plugin XEP-0428: Add missing "for" attribute:

The "for" attribute was missing from <fallback> element.

rel 461

libervia/backend/plugins/plugin_xep_0424.py

@@ -16,7 +16,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import time
-from typing import Any, Dict
+from typing import Any, Dict, cast
 
 from sqlalchemy.orm.attributes import flag_modified
 from twisted.internet import defer
@@ -31,6 +31,7 @@ from libervia.backend.core.core_types import MessageDataLegacy, SatXMPPEntity
 from libervia.backend.core.i18n import D_, _
 from libervia.backend.core.log import getLogger
 from libervia.backend.memory.sqla_mapping import History
+from libervia.backend.plugins.plugin_xep_0428 import XEP_0428
 from libervia.backend.tools.common import data_format
 
 log = getLogger(__name__)
@@ -111,8 +112,10 @@ class XEP_0424:
         message_elt["type"] = history.type
         retract_elt = message_elt.addElement((NS_MESSAGE_RETRACT, "retract"))
         retract_elt["id"] = retract_id
-        self.host.plugins["XEP-0428"].add_fallback_elt(
+        fallback = cast(XEP_0428, self.host.plugins["XEP-0428"])
+        fallback.add_fallback_elt(
             message_elt,
+            NS_MESSAGE_RETRACT,
             "[A message retraction has been requested, but your client doesn't support "
             "it]",
         )

libervia/backend/plugins/plugin_xep_0428.py

@@ -43,25 +43,35 @@ PLUGIN_INFO = {
 NS_FALLBACK = "urn:xmpp:fallback:0"
 
 
-class XEP_0428(object):
+class XEP_0428:
 
     def __init__(self, host):
         log.info(_("XEP-0428 (Fallback Indication) plugin initialization"))
         host.register_namespace("fallback", NS_FALLBACK)
 
     def add_fallback_elt(
-        self, message_elt: domish.Element, msg: Optional[str] = None
+        self,
+        message_elt: domish.Element,
+        for_: str,
+        msg: str|None = None
     ) -> None:
         """Add the fallback indication element
 
         @param message_elt: <message> element where the indication must be
             set
+        @param for_: Specification namespace that the fallback is meant to replace.
+          see https://xmpp.org/extensions/xep-0428.html#sect-idm46381699903600
         @param msg: message to show as fallback
             Will be added as <body>
         """
-        message_elt.addElement((NS_FALLBACK, "fallback"))
+        fallback_elt = message_elt.addElement((NS_FALLBACK, "fallback"))
+        fallback_elt["for"] = for_
         if msg is not None:
-            message_elt.addElement("body", content=msg)
+            body_elt = message_elt.body
+            if body_elt is None:
+                message_elt.addElement("body", content=msg)
+            else:
+                body_elt.addContent(msg)
 
     def has_fallback(self, message_elt: domish.Element) -> bool:
         """Tell if a message has a fallback indication"""