qapi: Reject "Returns" section when command doesn't return anything

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240227113921.236097-14-armbru@redhat.com>

scripts/qapi/parser.py

@@ -721,7 +721,12 @@ class QAPIDoc:
         self.features[feature.name].connect(feature)
 
     def check_expr(self, expr: QAPIExpression) -> None:
-        if 'command' not in expr:
+        if 'command' in expr:
+            if self.returns and 'returns' not in expr:
+                raise QAPISemError(
+                    self.returns.info,
+                    "'Returns' section, but command doesn't return anything")
+        else:
             if self.returns:
                 raise QAPISemError(
                     self.returns.info,

tests/qapi-schema/doc-invalid-return2.err

@@ -0,0 +1 @@
+doc-invalid-return2.json:5: 'Returns' section, but command doesn't return anything

tests/qapi-schema/doc-invalid-return2.json

@@ -0,0 +1,7 @@
+# Command doesn't return anything
+
+##
+# @foo:
+# Returns: blah
+##
+{ 'command': 'foo' }

tests/qapi-schema/meson.build

@@ -79,6 +79,7 @@ schemas = [
   'doc-invalid-end.json',
   'doc-invalid-end2.json',
   'doc-invalid-return.json',
+  'doc-invalid-return2.json',
   'doc-invalid-section.json',
   'doc-invalid-start.json',
   'doc-missing-colon.json',