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>
---
 scripts/qapi/expr.py                   |  2 +-
 scripts/qapi/schema.py                 |  4 ++++
 tests/qapi-schema/alternate-array.err  |  2 --
 tests/qapi-schema/alternate-array.json |  2 --
 tests/qapi-schema/alternate-array.out  | 18 ++++++++++++++++++
 5 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
index 3cb389e875..48578e1698 100644
--- a/scripts/qapi/expr.py
+++ b/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:
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index b7b3fc0ce4..3728340c37 100644
--- a/scripts/qapi/schema.py
+++ b/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):
diff --git a/tests/qapi-schema/alternate-array.err b/tests/qapi-schema/alternate-array.err
index b1aa1f4e8d..e69de29bb2 100644
--- a/tests/qapi-schema/alternate-array.err
+++ b/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
diff --git a/tests/qapi-schema/alternate-array.json b/tests/qapi-schema/alternate-array.json
index f241aac122..b878a2db77 100644
--- a/tests/qapi-schema/alternate-array.json
+++ b/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',
diff --git a/tests/qapi-schema/alternate-array.out b/tests/qapi-schema/alternate-array.out
index e69de29bb2..a657d85738 100644
--- a/tests/qapi-schema/alternate-array.out
+++ b/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
-- 
2.35.1

Paolo Bonzini <pbonzini@redhat.com> writes:

> 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>

I double-checked the generated code; it looks good to me.

Thanks for implementing this, and extra thanks for the tests!

Reviewed-by: Markus Armbruster <armbru@redhat.com>

On 3/22/22 10:48, Markus Armbruster wrote:
> I double-checked the generated code; it looks good to me.
> 
> Thanks for implementing this, and extra thanks for the tests!

Heh, the problem is having to build the infrastructure for tests.  If 
it's already there, patches like this are actually easier to write with 
tests than without!...

Paolo