color: be more conservative about setting ANSI mode on Windows (BC)

The current color mode detection on Windows assumes the presence of the
TERM environment variable assumes ANSI is supported. However, this isn't
always true. In MSYS (commonly found as part of MinGW), TERM is set to
"cygwin" and the auto resolved color mode of "ansi" results in escape
sequences getting printed literally to the terminal. The output is
very difficult to read and results in a bad user experience. A
workaround is to activate the pager and have it attend all commands (GNU
less in MSYS can render ANSI terminal sequences properly).

In Cygwin, TERM is set to "xterm." Furthermore, Cygwin supports
displaying these terminal sequences properly (unlike MSYS).

This patch changes the mode auto-detection logic on Windows to be more
conservative about selecting the "ansi" mode. We now only select the
"ansi" mode if TERM is set and it contains the string "xterm" or if
we were unable to talk to win32 APIs to determine the settings. There is
a chance this may take away "ansi" from a terminal that actually
supports it. The recourse for this would be to patch the detection to
act appropriately and to override color.mode until that patch has
landed. However, the author believes this regression is tolerable, since
it means MSYS users won't have gibberish printed by default.

Since MSYS's common pager (less) supports display of ANSI sequences,
there is room to patch the color extensions so it can select the ANSI
color mode if a pager is activated.

Mozilla (being an active user of MSYS) would really appreciate this
being part of the stable branch. However, since I believe it is BC, I
haven't explicitly requested application to stable since I figure that
request will be denied.

hgext/color.py

@@ -1,653 +1,667 b''
 # color.py color output for Mercurial commands
 #
 # Copyright (C) 2007 Kevin Christen <[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.
 
 '''colorize output from some commands
 
 The color extension colorizes output from several Mercurial commands.
 For example, the diff command shows additions in green and deletions
 in red, while the status command shows modified files in magenta. Many
 other commands have analogous colors. It is possible to customize
 these colors.
 
 Effects
 -------
 
 Other effects in addition to color, like bold and underlined text, are
 also available. By default, the terminfo database is used to find the
 terminal codes used to change color and effect.  If terminfo is not
 available, then effects are rendered with the ECMA-48 SGR control
 function (aka ANSI escape codes).
 
 The available effects in terminfo mode are 'blink', 'bold', 'dim',
 'inverse', 'invisible', 'italic', 'standout', and 'underline'; in
 ECMA-48 mode, the options are 'bold', 'inverse', 'italic', and
 'underline'.  How each is rendered depends on the terminal emulator.
 Some may not be available for a given terminal type, and will be
 silently ignored.
 
 Labels
 ------
 
 Text receives color effects depending on the labels that it has. Many
 default Mercurial commands emit labelled text. You can also define
 your own labels in templates using the label function, see :hg:`help
 templates`. A single portion of text may have more than one label. In
 that case, effects given to the last label will override any other
 effects. This includes the special "none" effect, which nullifies
 other effects.
 
 Labels are normally invisible. In order to see these labels and their
 position in the text, use the global --color=debug option. The same
 anchor text may be associated to multiple labels, e.g.
 
   [log.changeset changeset.secret|changeset:   22611:6f0a53c8f587]
 
 The following are the default effects for some default labels. Default
 effects may be overridden from your configuration file::
 
   [color]
   status.modified = blue bold underline red_background
   status.added = green bold
   status.removed = red bold blue_background
   status.deleted = cyan bold underline
   status.unknown = magenta bold underline
   status.ignored = black bold
 
   # 'none' turns off all effects
   status.clean = none
   status.copied = none
 
   qseries.applied = blue bold underline
   qseries.unapplied = black bold
   qseries.missing = red bold
 
   diff.diffline = bold
   diff.extended = cyan bold
   diff.file_a = red bold
   diff.file_b = green bold
   diff.hunk = magenta
   diff.deleted = red
   diff.inserted = green
   diff.changed = white
   diff.tab =
   diff.trailingwhitespace = bold red_background
 
   # Blank so it inherits the style of the surrounding label
   changeset.public =
   changeset.draft =
   changeset.secret =
 
   resolve.unresolved = red bold
   resolve.resolved = green bold
 
   bookmarks.current = green
 
   branches.active = none
   branches.closed = black bold
   branches.current = green
   branches.inactive = none
 
   tags.normal = green
   tags.local = black bold
 
   rebase.rebased = blue
   rebase.remaining = red bold
 
   shelve.age = cyan
   shelve.newest = green bold
   shelve.name = blue bold
 
   histedit.remaining = red bold
 
 Custom colors
 -------------
 
 Because there are only eight standard colors, this module allows you
 to define color names for other color slots which might be available
 for your terminal type, assuming terminfo mode.  For instance::
 
   color.brightblue = 12
   color.pink = 207
   color.orange = 202
 
 to set 'brightblue' to color slot 12 (useful for 16 color terminals
 that have brighter colors defined in the upper eight) and, 'pink' and
 'orange' to colors in 256-color xterm's default color cube.  These
 defined colors may then be used as any of the pre-defined eight,
 including appending '_background' to set the background to that color.
 
 Modes
 -----
 
 By default, the color extension will use ANSI mode (or win32 mode on
 Windows) if it detects a terminal. To override auto mode (to enable
 terminfo mode, for example), set the following configuration option::
 
   [color]
   mode = terminfo
 
 Any value other than 'ansi', 'win32', 'terminfo', or 'auto' will
 disable color.
 
 Note that on some systems, terminfo mode may cause problems when using
 color with the pager extension and less -R. less with the -R option
 will only display ECMA-48 color codes, and terminfo mode may sometimes
 emit codes that less doesn't understand. You can work around this by
 either using ansi mode (or auto mode), or by using less -r (which will
 pass through all terminal control codes, not just color control
 codes).
 '''
 
 import os
 
 from mercurial import cmdutil, commands, dispatch, extensions, subrepo, util
 from mercurial import ui as uimod
 from mercurial import templater, error
 from mercurial.i18n import _
 
 cmdtable = {}
 command = cmdutil.command(cmdtable)
 testedwith = 'internal'
 
 # start and stop parameters for effects
 _effects = {'none': 0, 'black': 30, 'red': 31, 'green': 32, 'yellow': 33,
             'blue': 34, 'magenta': 35, 'cyan': 36, 'white': 37, 'bold': 1,
             'italic': 3, 'underline': 4, 'inverse': 7, 'dim': 2,
             'black_background': 40, 'red_background': 41,
             'green_background': 42, 'yellow_background': 43,
             'blue_background': 44, 'purple_background': 45,
             'cyan_background': 46, 'white_background': 47}
 
 def _terminfosetup(ui, mode):
     '''Initialize terminfo data and the terminal if we're in terminfo mode.'''
 
     global _terminfo_params
     # If we failed to load curses, we go ahead and return.
     if not _terminfo_params:
         return
     # Otherwise, see what the config file says.
     if mode not in ('auto', 'terminfo'):
         return
 
     _terminfo_params.update((key[6:], (False, int(val)))
         for key, val in ui.configitems('color')
         if key.startswith('color.'))
 
     try:
         curses.setupterm()
     except curses.error, e:
         _terminfo_params = {}
         return
 
     for key, (b, e) in _terminfo_params.items():
         if not b:
             continue
         if not curses.tigetstr(e):
             # Most terminals don't support dim, invis, etc, so don't be
             # noisy and use ui.debug().
             ui.debug("no terminfo entry for %s\n" % e)
             del _terminfo_params[key]
     if not curses.tigetstr('setaf') or not curses.tigetstr('setab'):
         # Only warn about missing terminfo entries if we explicitly asked for
         # terminfo mode.
         if mode == "terminfo":
             ui.warn(_("no terminfo entry for setab/setaf: reverting to "
               "ECMA-48 color\n"))
         _terminfo_params = {}
 
 def _modesetup(ui, coloropt):
     global _terminfo_params
 
     if coloropt == 'debug':
         return 'debug'
 
     auto = (coloropt == 'auto')
     always = not auto and util.parsebool(coloropt)
     if not always and not auto:
         return None
 
     formatted = always or (os.environ.get('TERM') != 'dumb' and ui.formatted())
 
     mode = ui.config('color', 'mode', 'auto')
     realmode = mode
     if mode == 'auto':
-        if os.name == 'nt' and 'TERM' not in os.environ:
-            # looks line a cmd.exe console, use win32 API or nothing
+        if os.name == 'nt':
+            term = os.environ.get('TERM')
+            # TERM won't be defined in a vanilla cmd.exe environment.
+            if not term:
+                realmode = 'win32'
+
+            # UNIX-like environments on Windows such as Cygwin and MSYS will
+            # set TERM. They appear to make a best effort attempt at setting it
+            # to something appropriate. However, not all environments with TERM
+            # defined support ANSI. Since "ansi" could result in terminal
+            # gibberish, we error on the side of selecting "win32". However, if
+            # w32effects is not defined, we almost certainly don't support
+            # "win32", so don't even try.
+            if 'xterm' in term or not w32effects:
+                realmode = 'ansi'
+            else:
             realmode = 'win32'
         else:
             realmode = 'ansi'
 
     if realmode == 'win32':
         _terminfo_params = {}
         if not w32effects:
             if mode == 'win32':
                 # only warn if color.mode is explicitly set to win32
                 ui.warn(_('warning: failed to set color mode to %s\n') % mode)
             return None
         _effects.update(w32effects)
     elif realmode == 'ansi':
         _terminfo_params = {}
     elif realmode == 'terminfo':
         _terminfosetup(ui, mode)
         if not _terminfo_params:
             if mode == 'terminfo':
                 ## FIXME Shouldn't we return None in this case too?
                 # only warn if color.mode is explicitly set to win32
                 ui.warn(_('warning: failed to set color mode to %s\n') % mode)
             realmode = 'ansi'
     else:
         return None
 
     if always or (auto and formatted):
         return realmode
     return None
 
 try:
     import curses
     # Mapping from effect name to terminfo attribute name or color number.
     # This will also force-load the curses module.
     _terminfo_params = {'none': (True, 'sgr0'),
                         'standout': (True, 'smso'),
                         'underline': (True, 'smul'),
                         'reverse': (True, 'rev'),
                         'inverse': (True, 'rev'),
                         'blink': (True, 'blink'),
                         'dim': (True, 'dim'),
                         'bold': (True, 'bold'),
                         'invisible': (True, 'invis'),
                         'italic': (True, 'sitm'),
                         'black': (False, curses.COLOR_BLACK),
                         'red': (False, curses.COLOR_RED),
                         'green': (False, curses.COLOR_GREEN),
                         'yellow': (False, curses.COLOR_YELLOW),
                         'blue': (False, curses.COLOR_BLUE),
                         'magenta': (False, curses.COLOR_MAGENTA),
                         'cyan': (False, curses.COLOR_CYAN),
                         'white': (False, curses.COLOR_WHITE)}
 except ImportError:
     _terminfo_params = {}
 
 _styles = {'grep.match': 'red bold',
            'grep.linenumber': 'green',
            'grep.rev': 'green',
            'grep.change': 'green',
            'grep.sep': 'cyan',
            'grep.filename': 'magenta',
            'grep.user': 'magenta',
            'grep.date': 'magenta',
            'bookmarks.current': 'green',
            'branches.active': 'none',
            'branches.closed': 'black bold',
            'branches.current': 'green',
            'branches.inactive': 'none',
            'diff.changed': 'white',
            'diff.deleted': 'red',
            'diff.diffline': 'bold',
            'diff.extended': 'cyan bold',
            'diff.file_a': 'red bold',
            'diff.file_b': 'green bold',
            'diff.hunk': 'magenta',
            'diff.inserted': 'green',
            'diff.tab': '',
            'diff.trailingwhitespace': 'bold red_background',
            'changeset.public' : '',
            'changeset.draft' : '',
            'changeset.secret' : '',
            'diffstat.deleted': 'red',
            'diffstat.inserted': 'green',
            'histedit.remaining': 'red bold',
            'ui.prompt': 'yellow',
            'log.changeset': 'yellow',
            'patchbomb.finalsummary': '',
            'patchbomb.from': 'magenta',
            'patchbomb.to': 'cyan',
            'patchbomb.subject': 'green',
            'patchbomb.diffstats': '',
            'rebase.rebased': 'blue',
            'rebase.remaining': 'red bold',
            'resolve.resolved': 'green bold',
            'resolve.unresolved': 'red bold',
            'shelve.age': 'cyan',
            'shelve.newest': 'green bold',
            'shelve.name': 'blue bold',
            'status.added': 'green bold',
            'status.clean': 'none',
            'status.copied': 'none',
            'status.deleted': 'cyan bold underline',
            'status.ignored': 'black bold',
            'status.modified': 'blue bold',
            'status.removed': 'red bold',
            'status.unknown': 'magenta bold underline',
            'tags.normal': 'green',
            'tags.local': 'black bold'}
 
 
 def _effect_str(effect):
     '''Helper function for render_effects().'''
 
     bg = False
     if effect.endswith('_background'):
         bg = True
         effect = effect[:-11]
     attr, val = _terminfo_params[effect]
     if attr:
         return curses.tigetstr(val)
     elif bg:
         return curses.tparm(curses.tigetstr('setab'), val)
     else:
         return curses.tparm(curses.tigetstr('setaf'), val)
 
 def render_effects(text, effects):
     'Wrap text in commands to turn on each effect.'
     if not text:
         return text
     if not _terminfo_params:
         start = [str(_effects[e]) for e in ['none'] + effects.split()]
         start = '\033[' + ';'.join(start) + 'm'
         stop = '\033[' + str(_effects['none']) + 'm'
     else:
         start = ''.join(_effect_str(effect)
                         for effect in ['none'] + effects.split())
         stop = _effect_str('none')
     return ''.join([start, text, stop])
 
 def extstyles():
     for name, ext in extensions.extensions():
         _styles.update(getattr(ext, 'colortable', {}))
 
 def valideffect(effect):
     'Determine if the effect is valid or not.'
     good = False
     if not _terminfo_params and effect in _effects:
         good = True
     elif effect in _terminfo_params or effect[:-11] in _terminfo_params:
         good = True
     return good
 
 def configstyles(ui):
     for status, cfgeffects in ui.configitems('color'):
         if '.' not in status or status.startswith('color.'):
             continue
         cfgeffects = ui.configlist('color', status)
         if cfgeffects:
             good = []
             for e in cfgeffects:
                 if valideffect(e):
                     good.append(e)
                 else:
                     ui.warn(_("ignoring unknown color/effect %r "
                               "(configured in color.%s)\n")
                             % (e, status))
             _styles[status] = ' '.join(good)
 
 class colorui(uimod.ui):
     def popbuffer(self, labeled=False):
         if self._colormode is None:
             return super(colorui, self).popbuffer(labeled)
 
         self._bufferstates.pop()
         if labeled:
             return ''.join(self.label(a, label) for a, label
                            in self._buffers.pop())
         return ''.join(a for a, label in self._buffers.pop())
 
     _colormode = 'ansi'
     def write(self, *args, **opts):
         if self._colormode is None:
             return super(colorui, self).write(*args, **opts)
 
         label = opts.get('label', '')
         if self._buffers:
             self._buffers[-1].extend([(str(a), label) for a in args])
         elif self._colormode == 'win32':
             for a in args:
                 win32print(a, super(colorui, self).write, **opts)
         else:
             return super(colorui, self).write(
                 *[self.label(str(a), label) for a in args], **opts)
 
     def write_err(self, *args, **opts):
         if self._colormode is None:
             return super(colorui, self).write_err(*args, **opts)
 
         label = opts.get('label', '')
         if self._bufferstates and self._bufferstates[-1]:
             return self.write(*args, **opts)
         if self._colormode == 'win32':
             for a in args:
                 win32print(a, super(colorui, self).write_err, **opts)
         else:
             return super(colorui, self).write_err(
                 *[self.label(str(a), label) for a in args], **opts)
 
     def showlabel(self, msg, label):
         if label and msg:
             if msg[-1] == '\n':
                 return "[%s|%s]\n" % (label, msg[:-1])
             else:
                 return "[%s|%s]" % (label, msg)
         else:
             return msg
 
     def label(self, msg, label):
         if self._colormode is None:
             return super(colorui, self).label(msg, label)
 
         if self._colormode == 'debug':
             return self.showlabel(msg, label)
 
         effects = []
         for l in label.split():
             s = _styles.get(l, '')
             if s:
                 effects.append(s)
             elif valideffect(l):
                 effects.append(l)
         effects = ' '.join(effects)
         if effects:
             return '\n'.join([render_effects(s, effects)
                               for s in msg.split('\n')])
         return msg
 
 def templatelabel(context, mapping, args):
     if len(args) != 2:
         # i18n: "label" is a keyword
         raise error.ParseError(_("label expects two arguments"))
 
     # add known effects to the mapping so symbols like 'red', 'bold',
     # etc. don't need to be quoted
     mapping.update(dict([(k, k) for k in _effects]))
 
     thing = templater._evalifliteral(args[1], context, mapping)
 
     # apparently, repo could be a string that is the favicon?
     repo = mapping.get('repo', '')
     if isinstance(repo, str):
         return thing
 
     label = templater._evalifliteral(args[0], context, mapping)
 
     thing = templater.stringify(thing)
     label = templater.stringify(label)
 
     return repo.ui.label(thing, label)
 
 def uisetup(ui):
     if ui.plain():
         return
     if not isinstance(ui, colorui):
         colorui.__bases__ = (ui.__class__,)
         ui.__class__ = colorui
     def colorcmd(orig, ui_, opts, cmd, cmdfunc):
         mode = _modesetup(ui_, opts['color'])
         colorui._colormode = mode
         if mode and mode != 'debug':
             extstyles()
             configstyles(ui_)
         return orig(ui_, opts, cmd, cmdfunc)
     def colorgit(orig, gitsub, commands, env=None, stream=False, cwd=None):
         if gitsub.ui._colormode and len(commands) and commands[0] == "diff":
                 # insert the argument in the front,
                 # the end of git diff arguments is used for paths
                 commands.insert(1, '--color')
         return orig(gitsub, commands, env, stream, cwd)
     extensions.wrapfunction(dispatch, '_runcommand', colorcmd)
     extensions.wrapfunction(subrepo.gitsubrepo, '_gitnodir', colorgit)
     templater.funcs['label'] = templatelabel
 
 def extsetup(ui):
     commands.globalopts.append(
         ('', 'color', 'auto',
          # i18n: 'always', 'auto', 'never', and 'debug' are keywords
          # and should not be translated
          _("when to colorize (boolean, always, auto, never, or debug)"),
          _('TYPE')))
 
 @command('debugcolor', [], 'hg debugcolor')
 def debugcolor(ui, repo, **opts):
     global _styles
     _styles = {}
     for effect in _effects.keys():
         _styles[effect] = effect
     ui.write(('color mode: %s\n') % ui._colormode)
     ui.write(_('available colors:\n'))
     for label, colors in _styles.items():
         ui.write(('%s\n') % colors, label=label)
 
 if os.name != 'nt':
     w32effects = None
 else:
     import re, ctypes
 
     _kernel32 = ctypes.windll.kernel32
 
     _WORD = ctypes.c_ushort
 
     _INVALID_HANDLE_VALUE = -1
 
     class _COORD(ctypes.Structure):
         _fields_ = [('X', ctypes.c_short),
                     ('Y', ctypes.c_short)]
 
     class _SMALL_RECT(ctypes.Structure):
         _fields_ = [('Left', ctypes.c_short),
                     ('Top', ctypes.c_short),
                     ('Right', ctypes.c_short),
                     ('Bottom', ctypes.c_short)]
 
     class _CONSOLE_SCREEN_BUFFER_INFO(ctypes.Structure):
         _fields_ = [('dwSize', _COORD),
                     ('dwCursorPosition', _COORD),
                     ('wAttributes', _WORD),
                     ('srWindow', _SMALL_RECT),
                     ('dwMaximumWindowSize', _COORD)]
 
     _STD_OUTPUT_HANDLE = 0xfffffff5L # (DWORD)-11
     _STD_ERROR_HANDLE = 0xfffffff4L  # (DWORD)-12
 
     _FOREGROUND_BLUE = 0x0001
     _FOREGROUND_GREEN = 0x0002
     _FOREGROUND_RED = 0x0004
     _FOREGROUND_INTENSITY = 0x0008
 
     _BACKGROUND_BLUE = 0x0010
     _BACKGROUND_GREEN = 0x0020
     _BACKGROUND_RED = 0x0040
     _BACKGROUND_INTENSITY = 0x0080
 
     _COMMON_LVB_REVERSE_VIDEO = 0x4000
     _COMMON_LVB_UNDERSCORE = 0x8000
 
     # http://msdn.microsoft.com/en-us/library/ms682088%28VS.85%29.aspx
     w32effects = {
         'none': -1,
         'black': 0,
         'red': _FOREGROUND_RED,
         'green': _FOREGROUND_GREEN,
         'yellow': _FOREGROUND_RED | _FOREGROUND_GREEN,
         'blue': _FOREGROUND_BLUE,
         'magenta': _FOREGROUND_BLUE | _FOREGROUND_RED,
         'cyan': _FOREGROUND_BLUE | _FOREGROUND_GREEN,
         'white': _FOREGROUND_RED | _FOREGROUND_GREEN | _FOREGROUND_BLUE,
         'bold': _FOREGROUND_INTENSITY,
         'black_background': 0x100,                  # unused value > 0x0f
         'red_background': _BACKGROUND_RED,
         'green_background': _BACKGROUND_GREEN,
         'yellow_background': _BACKGROUND_RED | _BACKGROUND_GREEN,
         'blue_background': _BACKGROUND_BLUE,
         'purple_background': _BACKGROUND_BLUE | _BACKGROUND_RED,
         'cyan_background': _BACKGROUND_BLUE | _BACKGROUND_GREEN,
         'white_background': (_BACKGROUND_RED | _BACKGROUND_GREEN |
                              _BACKGROUND_BLUE),
         'bold_background': _BACKGROUND_INTENSITY,
         'underline': _COMMON_LVB_UNDERSCORE,  # double-byte charsets only
         'inverse': _COMMON_LVB_REVERSE_VIDEO, # double-byte charsets only
     }
 
     passthrough = set([_FOREGROUND_INTENSITY,
                        _BACKGROUND_INTENSITY,
                        _COMMON_LVB_UNDERSCORE,
                        _COMMON_LVB_REVERSE_VIDEO])
 
     stdout = _kernel32.GetStdHandle(
                   _STD_OUTPUT_HANDLE)  # don't close the handle returned
     if stdout is None or stdout == _INVALID_HANDLE_VALUE:
         w32effects = None
     else:
         csbi = _CONSOLE_SCREEN_BUFFER_INFO()
         if not _kernel32.GetConsoleScreenBufferInfo(
                     stdout, ctypes.byref(csbi)):
             # stdout may not support GetConsoleScreenBufferInfo()
             # when called from subprocess or redirected
             w32effects = None
         else:
             origattr = csbi.wAttributes
             ansire = re.compile('\033\[([^m]*)m([^\033]*)(.*)',
                                 re.MULTILINE | re.DOTALL)
 
     def win32print(text, orig, **opts):
         label = opts.get('label', '')
         attr = origattr
 
         def mapcolor(val, attr):
             if val == -1:
                 return origattr
             elif val in passthrough:
                 return attr | val
             elif val > 0x0f:
                 return (val & 0x70) | (attr & 0x8f)
             else:
                 return (val & 0x07) | (attr & 0xf8)
 
         # determine console attributes based on labels
         for l in label.split():
             style = _styles.get(l, '')
             for effect in style.split():
                 try:
                     attr = mapcolor(w32effects[effect], attr)
                 except KeyError:
                     # w32effects could not have certain attributes so we skip
                     # them if not found
                     pass
         # hack to ensure regexp finds data
         if not text.startswith('\033['):
             text = '\033[m' + text
 
         # Look for ANSI-like codes embedded in text
         m = re.match(ansire, text)
 
         try:
             while m:
                 for sattr in m.group(1).split(';'):
                     if sattr:
                         attr = mapcolor(int(sattr), attr)
                 _kernel32.SetConsoleTextAttribute(stdout, attr)
                 orig(m.group(2), **opts)
                 m = re.match(ansire, m.group(3))
         finally:
             # Explicitly reset original attributes
             _kernel32.SetConsoleTextAttribute(stdout, origattr)