hgext/pager.py

match: introduce boolean prefix() method

tl;dr: This is another step towards a (previously unstated) goal of
eliminating match.files() in conditions.

There are four types of matchers:

 * always: Matches everything, checked with always(), files() is empty

 * exact: Matches exact set of files, checked with isexact(), files()
   contains the files to match

 * patterns: Matches more complex patterns, checked with anypats(),
   files() contains roots of the matched patterns

 * prefix: Matches simple 'path:' patterns as prefixes ('foo' matches
   both 'foo' and 'foo/bar'), no single method to check, files()
   contains the prefixes to match

For completeness, it would be nice to have a method for checking for
the "prefix" type of matcher as well, so let's add that, making it
return True simply when none of the others do.

The larger goal here is to eliminate uses of match.files() in
conditions (i.e. bool(match.files())). The reason for this is that
there are scenarios when you would like to create a "prefix" matcher
that happens to match no files. One example is for 'hg files -I foo
bar'. The narrowmatcher also restricts the set of files given and it
would not surprise me if have bugs caused by that already. Note that
'if m.files() and not m.anypats()' and similar is sometimes used to
catch the "exact" and "prefix" cases above.

# pager.py - display output using a pager
#
# Copyright 2008 David Soria Parra <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
#
# To load the extension, add it to your configuration file:
#
#   [extension]
#   pager =
#
# Run "hg help pager" to get info on configuration.

'''browse command output with an external pager

To set the pager that should be used, set the application variable::

  [pager]
  pager = less -FRX

If no pager is set, the pager extensions uses the environment variable
$PAGER. If neither pager.pager, nor $PAGER is set, no pager is used.

You can disable the pager for certain commands by adding them to the
pager.ignore list::

  [pager]
  ignore = version, help, update

You can also enable the pager only for certain commands using
pager.attend. Below is the default list of commands to be paged::

  [pager]
  attend = annotate, cat, diff, export, glog, log, qdiff

Setting pager.attend to an empty value will cause all commands to be
paged.

If pager.attend is present, pager.ignore will be ignored.

Lastly, you can enable and disable paging for individual commands with
the attend-<command> option. This setting takes precedence over
existing attend and ignore options and defaults::

  [pager]
  attend-cat = false

To ignore global commands like :hg:`version` or :hg:`help`, you have
to specify them in your user configuration file.

The --pager=... option can also be used to control when the pager is
used. Use a boolean value like yes, no, on, off, or use auto for
normal behavior.

'''

import atexit, sys, os, signal, subprocess
from mercurial import commands, dispatch, util, extensions, cmdutil
from mercurial.i18n import _

# Note for extension authors: ONLY specify testedwith = 'internal' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'internal'

def _pagersubprocess(ui, p):
    pager = subprocess.Popen(p, shell=True, bufsize=-1,
                             close_fds=util.closefds, stdin=subprocess.PIPE,
                             stdout=sys.stdout, stderr=sys.stderr)

    stdout = os.dup(sys.stdout.fileno())
    stderr = os.dup(sys.stderr.fileno())
    os.dup2(pager.stdin.fileno(), sys.stdout.fileno())
    if ui._isatty(sys.stderr):
        os.dup2(pager.stdin.fileno(), sys.stderr.fileno())

    @atexit.register
    def killpager():
        if util.safehasattr(signal, "SIGINT"):
            signal.signal(signal.SIGINT, signal.SIG_IGN)
        pager.stdin.close()
        os.dup2(stdout, sys.stdout.fileno())
        os.dup2(stderr, sys.stderr.fileno())
        pager.wait()

def _runpager(ui, p):
    _pagersubprocess(ui, p)

def uisetup(ui):
    if '--debugger' in sys.argv or not ui.formatted():
        return

    def pagecmd(orig, ui, options, cmd, cmdfunc):
        p = ui.config("pager", "pager", os.environ.get("PAGER"))
        usepager = False
        always = util.parsebool(options['pager'])
        auto = options['pager'] == 'auto'

        if not p:
            pass
        elif always:
            usepager = True
        elif not auto:
            usepager = False
        else:
            attend = ui.configlist('pager', 'attend', attended)
            ignore = ui.configlist('pager', 'ignore')
            cmds, _ = cmdutil.findcmd(cmd, commands.table)

            for cmd in cmds:
                var = 'attend-%s' % cmd
                if ui.config('pager', var):
                    usepager = ui.configbool('pager', var)
                    break
                if (cmd in attend or
                     (cmd not in ignore and not attend)):
                    usepager = True
                    break

        setattr(ui, 'pageractive', usepager)

        if usepager:
            ui.setconfig('ui', 'formatted', ui.formatted(), 'pager')
            ui.setconfig('ui', 'interactive', False, 'pager')
            if util.safehasattr(signal, "SIGPIPE"):
                signal.signal(signal.SIGPIPE, signal.SIG_DFL)
            _runpager(ui, p)
        return orig(ui, options, cmd, cmdfunc)

    # Wrap dispatch._runcommand after color is loaded so color can see
    # ui.pageractive. Otherwise, if we loaded first, color's wrapped
    # dispatch._runcommand would run without having access to ui.pageractive.
    def afterloaded(loaded):
        extensions.wrapfunction(dispatch, '_runcommand', pagecmd)
    extensions.afterloaded('color', afterloaded)

def extsetup(ui):
    commands.globalopts.append(
        ('', 'pager', 'auto',
         _("when to paginate (boolean, always, auto, or never)"),
         _('TYPE')))

attended = ['annotate', 'cat', 'diff', 'export', 'glog', 'log', 'qdiff']