view tests/svn-safe-append.py @ 46089:8ff2d8359d0f

persistent-nodemap: properly ignore non-existent `.nd` data file

This code was meant to handle the case of a nodemap docket file
pointing to a nodemap data file that doesn’t exist (anymore),
but most likely caused an `UnboundLocalError` exception instead
when `data` was used on the next line without being defined.

This case is theoretically possible with a race condition
between two hg processes, but is hard to reproduce or test:

* Process A reads a docket file and finds a UID in it
  that points to a given data file name.
* Process B decides that this same data file needs compacting.
  It writes a new one with a different UID,
  overwrites the docket file,
  then removes the old data file.
* Only then process A tries to a open a file that doesn’t exist anymore.

Differential Revision: https://phab.mercurial-scm.org/D9533

#!/usr/bin/env python3

from __future__ import absolute_import

__doc__ = """Same as `echo a >> b`, but ensures a changed mtime of b.
Without this svn will not detect workspace changes."""

import os
import stat
import sys

if sys.version_info[0] >= 3:
    text = os.fsencode(sys.argv[1])
    fname = os.fsencode(sys.argv[2])
else:
    text = sys.argv[1]
    fname = sys.argv[2]

f = open(fname, "ab")
try:
    before = os.fstat(f.fileno())[stat.ST_MTIME]
    f.write(text)
    f.write(b"\n")
finally:
    f.close()
inc = 1
now = os.stat(fname)[stat.ST_MTIME]
while now == before:
    t = now + inc
    inc += 1
    os.utime(fname, (t, t))
    now = os.stat(fname)[stat.ST_MTIME]