setuponly: remove printing out/err from capman

AUTHORS

@@ -267,5 +267,6 @@ Wouter van Ackooy
 Xixi Zhao
 Xuan Luong
 Xuecong Liao
+Yoav Caspi
 Zac Hatfield-Dodds
 Zoltán Máté

changelog/5906.bugfix.rst

@@ -0,0 +1 @@
+Fix crash with ``KeyboardInterrupt`` during ``--setup-show``.

src/_pytest/setuponly.py

@@ -1,5 +1,3 @@
-import sys
-
 import pytest
 
 
@@ -51,7 +49,6 @@ def _show_fixture_action(fixturedef, msg):
     capman = config.pluginmanager.getplugin("capturemanager")
     if capman:
         capman.suspend_global_capture()
-        out, err = capman.read_global_capture()
 
     tw = config.get_terminal_writer()
     tw.line()
@@ -74,8 +71,6 @@ def _show_fixture_action(fixturedef, msg):
 
     if capman:
         capman.resume_global_capture()
-        sys.stdout.write(out)
-        sys.stderr.write(err)
 
 
 @pytest.hookimpl(tryfirst=True)

testing/python/setup_only.py

@@ -267,3 +267,39 @@ def test_arg(arg):
     result.stdout.fnmatch_lines(
         ["*SETUP    F arg*", "*test_arg (fixtures used: arg)F*", "*TEARDOWN F arg*"]
     )
+
+
+def test_setup_show_with_KeyboardInterrupt_in_test(testdir):
+    """ Verifies that setups are shown and tests are executed even if there was a KeyboardInterrupt in a test. """
+    p = testdir.makepyfile(
+        """
+        import pytest
+        @pytest.fixture
+        def arg():
+            assert True
+        def test_arg(arg):
+            raise KeyboardInterrupt()
+    """
+    )
+    result = testdir.runpytest("--setup-show", p, no_reraise_ctrlc=True)
+    assert result.ret == 2
+    result.stdout.fnmatch_lines(
+        ["*SETUP    F arg*", "*test_arg (fixtures used: arg)*", "*TEARDOWN F arg*"]
+    )
+
+
+def test_setup_show_with_KeyboardInterrupt_in_fixture(testdir):
+    """ Verifies that setups are shown and tests are executed even if there was a KeyboardInterrupt in a fixture. """
+    p = testdir.makepyfile(
+        """
+        import pytest
+        @pytest.fixture
+        def arg():
+            raise KeyboardInterrupt()
+        def test_arg(arg):
+            assert True
+    """
+    )
+    result = testdir.runpytest("--setup-show", p, no_reraise_ctrlc=True)
+    assert result.ret == 2
+    result.stdout.fnmatch_lines(["*SETUP    F arg*", "*KeyboardInterrupt*"])