added diff as new keyword (#28581)

added diff to fake options in ec2_vpc_nat_gateway test

lib/ansible/playbook/base.py

@@ -164,6 +164,7 @@ class Base(with_metaclass(BaseMeta, object)):
     _run_once            = FieldAttribute(isa='bool')
     _ignore_errors       = FieldAttribute(isa='bool')
     _check_mode          = FieldAttribute(isa='bool')
+    _diff                = FieldAttribute(isa='bool')
     _any_errors_fatal     = FieldAttribute(isa='bool', default=C.ANY_ERRORS_FATAL, always_post_validate=True)
 
     # param names which have been deprecated/removed

lib/ansible/playbook/play_context.py

@@ -242,11 +242,9 @@ class PlayContext(Base):
     _verbosity = FieldAttribute(isa='int', default=0)
     _only_tags = FieldAttribute(isa='set', default=set())
     _skip_tags = FieldAttribute(isa='set', default=set())
-    _check_mode = FieldAttribute(isa='bool', default=False)
     _force_handlers = FieldAttribute(isa='bool', default=False)
     _start_at_task = FieldAttribute(isa='string')
     _step = FieldAttribute(isa='bool', default=False)
-    _diff = FieldAttribute(isa='bool')
 
     # Fact gathering settings
     _gather_subset = FieldAttribute(isa='string', default=C.DEFAULT_GATHER_SUBSET)
@@ -336,6 +334,7 @@ class PlayContext(Base):
         self.become_user = options.become_user
 
         self.check_mode = boolean(options.check, strict=False)
+        self.diff = boolean(options.diff, strict=False)
 
         #  general flags (should we move out?)
         # for flag in ('connection', 'remote_user', 'private_key_file', 'verbosity', 'force_handlers', 'step', 'start_at_task', 'diff'):
@@ -511,6 +510,9 @@ class PlayContext(Base):
         if task.check_mode is not None:
             new_info.check_mode = task.check_mode
 
+        if task.diff is not None:
+            new_info.diff = task.diff
+
         return new_info
 
     def make_become_cmd(self, cmd, executable=None):