docs/qapidoc: generate entries for undocumented members

Presently, we never have any empty text entries for members. The next
patch will explicitly generate such sections, so enable support for it
in advance.

The parser will generate placeholder sections to indicate undocumented
members, but it's the qapidoc generator that's responsible for deciding
what to do with that stub section.

Signed-off-by: John Snow <[email protected]>
Message-ID: <[email protected]>
Acked-by: Markus Armbruster <[email protected]>
[Tweak the stub section text]
Signed-off-by: Markus Armbruster <[email protected]>

Author: jnsnow

docs/sphinx/qapidoc.py

@@ -233,11 +233,12 @@ def visit_member(self, section: QAPIDoc.ArgSection) -> None:
         # TODO: features for members (documented at entity-level,
         # but sometimes defined per-member. Should we add such
         # information to member descriptions when we can?)
-        assert section.text and section.member
+        assert section.member
         self.generate_field(
             self.member_field_type,
             section.member,
-            section.text,
+            # TODO drop fallbacks when undocumented members are outlawed
+            section.text if section.text else "Not documented",
             section.info,
         )