Fix loading namespaced doc_fragments from collections (#55249)

* Fix loading namespaced doc_fragments

The syntax for specifying a different fragment name was already
using '.' as a separator, so the code needed to be tweaked to
avoid choking on names like `testns.testcoll.fragname` and
`testns.testcoll.fragname.altvar`.

`get_plugin_class()` returns 'docfragment' for the fragment loader;
mangling `subdir` provides consistent alignment with the normal plugin
directory names and avoids needing special handling of plugin types
with 'module' in the name.

* Add changelog entry

changelogs/fragments/55249-doc_fragments_from_collections.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - Fixed loading namespaced documentation fragments from collections.

lib/ansible/plugins/loader.py

@@ -330,15 +330,12 @@ def _find_fq_plugin(self, fq_name, extension):
         package = splitname[0]
         resource = splitname[1]
 
-        append_plugin_type = self.class_name or self.subdir
-
-        if append_plugin_type:
-            # only current non-class special case, module_utils don't use this loader method
-            if append_plugin_type == 'library':
-                append_plugin_type = 'modules'
-            elif append_plugin_type != 'module_utils':
-                append_plugin_type = get_plugin_class(append_plugin_type)
-            package += '.plugins.{0}'.format(append_plugin_type)
+        append_plugin_type = self.subdir.replace('_plugins', '')
+
+        if append_plugin_type == 'library':
+            append_plugin_type = 'modules'
+
+        package += '.plugins.{0}'.format(append_plugin_type)
 
         if extension:
             resource += extension

lib/ansible/utils/plugin_docs.py

@@ -50,14 +50,20 @@ def add_fragments(doc, filename, fragment_loader):
     # Allow the module to specify a var other than DOCUMENTATION
     # to pull the fragment from, using dot notation as a separator
     for fragment_slug in fragments:
+        fallback_name = None
         fragment_slug = fragment_slug.lower()
         if '.' in fragment_slug:
-            fragment_name, fragment_var = fragment_slug.split('.', 1)
+            fallback_name = fragment_slug
+            fragment_name, fragment_var = fragment_slug.rsplit('.', 1)
             fragment_var = fragment_var.upper()
         else:
             fragment_name, fragment_var = fragment_slug, 'DOCUMENTATION'
 
         fragment_class = fragment_loader.get(fragment_name)
+        if fragment_class is None and fallback_name:
+            fragment_class = fragment_loader.get(fallback_name)
+            fragment_var = 'DOCUMENTATION'
+
         if fragment_class is None:
             raise AnsibleAssertionError('fragment_class is None')
 

test/integration/targets/collections/collection_root_user/ansible_collections/testns/testcoll/plugins/doc_fragments/frag.py

@@ -0,0 +1,14 @@
+class ModuleDocFragment(object):
+    DOCUMENTATION = r'''
+options:
+  normal_doc_frag:
+    description:
+    - an option
+'''
+
+    OTHER_DOCUMENTATION = r'''
+options:
+  other_doc_frag:
+    description:
+    - another option
+'''

test/integration/targets/collections/collection_root_user/ansible_collections/testns/testcoll/plugins/modules/testmodule.py

@@ -2,6 +2,14 @@
 
 import json
 
+DOCUMENTATION = r'''
+module: testmodule
+description: for testing
+extends_documentation_fragment:
+  - testns.testcoll.frag
+  - testns.testcoll.frag.other_documentation
+'''
+
 
 def main():
     print(json.dumps(dict(changed=False, source='user')))

test/integration/targets/collections/runme.sh

@@ -20,6 +20,9 @@ fi
 # test callback
 ANSIBLE_CALLBACK_WHITELIST=testns.testcoll.usercallback ansible localhost -m ping | grep "usercallback says ok"
 
+# test documentation
+ansible-doc testns.testcoll.testmodule -vvv | grep -- "- normal_doc_frag"
+
 # we need multiple plays, and conditional import_playbook is noisy and causes problems, so choose here which one to use...
 if [[ ${INVENTORY_PATH} == *.winrm ]]; then
   export TEST_PLAYBOOK=windows.yml