Force pkg_mgr yum for rhel < 8, dnf for rhel > 8 (#54010)

* Force pkg_mgr yum for rhel < 8, dnf for rhel > 8

This solves the scenario in which someone using RHEL or a clone
decides to install dnf, which can break their system in certain ways
under certain scenarios (a dnf bug that's been resolved upstream but
left user systems broken happened recently). Currently Red Hat
provides dnf to RHEL7 in an optional Tech Preview Channel under the
YUM4 branding, as does the CentOS Content Management SIG. There may
be others in the ecosystem I'm not familiar with.

Signed-off-by: Adam Miller <admiller@redhat.com>

* add changelog

Signed-off-by: Adam Miller <admiller@redhat.com>

changelogs/fragments/facts-pkg-mgr-rhel.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - facts - ensure that the default package manager for RHEL < 8 is yum, and dnf for newer

lib/ansible/module_utils/facts/system/pkg_mgr.py

@@ -78,6 +78,17 @@ class PkgMgrFactCollector(BaseFactCollector):
                 # If there's some new magical Fedora version in the future,
                 # just default to dnf
                 pkg_mgr_name = 'dnf'
+        else:
+            # If it's not Fedora and it's Red Hat family of distros, assume RHEL
+            # or a clone. For versions of RHEL < 8 that Ansible supports, the
+            # vendor supported official package manager is 'yum' and in RHEL 8+
+            # (as far as we know at the time of this writing) it is 'dnf'.
+            # If anyone wants to force a non-official package manager then they
+            # can define a provider to either the package or yum action plugins.
+            if int(collected_facts['ansible_distribution_major_version']) < 8:
+                pkg_mgr_name = 'yum'
+            else:
+                pkg_mgr_name = 'dnf'
         return pkg_mgr_name
 
     def _check_apt_flavor(self, pkg_mgr_name):
@@ -107,10 +118,9 @@ class PkgMgrFactCollector(BaseFactCollector):
                 pkg_mgr_name = pkg['name']
 
         # Handle distro family defaults when more than one package manager is
-        # installed, the ansible_fact entry should be the default package
+        # installed or available to the distro, the ansible_fact entry should be
-        # manager provided by the distro.
+        # the default package manager officially supported by the distro.
         if collected_facts['ansible_os_family'] == "RedHat":
-            if pkg_mgr_name not in ('yum', 'dnf'):
             pkg_mgr_name = self._check_rh_versions(pkg_mgr_name, collected_facts)
         elif collected_facts['ansible_os_family'] == 'Debian' and pkg_mgr_name != 'apt':
             # It's possible to install yum, dnf, zypper, rpm, etc inside of
@@ -124,11 +134,5 @@ class PkgMgrFactCollector(BaseFactCollector):
         if pkg_mgr_name == 'apt':
             pkg_mgr_name = self._check_apt_flavor(pkg_mgr_name)
 
-        # pacman has become available by distros other than those that are Arch
-        # based by virtue of a dependency to the systemd mkosi project, this
-        # handles some of those scenarios as they are reported/requested
-        if pkg_mgr_name == 'pacman' and collected_facts['ansible_os_family'] in ["RedHat"]:
-            pkg_mgr_name = self._check_rh_versions(collected_facts)
-
         facts_dict['pkg_mgr'] = pkg_mgr_name
         return facts_dict