[catapult] - Copy Telemetry's gsutilz over to third_party.

third_party/gsutil/gslib/wildcard_iterator.py

Index: third_party/gsutil/gslib/wildcard_iterator.py
diff --git a/third_party/gsutil/gslib/wildcard_iterator.py b/third_party/gsutil/gslib/wildcard_iterator.py
new file mode 100644
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+++ b/third_party/gsutil/gslib/wildcard_iterator.py
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+# -*- coding: utf-8 -*-
+# Copyright 2010 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Wildcard iterator class and supporting functions."""
+
+from __future__ import absolute_import
+
+import fnmatch
+import glob
+import os
+import re
+import sys
+import textwrap
+
+from gslib.bucket_listing_ref import BucketListingBucket
+from gslib.bucket_listing_ref import BucketListingObject
+from gslib.bucket_listing_ref import BucketListingPrefix
+from gslib.cloud_api import AccessDeniedException
+from gslib.cloud_api import CloudApi
+from gslib.cloud_api import NotFoundException
+from gslib.exception import CommandException
+from gslib.storage_url import ContainsWildcard
+from gslib.storage_url import StorageUrlFromString
+from gslib.storage_url import StripOneSlash
+from gslib.storage_url import WILDCARD_REGEX
+from gslib.translation_helper import GenerationFromUrlAndString
+from gslib.util import UTF8
+
+
+FLAT_LIST_REGEX = re.compile(r'(?P<before>.*?)\*\*(?P<after>.*)')
+
+
+class WildcardIterator(object):
+  """Class for iterating over Google Cloud Storage strings containing wildcards.
+
+  The base class is abstract; you should instantiate using the
+  wildcard_iterator() static factory method, which chooses the right
+  implementation depending on the base string.
+  """
+
+  # TODO: Standardize on __str__ and __repr__ here and elsewhere.  Define both
+  # and make one return the other.
+  def __repr__(self):
+    """Returns string representation of WildcardIterator."""
+    return 'WildcardIterator(%s)' % self.wildcard_url.url_string
+
+
+class CloudWildcardIterator(WildcardIterator):
+  """WildcardIterator subclass for buckets, bucket subdirs and objects.
+
+  Iterates over BucketListingRef matching the Url string wildcard. It's
+  much more efficient to first get metadata that's available in the Bucket
+  (for example to get the name and size of each object), because that
+  information is available in the object list results.
+  """
+
+  def __init__(self, wildcard_url, gsutil_api, all_versions=False,
+               debug=0, project_id=None):
+    """Instantiates an iterator that matches the wildcard URL.
+
+    Args:
+      wildcard_url: CloudUrl that contains the wildcard to iterate.
+      gsutil_api: Cloud storage interface.  Passed in for thread safety, also
+                  settable for testing/mocking.
+      all_versions: If true, the iterator yields all versions of objects
+                    matching the wildcard.  If false, yields just the live
+                    object version.
+      debug: Debug level to control debug output for iterator.
+      project_id: Project ID to use for bucket listings.
+    """
+    self.wildcard_url = wildcard_url
+    self.all_versions = all_versions
+    self.debug = debug
+    self.gsutil_api = gsutil_api
+    self.project_id = project_id
+
+  def __iter__(self, bucket_listing_fields=None,
+               expand_top_level_buckets=False):
+    """Iterator that gets called when iterating over the cloud wildcard.
+
+    In the case where no wildcard is present, returns a single matching object,
+    single matching prefix, or one of each if both exist.
+
+    Args:
+      bucket_listing_fields: Iterable fields to include in bucket listings.
+                             Ex. ['name', 'acl'].  Iterator is
+                             responsible for converting these to list-style
+                             format ['items/name', 'items/acl'] as well as
+                             adding any fields necessary for listing such as
+                             prefixes.  API implemenation is responsible for
+                             adding pagination fields.  If this is None,
+                             all fields are returned.
+      expand_top_level_buckets: If true, yield no BUCKET references.  Instead,
+                                expand buckets into top-level objects and
+                                prefixes.
+
+    Yields:
+      BucketListingRef of type BUCKET, OBJECT or PREFIX.
+    """
+    single_version_request = self.wildcard_url.HasGeneration()
+
+    # For wildcard expansion purposes, we need at a minimum the name of
+    # each object and prefix.  If we're not using the default of requesting
+    # all fields, make sure at least these are requested.  The Cloud API
+    # tolerates specifying the same field twice.
+    get_fields = None
+    if bucket_listing_fields:
+      get_fields = set()
+      for field in bucket_listing_fields:
+        get_fields.add(field)
+      bucket_listing_fields = self._GetToListFields(
+          get_fields=bucket_listing_fields)
+      bucket_listing_fields.update(['items/name', 'prefixes'])
+      get_fields.update(['name'])
+      # If we're making versioned requests, ensure generation and
+      # metageneration are also included.
+      if single_version_request or self.all_versions:
+        bucket_listing_fields.update(['items/generation',
+                                      'items/metageneration'])
+        get_fields.update(['generation', 'metageneration'])
+
+    # Handle bucket wildcarding, if any, in _ExpandBucketWildcards. Then
+    # iterate over the expanded bucket strings and handle any object
+    # wildcarding.
+    for bucket_listing_ref in self._ExpandBucketWildcards(bucket_fields=['id']):
+      bucket_url_string = bucket_listing_ref.url_string
+      if self.wildcard_url.IsBucket():
+        # IsBucket() guarantees there are no prefix or object wildcards, and
+        # thus this is a top-level listing of buckets.
+        if expand_top_level_buckets:
+          url = StorageUrlFromString(bucket_url_string)
+          for obj_or_prefix in self.gsutil_api.ListObjects(
+              url.bucket_name, delimiter='/', all_versions=self.all_versions,
+              provider=self.wildcard_url.scheme,
+              fields=bucket_listing_fields):
+            if obj_or_prefix.datatype == CloudApi.CsObjectOrPrefixType.OBJECT:
+              yield self._GetObjectRef(bucket_url_string, obj_or_prefix.data,
+                                       with_version=self.all_versions)
+            else:  # CloudApi.CsObjectOrPrefixType.PREFIX:
+              yield self._GetPrefixRef(bucket_url_string, obj_or_prefix.data)
+        else:
+          yield bucket_listing_ref
+      else:
+        # By default, assume a non-wildcarded URL is an object, not a prefix.
+        # This prevents unnecessary listings (which are slower, more expensive,
+        # and also subject to eventual consistency).
+        if (not ContainsWildcard(self.wildcard_url.url_string) and
+            self.wildcard_url.IsObject() and not self.all_versions):
+          try:
+            get_object = self.gsutil_api.GetObjectMetadata(
+                self.wildcard_url.bucket_name,
+                self.wildcard_url.object_name,
+                generation=self.wildcard_url.generation,
+                provider=self.wildcard_url.scheme,
+                fields=get_fields)
+            yield self._GetObjectRef(
+                self.wildcard_url.bucket_url_string, get_object,
+                with_version=(self.all_versions or single_version_request))
+            return
+          except (NotFoundException, AccessDeniedException):
+            # It's possible this is a prefix - try to list instead.
+            pass
+
+        # Expand iteratively by building prefix/delimiter bucket listing
+        # request, filtering the results per the current level's wildcard
+        # (if present), and continuing with the next component of the
+        # wildcard. See _BuildBucketFilterStrings() documentation for details.
+        if single_version_request:
+          url_string = '%s%s#%s' % (bucket_url_string,
+                                    self.wildcard_url.object_name,
+                                    self.wildcard_url.generation)
+        else:
+          # Rstrip any prefixes to correspond with rstripped prefix wildcard
+          # from _BuildBucketFilterStrings().
+          url_string = '%s%s' % (bucket_url_string,
+                                 StripOneSlash(self.wildcard_url.object_name)
+                                 or '/')  # Cover root object named '/' case.
+        urls_needing_expansion = [url_string]
+        while urls_needing_expansion:
+          url = StorageUrlFromString(urls_needing_expansion.pop(0))
+          (prefix, delimiter, prefix_wildcard, suffix_wildcard) = (
+              self._BuildBucketFilterStrings(url.object_name))
+          prog = re.compile(fnmatch.translate(prefix_wildcard))
+
+          # List bucket for objects matching prefix up to delimiter.
+          for obj_or_prefix in self.gsutil_api.ListObjects(
+              url.bucket_name, prefix=prefix, delimiter=delimiter,
+              all_versions=self.all_versions or single_version_request,
+              provider=self.wildcard_url.scheme,
+              fields=bucket_listing_fields):
+            if obj_or_prefix.datatype == CloudApi.CsObjectOrPrefixType.OBJECT:
+              gcs_object = obj_or_prefix.data
+              if prog.match(gcs_object.name):
+                if not suffix_wildcard or (
+                    StripOneSlash(gcs_object.name) == suffix_wildcard):
+                  if not single_version_request or (
+                      self._SingleVersionMatches(gcs_object.generation)):
+                    yield self._GetObjectRef(
+                        bucket_url_string, gcs_object, with_version=(
+                            self.all_versions or single_version_request))
+            else:  # CloudApi.CsObjectOrPrefixType.PREFIX
+              prefix = obj_or_prefix.data
+              # If the prefix ends with a slash, remove it.  Note that we only
+              # remove one slash so that we can successfully enumerate dirs
+              # containing multiple slashes.
+              rstripped_prefix = StripOneSlash(prefix)
+              if prog.match(rstripped_prefix):
+                if suffix_wildcard and rstripped_prefix != suffix_wildcard:
+                  # There's more wildcard left to expand.
+                  url_append_string = '%s%s' % (
+                      bucket_url_string, rstripped_prefix + '/' +
+                      suffix_wildcard)
+                  urls_needing_expansion.append(url_append_string)
+                else:
+                  # No wildcard to expand, just yield the prefix
+                  yield self._GetPrefixRef(bucket_url_string, prefix)
+
+  def _BuildBucketFilterStrings(self, wildcard):
+    """Builds strings needed for querying a bucket and filtering results.
+
+    This implements wildcard object name matching.
+
+    Args:
+      wildcard: The wildcard string to match to objects.
+
+    Returns:
+      (prefix, delimiter, prefix_wildcard, suffix_wildcard)
+      where:
+        prefix is the prefix to be sent in bucket GET request.
+        delimiter is the delimiter to be sent in bucket GET request.
+        prefix_wildcard is the wildcard to be used to filter bucket GET results.
+        suffix_wildcard is wildcard to be appended to filtered bucket GET
+          results for next wildcard expansion iteration.
+      For example, given the wildcard gs://bucket/abc/d*e/f*.txt we
+      would build prefix= abc/d, delimiter=/, prefix_wildcard=d*e, and
+      suffix_wildcard=f*.txt. Using this prefix and delimiter for a bucket
+      listing request will then produce a listing result set that can be
+      filtered using this prefix_wildcard; and we'd use this suffix_wildcard
+      to feed into the next call(s) to _BuildBucketFilterStrings(), for the
+      next iteration of listing/filtering.
+
+    Raises:
+      AssertionError if wildcard doesn't contain any wildcard chars.
+    """
+    # Generate a request prefix if the object name part of the wildcard starts
+    # with a non-wildcard string (e.g., that's true for 'gs://bucket/abc*xyz').
+    match = WILDCARD_REGEX.search(wildcard)
+    if not match:
+      # Input "wildcard" has no wildcard chars, so just return tuple that will
+      # cause a bucket listing to match the given input wildcard. Example: if
+      # previous iteration yielded gs://bucket/dir/ with suffix_wildcard abc,
+      # the next iteration will call _BuildBucketFilterStrings() with
+      # gs://bucket/dir/abc, and we will return prefix ='dir/abc',
+      # delimiter='/', prefix_wildcard='dir/abc', and suffix_wildcard=''.
+      prefix = wildcard
+      delimiter = '/'
+      prefix_wildcard = wildcard
+      suffix_wildcard = ''
+    else:
+      if match.start() > 0:
+        # Wildcard does not occur at beginning of object name, so construct a
+        # prefix string to send to server.
+        prefix = wildcard[:match.start()]
+        wildcard_part = wildcard[match.start():]
+      else:
+        prefix = None
+        wildcard_part = wildcard
+      end = wildcard_part.find('/')
+      if end != -1:
+        wildcard_part = wildcard_part[:end+1]
+      # Remove trailing '/' so we will match gs://bucket/abc* as well as
+      # gs://bucket/abc*/ with the same wildcard regex.
+      prefix_wildcard = StripOneSlash((prefix or '') + wildcard_part)
+      suffix_wildcard = wildcard[match.end():]
+      end = suffix_wildcard.find('/')
+      if end == -1:
+        suffix_wildcard = ''
+      else:
+        suffix_wildcard = suffix_wildcard[end+1:]
+      # To implement recursive (**) wildcarding, if prefix_wildcard
+      # suffix_wildcard starts with '**' don't send a delimiter, and combine
+      # suffix_wildcard at end of prefix_wildcard.
+      if prefix_wildcard.find('**') != -1:
+        delimiter = None
+        prefix_wildcard += suffix_wildcard
+        suffix_wildcard = ''
+      else:
+        delimiter = '/'
+    # The following debug output is useful for tracing how the algorithm
+    # walks through a multi-part wildcard like gs://bucket/abc/d*e/f*.txt
+    if self.debug > 1:
+      sys.stderr.write(
+          'DEBUG: wildcard=%s, prefix=%s, delimiter=%s, '
+          'prefix_wildcard=%s, suffix_wildcard=%s\n' %
+          (wildcard, prefix, delimiter, prefix_wildcard, suffix_wildcard))
+    return (prefix, delimiter, prefix_wildcard, suffix_wildcard)
+
+  def _SingleVersionMatches(self, listed_generation):
+    decoded_generation = GenerationFromUrlAndString(self.wildcard_url,
+                                                    listed_generation)
+    return str(self.wildcard_url.generation) == str(decoded_generation)
+
+  def _ExpandBucketWildcards(self, bucket_fields=None):
+    """Expands bucket and provider wildcards.
+
+    Builds a list of bucket url strings that can be iterated on.
+
+    Args:
+      bucket_fields: If present, populate only these metadata fields for
+                     buckets.  Example value: ['acl', 'defaultObjectAcl']
+
+    Yields:
+      BucketListingRefereneces of type BUCKET.
+    """
+    bucket_url = StorageUrlFromString(self.wildcard_url.bucket_url_string)
+    if (bucket_fields and set(bucket_fields) == set(['id']) and
+        not ContainsWildcard(self.wildcard_url.bucket_name)):
+      # If we just want the name of a non-wildcarded bucket URL,
+      # don't make an RPC.
+      yield BucketListingBucket(bucket_url)
+    elif(self.wildcard_url.IsBucket() and
+         not ContainsWildcard(self.wildcard_url.bucket_name)):
+      # If we have a non-wildcarded bucket URL, get just that bucket.
+      yield BucketListingBucket(
+          bucket_url, root_object=self.gsutil_api.GetBucket(
+              self.wildcard_url.bucket_name, provider=self.wildcard_url.scheme,
+              fields=bucket_fields))
+    else:
+      regex = fnmatch.translate(self.wildcard_url.bucket_name)
+      prog = re.compile(regex)
+
+      fields = self._GetToListFields(bucket_fields)
+      if fields:
+        fields.add('items/id')
+      for bucket in self.gsutil_api.ListBuckets(
+          fields=fields, project_id=self.project_id,
+          provider=self.wildcard_url.scheme):
+        if prog.match(bucket.id):
+          url = StorageUrlFromString(
+              '%s://%s/' % (self.wildcard_url.scheme, bucket.id))
+          yield BucketListingBucket(url, root_object=bucket)
+
+  def _GetToListFields(self, get_fields=None):
+    """Prepends 'items/' to the input fields and converts it to a set.
+
+    This way field sets requested for GetBucket can be used in ListBucket calls.
+    Note that the input set must contain only bucket or object fields; listing
+    fields such as prefixes or nextPageToken should be added after calling
+    this function.
+
+    Args:
+      get_fields: Iterable fields usable in GetBucket/GetObject calls.
+
+    Returns:
+      Set of fields usable in ListBuckets/ListObjects calls.
+    """
+    if get_fields:
+      list_fields = set()
+      for field in get_fields:
+        list_fields.add('items/' + field)
+      return list_fields
+
+  def _GetObjectRef(self, bucket_url_string, gcs_object, with_version=False):
+    """Creates a BucketListingRef of type OBJECT from the arguments.
+
+    Args:
+      bucket_url_string: Wildcardless string describing the containing bucket.
+      gcs_object: gsutil_api root Object for populating the BucketListingRef.
+      with_version: If true, return a reference with a versioned string.
+
+    Returns:
+      BucketListingRef of type OBJECT.
+    """
+    # Generation can be None in test mocks, so just return the
+    # live object for simplicity.
+    if with_version and gcs_object.generation is not None:
+      generation_str = GenerationFromUrlAndString(self.wildcard_url,
+                                                  gcs_object.generation)
+      object_string = '%s%s#%s' % (bucket_url_string, gcs_object.name,
+                                   generation_str)
+    else:
+      object_string = '%s%s' % (bucket_url_string, gcs_object.name)
+    object_url = StorageUrlFromString(object_string)
+    return BucketListingObject(object_url, root_object=gcs_object)
+
+  def _GetPrefixRef(self, bucket_url_string, prefix):
+    """Creates a BucketListingRef of type PREFIX from the arguments.
+
+    Args:
+      bucket_url_string: Wildcardless string describing the containing bucket.
+      prefix: gsutil_api Prefix for populating the BucketListingRef
+
+    Returns:
+      BucketListingRef of type PREFIX.
+    """
+    prefix_url = StorageUrlFromString('%s%s' % (bucket_url_string, prefix))
+    return BucketListingPrefix(prefix_url, root_object=prefix)
+
+  def IterBuckets(self, bucket_fields=None):
+    """Iterates over the wildcard, returning refs for each expanded bucket.
+
+    This ignores the object part of the URL entirely and expands only the
+    the bucket portion.  It will yield BucketListingRefs of type BUCKET only.
+
+    Args:
+      bucket_fields: Iterable fields to include in bucket listings.
+                     Ex. ['defaultObjectAcl', 'logging'].  This function is
+                     responsible for converting these to listing-style
+                     format ['items/defaultObjectAcl', 'items/logging'], as
+                     well as adding any fields necessary for listing such as
+                     'items/id'.  API implemenation is responsible for
+                     adding pagination fields.  If this is None, all fields are
+                     returned.
+
+    Yields:
+      BucketListingRef of type BUCKET, or empty iterator if no matches.
+    """
+    for blr in self._ExpandBucketWildcards(bucket_fields=bucket_fields):
+      yield blr
+
+  def IterAll(self, bucket_listing_fields=None, expand_top_level_buckets=False):
+    """Iterates over the wildcard, yielding bucket, prefix or object refs.
+
+    Args:
+      bucket_listing_fields: If present, populate only these metadata
+                             fields for listed objects.
+      expand_top_level_buckets: If true and the wildcard expands only to
+                                Bucket(s), yields the expansion of each bucket
+                                into a top-level listing of prefixes and objects
+                                in that bucket instead of a BucketListingRef
+                                to that bucket.
+
+    Yields:
+      BucketListingRef, or empty iterator if no matches.
+    """
+    for blr in self.__iter__(
+        bucket_listing_fields=bucket_listing_fields,
+        expand_top_level_buckets=expand_top_level_buckets):
+      yield blr
+
+  def IterObjects(self, bucket_listing_fields=None):
+    """Iterates over the wildcard, yielding only object BucketListingRefs.
+
+    Args:
+      bucket_listing_fields: If present, populate only these metadata
+                             fields for listed objects.
+
+    Yields:
+      BucketListingRefs of type OBJECT or empty iterator if no matches.
+    """
+    for blr in self.__iter__(bucket_listing_fields=bucket_listing_fields,
+                             expand_top_level_buckets=True):
+      if blr.IsObject():
+        yield blr
+
+
+class FileWildcardIterator(WildcardIterator):
+  """WildcardIterator subclass for files and directories.
+
+  If you use recursive wildcards ('**') only a single such wildcard is
+  supported. For example you could use the wildcard '**/*.txt' to list all .txt
+  files in any subdirectory of the current directory, but you couldn't use a
+  wildcard like '**/abc/**/*.txt' (which would, if supported, let you find .txt
+  files in any subdirectory named 'abc').
+  """
+
+  def __init__(self, wildcard_url, debug=0):
+    """Instantiates an iterator over BucketListingRefs matching wildcard URL.
+
+    Args:
+      wildcard_url: FileUrl that contains the wildcard to iterate.
+      debug: Debug level (range 0..3).
+    """
+    self.wildcard_url = wildcard_url
+    self.debug = debug
+
+  def __iter__(self):
+    """Iterator that gets called when iterating over the file wildcard.
+
+    In the case where no wildcard is present, returns a single matching file
+    or directory.
+
+    Raises:
+      WildcardException: if invalid wildcard found.
+
+    Yields:
+      BucketListingRef of type OBJECT (for files) or PREFIX (for directories)
+    """
+    wildcard = self.wildcard_url.object_name
+    match = FLAT_LIST_REGEX.match(wildcard)
+    if match:
+      # Recursive wildcarding request ('.../**/...').
+      # Example input: wildcard = '/tmp/tmp2pQJAX/**/*'
+      base_dir = match.group('before')[:-1]
+      remaining_wildcard = match.group('after')
+      # At this point for the above example base_dir = '/tmp/tmp2pQJAX' and
+      # remaining_wildcard = '/*'
+      if remaining_wildcard.startswith('*'):
+        raise WildcardException('Invalid wildcard with more than 2 consecutive '
+                                '*s (%s)' % wildcard)
+      # If there was no remaining wildcard past the recursive wildcard,
+      # treat it as if it were a '*'. For example, file://tmp/** is equivalent
+      # to file://tmp/**/*
+      if not remaining_wildcard:
+        remaining_wildcard = '*'
+      # Skip slash(es).
+      remaining_wildcard = remaining_wildcard.lstrip(os.sep)
+      filepaths = self._IterDir(base_dir, remaining_wildcard)
+    else:
+      # Not a recursive wildcarding request.
+      filepaths = glob.iglob(wildcard)
+    for filepath in filepaths:
+      expanded_url = StorageUrlFromString(filepath)
+      if os.path.isdir(filepath):
+        yield BucketListingPrefix(expanded_url)
+      else:
+        yield BucketListingObject(expanded_url)
+
+  def _IterDir(self, directory, wildcard):
+    """An iterator over the specified dir and wildcard."""
+    # UTF8-encode directory before passing it to os.walk() so if there are
+    # non-valid UTF8 chars in the file name (e.g., that can happen if the file
+    # originated on Windows) os.walk() will not attempt to decode and then die
+    # with a "codec can't decode byte" error, and instead we can catch the error
+    # at yield time and print a more informative error message.
+    for dirpath, unused_dirnames, filenames in os.walk(directory.encode(UTF8)):
+      for f in fnmatch.filter(filenames, wildcard):
+        try:
+          yield os.path.join(dirpath, f).decode(UTF8)
+        except UnicodeDecodeError:
+          # Note: We considered several ways to deal with this, but each had
+          # problems:
+          # 1. Raise an exception and try to catch in a higher layer (the
+          #    gsutil cp command), so we can properly support the gsutil cp -c
+          #    option. That doesn't work because raising an exception during
+          #    iteration terminates the generator.
+          # 2. Accumulate a list of bad filenames and skip processing each
+          #    during iteration, then raise at the end, with exception text
+          #    printing the bad paths. That doesn't work because iteration is
+          #    wrapped in PluralityCheckableIterator, so it's possible there
+          #    are not-yet-performed copy operations at the time we reach the
+          #    end of the iteration and raise the exception - which would cause
+          #    us to skip copying validly named files. Moreover, the gsutil
+          #    cp command loops over argv, so if you run the command gsutil cp
+          #    -rc dir1 dir2 gs://bucket, an invalid unicode name inside dir1
+          #    would cause dir2 never to be visited.
+          # 3. Print the invalid pathname and skip it during iteration. That
+          #    would work but would mean gsutil cp could exit with status 0
+          #    even though some files weren't copied.
+          # 4. Change the WildcardIterator to include an error status along with
+          #    the result. That would solve the problem but would be a
+          #    substantial change (WildcardIterator is used in many parts of
+          #    gsutil), and we didn't feel that magnitude of change was
+          #    warranted by this relatively uncommon corner case.
+          # Instead we chose to abort when one such file is encountered, and
+          # require the user to remove or rename the files and try again.
+          raise CommandException('\n'.join(textwrap.wrap(
+              'Invalid Unicode path encountered (%s). gsutil cannot proceed '
+              'with such files present. Please remove or rename this file and '
+              'try again. NOTE: the path printed above replaces the '
+              'problematic characters with a hex-encoded printable '
+              'representation. For more details (including how to convert to a '
+              'gsutil-compatible encoding) see `gsutil help encoding`.' %
+              repr(os.path.join(dirpath, f)))))
+
+  # pylint: disable=unused-argument
+  def IterObjects(self, bucket_listing_fields=None):
+    """Iterates over the wildcard, yielding only object (file) refs.
+
+    Args:
+      bucket_listing_fields: Ignored as filesystems don't have buckets.
+
+    Yields:
+      BucketListingRefs of type OBJECT or empty iterator if no matches.
+    """
+    for bucket_listing_ref in self.IterAll():
+      if bucket_listing_ref.IsObject():
+        yield bucket_listing_ref
+
+  # pylint: disable=unused-argument
+  def IterAll(self, bucket_listing_fields=None, expand_top_level_buckets=False):
+    """Iterates over the wildcard, yielding BucketListingRefs.
+
+    Args:
+      bucket_listing_fields: Ignored; filesystems don't have buckets.
+      expand_top_level_buckets: Ignored; filesystems don't have buckets.
+
+    Yields:
+      BucketListingRefs of type OBJECT (file) or PREFIX (directory),
+      or empty iterator if no matches.
+    """
+    for bucket_listing_ref in self.__iter__():
+      yield bucket_listing_ref
+
+  def IterBuckets(self, unused_bucket_fields=None):
+    """Placeholder to allow polymorphic use of WildcardIterator.
+
+    Args:
+      unused_bucket_fields: Ignored; filesystems don't have buckets.
+
+    Raises:
+      WildcardException: in all cases.
+    """
+    raise WildcardException(
+        'Iterating over Buckets not possible for file wildcards')
+
+
+class WildcardException(StandardError):
+  """Exception raised for invalid wildcard URLs."""
+
+  def __init__(self, reason):
+    StandardError.__init__(self)
+    self.reason = reason
+
+  def __repr__(self):
+    return 'WildcardException: %s' % self.reason
+
+  def __str__(self):
+    return 'WildcardException: %s' % self.reason
+
+
+def CreateWildcardIterator(url_str, gsutil_api, all_versions=False, debug=0,
+                           project_id=None):
+  """Instantiate a WildcardIterator for the given URL string.
+
+  Args:
+    url_str: URL string naming wildcard object(s) to iterate.
+    gsutil_api: Cloud storage interface.  Passed in for thread safety, also
+                settable for testing/mocking.
+    all_versions: If true, the iterator yields all versions of objects
+                  matching the wildcard.  If false, yields just the live
+                  object version.
+    debug: Debug level to control debug output for iterator.
+    project_id: Project id to use for bucket listings.
+
+  Returns:
+    A WildcardIterator that handles the requested iteration.
+  """
+
+  url = StorageUrlFromString(url_str)
+  if url.IsFileUrl():
+    return FileWildcardIterator(url, debug=debug)
+  else:  # Cloud URL
+    return CloudWildcardIterator(
+        url, gsutil_api, all_versions=all_versions, debug=debug,
+        project_id=project_id)