qapi: add 'if' to alternate members

Add 'if' key to alternate members:

{ 'alternate': 'TestIfAlternate', 'data':
  { 'alt': { 'type': 'TestStruct', 'if': 'COND' } } }

Generated code is not changed by this patch but with "qapi: add #if
conditions to generated code".

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20181213123724.4866-17-marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/devel/qapi-code-gen.txt

@@ -754,7 +754,7 @@ gets its generated code guarded like this:
 
 Where a member can be defined with a single string value for its type,
 it is also possible to supply a dictionary instead with both 'type'
-and 'if' keys. (TODO: alternate)
+and 'if' keys.
 
 Example: a conditional 'bar' member
 

scripts/qapi/common.py

@@ -833,7 +833,7 @@ def check_alternate(expr, info):
         check_name(info, "Member of alternate '%s'" % name, key)
         check_known_keys(info,
                          "member '%s' of alternate '%s'" % (key, name),
-                         value, ['type'], [])
+                         value, ['type'], ['if'])
         typ = value['type']
 
         # Ensure alternates have no type conflicts.
@@ -1754,8 +1754,8 @@ class QAPISchema(object):
                                               self._make_members(data, info),
                                               None))
 
-    def _make_variant(self, case, typ):
-        return QAPISchemaObjectTypeVariant(case, typ)
+    def _make_variant(self, case, typ, ifcond):
+        return QAPISchemaObjectTypeVariant(case, typ, ifcond)
 
     def _make_simple_variant(self, case, typ, ifcond, info):
         if isinstance(typ, list):
@@ -1778,7 +1778,7 @@ class QAPISchema(object):
                 name, info, doc, ifcond,
                 'base', self._make_members(base, info))
         if tag_name:
-            variants = [self._make_variant(key, value['type'])
+            variants = [self._make_variant(key, value['type'], value.get('if'))
                         for (key, value) in data.items()]
             members = []
         else:
@@ -1799,7 +1799,7 @@ class QAPISchema(object):
         name = expr['alternate']
         data = expr['data']
         ifcond = expr.get('if')
-        variants = [self._make_variant(key, value['type'])
+        variants = [self._make_variant(key, value['type'], value.get('if'))
                     for (key, value) in data.items()]
         tag_member = QAPISchemaObjectTypeMember('type', 'QType', False)
         self._def_entity(

tests/qapi-schema/qapi-schema-test.json

@@ -218,7 +218,9 @@
 { 'command': 'TestIfUnionCmd', 'data': { 'union_cmd_arg': 'TestIfUnion' },
   'if': 'defined(TEST_IF_UNION)' }
 
-{ 'alternate': 'TestIfAlternate', 'data': { 'foo': 'int', 'bar': 'TestStruct' },
+{ 'alternate': 'TestIfAlternate', 'data':
+  { 'foo': 'int',
+    'bar': { 'type': 'TestStruct', 'if': 'defined(TEST_IF_ALT_BAR)'} },
   'if': 'defined(TEST_IF_ALT) && defined(TEST_IF_STRUCT)' }
 
 { 'command': 'TestIfAlternateCmd', 'data': { 'alt_cmd_arg': 'TestIfAlternate' },

tests/qapi-schema/qapi-schema-test.out

@@ -300,6 +300,7 @@ alternate TestIfAlternate
     tag type
     case foo: int
     case bar: TestStruct
+        if ['defined(TEST_IF_ALT_BAR)']
     if ['defined(TEST_IF_ALT) && defined(TEST_IF_STRUCT)']
 object q_obj_TestIfAlternateCmd-arg
     member alt_cmd_arg: TestIfAlternate optional=False