Use 'Linux' (dark bg) colours for Windows

This puts the colours in inspect output and tracebacks back to what
they were in IPython 4.x, but leaves the prompt colouring as in 5.0.
I tried changing the colour scheme to 'Linux' entirely for Windows,
but that selects Monokai as the theme for prompt_toolkit, which looks
pretty horrible in 16 colours (at least to my eyes).

This is admittedly a hack, but hopefully our legacy colour system is
on the way out anyway.

Closes gh-9723

IPython/utils/PyColorize.py

@@ -1,374 +1,382 b''
 # -*- coding: utf-8 -*-
 """
 Class and program to colorize python source code for ANSI terminals.
 
 Based on an HTML code highlighter by Jurgen Hermann found at:
 http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52298
 
 Modifications by Fernando Perez ([e-mail]).
 
 Information on the original HTML highlighter follows:
 
 MoinMoin - Python Source Parser
 
 Title: Colorize Python source using the built-in tokenizer
 
 Submitter: Jurgen Hermann
 Last Updated:2001/04/06
 
 Version no:1.2
 
 Description:
 
 This code is part of MoinMoin (http://moin.sourceforge.net/) and converts
 Python source code to HTML markup, rendering comments, keywords,
 operators, numeric and string literals in different colors.
 
 It shows how to use the built-in keyword, token and tokenize modules to
 scan Python source code and re-emit it with no changes to its original
 formatting (which is the hard part).
 """
 from __future__ import print_function
 from __future__ import absolute_import
 from __future__ import unicode_literals
 
 __all__ = ['ANSICodeColors','Parser']
 
 _scheme_default = 'Linux'
 
 
 # Imports
 import keyword
 import os
 import sys
 import token
 import tokenize
 
 try:
     generate_tokens = tokenize.generate_tokens
 except AttributeError:
     # Python 3. Note that we use the undocumented _tokenize because it expects
     # strings, not bytes. See also Python issue #9969.
     generate_tokens = tokenize._tokenize
 
 from IPython.utils.coloransi import TermColors, InputTermColors ,ColorScheme, ColorSchemeTable
 from IPython.utils.py3compat import PY3
 
 from .colorable import Colorable
 
 if PY3:
     from io import StringIO
 else:
     from StringIO import StringIO
 
 #############################################################################
 ### Python Source Parser (does Hilighting)
 #############################################################################
 
 _KEYWORD = token.NT_OFFSET + 1
 _TEXT    = token.NT_OFFSET + 2
 
 #****************************************************************************
 # Builtin color schemes
 
 Colors = TermColors  # just a shorthand
 
 # Build a few color schemes
 NoColor = ColorScheme(
     'NoColor',{
     'header'         : Colors.NoColor,
     token.NUMBER     : Colors.NoColor,
     token.OP         : Colors.NoColor,
     token.STRING     : Colors.NoColor,
     tokenize.COMMENT : Colors.NoColor,
     token.NAME       : Colors.NoColor,
     token.ERRORTOKEN : Colors.NoColor,
 
     _KEYWORD         : Colors.NoColor,
     _TEXT            : Colors.NoColor,
 
     'in_prompt'      : InputTermColors.NoColor,  # Input prompt
     'in_number'      : InputTermColors.NoColor,  # Input prompt number
     'in_prompt2'     : InputTermColors.NoColor, # Continuation prompt
     'in_normal'      : InputTermColors.NoColor,  # color off (usu. Colors.Normal)
 
     'out_prompt'     : Colors.NoColor, # Output prompt
     'out_number'     : Colors.NoColor, # Output prompt number
 
     'normal'         : Colors.NoColor  # color off (usu. Colors.Normal)
     }  )
 
 LinuxColors = ColorScheme(
     'Linux',{
     'header'         : Colors.LightRed,
     token.NUMBER     : Colors.LightCyan,
     token.OP         : Colors.Yellow,
     token.STRING     : Colors.LightBlue,
     tokenize.COMMENT : Colors.LightRed,
     token.NAME       : Colors.Normal,
     token.ERRORTOKEN : Colors.Red,
 
     _KEYWORD         : Colors.LightGreen,
     _TEXT            : Colors.Yellow,
 
     'in_prompt'      : InputTermColors.Green,
     'in_number'      : InputTermColors.LightGreen,
     'in_prompt2'     : InputTermColors.Green,
     'in_normal'      : InputTermColors.Normal,  # color off (usu. Colors.Normal)
 
     'out_prompt'     : Colors.Red,
     'out_number'     : Colors.LightRed,
 
     'normal'         : Colors.Normal  # color off (usu. Colors.Normal)
     } )
 
 NeutralColors = ColorScheme(
     'Neutral',{
     'header'         : Colors.Red,
     token.NUMBER     : Colors.Cyan,
     token.OP         : Colors.Blue,
     token.STRING     : Colors.Blue,
     tokenize.COMMENT : Colors.Red,
     token.NAME       : Colors.Normal,
     token.ERRORTOKEN : Colors.Red,
 
     _KEYWORD         : Colors.Green,
     _TEXT            : Colors.Blue,
 
     'in_prompt'      : InputTermColors.Blue,
     'in_number'      : InputTermColors.LightBlue,
     'in_prompt2'     : InputTermColors.Blue,
     'in_normal'      : InputTermColors.Normal,  # color off (usu. Colors.Normal)
 
     'out_prompt'     : Colors.Red,
     'out_number'     : Colors.LightRed,
 
     'normal'         : Colors.Normal  # color off (usu. Colors.Normal)
     }  )
 
-
+# Hack: the 'neutral' colours are not very visible on a dark background on
+# Windows. Since Windows command prompts have a dark background by default, and
+# relatively few users are likely to alter that, we will use the 'Linux' colours,
+# designed for a dark background, as the default on Windows. Changing it here
+# avoids affecting the prompt colours rendered by prompt_toolkit, where the
+# neutral defaults do work OK.
+
+if os.name == 'nt':
+    NeutralColors = LinuxColors.copy(name='Neutral')
 
 LightBGColors = ColorScheme(
     'LightBG',{
     'header'         : Colors.Red,
     token.NUMBER     : Colors.Cyan,
     token.OP         : Colors.Blue,
     token.STRING     : Colors.Blue,
     tokenize.COMMENT : Colors.Red,
     token.NAME       : Colors.Normal,
     token.ERRORTOKEN : Colors.Red,
 
 
     _KEYWORD         : Colors.Green,
     _TEXT            : Colors.Blue,
 
     'in_prompt'      : InputTermColors.Blue,
     'in_number'      : InputTermColors.LightBlue,
     'in_prompt2'     : InputTermColors.Blue,
     'in_normal'      : InputTermColors.Normal,  # color off (usu. Colors.Normal)
 
     'out_prompt'     : Colors.Red,
     'out_number'     : Colors.LightRed,
 
     'normal'         : Colors.Normal  # color off (usu. Colors.Normal)
     }  )
 
 # Build table of color schemes (needed by the parser)
 ANSICodeColors = ColorSchemeTable([NoColor,LinuxColors,LightBGColors, NeutralColors],
                                   _scheme_default)
 
 class Parser(Colorable):
     """ Format colored Python source.
     """
 
     def __init__(self, color_table=None, out = sys.stdout, parent=None, style=None):
         """ Create a parser with a specified color table and output channel.
 
         Call format() to process code.
         """
 
         super(Parser, self).__init__(parent=parent)
 
         self.color_table = color_table and color_table or ANSICodeColors
         self.out = out
 
     def format(self, raw, out = None, scheme = ''):
         return self.format2(raw, out, scheme)[0]
 
     def format2(self, raw, out = None, scheme = ''):
         """ Parse and send the colored source.
 
         If out and scheme are not specified, the defaults (given to
         constructor) are used.
 
         out should be a file-type object. Optionally, out can be given as the
         string 'str' and the parser will automatically return the output in a
         string."""
 
         string_output = 0
         if out == 'str' or self.out == 'str' or \
            isinstance(self.out,StringIO):
             # XXX - I don't really like this state handling logic, but at this
             # point I don't want to make major changes, so adding the
             # isinstance() check is the simplest I can do to ensure correct
             # behavior.
             out_old = self.out
             self.out = StringIO()
             string_output = 1
         elif out is not None:
             self.out = out
 
         # Fast return of the unmodified input for NoColor scheme
         if scheme == 'NoColor':
             error = False
             self.out.write(raw)
             if string_output:
                 return raw,error
             else:
                 return None,error
 
         # local shorthands
         colors = self.color_table[scheme].colors
         self.colors = colors # put in object so __call__ sees it
 
         # Remove trailing whitespace and normalize tabs
         self.raw = raw.expandtabs().rstrip()
 
         # store line offsets in self.lines
         self.lines = [0, 0]
         pos = 0
         raw_find = self.raw.find
         lines_append = self.lines.append
         while 1:
             pos = raw_find('\n', pos) + 1
             if not pos: break
             lines_append(pos)
         lines_append(len(self.raw))
 
         # parse the source and write it
         self.pos = 0
         text = StringIO(self.raw)
 
         error = False
         try:
             for atoken in generate_tokens(text.readline):
                 self(*atoken)
         except tokenize.TokenError as ex:
             msg = ex.args[0]
             line = ex.args[1][0]
             self.out.write("%s\n\n*** ERROR: %s%s%s\n" %
                            (colors[token.ERRORTOKEN],
                             msg, self.raw[self.lines[line]:],
                             colors.normal)
                            )
             error = True
         self.out.write(colors.normal+'\n')
         if string_output:
             output = self.out.getvalue()
             self.out = out_old
             return (output, error)
         return (None, error)
 
     def __call__(self, toktype, toktext, start_pos, end_pos, line):
         """ Token handler, with syntax highlighting."""
         (srow,scol) = start_pos
         (erow,ecol) = end_pos
         colors = self.colors
         owrite = self.out.write
 
         # line separator, so this works across platforms
         linesep = os.linesep
 
         # calculate new positions
         oldpos = self.pos
         newpos = self.lines[srow] + scol
         self.pos = newpos + len(toktext)
 
         # send the original whitespace, if needed
         if newpos > oldpos:
             owrite(self.raw[oldpos:newpos])
 
         # skip indenting tokens
         if toktype in [token.INDENT, token.DEDENT]:
             self.pos = newpos
             return
 
         # map token type to a color group
         if token.LPAR <= toktype <= token.OP:
             toktype = token.OP
         elif toktype == token.NAME and keyword.iskeyword(toktext):
             toktype = _KEYWORD
         color = colors.get(toktype, colors[_TEXT])
 
         #print '<%s>' % toktext,    # dbg
 
         # Triple quoted strings must be handled carefully so that backtracking
         # in pagers works correctly. We need color terminators on _each_ line.
         if linesep in toktext:
             toktext = toktext.replace(linesep, '%s%s%s' %
                                       (colors.normal,linesep,color))
 
         # send text
         owrite('%s%s%s' % (color,toktext,colors.normal))
 
 def main(argv=None):
     """Run as a command-line script: colorize a python file or stdin using ANSI
     color escapes and print to stdout.
 
     Inputs:
 
       - argv(None): a list of strings like sys.argv[1:] giving the command-line
         arguments. If None, use sys.argv[1:].
     """
 
     usage_msg = """%prog [options] [filename]
 
 Colorize a python file or stdin using ANSI color escapes and print to stdout.
 If no filename is given, or if filename is -, read standard input."""
 
     import optparse
     parser = optparse.OptionParser(usage=usage_msg)
     newopt = parser.add_option
     newopt('-s','--scheme',metavar='NAME',dest='scheme_name',action='store',
            choices=['Linux','LightBG','NoColor'],default=_scheme_default,
            help="give the color scheme to use. Currently only 'Linux'\
  (default) and 'LightBG' and 'NoColor' are implemented (give without\
  quotes)")
 
     opts,args = parser.parse_args(argv)
 
     if len(args) > 1:
         parser.error("you must give at most one filename.")
 
     if len(args) == 0:
         fname = '-' # no filename given; setup to read from stdin
     else:
         fname = args[0]
 
     if fname == '-':
         stream = sys.stdin
     else:
         try:
             stream = open(fname)
         except IOError as msg:
             print(msg, file=sys.stderr)
             sys.exit(1)
 
     parser = Parser()
 
     # we need nested try blocks because pre-2.5 python doesn't support unified
     # try-except-finally
     try:
         try:
             # write colorized version to stdout
             parser.format(stream.read(),scheme=opts.scheme_name)
         except IOError as msg:
             # if user reads through a pager and quits, don't print traceback
             if msg.args != (32,'Broken pipe'):
                 raise
     finally:
         if stream is not sys.stdin:
             stream.close() # in case a non-handled exception happened above
 
 if __name__ == "__main__":
     main()