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_COLORED_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/hy#1429, closes hylang/hy#1510.

hy/errors.py

@@ -15,6 +15,7 @@ from clint.textui import colored
 
 _hy_filter_internal_errors = _initialize_env_var('HY_FILTER_INTERNAL_ERRORS',
                                                  True)
+_hy_colored_errors = _initialize_env_var('HY_COLORED_ERRORS', False)
 
 
 class HyError(Exception):
@@ -73,9 +74,16 @@ class HyTypeError(HyLanguageError, TypeError):
                                           source)
 
     def __str__(self):
+        global _hy_colored_errors
 
         result = ""
 
+        if _hy_colored_errors:
+            from clint.textui import colored
+            red, green, yellow = colored.red, colored.green, colored.yellow
+        else:
+            red = green = yellow = lambda x: x
+
         if all(getattr(self.expression, x, None) is not None
                for x in ("start_line", "start_column", "end_column")):
 
@@ -97,28 +105,28 @@ class HyTypeError(HyLanguageError, TypeError):
                                                                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' % red("".join(line))
-                        result += '  %s\n' % colored.green("-"*len(line))
+                        result += '  %s\n' % green("-"*len(line))
 
                 # write the last line
-                result += '  %s\n' % colored.red("".join(source[-1]))
+                result += '  %s\n' % red("".join(source[-1]))
-                result += '  %s\n' % colored.green('-'*(end-1) + '^')
+                result += '  %s\n' % green('-'*(end-1) + '^')
 
         else:
             result += '  File "%s", unknown location\n' % self.filename
 
-        result += colored.yellow("%s: %s\n\n" %
+        result += yellow("%s: %s\n\n" %
-                                 (self.__class__.__name__,
+                         (self.__class__.__name__,
-                                  self.message))
+                          self.message))
 
         return result
 
@@ -199,18 +207,21 @@ class HySyntaxError(HyLanguageError, SyntaxError):
         return HySyntaxError(message, filename, lineno, colno, source)
 
     def __str__(self):
+        global _hy_colored_errors
 
         output = traceback.format_exception_only(SyntaxError,
                                                  SyntaxError(*self.args))
 
-        output[-1] = colored.yellow(output[-1])
+        if _hy_colored_errors:
-        if len(self.source) > 0:
+            from hy.errors import colored
-            output[-2] = colored.green(output[-2])
+            output[-1] = colored.yellow(output[-1])
-            for line in output[::-2]:
+            if len(self.source) > 0:
-                if line.strip().startswith(
+                output[-2] = colored.green(output[-2])
-                        'File "{}", line'.format(self.filename)):
+                for line in output[::-2]:
-                    break
+                    if line.strip().startswith(
-            output[-3] = colored.red(output[-3])
+                            '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

@@ -1,16 +1,17 @@
 # Copyright 2019 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
+
 from contextlib import contextmanager
 from math import isnan, isinf
+from hy import _initialize_env_var
 from hy._compat import PY3, str_type, bytes_type, long_type, string_types
 from fractions import Fraction
 from clint.textui import colored
 
-
 PRETTY = True
+_hy_colored_ast_objects = _initialize_env_var('HY_COLORED_AST_OBJECTS', False)
 
 
 @contextmanager
@@ -271,8 +272,9 @@ class HySequence(HyObject, list):
         return str(self) if PRETTY else super(HySequence, self).__repr__()
 
     def __str__(self):
+        global _hy_colored_ast_objects
         with pretty():
-            c = self.color
+            c = self.color if _hy_colored_ast_objects else str
             if self:
                 return ("{}{}\n  {}{}").format(
                     c(self.__class__.__name__),
@@ -298,10 +300,12 @@ class HyDict(HySequence):
     """
     HyDict (just a representation of a dict)
     """
+    color = staticmethod(colored.green)
 
     def __str__(self):
+        global _hy_colored_ast_objects
         with pretty():
-            g = colored.green
+            g = self.color if _hy_colored_ast_objects else str
             if self:
                 pairs = []
                 for k, v in zip(self[::2],self[1::2]):