qapi-schema: support alternates with array type

Detect array types as alternate branches, and turn the JSON list into
a QAPISchemaArrayType.  Array types in an alternate are represented with
QTYPE_QLIST in the type field.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220321164243.200569-2-pbonzini@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

scripts/qapi/expr.py

@@ -554,7 +554,7 @@ def check_alternate(expr: _JSONObject, info: QAPISourceInfo) -> None:
         check_name_lower(key, info, source)
         check_keys(value, info, source, ['type'], ['if'])
         check_if(value, info, source)
-        check_type(value['type'], info, source)
+        check_type(value['type'], info, source, allow_array=True)
 
 
 def check_command(expr: _JSONObject, info: QAPISourceInfo) -> None:

scripts/qapi/schema.py

@@ -243,6 +243,7 @@ def alternate_qtype(self):
             'number':  'QTYPE_QNUM',
             'int':     'QTYPE_QNUM',
             'boolean': 'QTYPE_QBOOL',
+            'array':   'QTYPE_QLIST',
             'object':  'QTYPE_QDICT'
         }
         return json2qtype.get(self.json_type())
@@ -1069,6 +1070,9 @@ def _def_struct_type(self, expr, info, doc):
             None))
 
     def _make_variant(self, case, typ, ifcond, info):
+        if isinstance(typ, list):
+            assert len(typ) == 1
+            typ = self._make_array_type(typ[0], info)
         return QAPISchemaVariant(case, info, typ, ifcond)
 
     def _def_union_type(self, expr, info, doc):

tests/qapi-schema/alternate-array.err

@@ -1,2 +0,0 @@
-alternate-array.json: In alternate 'Alt':
-alternate-array.json:5: 'data' member 'two' cannot be an array

tests/qapi-schema/alternate-array.json

@@ -1,5 +1,3 @@
-# we do not allow array branches in alternates
-# TODO: should we support this?
 { 'struct': 'One',
   'data': { 'name': 'str' } }
 { 'alternate': 'Alt',

tests/qapi-schema/alternate-array.out

@@ -0,0 +1,18 @@
+module ./builtin
+object q_empty
+enum QType
+    prefix QTYPE
+    member none
+    member qnull
+    member qnum
+    member qstring
+    member qdict
+    member qlist
+    member qbool
+module alternate-array.json
+object One
+    member name: str optional=False
+alternate Alt
+    tag type
+    case one: One
+    case two: intList