comparison mercurial/ui.py @ 31954:e518192d6bac

pager: set some environment variables if they're not set

Git did this already [1] [2]. We want this behavior too [3].

This provides a better default user experience (like, supporting colors) if
users have things like "PAGER=less" set, which is not uncommon.

The environment variables are provided by a method so extensions can
override them on demand.

[1]: https://github.com/git/git/blob/6a5ff7acb5965718cc7016c0ab6c601454fd7cde/pager.c#L87
[2]: https://github.com/git/git/blob/6a5ff7acb5965718cc7016c0ab6c601454fd7cde/Makefile#L1545
[3]: https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-March/094780.html

31953:cc2382b60007

        fallbackpager = 'more'
        pagercmd = self.config('pager', 'pager', fallbackpager)
        if not pagercmd:
            return

        self.debug('starting pager for command %r\n' % command)
        self.flush()

        wasformatted = self.formatted()
        if util.safehasattr(signal, "SIGPIPE"):
            signal.signal(signal.SIGPIPE, _catchterm)
        if self._runpager(pagercmd):
            self.pageractive = True
            # Preserve the formatted-ness of the UI. This is important
            # because we mess with stdout, which might confuse
            # auto-detection of things being formatted.
            self.setconfig('ui', 'formatted', wasformatted, 'pager')

            # If the pager can't be spawned in dispatch when --pager=on is
            # given, don't try again when the command runs, to avoid a duplicate
            # warning about a missing pager command.
            self.disablepager()

    def _runpager(self, command):
        """Actually start the pager and set up file descriptors.

        This is separate in part so that extensions (like chg) can
        override how a pager is invoked.
        """

        try:
            pager = subprocess.Popen(
                command, shell=shell, bufsize=-1,
                close_fds=util.closefds, stdin=subprocess.PIPE,
                stdout=util.stdout, stderr=util.stderr)
        except OSError as e:
            if e.errno == errno.ENOENT and not shell:
                self.warn(_("missing pager command '%s', skipping pager\n")
                          % command)
                return False

31954:e518192d6bac

        fallbackpager = 'more'
        pagercmd = self.config('pager', 'pager', fallbackpager)
        if not pagercmd:
            return

        pagerenv = {}
        for name, value in rcutil.defaultpagerenv().items():
            if name not in encoding.environ:
                pagerenv[name] = value

        self.debug('starting pager for command %r\n' % command)
        self.flush()

        wasformatted = self.formatted()
        if util.safehasattr(signal, "SIGPIPE"):
            signal.signal(signal.SIGPIPE, _catchterm)
        if self._runpager(pagercmd, pagerenv):
            self.pageractive = True
            # Preserve the formatted-ness of the UI. This is important
            # because we mess with stdout, which might confuse
            # auto-detection of things being formatted.
            self.setconfig('ui', 'formatted', wasformatted, 'pager')

            # If the pager can't be spawned in dispatch when --pager=on is
            # given, don't try again when the command runs, to avoid a duplicate
            # warning about a missing pager command.
            self.disablepager()

    def _runpager(self, command, env=None):
        """Actually start the pager and set up file descriptors.

        This is separate in part so that extensions (like chg) can
        override how a pager is invoked.
        """

        try:
            pager = subprocess.Popen(
                command, shell=shell, bufsize=-1,
                close_fds=util.closefds, stdin=subprocess.PIPE,
                stdout=util.stdout, stderr=util.stderr,
                env=util.shellenviron(env))
        except OSError as e:
            if e.errno == errno.ENOENT and not shell:
                self.warn(_("missing pager command '%s', skipping pager\n")
                          % command)
                return False