fetch.py

# Copyright (C) 2021 The Android Open Source Project
#
# 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.

"""This module contains functions used to fetch files from various sources."""

import subprocess
import sys
from urllib.parse import urlparse
from urllib.request import urlopen

from error import RepoExitError


class FetchFileError(RepoExitError):
    """Exit error when fetch_file fails."""


def fetch_file(url, verbose=False):
    """Fetch a file from the specified source using the appropriate protocol.

    Returns:
        The contents of the file as bytes.
    """
    scheme = urlparse(url).scheme
    if scheme == "gs":
        cmd = ["gsutil", "cat", url]
        errors = []
        try:
            result = subprocess.run(
                cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, check=True
            )
            if result.stderr and verbose:
                print(
                    'warning: non-fatal error running "gsutil": %s'
                    % result.stderr,
                    file=sys.stderr,
                )
            return result.stdout
        except subprocess.CalledProcessError as e:
            errors.append(e)
            print(
                'fatal: error running "gsutil": %s' % e.stderr, file=sys.stderr
            )
        raise FetchFileError(aggregate_errors=errors)
    with urlopen(url) as f:
        return f.read()