default: callback plugin allow unreachable task to stderr (#50533)

Provide toggle flag to allow display of unreachable task to stderr
using default callback plugin.

Fixes: #48069

Signed-off-by: Abhijeet Kasurde <akasurde@redhat.com>

test/integration/targets/callback_default/runme.sh

@@ -36,6 +36,15 @@ cleanup() {
 	if [[ $INIT = 0 ]]; then
 		rm -rf "${OUTFILE}.*"
 	fi
+
+	if [[ -f "${BASEFILE}.unreachable.stdout" ]]; then
+	    rm -rf "${BASEFILE}.unreachable.stdout"
+	fi
+
+	if [[ -f "${BASEFILE}.unreachable.stderr" ]]; then
+	    rm -rf "${BASEFILE}.unreachable.stderr"
+	fi
+
 	# Restore TTY cols
 	if [[ -n ${TTY_COLS:-} ]]; then
 		stty cols "${TTY_COLS}"
@@ -105,3 +114,17 @@ export ANSIBLE_DISPLAY_OK_HOSTS=1
 export ANSIBLE_DISPLAY_FAILED_STDERR=1
 
 run_test failed_to_stderr
+
+# Default settings with unreachable tasks
+export DISPLAY_SKIPPED_HOSTS=1
+export ANSIBLE_DISPLAY_OK_HOSTS=1
+export ANSIBLE_DISPLAY_FAILED_STDERR=1
+
+# Check if UNREACHBLE is available in stderr
+set +e
+ansible-playbook -i ../../inventory test_2.yml > >(set +x; tee "${BASEFILE}.unreachable.stdout";) 2> >(set +x; tee "${BASEFILE}.unreachable.stderr" >&2) || true
+set -e
+if test "$(grep -c 'UNREACHABLE' "${BASEFILE}.unreachable.stderr")" -ne 1; then
+    echo "Test failed"
+    exit 1
+fi

test/integration/targets/callback_default/test_2.yml

@@ -0,0 +1,6 @@
+- hosts: nonexistent
+  gather_facts: no
+  tasks:
+    - name: Test task for unreachable host
+      command: echo foo
+      ignore_errors: True