tests/hghave.py

merge: minimize conflicts when common base is not shown (issue4447)

Previously, two changes that were nearly, but not quite, identical would result
in large merge conflict regions that looked very similar, and were thus very
confusing to users, and lead people used to other source control systems to
claim that "mercurial's merge algorithms suck". In the relatively common case
of a new file being introduced in two branches with very slight modifications,
the old behavior would show the entire file as a conflict, and it would be very
difficult for a user to determine what was going on.

In the past, mercurial attempted to solve this with a "very smart" algorithm
that would find all common lines, but this has significant problems as
described in 2ea6d906cf9b.

Instead, we use a "very dumb" algorithm introduced in the previous patch that
simply matches lines at the periphery of conflict regions. This minimizes most
conflict regions well, though there may still be some degenerate edge cases,
like small modification to the beginning and end of a large file.

from __future__ import absolute_import

import errno
import os
import re
import socket
import stat
import subprocess
import sys
import tempfile

tempprefix = 'hg-hghave-'

checks = {
    "true": (lambda: True, "yak shaving"),
    "false": (lambda: False, "nail clipper"),
}

def check(name, desc):
    def decorator(func):
        checks[name] = (func, desc)
        return func
    return decorator

def checkfeatures(features):
    result = {
        'error': [],
        'missing': [],
        'skipped': [],
    }

    for feature in features:
        negate = feature.startswith('no-')
        if negate:
            feature = feature[3:]

        if feature not in checks:
            result['missing'].append(feature)
            continue

        check, desc = checks[feature]
        try:
            available = check()
        except Exception:
            result['error'].append('hghave check failed: %s' % feature)
            continue

        if not negate and not available:
            result['skipped'].append('missing feature: %s' % desc)
        elif negate and available:
            result['skipped'].append('system supports %s' % desc)

    return result

def require(features):
    """Require that features are available, exiting if not."""
    result = checkfeatures(features)

    for missing in result['missing']:
        sys.stderr.write('skipped: unknown feature: %s\n' % missing)
    for msg in result['skipped']:
        sys.stderr.write('skipped: %s\n' % msg)
    for msg in result['error']:
        sys.stderr.write('%s\n' % msg)

    if result['missing']:
        sys.exit(2)

    if result['skipped'] or result['error']:
        sys.exit(1)

def matchoutput(cmd, regexp, ignorestatus=False):
    """Return the match object if cmd executes successfully and its output
    is matched by the supplied regular expression.
    """
    r = re.compile(regexp)
    try:
        p = subprocess.Popen(
            cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    except OSError as e:
        if e.errno != errno.ENOENT:
            raise
        ret = -1
    ret = p.wait()
    s = p.stdout.read()
    return (ignorestatus or not ret) and r.search(s)

@check("baz", "GNU Arch baz client")
def has_baz():
    return matchoutput('baz --version 2>&1', r'baz Bazaar version')

@check("bzr", "Canonical's Bazaar client")
def has_bzr():
    try:
        import bzrlib
        return bzrlib.__doc__ is not None
    except ImportError:
        return False

@check("bzr114", "Canonical's Bazaar client >= 1.14")
def has_bzr114():
    try:
        import bzrlib
        return (bzrlib.__doc__ is not None
                and bzrlib.version_info[:2] >= (1, 14))
    except ImportError:
        return False

@check("cvs", "cvs client/server")
def has_cvs():
    re = r'Concurrent Versions System.*?server'
    return matchoutput('cvs --version 2>&1', re) and not has_msys()

@check("cvs112", "cvs client/server >= 1.12")
def has_cvs112():
    re = r'Concurrent Versions System \(CVS\) 1.12.*?server'
    return matchoutput('cvs --version 2>&1', re) and not has_msys()

@check("darcs", "darcs client")
def has_darcs():
    return matchoutput('darcs --version', r'2\.[2-9]', True)

@check("mtn", "monotone client (>= 1.0)")
def has_mtn():
    return matchoutput('mtn --version', r'monotone', True) and not matchoutput(
        'mtn --version', r'monotone 0\.', True)

@check("eol-in-paths", "end-of-lines in paths")
def has_eol_in_paths():
    try:
        fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix, suffix='\n\r')
        os.close(fd)
        os.remove(path)
        return True
    except (IOError, OSError):
        return False

@check("execbit", "executable bit")
def has_executablebit():
    try:
        EXECFLAGS = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
        fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
        try:
            os.close(fh)
            m = os.stat(fn).st_mode & 0o777
            new_file_has_exec = m & EXECFLAGS
            os.chmod(fn, m ^ EXECFLAGS)
            exec_flags_cannot_flip = ((os.stat(fn).st_mode & 0o777) == m)
        finally:
            os.unlink(fn)
    except (IOError, OSError):
        # we don't care, the user probably won't be able to commit anyway
        return False
    return not (new_file_has_exec or exec_flags_cannot_flip)

@check("icasefs", "case insensitive file system")
def has_icasefs():
    # Stolen from mercurial.util
    fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
    os.close(fd)
    try:
        s1 = os.stat(path)
        d, b = os.path.split(path)
        p2 = os.path.join(d, b.upper())
        if path == p2:
            p2 = os.path.join(d, b.lower())
        try:
            s2 = os.stat(p2)
            return s2 == s1
        except OSError:
            return False
    finally:
        os.remove(path)

@check("fifo", "named pipes")
def has_fifo():
    if getattr(os, "mkfifo", None) is None:
        return False
    name = tempfile.mktemp(dir='.', prefix=tempprefix)
    try:
        os.mkfifo(name)
        os.unlink(name)
        return True
    except OSError:
        return False

@check("killdaemons", 'killdaemons.py support')
def has_killdaemons():
    return True

@check("cacheable", "cacheable filesystem")
def has_cacheable_fs():
    from mercurial import util

    fd, path = tempfile.mkstemp(dir='.', prefix=tempprefix)
    os.close(fd)
    try:
        return util.cachestat(path).cacheable()
    finally:
        os.remove(path)

@check("lsprof", "python lsprof module")
def has_lsprof():
    try:
        import _lsprof
        _lsprof.Profiler # silence unused import warning
        return True
    except ImportError:
        return False

@check("gettext", "GNU Gettext (msgfmt)")
def has_gettext():
    return matchoutput('msgfmt --version', 'GNU gettext-tools')

@check("git", "git command line client")
def has_git():
    return matchoutput('git --version 2>&1', r'^git version')

@check("docutils", "Docutils text processing library")
def has_docutils():
    try:
        from docutils.core import publish_cmdline
        publish_cmdline # silence unused import
        return True
    except ImportError:
        return False

def getsvnversion():
    m = matchoutput('svn --version --quiet 2>&1', r'^(\d+)\.(\d+)')
    if not m:
        return (0, 0)
    return (int(m.group(1)), int(m.group(2)))

@check("svn15", "subversion client and admin tools >= 1.5")
def has_svn15():
    return getsvnversion() >= (1, 5)

@check("svn13", "subversion client and admin tools >= 1.3")
def has_svn13():
    return getsvnversion() >= (1, 3)

@check("svn", "subversion client and admin tools")
def has_svn():
    return matchoutput('svn --version 2>&1', r'^svn, version') and \
        matchoutput('svnadmin --version 2>&1', r'^svnadmin, version')

@check("svn-bindings", "subversion python bindings")
def has_svn_bindings():
    try:
        import svn.core
        version = svn.core.SVN_VER_MAJOR, svn.core.SVN_VER_MINOR
        if version < (1, 4):
            return False
        return True
    except ImportError:
        return False

@check("p4", "Perforce server and client")
def has_p4():
    return (matchoutput('p4 -V', r'Rev\. P4/') and
            matchoutput('p4d -V', r'Rev\. P4D/'))

@check("symlink", "symbolic links")
def has_symlink():
    if getattr(os, "symlink", None) is None:
        return False
    name = tempfile.mktemp(dir='.', prefix=tempprefix)
    try:
        os.symlink(".", name)
        os.unlink(name)
        return True
    except (OSError, AttributeError):
        return False

@check("hardlink", "hardlinks")
def has_hardlink():
    from mercurial import util
    fh, fn = tempfile.mkstemp(dir='.', prefix=tempprefix)
    os.close(fh)
    name = tempfile.mktemp(dir='.', prefix=tempprefix)
    try:
        util.oslink(fn, name)
        os.unlink(name)
        return True
    except OSError:
        return False
    finally:
        os.unlink(fn)

@check("tla", "GNU Arch tla client")
def has_tla():
    return matchoutput('tla --version 2>&1', r'The GNU Arch Revision')

@check("gpg", "gpg client")
def has_gpg():
    return matchoutput('gpg --version 2>&1', r'GnuPG')

@check("unix-permissions", "unix-style permissions")
def has_unix_permissions():
    d = tempfile.mkdtemp(dir='.', prefix=tempprefix)
    try:
        fname = os.path.join(d, 'foo')
        for umask in (0o77, 0o07, 0o22):
            os.umask(umask)
            f = open(fname, 'w')
            f.close()
            mode = os.stat(fname).st_mode
            os.unlink(fname)
            if mode & 0o777 != ~umask & 0o666:
                return False
        return True
    finally:
        os.rmdir(d)

@check("unix-socket", "AF_UNIX socket family")
def has_unix_socket():
    return getattr(socket, 'AF_UNIX', None) is not None

@check("root", "root permissions")
def has_root():
    return getattr(os, 'geteuid', None) and os.geteuid() == 0

@check("pyflakes", "Pyflakes python linter")
def has_pyflakes():
    return matchoutput("sh -c \"echo 'import re' 2>&1 | pyflakes\"",
                       r"<stdin>:1: 're' imported but unused",
                       True)

@check("pygments", "Pygments source highlighting library")
def has_pygments():
    try:
        import pygments
        pygments.highlight # silence unused import warning
        return True
    except ImportError:
        return False

@check("json", "some json module available")
def has_json():
    try:
        import json
        json.dumps
        return True
    except ImportError:
        try:
            import simplejson as json
            json.dumps
            return True
        except ImportError:
            pass
    return False

@check("outer-repo", "outer repo")
def has_outer_repo():
    # failing for other reasons than 'no repo' imply that there is a repo
    return not matchoutput('hg root 2>&1',
                           r'abort: no repository found', True)

@check("ssl", ("(python >= 2.6 ssl module and python OpenSSL) "
               "OR python >= 2.7.9 ssl"))
def has_ssl():
    try:
        import ssl
        if getattr(ssl, 'create_default_context', False):
            return True
        import OpenSSL
        OpenSSL.SSL.Context
        return True
    except ImportError:
        return False

@check("sslcontext", "python >= 2.7.9 ssl")
def has_sslcontext():
    try:
        import ssl
        ssl.SSLContext
        return True
    except (ImportError, AttributeError):
        return False

@check("defaultcacerts", "can verify SSL certs by system's CA certs store")
def has_defaultcacerts():
    from mercurial import sslutil
    return sslutil._defaultcacerts() != '!'

@check("windows", "Windows")
def has_windows():
    return os.name == 'nt'

@check("system-sh", "system() uses sh")
def has_system_sh():
    return os.name != 'nt'

@check("serve", "platform and python can manage 'hg serve -d'")
def has_serve():
    return os.name != 'nt' # gross approximation

@check("test-repo", "running tests from repository")
def has_test_repo():
    t = os.environ["TESTDIR"]
    return os.path.isdir(os.path.join(t, "..", ".hg"))

@check("tic", "terminfo compiler and curses module")
def has_tic():
    try:
        import curses
        curses.COLOR_BLUE
        return matchoutput('test -x "`which tic`"', '')
    except ImportError:
        return False

@check("msys", "Windows with MSYS")
def has_msys():
    return os.getenv('MSYSTEM')

@check("aix", "AIX")
def has_aix():
    return sys.platform.startswith("aix")

@check("osx", "OS X")
def has_osx():
    return sys.platform == 'darwin'

@check("docker", "docker support")
def has_docker():
    pat = r'A self-sufficient runtime for linux containers\.'
    if matchoutput('docker --help', pat):
        if 'linux' not in sys.platform:
            # TODO: in theory we should be able to test docker-based
            # package creation on non-linux using boot2docker, but in
            # practice that requires extra coordination to make sure
            # $TESTTEMP is going to be visible at the same path to the
            # boot2docker VM. If we figure out how to verify that, we
            # can use the following instead of just saying False:
            # return 'DOCKER_HOST' in os.environ
            return False

        return True
    return False

@check("debhelper", "debian packaging tools")
def has_debhelper():
    dpkg = matchoutput('dpkg --version',
                       "Debian `dpkg' package management program")
    dh = matchoutput('dh --help',
                     'dh is a part of debhelper.', ignorestatus=True)
    dh_py2 = matchoutput('dh_python2 --help',
                         'other supported Python versions')
    return dpkg and dh and dh_py2

@check("absimport", "absolute_import in __future__")
def has_absimport():
    import __future__
    from mercurial import util
    return util.safehasattr(__future__, "absolute_import")

@check("py3k", "running with Python 3.x")
def has_py3k():
    return 3 == sys.version_info[0]

@check("pure", "running with pure Python code")
def has_pure():
    return any([
        os.environ.get("HGMODULEPOLICY") == "py",
        os.environ.get("HGTEST_RUN_TESTS_PURE") == "--pure",
    ])

@check("slow", "allow slow tests")
def has_slow():
    return os.environ.get('HGTEST_SLOW') == 'slow'

@check("hypothesis", "is Hypothesis installed")
def has_hypothesis():
    try:
        import hypothesis
        hypothesis.given
        return True
    except ImportError:
        return False