Enable file module to disable diff_mode (#83700)

Several tasks within the modification_time.yml and state_link.yml task
lists have explicitly enabled diff_mode because these tests previously
assumed a diff attribute would always be returned from the file module.

changelogs/fragments/83700-enable-file-disable-diff.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - file - enable file module to disable diff_mode (https://github.com/ansible/ansible/issues/80817).

lib/ansible/modules/file.py

@@ -1007,6 +1007,9 @@ def main():
     elif state == 'absent':
         result = ensure_absent(path)
 
+    if not module._diff:
+        result.pop('diff', None)
+
     module.exit_json(**result)
 
 

test/integration/targets/file/tasks/diff.yml

@@ -0,0 +1,44 @@
+# file module tests for diff being returned in results
+
+- name: Initialize the test output dir
+  import_tasks: initialize.yml
+
+- name: Create an empty file
+  file:
+    state: touch
+    mode: "755"
+    path: "{{ remote_tmp_dir_test }}/foobar.txt"
+  register: temp_file
+
+- name: Confirm diff was not returned in results
+  assert:
+    that:
+      - temp_file.diff is not defined
+
+- name: Toggle permissions on said empty file
+  file:
+    state: file
+    mode: "644"
+    path: "{{ temp_file.dest }}"
+  register: temp_file
+  diff: true
+
+- name: Confirm diff was returned in results
+  assert:
+    that:
+      - temp_file.diff is defined
+
+- name: Toggle permissions on said empty file...again
+  file:
+    state: file
+    mode: "755"
+    path: "{{ temp_file.path }}"
+  register: temp_file
+  diff: false
+  environment:
+    ANSIBLE_DIFF_ALWAYS: True
+
+- name: Confirm diff was not returned in results
+  assert:
+    that:
+      - temp_file.diff is not defined

test/integration/targets/file/tasks/main.yml

@@ -55,6 +55,9 @@
 - name: Test modification time
   import_tasks: modification_time.yml
 
+- name: Test diff_mode
+  import_tasks: diff.yml
+
 # These tests need to be organized by state parameter into separate files later
 
 - name: verify that we are checking a file and it is present

test/integration/targets/file/tasks/modification_time.yml

@@ -19,6 +19,7 @@
     modification_time_format: "%Y%m%d%H%M.%S"
   check_mode: true
   register: file_change_check_mode
+  diff: true
 
 - name: Re-stat the file
   stat:
@@ -41,6 +42,7 @@
     modification_time: "{{ modification_timestamp }}"
     modification_time_format: "%Y%m%d%H%M.%S"
   register: file_change_no_check_mode
+  diff: true
 
 - name: Stat of the file after the change
   stat:
@@ -61,6 +63,7 @@
     modification_time: "{{ modification_timestamp }}"
     modification_time_format: "%Y%m%d%H%M.%S"
   register: file_change_no_check_mode_second
+  diff: true
 
 - name: Confirm no changes made registered
   assert:

test/integration/targets/file/tasks/state_link.yml

@@ -29,6 +29,7 @@
 - name: change soft link to relative
   file: src={{output_file|basename}} dest={{remote_tmp_dir_test}}/soft.txt state=link
   register: file2_result
+  diff: true
 
 - name: Get stat info for the link
   stat: