Add a global option to disable colors (pypa#4739)

* Add a global option to disable colors

 This is a fix for issue pypa#2449

 All it does is simply add a global option --no-color

 Internally it switches ColorizedStreamHandler to StreamHandler if
 this flag is detected.

* Fix lint errors

 * not sure it makes the code more readable though ...

* Fix typo

* Choose logging class before assigning

 * As requested per review
 * Make the code shorter and easier to follow

* Be polite to followers, add commas

* Add functional test for the --no-color output

* Better detection of windows

* Fix fragile tests - can't trust script --quiet

 * The version found in Travis-CI does not respect this flag
   It added a prefix line and suffix line found if one does not
   add the flag --quiet (script from util-linux 2.26.2).

   As such the out  put is:

     Script started on Fri 27 Oct 2017 07:17:30 AM CEST
     \x1b[31mCannot uninstall requirement noSuchPackage, not installed\x1b[0m\n

     Script done on Fri 27 Oct 2017 07:17:31 AM CEST

  With this change, the test should pass, and is hopefully more stable.

* Simplify testing for color or no-color

docs/reference/pip.rst

@@ -22,7 +22,9 @@ Console logging
 ~~~~~~~~~~~~~~~
 
 pip offers :ref:`-v, --verbose <--verbose>` and :ref:`-q, --quiet <--quiet>`
-to control the console log level.
+to control the console log level. By default, some messages (error and warnings)
+are colored in the terminal. If you want to suppress the colored output use
+:ref:`--no-color <--no-color>`.
 
 
 .. _`FileLogging`:

news/2449.feature

@@ -0,0 +1,2 @@
+Add `--no-color` to `pip`. All colored output is disabled
+if this flag is detected.

src/pip/_internal/basecommand.py

@@ -132,6 +132,11 @@ def main(self, args):
         if options.log:
             root_level = "DEBUG"
 
+        if options.no_color:
+            logger_class = "logging.StreamHandler"
+        else:
+            logger_class = "pip._internal.utils.logging.ColorizedStreamHandler"
+
         logging.config.dictConfig({
             "version": 1,
             "disable_existing_loggers": False,
@@ -150,16 +155,14 @@ def main(self, args):
             "handlers": {
                 "console": {
                     "level": level,
-                    "class":
-                        "pip._internal.utils.logging.ColorizedStreamHandler",
+                    "class": logger_class,
                     "stream": self.log_streams[0],
                     "filters": ["exclude_warnings"],
                     "formatter": "indent",
                 },
                 "console_errors": {
                     "level": "WARNING",
-                    "class":
-                        "pip._internal.utils.logging.ColorizedStreamHandler",
+                    "class": logger_class,
                     "stream": self.log_streams[1],
                     "formatter": "indent",
                 },

src/pip/_internal/cmdoptions.py

@@ -102,6 +102,15 @@ def getname(n):
     help='Give more output. Option is additive, and can be used up to 3 times.'
 )
 
+no_color = partial(
+    Option,
+    '--no-color',
+    dest='no_color',
+    action='store_true',
+    default=False,
+    help="Suppress colored output",
+)
+
 version = partial(
     Option,
     '-V', '--version',
@@ -566,6 +575,7 @@ def _merge_hash(option, opt_str, value, parser):
         cache_dir,
         no_cache,
         disable_pip_version_check,
+        no_color,
     ]
 }
 

tests/functional/test_no_color.py

@@ -0,0 +1,41 @@
+"""
+Test specific for the --no-color option
+"""
+import os
+import platform
+import subprocess as sp
+import sys
+
+import pytest
+
+
+@pytest.mark.skipif(sys.platform == 'win32',
+                    reason="does not run on windows")
+def test_no_color(script):
+
+    """
+    Test uninstalling an existing package - should out put red error
+
+    We must use subprocess with the script command, since redirection
+    in unix platform causes text coloring to disapper. Thus, we can't
+    use the testing infrastructure that other options has.
+    """
+
+    sp.Popen("script --flush --quiet --return /tmp/colored-output.txt"
+             " --command \"pip uninstall noSuchPackage\"", shell=True,
+             stdout=sp.PIPE, stderr=sp.PIPE).communicate()
+
+    with open("/tmp/colored-output.txt", "r") as result:
+        assert "\x1b[31m" in result.read()
+
+    os.unlink("/tmp/colored-output.txt")
+
+    sp.Popen("script --flush --quiet --return /tmp/no-color-output.txt"
+             " --command \"pip --no-color uninstall noSuchPackage\"",
+             shell=True,
+             stdout=sp.PIPE, stderr=sp.PIPE).communicate()
+
+    with open("/tmp/no-color-output.txt", "r") as result:
+        assert "\x1b[31m" not in result.read()
+
+    os.unlink("/tmp/no-color-output.txt")