cli: handle empty PAGER value (#86909)

Fixes: #86898

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

changelogs/fragments/pager.yml

@@ -0,0 +1,3 @@
+---
+bugfixes:
+    - cli - handle empty value for PAGER (https://github.com/ansible/ansible/issues/86898).

lib/ansible/cli/__init__.py

@@ -514,17 +514,19 @@ class CLI(ABC):
             p = subprocess.Popen('less --version', shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             p.communicate()
             if p.returncode == 0:
-                CLI.pager_pipe(text, 'less')
+                CLI.pager_pipe(text, pager='less')
             else:
                 display.display(text, screen_only=True)
 
     @staticmethod
-    def pager_pipe(text):
+    def pager_pipe(text, pager=None):
         """ pipe text through a pager """
-        if 'less' in CLI.PAGER:
+        pager_cmd = pager or CLI.PAGER
+
+        if 'less' in pager_cmd:
             os.environ['LESS'] = CLI.LESS_OPTS
         try:
-            cmd = subprocess.Popen(CLI.PAGER, shell=True, stdin=subprocess.PIPE, stdout=sys.stdout)
+            cmd = subprocess.Popen(pager_cmd, shell=True, stdin=subprocess.PIPE, stdout=sys.stdout)
             cmd.communicate(input=to_bytes(text))
         except (OSError, KeyboardInterrupt):
             pass

test/integration/targets/ansible-doc/runme.sh

@@ -59,6 +59,16 @@ current_out="$(ansible-doc --playbook-dir ./ testns.testcol.yolo --type test | s
 expected_out="$(sed '1 s/\(^> TEST testns\.testcol\.yolo\).*(.*)$/\1/' yolo-text.output)"
 test "$current_out" == "$expected_out"
 
+# PAGER is set to less by default, so we need to test with other pagers
+for pager in more cat; do
+    echo "testing with pager $pager"
+    PAGER=$pager ansible-doc --list testns.testcol --playbook-dir ./ 2>&1 | grep "${GREP_OPTS[@]}" -v "Invalid collection name"
+done
+
+# set pager to empty string
+echo "testing with pager empty"
+PAGER="" ansible-doc --list testns.testcol --playbook-dir ./ 2>&1 | grep "${GREP_OPTS[@]}" -v "Invalid collection name"
+
 # ensure we do work with valid collection name for list
 ansible-doc --list testns.testcol --playbook-dir ./ 2>&1 | grep -v "Invalid collection name"