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#!/usr/bin/env python3
# Copyright (c) 2024 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Tool for generating a unified git diff outside of a git workspace.
This is intended as a preprocessor for presubmit_support.py.
"""
from __future__ import annotations
import argparse
import base64
import concurrent.futures
import os
import platform
import sys
import gclient_utils
from gerrit_util import (CreateHttpConn, ReadHttpResponse,
MAX_CONCURRENT_CONNECTION)
import subprocess2
DEV_NULL = "/dev/null"
HEADER_DELIMITER = "@@"
def fetch_content(host: str, repo: str, ref: str, file: str) -> bytes:
"""Fetches the content of a file from Gitiles.
If the file does not exist at the commit, returns an empty bytes object.
Args:
host: Gerrit host.
repo: Gerrit repo.
ref: Gerrit commit.
file: Path of file to fetch.
Returns:
Bytes of the file at the commit or an empty bytes object if the file
does not exist at the commit.
"""
conn = CreateHttpConn(f"{host}.googlesource.com",
f"{repo}/+show/{ref}/{file}?format=text")
response = ReadHttpResponse(conn, accept_statuses=[200, 404])
return base64.b64decode(response.read())
def git_diff(src: str | None,
dest: str | None,
unified: int | None = None) -> str:
"""Returns the result of `git diff --no-index` between two paths.
If a path is not specified, the diff is against /dev/null. At least one of
src or dest must be specified.
Args:
src: Source path.
dest: Destination path.
unified: Number of lines of context. If None, git diff uses 3 as
the default value.
Returns:
A string containing the git diff.
"""
args = ["git", "diff", "--no-index"]
if unified is not None:
# git diff doesn't error out even if it's given a negative <n> value.
# e.g., --unified=-3323, -U-3
#
# It just ignores the value and treats it as 0.
# hence, this script doesn't bother validating the <n> value.
args.append(f"-U{unified}")
args.extend(["--", src or DEV_NULL, dest or DEV_NULL])
return subprocess2.capture(args).decode("utf-8")
def _process_diff(diff: str, src_root: str, dst_root: str) -> str:
"""Adjust paths in the diff header so they're relative to the root.
This also modifies paths on Windows to use forward slashes.
"""
if not diff:
return ""
has_chunk_header = HEADER_DELIMITER in diff
if has_chunk_header:
header, body = diff.split(HEADER_DELIMITER, maxsplit=1)
else:
# Only the file mode changed.
header = diff
norm_src = src_root.rstrip(os.sep)
norm_dst = dst_root.rstrip(os.sep)
if platform.system() == "Windows":
# Absolute paths on Windows use the format:
# "a/C:\\abspath\\to\\file.txt"
header = header.replace("\\\\", "\\")
header = header.replace('"', "")
header = header.replace(norm_src + "\\", "")
header = header.replace(norm_dst + "\\", "")
else:
# Other systems use:
# a/abspath/to/file.txt
header = header.replace(norm_src, "")
header = header.replace(norm_dst, "")
if has_chunk_header:
return header + HEADER_DELIMITER + body
return header
def _create_diff(host: str, repo: str, ref: str, root: str, file: str,
unified: int | None) -> str:
new_file = os.path.join(root, file)
if not os.path.exists(new_file):
new_file = None
with gclient_utils.temporary_directory() as tmp_root:
old_file = None
old_content = fetch_content(host, repo, ref, file)
if old_content:
old_file = os.path.join(tmp_root, file)
os.makedirs(os.path.dirname(old_file), exist_ok=True)
with open(old_file, "wb") as f:
f.write(old_content)
if not old_file and not new_file:
raise RuntimeError(f"Could not access file {file} from {root} "
f"or from {host}/{repo}:{ref}.")
diff = git_diff(old_file, new_file, unified)
return _process_diff(diff, tmp_root, root)
def create_diffs(host: str,
repo: str,
ref: str,
root: str,
files: list[str],
unified: int | None = None) -> dict[str, str]:
"""Calculates diffs of files in a directory against a commit.
Args:
host: Gerrit host.
repo: Gerrit repo.
ref: Gerrit commit.
root: Path of local directory containing modified files.
files: List of file paths relative to root.
unified: Number of lines of context. If None, git diff uses 3 as
the default value.
Returns:
A dict mapping file paths to diffs.
Raises:
RuntimeError: If a file is missing in both the root and the repo.
"""
diffs = {}
with concurrent.futures.ThreadPoolExecutor(
max_workers=MAX_CONCURRENT_CONNECTION) as executor:
futures_to_file = {
executor.submit(_create_diff, host, repo, ref, root, file, unified):
file
for file in files
}
for future in concurrent.futures.as_completed(futures_to_file):
file = futures_to_file[future]
diffs[file] = future.result()
return diffs
def main(argv):
parser = argparse.ArgumentParser(
usage="%(prog)s [options] <files...>",
description="Makes a unified git diff against a Gerrit commit.",
)
parser.add_argument("--output", help="File to write the diff to.")
parser.add_argument("--host", required=True, help="Gerrit host.")
parser.add_argument("--repo", required=True, help="Gerrit repo.")
parser.add_argument("--ref",
required=True,
help="Gerrit ref to diff against.")
parser.add_argument("--root",
required=True,
help="Folder containing modified files.")
parser.add_argument("-U",
"--unified",
required=False,
type=int,
help="generate diffs with <n> lines context",
metavar='<n>')
parser.add_argument(
"files",
nargs="+",
help="List of changed files. Paths are relative to the repo root.",
)
options = parser.parse_args(argv)
diffs = create_diffs(options.host, options.repo, options.ref, options.root,
options.files, options.unified)
unified_diff = "\n".join([d for d in diffs.values() if d])
if options.output:
with open(options.output, "w") as f:
f.write(unified_diff)
else:
print(unified_diff)
return 0
if __name__ == "__main__":
sys.exit(main(sys.argv[1:]))
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