pamd - fixed single line issue (#2989)

* fixed pamd single line issue

* added changelog fragment

* supported case for 0 lines, improved test

changelogs/fragments/2989-pamd-single-line.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - pamd - fixed problem with files containing only one or two lines (https://github.com/ansible-collections/community.general/issues/2925).

plugins/modules/system/pamd.py

@@ -733,14 +733,19 @@ class PamdService(object):
         lines = []
         current_line = self._head
 
+        mark = "# Updated by Ansible - %s" % datetime.now().isoformat()
         while current_line is not None:
             lines.append(str(current_line))
             current_line = current_line.next
 
+        if len(lines) <= 1:
+            lines.insert(0, "")
+            lines.insert(1, mark)
+        else:
             if lines[1].startswith("# Updated by Ansible"):
-            lines.pop(1)
-
-        lines.insert(1, "# Updated by Ansible - " + datetime.now().isoformat())
+                lines[1] = mark
+            else:
+                lines.insert(1, mark)
 
         return '\n'.join(lines) + '\n'
 

tests/integration/targets/pamd/aliases

@@ -0,0 +1,5 @@
+shippable/posix/group1
+skip/aix
+skip/freebsd
+skip/osx
+skip/macos

tests/integration/targets/pamd/tasks/main.yml

@@ -0,0 +1,56 @@
+# (c) 2021, Alexei Znamensky
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+- name: Set value for temp limit configuration
+  set_fact:
+    test_pamd_file: "/tmp/pamd_file"
+
+- name: Copy temporary pam.d file
+  copy:
+    content: "session required pam_lastlog.so silent showfailed"
+    dest: "{{ test_pamd_file }}"
+
+- name: Test working on a single-line file works (2925)
+  community.general.pamd:
+    path: /tmp
+    name: pamd_file
+    type: session
+    control: required
+    module_path: pam_lastlog.so
+    module_arguments: silent
+    state: args_absent
+  register: pamd_file_output
+
+- name: Check if changes made
+  assert:
+    that:
+      - pamd_file_output is changed
+
+- name: Copy temporary pam.d file
+  copy:
+    content: ""
+    dest: "{{ test_pamd_file }}"
+
+# This test merely demonstrates that, as-is, module will not perform any changes on an empty file
+# All the existing values for "state" will first search for a rule matching type, control, module_path
+# and will not perform any change whatsoever if no existing rules match.
+- name: Test working on a empty file works (2925)
+  community.general.pamd:
+    path: /tmp
+    name: pamd_file
+    type: session
+    control: required
+    module_path: pam_lastlog.so
+    module_arguments: silent
+  register: pamd_file_output_empty
+
+- name: Read back the file
+  slurp:
+    src: "{{ test_pamd_file }}"
+  register: pamd_file_slurp
+
+- name: Check if changes made
+  assert:
+    that:
+      - pamd_file_output_empty is not changed
+      - pamd_file_slurp.content|b64decode == ''