Make capsys more like stdio streams in python3. Resolves #1407.

AUTHORS

@@ -13,6 +13,7 @@ Andrzej Ostrowski
 Andy Freeland
 Anthon van der Neut
 Antony Lee
+Anthony Sottile
 Armin Rigo
 Aron Curzon
 Aviv Palivoda

CHANGELOG.rst

@@ -55,6 +55,14 @@ Changes
   Thanks `@The-Compiler`_ for the PR.
 
 
+Bug Fixes
+---------
+
+* Fix ``AttributeError`` on ``sys.stdout.buffer`` / ``sys.stderr.buffer``
+  while using ``capsys`` fixture in python 3. (`#1407`_).
+  Thanks to `@asottile`_.
+
+
 .. _@davidszotten: https://github.com/davidszotten
 .. _@fushi: https://github.com/fushi
 .. _@mattduck: https://github.com/mattduck
@@ -65,6 +73,7 @@ Changes
 .. _@unsignedint: https://github.com/unsignedint
 .. _@Kriechi: https://github.com/Kriechi
 
+.. _#1407: https://github.com/pytest-dev/pytest/issues/1407
 .. _#1512: https://github.com/pytest-dev/pytest/issues/1512
 .. _#1874: https://github.com/pytest-dev/pytest/pull/1874
 .. _#1952: https://github.com/pytest-dev/pytest/pull/1952

_pytest/capture.py

@@ -12,8 +12,8 @@ from tempfile import TemporaryFile
 
 import py
 import pytest
+from _pytest.compat import CaptureIO
 
-from py.io import TextIO
 unicode = py.builtin.text
 
 patchsysdict = {0: 'stdin', 1: 'stdout', 2: 'stderr'}
@@ -403,7 +403,7 @@ class SysCapture(object):
             if name == "stdin":
                 tmpfile = DontReadFromInput()
             else:
-                tmpfile = TextIO()
+                tmpfile = CaptureIO()
         self.tmpfile = tmpfile
 
     def start(self):

_pytest/compat.py

@@ -251,3 +251,19 @@ else:
         except UnicodeError:
             errors = 'replace'
             return v.encode('ascii', errors)
+
+
+if _PY2:
+    from py.io import TextIO as CaptureIO
+else:
+    import io
+
+    class CaptureIO(io.TextIOWrapper):
+        def __init__(self):
+            super(CaptureIO, self).__init__(
+                io.BytesIO(),
+                encoding='UTF-8', newline='', write_through=True,
+            )
+
+        def getvalue(self):
+            return self.buffer.getvalue().decode('UTF-8')

testing/test_capture.py

@@ -281,7 +281,7 @@ class TestLoggingInteraction(object):
             def test_logging():
                 import logging
                 import pytest
-                stream = capture.TextIO()
+                stream = capture.CaptureIO()
                 logging.basicConfig(stream=stream)
                 stream.close() # to free memory/release resources
         """)
@@ -622,16 +622,16 @@ def test_error_during_readouterr(testdir):
     ])
 
 
-class TestTextIO(object):
+class TestCaptureIO(object):
     def test_text(self):
-        f = capture.TextIO()
+        f = capture.CaptureIO()
         f.write("hello")
         s = f.getvalue()
         assert s == "hello"
         f.close()
 
     def test_unicode_and_str_mixture(self):
-        f = capture.TextIO()
+        f = capture.CaptureIO()
         if sys.version_info >= (3, 0):
             f.write("\u00f6")
             pytest.raises(TypeError, "f.write(bytes('hello', 'UTF-8'))")
@@ -642,6 +642,18 @@ class TestTextIO(object):
             f.close()
             assert isinstance(s, unicode)
 
+    @pytest.mark.skipif(
+        sys.version_info[0] == 2,
+        reason='python 3 only behaviour',
+    )
+    def test_write_bytes_to_buffer(self):
+        """In python3, stdout / stderr are text io wrappers (exposing a buffer
+        property of the underlying bytestream).  See issue #1407
+        """
+        f = capture.CaptureIO()
+        f.buffer.write(b'foo\r\n')
+        assert f.getvalue() == 'foo\r\n'
+
 
 def test_bytes_io():
     f = py.io.BytesIO()
@@ -900,8 +912,8 @@ class TestStdCapture(object):
         with self.getcapture() as cap:
             sys.stdout.write("hello")
             sys.stderr.write("world")
-            sys.stdout = capture.TextIO()
-            sys.stderr = capture.TextIO()
+            sys.stdout = capture.CaptureIO()
+            sys.stderr = capture.CaptureIO()
             print ("not seen")
             sys.stderr.write("not seen\n")
             out, err = cap.readouterr()