Fix 'distribution' fact for ArchLinux (ansible#30723)

* Fix 'distribution' fact for ArchLinux

Allow empty wasn't breaking out of the process_dist_files
loop, so a empty /etc/arch-release would continue searching
and eventually try /etc/os-release. The os-release parsing
works, but the distro name there is 'Arch Linux' which does
not match the 2.3 behavior of 'Archlinux'

Add a OS_RELEASE_ALIAS map for the cases where we need to get
the distro name from os-release but use an alias.

We can't include 'Archlinux' in SEARCH_STRING because a name match on its keys
but without a match on the content causes a fallback to using the first
whitespace seperated item from the file content as the name.
For os-release, that is in form 'NAME=Arch Linux'

With os-release returning the right name, this also supports the
case where there is no /etc/arch-release, but there is a /etc/os-release

Fixes ansible#30600

* pep8 and comment cleanup

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

@@ -64,6 +64,7 @@ class DistributionFiles:
         {'path': '/etc/system-release', 'name': 'Amazon'},
         {'path': '/etc/alpine-release', 'name': 'Alpine'},
         {'path': '/etc/arch-release', 'name': 'Archlinux', 'allowempty': True},
+        {'path': '/etc/os-release', 'name': 'Archlinux'},
         {'path': '/etc/os-release', 'name': 'SUSE'},
         {'path': '/etc/SuSE-release', 'name': 'SUSE'},
         {'path': '/etc/gentoo-release', 'name': 'Gentoo'},
@@ -84,6 +85,13 @@ class DistributionFiles:
         'SMGL': 'Source Mage GNU/Linux',
     }
 
+    # We can't include this in SEARCH_STRING because a name match on its keys
+    # causes a fallback to using the first whitespace seperated item from the file content
+    # as the name. For os-release, that is in form 'NAME=Arch'
+    OS_RELEASE_ALIAS = {
+        'Archlinux': 'Arch Linux'
+    }
+
     def __init__(self, module):
         self.module = module
 
@@ -114,16 +122,19 @@ def _parse_dist_file(self, name, dist_file_content, path, collected_facts):
 
             return True, dist_file_dict
 
+        if name in self.OS_RELEASE_ALIAS:
+            if self.OS_RELEASE_ALIAS[name] in dist_file_content:
+                dist_file_dict['distribution'] = name
+                return True, dist_file_dict
+
         # call a dedicated function for parsing the file content
         # TODO: replace with a map or a class
         try:
             # FIXME: most of these dont actually look at the dist file contents, but random other stuff
             distfunc_name = 'parse_distribution_file_' + name
             # print('distfunc_name: %s' % distfunc_name)
-
             distfunc = getattr(self, distfunc_name)
             # print('distfunc: %s' % distfunc)
-
             parsed, dist_file_dict = distfunc(name, dist_file_content, path, collected_facts)
             return parsed, dist_file_dict
         except AttributeError as exc:
@@ -165,6 +176,12 @@ def process_dist_files(self):
 
             has_dist_file, dist_file_content = self._get_dist_file_content(path, allow_empty=allow_empty)
 
+            # but we allow_empty. For example, ArchLinux with an empty /etc/arch-release and a
+            # /etc/os-release with a different name
+            if has_dist_file and allow_empty:
+                dist_file_facts['distribution'] = name
+                break
+
             if not has_dist_file:
                 # keep looking
                 continue
@@ -180,7 +197,7 @@ def process_dist_files(self):
 
             dist_file_facts['distribution_file_parsed'] = parsed_dist_file
 
-            # finally found the right os dist file and were able to parse it
+            # finally found the right os dit file and were able to parse it
             if parsed_dist_file:
                 dist_file_facts.update(parsed_dist_file_facts)
                 break

test/units/module_utils/test_distribution_version.py

@@ -815,6 +815,48 @@
             "distribution_version": "NA"
         }
     },
+
+    # ArchLinux with an empty /etc/arch-release and a /etc/os-release with "NAME=Arch Linux"
+    {
+        "platform.dist": [
+            "",
+            "",
+            ""
+        ],
+        "input": {
+            "/etc/os-release": "NAME=\"Arch Linux\"\nPRETTY_NAME=\"Arch Linux\"\nID=arch\nID_LIKE=archlinux\nANSI_COLOR=\"0;36\"\nHOME_URL=\"https://www.archlinux.org/\"\nSUPPORT_URL=\"https://bbs.archlinux.org/\"\nBUG_REPORT_URL=\"https://bugs.archlinux.org/\"\n\n",  # noqa
+            "/etc/arch-release": "",
+        },
+        "name": "Arch Linux NA",
+        "result": {
+            "distribution_release": "NA",
+            "distribution": "Archlinux",
+            "distribution_major_version": "NA",
+            "os_family": "Archlinux",
+            "distribution_version": "NA"
+        }
+    },
+
+    # ArchLinux with no /etc/arch-release but with a /etc/os-release with NAME=Arch Linux
+    # The fact needs to map 'Arch Linux' to 'Archlinux' for compat with 2.3 and earlier facts
+    {
+        "platform.dist": [
+            "",
+            "",
+            ""
+        ],
+        "input": {
+            "/etc/os-release": "NAME=\"Arch Linux\"\nPRETTY_NAME=\"Arch Linux\"\nID=arch\nID_LIKE=archlinux\nANSI_COLOR=\"0;36\"\nHOME_URL=\"https://www.archlinux.org/\"\nSUPPORT_URL=\"https://bbs.archlinux.org/\"\nBUG_REPORT_URL=\"https://bugs.archlinux.org/\"\n\n",  # noqa
+        },
+        "name": "Arch Linux no arch-release NA",
+        "result": {
+            "distribution_release": "NA",
+            "distribution": "Archlinux",
+            "distribution_major_version": "NA",
+            "os_family": "Archlinux",
+            "distribution_version": "NA"
+        }
+    }
 ]