mirror of https://github.com/python/cpython
93 lines
2.7 KiB
Python
93 lines
2.7 KiB
Python
"""
|
|
A script that replaces an old file with a new one, only if the contents
|
|
actually changed. If not, the new file is simply deleted.
|
|
|
|
This avoids wholesale rebuilds when a code (re)generation phase does not
|
|
actually change the in-tree generated code.
|
|
"""
|
|
|
|
import contextlib
|
|
import os
|
|
import os.path
|
|
import sys
|
|
|
|
|
|
@contextlib.contextmanager
|
|
def updating_file_with_tmpfile(filename, tmpfile=None):
|
|
"""A context manager for updating a file via a temp file.
|
|
|
|
The context manager provides two open files: the source file open
|
|
for reading, and the temp file, open for writing.
|
|
|
|
Upon exiting: both files are closed, and the source file is replaced
|
|
with the temp file.
|
|
"""
|
|
# XXX Optionally use tempfile.TemporaryFile?
|
|
if not tmpfile:
|
|
tmpfile = filename + '.tmp'
|
|
elif os.path.isdir(tmpfile):
|
|
tmpfile = os.path.join(tmpfile, filename + '.tmp')
|
|
|
|
with open(filename, 'rb') as infile:
|
|
line = infile.readline()
|
|
|
|
if line.endswith(b'\r\n'):
|
|
newline = "\r\n"
|
|
elif line.endswith(b'\r'):
|
|
newline = "\r"
|
|
elif line.endswith(b'\n'):
|
|
newline = "\n"
|
|
else:
|
|
raise ValueError(f"unknown end of line: {filename}: {line!a}")
|
|
|
|
with open(tmpfile, 'w', newline=newline) as outfile:
|
|
with open(filename) as infile:
|
|
yield infile, outfile
|
|
update_file_with_tmpfile(filename, tmpfile)
|
|
|
|
|
|
def update_file_with_tmpfile(filename, tmpfile, *, create=False):
|
|
try:
|
|
targetfile = open(filename, 'rb')
|
|
except FileNotFoundError:
|
|
if not create:
|
|
raise # re-raise
|
|
outcome = 'created'
|
|
os.replace(tmpfile, filename)
|
|
else:
|
|
with targetfile:
|
|
old_contents = targetfile.read()
|
|
with open(tmpfile, 'rb') as f:
|
|
new_contents = f.read()
|
|
# Now compare!
|
|
if old_contents != new_contents:
|
|
outcome = 'updated'
|
|
os.replace(tmpfile, filename)
|
|
else:
|
|
outcome = 'same'
|
|
os.unlink(tmpfile)
|
|
return outcome
|
|
|
|
|
|
if __name__ == '__main__':
|
|
import argparse
|
|
parser = argparse.ArgumentParser()
|
|
parser.add_argument('--create', action='store_true')
|
|
parser.add_argument('--exitcode', action='store_true')
|
|
parser.add_argument('filename', help='path to be updated')
|
|
parser.add_argument('tmpfile', help='path with new contents')
|
|
args = parser.parse_args()
|
|
kwargs = vars(args)
|
|
setexitcode = kwargs.pop('exitcode')
|
|
|
|
outcome = update_file_with_tmpfile(**kwargs)
|
|
if setexitcode:
|
|
if outcome == 'same':
|
|
sys.exit(0)
|
|
elif outcome == 'updated':
|
|
sys.exit(1)
|
|
elif outcome == 'created':
|
|
sys.exit(2)
|
|
else:
|
|
raise NotImplementedError
|