs.key import Key
 from boto.s3.bucketlistresultset import BucketListResultSet
 from boto.s3.connection import SubdomainCallingFormat
 from boto.s3.prefix import Prefix
 
-# Predefined (aka "canned") ACLs that provide a "base coat" of permissions for
-# each file in Google Storage.  See CannedACLStrings in
-# https://github.com/boto/boto/blob/develop/boto/gs/acl.py
-# Also see https://developers.google.com/storage/docs/accesscontrol
-PREDEFINED_ACL_AUTHENTICATED_READ        = 'authenticated-read'
-PREDEFINED_ACL_BUCKET_OWNER_FULL_CONTROL = 'bucket-owner-full-control'
-PREDEFINED_ACL_BUCKET_OWNER_READ         = 'bucket-owner-read'
-PREDEFINED_ACL_PRIVATE                   = 'private'
-PREDEFINED_ACL_PROJECT_PRIVATE           = 'project-private'
-PREDEFINED_ACL_PUBLIC_READ               = 'public-read'
-PREDEFINED_ACL_PUBLIC_READ_WRITE         = 'public-read-write'
-
-# "Fine-grained" permissions that may be set per user/group on each file in
-# Google Storage.  See SupportedPermissions in
-# https://github.com/boto/boto/blob/develop/boto/gs/acl.py
-# Also see https://developers.google.com/storage/docs/accesscontrol
-PERMISSION_NONE  = None
-PERMISSION_OWNER = 'FULL_CONTROL'
-PERMISSION_READ  = 'READ'
-PERMISSION_WRITE = 'WRITE'
-
-# Types of identifiers we can use to set "fine-grained" ACLs.
-ID_TYPE_GROUP_BY_DOMAIN = acl.GROUP_BY_DOMAIN
-ID_TYPE_GROUP_BY_EMAIL  = acl.GROUP_BY_EMAIL
-ID_TYPE_GROUP_BY_ID     = acl.GROUP_BY_ID
-ID_TYPE_USER_BY_EMAIL   = acl.USER_BY_EMAIL
-ID_TYPE_USER_BY_ID      = acl.USER_BY_ID
-
-# Which field we get/set in ACL entries, depending on ID_TYPE.
-FIELD_BY_ID_TYPE = {
-    ID_TYPE_GROUP_BY_DOMAIN: 'domain',
-    ID_TYPE_GROUP_BY_EMAIL: 'email_address',
-    ID_TYPE_GROUP_BY_ID: 'id',
-    ID_TYPE_USER_BY_EMAIL: 'email_address',
-    ID_TYPE_USER_BY_ID: 'id',
-}
-
 
 class AnonymousGSConnection(GSConnection):
   """GSConnection class that allows anonymous connections.
 
   The GSConnection class constructor in
   https://github.com/boto/boto/blob/develop/boto/gs/connection.py doesn't allow
   for anonymous connections (connections without credentials), so we have to
   override it.
   """
   def __init__(self):
     super(GSConnection, self).__init__(
         # This is the important bit we need to add...
         anon=True,
         # ...and these are just copied in from GSConnection.__init__()
         bucket_class=Bucket,
         calling_format=SubdomainCallingFormat(),
         host=GSConnection.DefaultHost,
         provider='google')
 
 
 class GSUtils(object):
   """Utilities for accessing Google Cloud Storage, using the boto library."""
 
+  class Permission:
+    """Fine-grained permissions that may be set per user/group on each file.
+
+    See SupportedPermissions in
+    https://github.com/boto/boto/blob/develop/boto/gs/acl.py
+    Also see https://developers.google.com/storage/docs/accesscontrol
+    """
+    EMPTY = None
+    OWNER = 'FULL_CONTROL'
+    READ  = 'READ'
+    WRITE = 'WRITE'
+
+  class PredefinedACL:
+    """Canned ACLs that provide a "base coat" of permissions for each file.
+
+    See CannedACLStrings in
+    https://github.com/boto/boto/blob/develop/boto/gs/acl.py
+    Also see https://developers.google.com/storage/docs/accesscontrol
+    """
+    AUTHENTICATED_READ        = 'authenticated-read'
+    BUCKET_OWNER_FULL_CONTROL = 'bucket-owner-full-control'
+    BUCKET_OWNER_READ         = 'bucket-owner-read'
+    PRIVATE                   = 'private'
+    PROJECT_PRIVATE           = 'project-private'
+    PUBLIC_READ               = 'public-read'
+    PUBLIC_READ_WRITE         = 'public-read-write'
+
+  class IdType:
+    """Types of identifiers we can use to set "fine-grained" ACLs."""
+    GROUP_BY_DOMAIN = acl.GROUP_BY_DOMAIN
+    GROUP_BY_EMAIL  = acl.GROUP_BY_EMAIL
+    GROUP_BY_ID     = acl.GROUP_BY_ID
+    USER_BY_EMAIL   = acl.USER_BY_EMAIL
+    USER_BY_ID      = acl.USER_BY_ID
+
+
   def __init__(self, boto_file_path=None):
     """Constructor.
 
     Params:
       boto_file_path: full path (local-OS-style) on local disk where .boto
           credentials file can be found.  If None, then the GSUtils object
           created will be able to access only public files in Google Storage.
 
     Raises an exception if no file is found at boto_file_path, or if the file
     found there is malformed.
     """
     self._gs_access_key_id = None
     self._gs_secret_access_key = None
     if boto_file_path:
       print 'Reading boto file from %s' % boto_file_path
       boto_dict = _config_file_as_dict(filepath=boto_file_path)
       self._gs_access_key_id = boto_dict['gs_access_key_id']
       self._gs_secret_access_key = boto_dict['gs_secret_access_key']
+    # Which field we get/set in ACL entries, depending on IdType.
+    self._field_by_id_type = {
+        self.IdType.GROUP_BY_DOMAIN: 'domain',
+        self.IdType.GROUP_BY_EMAIL:  'email_address',
+        self.IdType.GROUP_BY_ID:     'id',
+        self.IdType.USER_BY_EMAIL:   'email_address',
+        self.IdType.USER_BY_ID:      'id',
+    }
 
   def delete_file(self, bucket, path):
     """Delete a single file within a GS bucket.
 
     TODO(epoger): what if bucket or path does not exist?  Should probably raise
     an exception.  Implement, and add a test to exercise this.
 
     Params:
       bucket: GS bucket to delete a file from
       path: full path (Posix-style) of the file within the bucket to delete
@@ skipping 14 matching lines @@
 
     TODO(epoger): Add the only_if_modified param provided by upload_file() in
     https://github.com/google/skia-buildbot/blob/master/slave/skia_slave_scripts/utils/old_gs_utils.py ,
     so we can replace that function with this one.
 
     params:
       source_path: full path (local-OS-style) on local disk to read from
       dest_bucket: GCS bucket to copy the file to
       dest_path: full path (Posix-style) within that bucket
       predefined_acl: which predefined ACL to apply to the file on Google
-          Storage; must be one of the PREDEFINED_ACL_* constants defined above.
+          Storage; must be one of the PredefinedACL values defined above.
           If None, inherits dest_bucket's default object ACL.
           TODO(epoger): add unittests for this param, although it seems to work
           in my manual testing
       fine_grained_acl_list: list of (id_type, id_value, permission) tuples
           to apply to the uploaded file (on top of the predefined_acl),
           or None if predefined_acl is sufficient
     """
     b = self._connect_to_bucket(bucket_name=dest_bucket)
     item = Key(b)
     item.key = dest_path
@@ skipping 17 matching lines @@
                           predefined_acl=None, fine_grained_acl_list=None):
     """Recursively upload contents of a local directory to Google Storage.
 
     params:
       source_dir: full path (local-OS-style) on local disk of directory to copy
           contents of
       dest_bucket: GCS bucket to copy the files into
       dest_dir: full path (Posix-style) within that bucket; write the files into
           this directory
       predefined_acl: which predefined ACL to apply to the files on Google
-          Storage; must be one of the PREDEFINED_ACL_* constants defined above.
+          Storage; must be one of the PredefinedACL values defined above.
           If None, inherits dest_bucket's default object ACL.
           TODO(epoger): add unittests for this param, although it seems to work
           in my manual testing
       fine_grained_acl_list: list of (id_type, id_value, permission) tuples
           to apply to every file uploaded (on top of the predefined_acl),
           or None if predefined_acl is sufficient
 
     The copy operates as a "merge with overwrite": any files in source_dir will
     be "overlaid" on top of the existing content in dest_dir.  Existing files
     with the same names will be overwritten.
@@ skipping 110 matching lines @@
     other than that returned by this call, if they have been granted those
     rights based on *other* id_types (e.g., perhaps they have group access
     rights, beyond their individual access rights).
 
     TODO(epoger): What if the remote file does not exist?  This should probably
     raise an exception in that case.
 
     Params:
       bucket: GS bucket
       path: full path (Posix-style) to the file within that bucket
-      id_type: must be one of the ID_TYPE_* constants defined above
+      id_type: must be one of the IdType values defined above
       id_value: get permissions for users whose id_type field contains this
           value
 
-    Returns: the PERMISSION_* constant which has been set for users matching
-        this id_type/id_value, on this file; or PERMISSION_NONE if no such
+    Returns: the Permission value which has been set for users matching
+        this id_type/id_value, on this file; or Permission.EMPTY if no such
         permissions have been set.
     """
-    field = FIELD_BY_ID_TYPE[id_type]
+    field = self._field_by_id_type[id_type]
     b = self._connect_to_bucket(bucket_name=bucket)
     acls = b.get_acl(key_name=path)
     matching_entries = [entry for entry in acls.entries.entry_list
                         if (entry.scope.type == id_type) and
                         (getattr(entry.scope, field) == id_value)]
     if matching_entries:
       assert len(matching_entries) == 1, '%d == 1' % len(matching_entries)
       return matching_entries[0].permission
     else:
-      return PERMISSION_NONE
+      return self.Permission.EMPTY
 
   def set_acl(self, bucket, path, id_type, id_value, permission):
     """Set partial access permissions on a single file in Google Storage.
 
     Note that a single set_acl() call will not guarantee what access rights any
     given user will have on a given file, because permissions are additive.
     (E.g., if you set READ permission for a group, but a member of that group
     already has WRITE permission, that member will still have WRITE permission.)
     TODO(epoger): Do we know that for sure?  I *think* that's how it works...
 
     If there is already a permission set on this file for this id_type/id_value
     combination, this call will overwrite it.
 
     TODO(epoger): What if the remote file does not exist?  This should probably
     raise an exception in that case.
 
     Params:
       bucket: GS bucket
       path: full path (Posix-style) to the file within that bucket
-      id_type: must be one of the ID_TYPE_* constants defined above
+      id_type: must be one of the IdType values defined above
       id_value: add permission for users whose id_type field contains this value
       permission: permission to add for users matching id_type/id_value;
-          must be one of the PERMISSION_* constants defined above.
-          If PERMISSION_NONE, then any permissions will be granted to this
+          must be one of the Permission values defined above.
+          If Permission.EMPTY, then any permissions will be granted to this
           particular id_type/id_value will be removed... but, given that
           permissions are additive, specific users may still have access rights
           based on permissions given to *other* id_type/id_value pairs.
 
     Example Code:
       bucket = 'gs://bucket-name'
       path = 'path/to/file'
-      id_type = ID_TYPE_USER_BY_EMAIL
+      id_type = IdType.USER_BY_EMAIL
       id_value = 'epoger@google.com'
-      set_acl(bucket, path, id_type, id_value, PERMISSION_READ)
-      assert PERMISSION_READ == get_acl(bucket, path, id_type, id_value)
-      set_acl(bucket, path, id_type, id_value, PERMISSION_WRITE)
-      assert PERMISSION_WRITE == get_acl(bucket, path, id_type, id_value)
+      set_acl(bucket, path, id_type, id_value, Permission.READ)
+      assert Permission.READ == get_acl(bucket, path, id_type, id_value)
+      set_acl(bucket, path, id_type, id_value, Permission.WRITE)
+      assert Permission.WRITE == get_acl(bucket, path, id_type, id_value)
     """
-    field = FIELD_BY_ID_TYPE[id_type]
+    field = self._field_by_id_type[id_type]
     b = self._connect_to_bucket(bucket_name=bucket)
     acls = b.get_acl(key_name=path)
 
     # Remove any existing entries that refer to the same id_type/id_value,
     # because the API will fail if we try to set more than one.
     matching_entries = [entry for entry in acls.entries.entry_list
                         if (entry.scope.type == id_type) and
                         (getattr(entry.scope, field) == id_value)]
     if matching_entries:
       assert len(matching_entries) == 1, '%d == 1' % len(matching_entries)
       acls.entries.entry_list.remove(matching_entries[0])
 
     # Add a new entry to the ACLs.
-    if permission != PERMISSION_NONE:
+    if permission != self.Permission.EMPTY:
       args = {'type': id_type, 'permission': permission}
       args[field] = id_value
       new_entry = acl.Entry(**args)
       acls.entries.entry_list.append(new_entry)
 
     # Finally, write back the modified ACLs.
     b.set_acl(acl_or_str=acls, key_name=path)
 
   def list_bucket_contents(self, bucket, subdir=None):
     """Returns files in the Google Storage bucket as a (dirs, files) tuple.
@@ skipping 37 matching lines @@
 
   def _create_connection(self):
     """Returns a GSConnection object we can use to access Google Storage."""
     if self._gs_access_key_id:
       return GSConnection(
           gs_access_key_id=self._gs_access_key_id,
           gs_secret_access_key=self._gs_secret_access_key)
     else:
       return AnonymousGSConnection()
 
+
 def _config_file_as_dict(filepath):
   """Reads a boto-style config file into a dict.
 
   Parses all lines from the file of this form: key = value
   TODO(epoger): Create unittest.
 
   Params:
     filepath: path to config file on local disk
 
   Returns: contents of the config file, as a dictionary
@@ skipping 16 matching lines @@
   exist yet.
 
   Args:
     path: full path of directory to create
   """
   try:
     os.makedirs(path)
   except OSError as e:
     if e.errno != errno.EEXIST:
       raise
-
-
-def _test_public_read():
-  """Make sure we can read from public files without .boto file credentials."""
-  gs = GSUtils()
-  gs.list_bucket_contents(bucket='chromium-skia-gm-summaries', subdir=None)
-
-
-def _test_authenticated_round_trip():
-  try:
-    gs = GSUtils(boto_file_path=os.path.expanduser(os.path.join('~','.boto')))
-  except:
-    print """
-Failed to instantiate GSUtils object with default .boto file path.
-Do you have a ~/.boto file that provides the credentials needed to read
-and write gs://chromium-skia-gm ?
-"""
-    raise
-
-  bucket = 'chromium-skia-gm'
-  remote_dir = 'gs_utils_test/%d' % random.randint(0, sys.maxint)
-  subdir = 'subdir'
-  filenames_to_upload = ['file1', 'file2']
-
-  # Upload test files to Google Storage, checking that their fine-grained
-  # ACLs were set correctly.
-  id_type = ID_TYPE_GROUP_BY_DOMAIN
-  id_value = 'chromium.org'
-  set_permission = PERMISSION_READ
-  local_src_dir = tempfile.mkdtemp()
-  os.mkdir(os.path.join(local_src_dir, subdir))
-  try:
-    for filename in filenames_to_upload:
-      with open(os.path.join(local_src_dir, subdir, filename), 'w') as f:
-        f.write('contents of %s\n' % filename)
-      dest_path = posixpath.join(remote_dir, subdir, filename)
-      gs.upload_file(
-          source_path=os.path.join(local_src_dir, subdir, filename),
-          dest_bucket=bucket, dest_path=dest_path,
-          fine_grained_acl_list=[(id_type, id_value, set_permission)])
-      got_permission = gs.get_acl(bucket=bucket, path=dest_path,
-                                  id_type=id_type, id_value=id_value)
-      assert got_permission == set_permission, '%s == %s' % (
-          got_permission, set_permission)
-  finally:
-    shutil.rmtree(local_src_dir)
-
-  # Get a list of the files we uploaded to Google Storage.
-  (dirs, files) = gs.list_bucket_contents(
-      bucket=bucket, subdir=remote_dir)
-  assert dirs == [subdir], '%s == [%s]' % (dirs, subdir)
-  assert files == [], '%s == []' % files
-  (dirs, files) = gs.list_bucket_contents(
-      bucket=bucket, subdir=posixpath.join(remote_dir, subdir))
-  assert dirs == [], '%s == []' % dirs
-  assert files == filenames_to_upload, '%s == %s' % (files, filenames_to_upload)
-
-  # Manipulate ACLs on one of those files, and verify them.
-  # TODO(epoger): Test id_types other than ID_TYPE_GROUP_BY_DOMAIN ?
-  # TODO(epoger): Test setting multiple ACLs on the same file?
-  id_type = ID_TYPE_GROUP_BY_DOMAIN
-  id_value = 'google.com'
-  fullpath = posixpath.join(remote_dir, subdir, filenames_to_upload[0])
-  # Make sure ACL is empty to start with ...
-  gs.set_acl(bucket=bucket, path=fullpath,
-             id_type=id_type, id_value=id_value, permission=PERMISSION_NONE)
-  permission = gs.get_acl(bucket=bucket, path=fullpath,
-                          id_type=id_type, id_value=id_value)
-  assert permission == PERMISSION_NONE, '%s == %s' % (
-      permission, PERMISSION_NONE)
-  # ... set it to OWNER ...
-  gs.set_acl(bucket=bucket, path=fullpath,
-             id_type=id_type, id_value=id_value, permission=PERMISSION_OWNER)
-  permission = gs.get_acl(bucket=bucket, path=fullpath,
-                          id_type=id_type, id_value=id_value)
-  assert permission == PERMISSION_OWNER, '%s == %s' % (
-      permission, PERMISSION_OWNER)
-  # ... now set it to READ ...
-  gs.set_acl(bucket=bucket, path=fullpath,
-             id_type=id_type, id_value=id_value, permission=PERMISSION_READ)
-  permission = gs.get_acl(bucket=bucket, path=fullpath,
-                          id_type=id_type, id_value=id_value)
-  assert permission == PERMISSION_READ, '%s == %s' % (
-      permission, PERMISSION_READ)
-  # ... and clear it again to finish.
-  gs.set_acl(bucket=bucket, path=fullpath,
-             id_type=id_type, id_value=id_value, permission=PERMISSION_NONE)
-  permission = gs.get_acl(bucket=bucket, path=fullpath,
-                          id_type=id_type, id_value=id_value)
-  assert permission == PERMISSION_NONE, '%s == %s' % (
-      permission, PERMISSION_NONE)
-
-  # Download the files we uploaded to Google Storage, and validate contents.
-  local_dest_dir = tempfile.mkdtemp()
-  try:
-    for filename in filenames_to_upload:
-      gs.download_file(source_bucket=bucket,
-                       source_path=posixpath.join(remote_dir, subdir, filename),
-                       dest_path=os.path.join(local_dest_dir, subdir, filename),
-                       create_subdirs_if_needed=True)
-      with open(os.path.join(local_dest_dir, subdir, filename)) as f:
-        file_contents = f.read()
-      assert file_contents == 'contents of %s\n' % filename, (
-          '%s == "contents of %s\n"' % (file_contents, filename))
-  finally:
-    shutil.rmtree(local_dest_dir)
-
-  # Delete all the files we uploaded to Google Storage.
-  for filename in filenames_to_upload:
-    gs.delete_file(bucket=bucket,
-                   path=posixpath.join(remote_dir, subdir, filename))
-
-  # Confirm that we deleted all the files we uploaded to Google Storage.
-  (dirs, files) = gs.list_bucket_contents(
-      bucket=bucket, subdir=posixpath.join(remote_dir, subdir))
-  assert dirs == [], '%s == []' % dirs
-  assert files == [], '%s == []' % files
-
-
-def _test_dir_upload_and_download():
-  """Test upload_dir_contents() and download_dir_contents()."""
-  try:
-    gs = GSUtils(boto_file_path=os.path.expanduser(os.path.join('~','.boto')))
-  except:
-    print """
-Failed to instantiate GSUtils object with default .boto file path.
-Do you have a ~/.boto file that provides the credentials needed to read
-and write gs://chromium-skia-gm ?
-"""
-    raise
-
-  bucket = 'chromium-skia-gm'
-  remote_dir = 'gs_utils_test/%d' % random.randint(0, sys.maxint)
-  subdir = 'subdir'
-  filenames = ['file1', 'file2']
-
-  # Create directory tree on local disk and upload it.
-  id_type = ID_TYPE_GROUP_BY_DOMAIN
-  id_value = 'chromium.org'
-  set_permission = PERMISSION_READ
-  local_src_dir = tempfile.mkdtemp()
-  os.mkdir(os.path.join(local_src_dir, subdir))
-  try:
-    for filename in filenames:
-      with open(os.path.join(local_src_dir, subdir, filename), 'w') as f:
-        f.write('contents of %s\n' % filename)
-    gs.upload_dir_contents(
-        source_dir=local_src_dir, dest_bucket=bucket, dest_dir=remote_dir,
-        predefined_acl=PREDEFINED_ACL_PRIVATE,
-        fine_grained_acl_list=[(id_type, id_value, set_permission)])
-  finally:
-    shutil.rmtree(local_src_dir)
-
-  # Validate the list of the files we uploaded to Google Storage.
-  (dirs, files) = gs.list_bucket_contents(
-      bucket=bucket, subdir=remote_dir)
-  assert dirs == [subdir], '%s == [%s]' % (dirs, subdir)
-  assert files == [], '%s == []' % files
-  (dirs, files) = gs.list_bucket_contents(
-      bucket=bucket, subdir=posixpath.join(remote_dir, subdir))
-  assert dirs == [], '%s == []' % dirs
-  assert files == filenames, '%s == %s' % (files, filenames)
-
-  # Check the fine-grained ACLs we set in Google Storage.
-  for filename in filenames:
-    got_permission = gs.get_acl(
-        bucket=bucket, path=posixpath.join(remote_dir, subdir, filename),
-        id_type=id_type, id_value=id_value)
-    assert got_permission == set_permission, '%s == %s' % (
-        got_permission, set_permission)
-
-  # Download the directory tree we just uploaded, make sure its contents
-  # are what we expect, and then delete the tree in Google Storage.
-  local_dest_dir = tempfile.mkdtemp()
-  try:
-    gs.download_dir_contents(source_bucket=bucket, source_dir=remote_dir,
-                             dest_dir=local_dest_dir)
-    for filename in filenames:
-      with open(os.path.join(local_dest_dir, subdir, filename)) as f:
-        file_contents = f.read()
-      assert file_contents == 'contents of %s\n' % filename, (
-          '%s == "contents of %s\n"' % (file_contents, filename))
-  finally:
-    shutil.rmtree(local_dest_dir)
-    for filename in filenames:
-      gs.delete_file(bucket=bucket,
-                     path=posixpath.join(remote_dir, subdir, filename))
-
-
-# TODO(epoger): How should we exercise these self-tests?
-# See http://skbug.com/2751
-if __name__ == '__main__':
-  _test_public_read()
-  _test_authenticated_round_trip()
-  _test_dir_upload_and_download()
-  # TODO(epoger): Add _test_unauthenticated_access() to make sure we raise
-  # an exception when we try to access without needed credentials.