cron: removal of deprecations and minor fix (#73591)

* removal of deprecations and minor fix

  name or cron_file is required.
  reboot was removed.
  updated docs to clarify usage.
  now using cron_file=/etc/crontab is an error

  fixes #37355

changelogs/fragments/cron_removals.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - cron, removed previously deprecated 'reboot' and now requires either 'name' as unique identifier.

lib/ansible/modules/cron.py

@@ -57,12 +57,14 @@ options:
   cron_file:
     description:
       - If specified, uses this file instead of an individual user's crontab.
+        The assumption is that this file is exclusively managed by the module,
+        do not use if the file contains multiple entries, NEVER use for /etc/crontab.
       - If this is a relative path, it is interpreted with respect to I(/etc/cron.d).
-      - If it is absolute, it will typically be C(/etc/crontab).
       - Many linux distros expect (and some require) the filename portion to consist solely
         of upper- and lower-case letters, digits, underscores, and hyphens.
-      - To use the I(cron_file) parameter you must specify the I(user) as well.
-    type: str
+      - Using this parameter requires you to specify the I(user) as well, unless I(state) is not I(present).
+      - Either this parameter or I(name) is required
+    type: path
   backup:
     description:
       - If set, create a backup of the crontab before it is modified.
@@ -232,6 +234,7 @@ class CronTab(object):
         self.cron_cmd = self.module.get_bin_path('crontab', required=True)
 
         if cron_file:
+
             if os.path.isabs(cron_file):
                 self.cron_file = cron_file
                 self.b_cron_file = to_bytes(cron_file, errors='surrogate_or_strict')
@@ -557,7 +560,7 @@ def main():
             name=dict(type='str', required=True),
             user=dict(type='str'),
             job=dict(type='str', aliases=['value']),
-            cron_file=dict(type='str'),
+            cron_file=dict(type='path'),
             state=dict(type='str', default='present', choices=['present', 'absent']),
             backup=dict(type='bool', default=False),
             minute=dict(type='str', default='*'),
@@ -600,6 +603,10 @@ def main():
     warnings = list()
 
     if cron_file:
+
+        if cron_file == '/etc/crontab':
+            module.fail_json(msg="Will not manage /etc/crontab via cron_file, see documentation.")
+
         cron_file_basename = os.path.basename(cron_file)
         if not re.search(r'^[A-Z0-9_-]+$', cron_file_basename, re.I):
             warnings.append('Filename portion of cron_file ("%s") should consist' % cron_file_basename +
@@ -632,14 +639,14 @@ def main():
     if special_time and platform.system() == 'SunOS':
         module.fail_json(msg="Solaris does not support special_time=... or @reboot")
 
-    if cron_file and do_install:
-        if not user:
+    if do_install:
+        if cron_file and not user:
             module.fail_json(msg="To use cron_file=... parameter you must specify user=... as well")
 
-    if job is None and do_install:
+        if job is None:
             module.fail_json(msg="You must specify 'job' to install a new cron job or variable")
 
-    if (insertafter or insertbefore) and not env and do_install:
+        if (insertafter or insertbefore) and not env:
             module.fail_json(msg="Insertafter and insertbefore parameters are valid only with env=yes")
 
     # if requested make a backup before making a change