Ticket 50137 - create should not check in non-stateful mode for exist

Bug Description: In def create, we should do a existance check for an
entry before creating. However, depending on access control this may not
work as intended because you can create without sight of the target, and
then this may cause misleading exceptions preventing the create.

Fix Description: In stateless mode, don't check the existance of the
entry before create.

In stateful ensure mode, continue to check for the existance.

https://pagure.io/389-ds-base/issue/50137

Author: William Brown <william@blackhats.net.au>

Review by: ???

src/lib389/lib389/_mapped_object.py

@@ -766,11 +766,14 @@ def _create(self, rdn=None, properties=None, basedn=None, ensure=False):
 
         exists = False
 
-        try:
-            self._instance.search_ext_s(dn, ldap.SCOPE_BASE, self._object_filter, attrsonly=1, serverctrls=self._server_controls, clientctrls=self._client_controls, escapehatch='i am sure')
-            exists = True
-        except ldap.NO_SUCH_OBJECT:
-            pass
+        if ensure:
+            # If we are running in stateful ensure mode, we need to check if the object exists, and
+            # we can see the state that it is in.
+            try:
+                self._instance.search_ext_s(dn, ldap.SCOPE_BASE, self._object_filter, attrsonly=1, serverctrls=self._server_controls, clientctrls=self._client_controls, escapehatch='i am sure')
+                exists = True
+            except ldap.NO_SUCH_OBJECT:
+                pass
 
         if exists and ensure:
             # update properties
@@ -781,19 +784,27 @@ def _create(self, rdn=None, properties=None, basedn=None, ensure=False):
             for k, v in list(valid_props.items()):
                 mods.append((ldap.MOD_REPLACE, k, v))
             self._instance.modify_ext_s(self._dn, mods, serverctrls=self._server_controls, clientctrls=self._client_controls, escapehatch='i am sure')
-        elif exists and not ensure:
-            # raise "already exists."
-            raise ldap.ALREADY_EXISTS("Entry %s already exists" % dn)
-        if not exists:
+        elif not exists:
+            # This case is reached in two cases. One is we are in ensure mode, and we KNOW the entry
+            # doesn't exist.
+            # The alternate, is that we are in a non-stateful create, so we "just create" and see
+            # what happens. I believe the technical term is "yolo create".
             self._log.debug('Creating %s' % dn)
             e = Entry(dn)
             e.update({'objectclass': ensure_list_bytes(self._create_objectclasses)})
             e.update(valid_props)
             # We rely on exceptions here to indicate failure to the parent.
             self._log.debug('Creating entry %s : %s' % (dn, e))
             self._instance.add_ext_s(e, serverctrls=self._server_controls, clientctrls=self._client_controls, escapehatch='i am sure')
-            # If it worked, we need to fix our instance dn
+            # If it worked, we need to fix our instance dn for the object's self reference. Because
+            # we may not have a self reference yet (just created), it may have changed (someone
+            # set dn, but validate altered it).
             self._dn = dn
+        else:
+            # This case can't be reached now that we only check existance on ensure.
+            # However, it's good to keep it for "complete" behaviour, exhausting all states.
+            # We could highlight bugs ;)
+            raise AssertionError("Impossible State Reached in _create")
         return self
 
     def create(self, rdn=None, properties=None, basedn=None):