tests/qapi-schema: Cover duplicate 'Features:' line

We don't actually recognize the second 'Features:' line.  Instead, we
treat it as an untagged section.

If it was followed by feature description, we'd reject that like
"description of '@feat2:' follows a section".  Less than clear.

To be improved shortly.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240216145841.2099240-3-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

tests/qapi-schema/doc-duplicate-features.json

@@ -0,0 +1,11 @@
+# Duplicate 'Features:' line
+
+##
+# @foo:
+#
+# Features:
+# @feat: mumble
+#
+# Features:
+##
+{ 'command': 'foo', 'features': ['feat'] }

tests/qapi-schema/doc-duplicate-features.out

@@ -0,0 +1,22 @@
+module ./builtin
+object q_empty
+enum QType
+    prefix QTYPE
+    member none
+    member qnull
+    member qnum
+    member qstring
+    member qdict
+    member qlist
+    member qbool
+module doc-duplicate-features.json
+command foo None -> None
+    gen=True success_response=True boxed=False oob=False preconfig=False
+    feature feat
+doc symbol=foo
+    body=
+
+    feature=feat
+mumble
+    section=None
+Features:

tests/qapi-schema/meson.build

@@ -66,6 +66,7 @@ schemas = [
   'doc-bad-union-member.json',
   'doc-before-include.json',
   'doc-before-pragma.json',
+  'doc-duplicate-features.json',
   'doc-duplicated-arg.json',
   'doc-duplicated-return.json',
   'doc-duplicated-since.json',