Add disabled() method to capsys and capfd

Fix pytest-dev#1599

CHANGELOG.rst

@@ -34,6 +34,10 @@
 * New ``pytest_make_parametrize_id`` hook.
   Thanks `@palaviv`_ for the PR.
 
+* ``capsys`` and ``capfd`` now have a ``disabled()`` method, which is a context manager
+  that can be used to temporarily disable capture within a test.
+  Thanks `@nicoddemus`_ for the PR.
+
 * New cli flag ``--fixtures-per-test`` that shows which fixtures are being used
   for each selected test item. Features doc strings of fixtures by default.
   Can also show where fixtures are defined if combined with ``-v``.

_pytest/capture.py

@@ -4,6 +4,7 @@
 """
 from __future__ import with_statement
 
+import contextlib
 import sys
 import os
 from tempfile import TemporaryFile
@@ -146,8 +147,8 @@ def pytest_keyboard_interrupt(self, excinfo):
     def pytest_internalerror(self, excinfo):
         self.reset_capturings()
 
-    def suspendcapture_item(self, item, when):
-        out, err = self.suspendcapture()
+    def suspendcapture_item(self, item, when, in_=False):
+        out, err = self.suspendcapture(in_=in_)
         item.add_report_section(when, "stdout", out)
         item.add_report_section(when, "stderr", err)
 
@@ -162,7 +163,7 @@ def capsys(request):
     """
     if "capfd" in request._funcargs:
         raise request.raiseerror(error_capsysfderror)
-    request.node._capfuncarg = c = CaptureFixture(SysCapture)
+    request.node._capfuncarg = c = CaptureFixture(SysCapture, request)
     return c
 
 @pytest.fixture
@@ -175,17 +176,18 @@ def capfd(request):
         request.raiseerror(error_capsysfderror)
     if not hasattr(os, 'dup'):
         pytest.skip("capfd funcarg needs os.dup")
-    request.node._capfuncarg = c = CaptureFixture(FDCapture)
+    request.node._capfuncarg = c = CaptureFixture(FDCapture, request)
     return c
 
 
 class CaptureFixture:
-    def __init__(self, captureclass):
+    def __init__(self, captureclass, request):
         self.captureclass = captureclass
+        self.request = request
 
     def _start(self):
         self._capture = MultiCapture(out=True, err=True, in_=False,
-                                       Capture=self.captureclass)
+                                     Capture=self.captureclass)
         self._capture.start_capturing()
 
     def close(self):
@@ -200,6 +202,15 @@ def readouterr(self):
         except AttributeError:
             return self._outerr
 
+    @contextlib.contextmanager
+    def disabled(self):
+        capmanager = self.request.config.pluginmanager.getplugin('capturemanager')
+        capmanager.suspendcapture_item(self.request.node, "call", in_=True)
+        try:
+            yield
+        finally:
+            capmanager.resumecapture()
+
 
 def safe_text_dupfile(f, mode, default_encoding="UTF8"):
     """ return a open text file object that's a duplicate of f on the

doc/en/capture.rst

@@ -115,4 +115,19 @@ same interface but allows to also capture output from
 libraries or subprocesses that directly write to operating
 system level output streams (FD1 and FD2).
 
+
+.. versionadded:: 2.10
+
+To temporarily disable capture within a test, both ``capsys``
+and ``capfd`` have a ``disabled()`` method that can be used
+as a context manager, disabling capture inside the ``with`` block:
+
+.. code-block:: python
+
+    def test_disabling_capturing(capsys):
+        print('this output is captured')
+        with capsys.disabled():
+            print('output not captured, going directly to sys.stdout')
+        print('this output is also captured')
+
 .. include:: links.inc

testing/test_capture.py

@@ -480,6 +480,22 @@ def test_log(capsys):
         result = testdir.runpytest_subprocess(p)
         assert 'closed' not in result.stderr.str()
 
+    @pytest.mark.parametrize('fixture', ['capsys', 'capfd'])
+    def test_disabled_capture_fixture(self, testdir, fixture):
+        testdir.makepyfile("""
+            def test_disabled({fixture}):
+                print('captured before')
+                with {fixture}.disabled():
+                    print('while capture is disabled')
+                print('captured after')
+        """.format(fixture=fixture))
+        result = testdir.runpytest_subprocess()
+        result.stdout.fnmatch_lines("""
+            *while capture is disabled*
+        """)
+        assert 'captured before' not in result.stdout.str()
+        assert 'captured after' not in result.stdout.str()
+
 
 def test_setup_failure_does_not_kill_capturing(testdir):
     sub1 = testdir.mkpydir("sub1")