Merge "Avoid ASCII encoding errors when output is redirected" into stable/mitaka

cliff/app.py

@@ -1,11 +1,13 @@
 """Application base class.
 """
 
+import codecs
 import inspect
 import locale
 import logging
 import logging.handlers
 import os
+import six
 import sys
 
 from cliff import argparse
@@ -70,6 +72,45 @@ class App(object):
             locale.setlocale(locale.LC_ALL, '')
         except locale.Error:
             pass
+
+        # Unicode must be encoded/decoded for text I/O streams, the
+        # correct encoding for the stream must be selected and it must
+        # be capable of handling the set of characters in the stream
+        # or Python will raise a codec error. The correct codec is
+        # selected based on the locale. Python2 uses the locales
+        # encoding but only when the I/O stream is attached to a
+        # terminal (TTY) otherwise it uses the default ASCII
+        # encoding. The effect is internationalized text written to
+        # the terminal works as expected but if command line output is
+        # redirected (file or pipe) the ASCII codec is used and the
+        # program aborts with a codec error.
+        #
+        # The default I/O streams stdin, stdout and stderr can be
+        # wrapped in a codec based on the locale thus assuring the
+        # users desired encoding is always used no matter the I/O
+        # destination. Python3 does this by default.
+        #
+        # If the caller supplies an I/O stream we use it unmodified on
+        # the assumption the caller has taken all responsibility for
+        # the stream.  But with Python2 if the caller allows us to
+        # default the I/O streams to sys.stdin, sys.stdout and
+        # sys.stderr we apply the locales encoding just as Python3
+        # would do. We also check to make sure the main Python program
+        # has not already already wrapped sys.stdin, sys.stdout and
+        # sys.stderr as this is a common recommendation.
+
+        if six.PY2:
+            encoding = locale.getpreferredencoding()
+            if encoding:
+                if not (stdin or isinstance(sys.stdin, codecs.StreamReader)):
+                    stdin = codecs.getreader(encoding)(sys.stdin)
+
+                if not (stdout or isinstance(sys.stdout, codecs.StreamWriter)):
+                    stdout = codecs.getwriter(encoding)(sys.stdout)
+
+                if not (stderr or isinstance(sys.stderr, codecs.StreamWriter)):
+                    stderr = codecs.getwriter(encoding)(sys.stderr)
+
         self.stdin = stdin or sys.stdin
         self.stdout = stdout or sys.stdout
         self.stderr = stderr or sys.stderr

cliff/tests/test_app.py

@@ -5,7 +5,11 @@ try:
 except ImportError:
     from io import StringIO
 
+import codecs
+import locale
 import mock
+import six
+import sys
 
 from cliff.app import App
 from cliff.command import Command
@@ -398,3 +402,82 @@ def test_verbose():
         pass
     else:
         raise Exception('Exception was not thrown')
+
+
+def test_io_streams():
+    cmd_mgr = CommandManager('cliff.tests')
+    io = mock.Mock()
+
+    if six.PY2:
+        stdin_save = sys.stdin
+        stdout_save = sys.stdout
+        stderr_save = sys.stderr
+        encoding = locale.getpreferredencoding() or 'utf-8'
+
+        app = App('no io streams', 1, cmd_mgr)
+        assert isinstance(app.stdin, codecs.StreamReader)
+        assert isinstance(app.stdout, codecs.StreamWriter)
+        assert isinstance(app.stderr, codecs.StreamWriter)
+
+        app = App('with stdin io stream', 1, cmd_mgr, stdin=io)
+        assert app.stdin is io
+        assert isinstance(app.stdout, codecs.StreamWriter)
+        assert isinstance(app.stderr, codecs.StreamWriter)
+
+        app = App('with stdout io stream', 1, cmd_mgr, stdout=io)
+        assert isinstance(app.stdin, codecs.StreamReader)
+        assert app.stdout is io
+        assert isinstance(app.stderr, codecs.StreamWriter)
+
+        app = App('with stderr io stream', 1, cmd_mgr, stderr=io)
+        assert isinstance(app.stdin, codecs.StreamReader)
+        assert isinstance(app.stdout, codecs.StreamWriter)
+        assert app.stderr is io
+
+        try:
+            sys.stdin = codecs.getreader(encoding)(sys.stdin)
+            app = App('with wrapped sys.stdin io stream', 1, cmd_mgr)
+            assert app.stdin is sys.stdin
+            assert isinstance(app.stdout, codecs.StreamWriter)
+            assert isinstance(app.stderr, codecs.StreamWriter)
+        finally:
+            sys.stdin = stdin_save
+
+        try:
+            sys.stdout = codecs.getwriter(encoding)(sys.stdout)
+            app = App('with wrapped stdout io stream', 1, cmd_mgr)
+            assert isinstance(app.stdin, codecs.StreamReader)
+            assert app.stdout is sys.stdout
+            assert isinstance(app.stderr, codecs.StreamWriter)
+        finally:
+            sys.stdout = stdout_save
+
+        try:
+            sys.stderr = codecs.getwriter(encoding)(sys.stderr)
+            app = App('with wrapped stderr io stream', 1, cmd_mgr)
+            assert isinstance(app.stdin, codecs.StreamReader)
+            assert isinstance(app.stdout, codecs.StreamWriter)
+            assert app.stderr is sys.stderr
+        finally:
+            sys.stderr = stderr_save
+
+    else:
+        app = App('no io streams', 1, cmd_mgr)
+        assert app.stdin is sys.stdin
+        assert app.stdout is sys.stdout
+        assert app.stderr is sys.stderr
+
+        app = App('with stdin io stream', 1, cmd_mgr, stdin=io)
+        assert app.stdin is io
+        assert app.stdout is sys.stdout
+        assert app.stderr is sys.stderr
+
+        app = App('with stdout io stream', 1, cmd_mgr, stdout=io)
+        assert app.stdin is sys.stdin
+        assert app.stdout is io
+        assert app.stderr is sys.stderr
+
+        app = App('with stderr io stream', 1, cmd_mgr, stderr=io)
+        assert app.stdin is sys.stdin
+        assert app.stdout is sys.stdout
+        assert app.stderr is io