lookups, make file searching use better is_role (ansible#82290)

* lookups, make file searching use better is_role

 The dwim function will internally try by detecting tasks/main['','.yml','.yaml]
 but this is far from optimial, the existince of role path in vars is much better
 indicator that we can use to pass a hint


* updated test to avoid main.yml

changelogs/fragments/dwim_is_role_fix.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - dwim functions for lookups should be better at detectging role context even in abscense of tasks/main.

lib/ansible/plugins/lookup/__init__.py

@@ -115,7 +115,7 @@ def find_file_in_search_path(self, myvars, subdir, needle, ignore_missing=False)
 
         result = None
         try:
-            result = self._loader.path_dwim_relative_stack(paths, subdir, needle)
+            result = self._loader.path_dwim_relative_stack(paths, subdir, needle, is_role=bool('role_path' in myvars))
         except AnsibleFileNotFound:
             if not ignore_missing:
                 self._display.warning("Unable to find '%s' in expected paths (use -vvvvv to see paths)" % needle)

test/integration/targets/path_lookups/testplay.yml

@@ -4,9 +4,11 @@
   pre_tasks:
     - name: remove {{ remove }}
       file: path={{ playbook_dir }}/{{ remove }} state=absent
-  roles:
-    - showfile
-  post_tasks:
+  tasks:
+    - import_role:
+        name: showfile
+        tasks_from: notmain.yml
+
     - name: from play
       set_fact: play_result="{{lookup('file', 'testfile')}}"