Make colored output configurable

Colored exception output is now disabled by default and configurable through
`hy.errors._hy_colored_errors` and the environment variable
`HY_FILTER_INTERNAL_ERRORS`.

Likewise, Hy model/AST color printing is now configurable and disabled by
default.  The corresponding variables are `hy.models._hy_colored_ast_objects`
and `HY_COLORED_AST_OBJECTS`.

Closes hylang#1429, closes hylang#1510.

hy/errors.py

@@ -10,9 +10,7 @@
 from functools import reduce
 from contextlib import contextmanager
 
-from clint.textui import colored
-
-
+_hy_colored_errors = False
 _hy_filter_internal_errors = True
 
 
@@ -22,6 +20,11 @@ def filter_errors():
                           _hy_filter_internal_errors)
 
 
+def colored_errors():
+    global _hy_colored_errors
+    return os.environ.get('HY_COLORED_ERRORS', _hy_colored_errors)
+
+
 class HyError(Exception):
     def __init__(self, message, *args):
         self.message = message
@@ -84,6 +87,13 @@ def __str__(self):
         has_syntax_info = all(hasattr(self.expression, x)
                               for x in ("start_line", "start_column",
                                         "end_column", "end_line"))
+
+        if colored_errors():
+            from clint.textui import colored
+            red, green, yellow = colored.red, colored.green, colored.yellow
+        else:
+            red = green = yellow = lambda x: x
+
         if has_syntax_info:
             line = self.expression.start_line
             start = self.expression.start_column
@@ -103,28 +113,28 @@ def __str__(self):
                                                                start)
 
             if len(source) == 1:
-                result += '  %s\n' % colored.red(source[0])
+                result += '  %s\n' % red(source[0])
                 result += '  %s%s\n' % (' '*(start-1),
-                                        colored.green('^' + '-'*(length-1) + '^'))
+                                        green('^' + '-'*(length-1) + '^'))
             if len(source) > 1:
-                result += '  %s\n' % colored.red(source[0])
+                result += '  %s\n' % red(source[0])
                 result += '  %s%s\n' % (' '*(start-1),
-                                        colored.green('^' + '-'*length))
+                                        green('^' + '-'*length))
                 if len(source) > 2:  # write the middle lines
                     for line in source[1:-1]:
-                        result += '  %s\n' % colored.red("".join(line))
-                        result += '  %s\n' % colored.green("-"*len(line))
+                        result += '  %s\n' % red("".join(line))
+                        result += '  %s\n' % green("-"*len(line))
 
                 # write the last line
-                result += '  %s\n' % colored.red("".join(source[-1]))
-                result += '  %s\n' % colored.green('-'*(end-1) + '^')
+                result += '  %s\n' % red("".join(source[-1]))
+                result += '  %s\n' % green('-'*(end-1) + '^')
 
         else:
             result += '  File "%s", unknown location\n' % self.filename
 
-        result += colored.yellow("%s: %s\n\n" %
-                                 (self.__class__.__name__,
-                                  self.message))
+        result += yellow("%s: %s\n\n" %
+                         (self.__class__.__name__,
+                          self.message))
 
         return result
 
@@ -209,14 +219,16 @@ def __str__(self):
         output = traceback.format_exception_only(SyntaxError,
                                                  SyntaxError(*self.args))
 
-        output[-1] = colored.yellow(output[-1])
-        if len(self.source) > 0:
-            output[-2] = colored.green(output[-2])
-            for line in output[::-2]:
-                if line.strip().startswith(
-                        'File "{}", line'.format(self.filename)):
-                    break
-            output[-3] = colored.red(output[-3])
+        if colored_errors():
+            from hy.errors import colored
+            output[-1] = colored.yellow(output[-1])
+            if len(self.source) > 0:
+                output[-2] = colored.green(output[-2])
+                for line in output[::-2]:
+                    if line.strip().startswith(
+                            'File "{}", line'.format(self.filename)):
+                        break
+                output[-3] = colored.red(output[-3])
 
         # Avoid "...expected str instance, ColoredString found"
         return reduce(lambda x, y: x + y, output)

hy/models.py

@@ -1,8 +1,10 @@
 # Copyright 2018 the authors.
 # This file is part of Hy, which is free software licensed under the Expat
 # license. See the LICENSE.
-
 from __future__ import unicode_literals
+
+import os
+
 from contextlib import contextmanager
 from math import isnan, isinf
 from hy._compat import PY3, str_type, bytes_type, long_type, string_types
@@ -11,6 +13,12 @@
 
 
 PRETTY = True
+_hy_colored_ast_objects = False
+
+
+def colored_ast_objects():
+    global _hy_colored_ast_objects
+    return os.environ.get('HY_COLORED_AST_OBJECTS', _hy_colored_ast_objects)
 
 
 @contextmanager
@@ -272,7 +280,7 @@ def __repr__(self):
 
     def __str__(self):
         with pretty():
-            c = self.color
+            c = self.color if colored_ast_objects() else str
             if self:
                 return ("{}{}\n  {}{}").format(
                     c(self.__class__.__name__),
@@ -298,10 +306,11 @@ class HyDict(HySequence):
     """
     HyDict (just a representation of a dict)
     """
+    color = staticmethod(colored.green)
 
     def __str__(self):
         with pretty():
-            g = colored.green
+            g = self.color if colored_ast_objects() else str
             if self:
                 pairs = []
                 for k, v in zip(self[::2],self[1::2]):