Deprecate TerminalReporter.writer access

Related to pytest-dev#2984

Author: nicoddemus

_pytest/deprecated.py

@@ -50,3 +50,6 @@ class RemovedInPytest4Warning(DeprecationWarning):
     "Metafunc.addcall is deprecated and scheduled to be removed in pytest 4.0.\n"
     "Please use Metafunc.parametrize instead."
 )
+
+TERMINAL_REPORTER_WARNING = RemovedInPytest4Warning('The "writer" attribute is deprecated and '
+                                                    'will be removed in a future release.')

_pytest/terminal.py

@@ -8,13 +8,15 @@
 import platform
 import sys
 import time
+import warnings
 
 import pluggy
 import py
 import six
 
 import pytest
 from _pytest import nodes
+from _pytest.deprecated import TERMINAL_REPORTER_WARNING
 from _pytest.main import EXIT_OK, EXIT_TESTSFAILED, EXIT_INTERRUPTED, \
     EXIT_USAGEERROR, EXIT_NOTESTSCOLLECTED
 
@@ -155,6 +157,16 @@ def __init__(self, config, file=None):
         self._progress_items_reported = 0
         self._show_progress_info = self.config.getini('console_output_style') == 'progress'
 
+    @property
+    def writer(self):
+        warnings.warn(TERMINAL_REPORTER_WARNING)
+        return self._tw
+
+    @writer.setter
+    def writer(self, writer):
+        warnings.warn(TERMINAL_REPORTER_WARNING)
+        self._tw = writer
+
     def hasopt(self, char):
         char = {'xfailed': 'x', 'skipped': 's'}.get(char, char)
         return char in self.reportchars

changelog/2984.removal

@@ -0,0 +1 @@
+``TerminalReporter.writer`` has been deprecated and will be removed in a future release. This attribute is an internal API which was not meant to be exposed as public, if needed use the functions of ``TerminalReporter`` directly.

testing/deprecated_test.py

@@ -101,12 +101,16 @@ def test_func(i):
     ])
 
 
-def test_terminal_reporter_writer_attr(pytestconfig):
-    """Check that TerminalReporter._tw is also available as 'writer' (#2984)
-    This attribute is planned to be deprecated in 3.4.
+def test_terminal_reporter_writer_deprecated(pytestconfig):
+    """TerminalReporter.writer is deprecated and meant to be removed in 3.4 (#2984)
     """
     terminal_reporter = pytestconfig.pluginmanager.get_plugin('terminalreporter')
-    assert terminal_reporter.writer is terminal_reporter._tw
+    with pytest.deprecated_call():
+        # getter
+        _ = terminal_reporter.writer  # noqa
+    with pytest.deprecated_call():
+        # setter
+        terminal_reporter.writer = terminal_reporter._tw
 
 
 def test_pytest_catchlog_deprecated(testdir):