Set MU on key fields only if explicitly marked MU

Needed to work around bugs in RTI's XCDR1 mutable encoding implementation.

Signed-off-by: Erik Boasson <[email protected]>

Author: eboasson

cyclonedds/idl/_machinery.py

@@ -1123,7 +1123,11 @@ def serialize(self, buffer, value, serialize_kind=SerializeKind.DataSample, key_
                 # TODO: use compact variant when member id and the max serialized size of the type are small enough
                 buffer.write('H', 2, XCDR1.PL_SHORT_PID_EXTENDED | XCDR1.PL_SHORT_FLAG_MU)
                 buffer.write('H', 2, XCDR1.PL_SHORT_PID_EXT_LEN)
-                mu_flag = (1 if mutablemember.must_understand or m_key_enabled != KeyEnabled.Never else 0) << 30
+                # It appears RTI can't handle "must understand" on key fields, even though
+                # XTypes 1.3 requires it.  This should read:
+                #   mu_flag = (1 if mutablemember.must_understand or
+                #              m_key_enabled != KeyEnabled.Never else 0) << 30
+                mu_flag = (1 if mutablemember.must_understand else 0) << 30
                 buffer.write('I', 4, mu_flag | mutablemember.memberid)
                 assert mutablemember.lentype == LenType.NextIntLen
 

cyclonedds/idl/_xt_builder.py

@@ -1038,7 +1038,7 @@ def _xt_member_flag(cls, entity: Any, name: str, _type: type) -> xt.MemberFlag:
         if _is_optional(_type):
             flag.IS_OPTIONAL = True
 
-        if annotations.get("must_understand", False) or annotations.get("key", False) or in_keylist:
+        if annotations.get("must_understand", False):
             flag.IS_MUST_UNDERSTAND = True
 
         if annotations.get("key", False) or in_keylist: