qapi: Improve error position for bogus invalid "Returns" section

When something other than a command has a "Returns" section, the error
message points to the beginning of the definition comment.  Point to
the "Returns" section instead.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240216145841.2099240-7-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

scripts/qapi/parser.py

@@ -759,9 +759,13 @@ class QAPIDoc:
         self.features[feature.name].connect(feature)
 
     def check_expr(self, expr: QAPIExpression) -> None:
-        if self.has_section('Returns') and 'command' not in expr:
-            raise QAPISemError(self.info,
-                               "'Returns:' is only valid for commands")
+        if 'command' not in expr:
+            sec = next((sec for sec in self.sections
+                        if sec.name == 'Returns'),
+                       None)
+            if sec:
+                raise QAPISemError(sec.info,
+                                   "'Returns:' is only valid for commands")
 
     def check(self) -> None:
 

tests/qapi-schema/doc-invalid-return.err

@@ -1 +1 @@
-doc-invalid-return.json:3: 'Returns:' is only valid for commands
+doc-invalid-return.json:5: 'Returns:' is only valid for commands