view tests/printenv.py @ 31478:9335dc6b2a9c

pager: avoid shell=True on subprocess.Popen for better errors (issue5491)

man(1) behaves as poorly as Mercurial without this change. This cribs
from git's run-command[0], which has a list of characters that imply a
string that needs to be run using 'sh -c'. If none of those characters
are present in the command string, we can use shell=False mode on
subprocess and get significantly better error messages (see the test)
when the pager process is invalid. With a complicated pager command
(that contains one of the unsafe characters), we behave as we do today
(which is no worse than git manages.)

I briefly tried tapdancing in a thread to catch early pager exits, but
it's just too perilous: you get races between fd duping operations and
a bad pager exiting, and it's too hard to differentiate between a
slow-bad-pager result and a fast-human-quit-pager-early result.

I've observed some weird variation in exit code handling in the "bad
experience" case in test-pager.t: on my Mac hg predictably exits
nonzero, but on Linux hg always exits zero in that case. For now,
we'll work around it with || true. :(

0: https://github.com/git/git/blob/cddbda4bc87b9d2c985b6749b1cf026b15e2d3e7/run-command.c#L201

#!/usr/bin/env python
#
# simple script to be used in hooks
#
# put something like this in the repo .hg/hgrc:
#
#     [hooks]
#     changegroup = python "$TESTDIR/printenv.py" <hookname> [exit] [output]
#
#   - <hookname> is a mandatory argument (e.g. "changegroup")
#   - [exit] is the exit code of the hook (default: 0)
#   - [output] is the name of the output file (default: use sys.stdout)
#              the file will be opened in append mode.
#
from __future__ import absolute_import
import os
import sys

try:
    import msvcrt
    msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
    msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
    msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
except ImportError:
    pass

exitcode = 0
out = sys.stdout

name = sys.argv[1]
if len(sys.argv) > 2:
    exitcode = int(sys.argv[2])
    if len(sys.argv) > 3:
        out = open(sys.argv[3], "ab")

# variables with empty values may not exist on all platforms, filter
# them now for portability sake.
env = [(k, v) for k, v in os.environ.iteritems()
       if k.startswith("HG_") and v]
env.sort()

out.write("%s hook: " % name)
if os.name == 'nt':
    filter = lambda x: x.replace('\\', '/')
else:
    filter = lambda x: x
vars = ["%s=%s" % (k, filter(v)) for k, v in env]
out.write(" ".join(vars))
out.write("\n")
out.close()

sys.exit(exitcode)