qapi: Introduce a first class 'null' type

I expect the 'null' type to be useful mostly for members of alternate
types.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

4 files changed, 18 insertions, 1 deletions

diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index 91ffb2648c..c72dbd8050 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -93,7 +93,8 @@
 { 'struct': 'WrapAlternate',
   'data': { 'alt': 'UserDefAlternate' } }
 { 'alternate': 'UserDefAlternate',
-  'data': { 'udfu': 'UserDefFlatUnion', 'e': 'EnumOne', 'i': 'int' } }
+  'data': { 'udfu': 'UserDefFlatUnion', 'e': 'EnumOne', 'i': 'int',
+            'n': 'null' } }
 
 { 'struct': 'UserDefC',
   'data': { 'string1': 'str', 'string2': 'str' } }
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index b88b8aae6f..3b1e9082d3 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -64,6 +64,7 @@ alternate UserDefAlternate
     case udfu: UserDefFlatUnion
     case e: EnumOne
     case i: int
+    case n: null
 object UserDefB
     member intb: int optional=False
     member a-b: bool optional=True
diff --git a/tests/test-qobject-input-visitor.c b/tests/test-qobject-input-visitor.c
index f98caf9818..f4518441d3 100644
--- a/tests/test-qobject-input-visitor.c
+++ b/tests/test-qobject-input-visitor.c
@@ -583,6 +583,11 @@ static void test_visitor_in_alternate(TestInputVisitorData *data,
     g_assert_cmpint(tmp->u.e, ==, ENUM_ONE_VALUE1);
     qapi_free_UserDefAlternate(tmp);
 
+    v = visitor_input_test_init(data, "null");
+    visit_type_UserDefAlternate(v, NULL, &tmp, &error_abort);
+    g_assert_cmpint(tmp->type, ==, QTYPE_QNULL);
+    qapi_free_UserDefAlternate(tmp);
+
     v = visitor_input_test_init(data, "{'integer':1, 'string':'str', "
                                 "'enum1':'value1', 'boolean':true}");
     visit_type_UserDefAlternate(v, NULL, &tmp, &error_abort);
diff --git a/tests/test-qobject-output-visitor.c b/tests/test-qobject-output-visitor.c
index 8f1fcd49cb..7eb162059c 100644
--- a/tests/test-qobject-output-visitor.c
+++ b/tests/test-qobject-output-visitor.c
@@ -424,6 +424,16 @@ static void test_visitor_out_alternate(TestOutputVisitorData *data,
 
     visitor_reset(data);
     tmp = g_new0(UserDefAlternate, 1);
+    tmp->type = QTYPE_QNULL;
+    tmp->u.n = qnull();
+
+    visit_type_UserDefAlternate(data->ov, NULL, &tmp, &error_abort);
+    g_assert_cmpint(qobject_type(visitor_get(data)), ==, QTYPE_QNULL);
+
+    qapi_free_UserDefAlternate(tmp);
+
+    visitor_reset(data);
+    tmp = g_new0(UserDefAlternate, 1);
     tmp->type = QTYPE_QDICT;
     tmp->u.udfu.integer = 1;
     tmp->u.udfu.string = g_strdup("str");