qapi script: do not allow string discriminator

Since enum based discriminators provide better type-safety and
ensure that future qapi additions do not forget to adjust dependent
unions, forbid using string as discriminator from now on.
Signed-off-by: NWenchao Xia <wenchaoqemu@gmail.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

docs/qapi-code-gen.txt

@@ -123,10 +123,7 @@ And it looks like this on the wire:
 
 Flat union types avoid the nesting on the wire. They are used whenever a
 specific field of the base type is declared as the discriminator ('type' is
-then no longer generated). The discriminator can be a string field or a
-predefined enum field. If it is a string field, a hidden enum type will be
-generated as "[UNION_NAME]Kind". If it is an enum field, a compile time check
-will be done to verify the correctness. It is recommended to use an enum field.
+then no longer generated). The discriminator must be of enumeration type.
 The above example can then be modified as follows:
 
  { 'enum': 'BlockdevDriver', 'data': [ 'raw', 'qcow2' ] }

scripts/qapi.py

@@ -239,6 +239,11 @@ def check_union(expr, expr_info):
                                 "type '%s'"
                                 % (discriminator, base))
         enum_define = find_enum(discriminator_type)
+        # Do not allow string discriminator
+        if not enum_define:
+            raise QAPIExprError(expr_info,
+                                "Discriminator '%s' must be of enumeration "
+                                "type" % discriminator)
 
     # Check every branch
     for (key, value) in members.items():

tests/Makefile

@@ -145,7 +145,8 @@ check-qapi-schema-y := $(addprefix tests/qapi-schema/, \
         unclosed-list.json unclosed-object.json unclosed-string.json \
         duplicate-key.json union-invalid-base.json flat-union-no-base.json \
         flat-union-invalid-discriminator.json \
-        flat-union-invalid-branch-key.json flat-union-reverse-define.json)
+        flat-union-invalid-branch-key.json flat-union-reverse-define.json \
+        flat-union-string-discriminator.json)
 
 GENERATED_HEADERS += tests/test-qapi-types.h tests/test-qapi-visit.h tests/test-qmp-commands.h
 

tests/qapi-schema/flat-union-string-discriminator.err

+<stdin>:13: Discriminator 'kind' must be of enumeration type

tests/qapi-schema/flat-union-string-discriminator.exit

+1

tests/qapi-schema/flat-union-string-discriminator.json

+{ 'enum': 'TestEnum',
+  'data': [ 'value1', 'value2' ] }
+
+{ 'type': 'TestBase',
+  'data': { 'enum1': 'TestEnum', 'kind': 'str' } }
+
+{ 'type': 'TestTypeA',
+  'data': { 'string': 'str' } }
+
+{ 'type': 'TestTypeB',
+  'data': { 'integer': 'int' } }
+
+{ 'union': 'TestUnion',
+  'base': 'TestBase',
+  'discriminator': 'kind',
+  'data': { 'kind1': 'TestTypeA',
+            'kind2': 'TestTypeB' } }

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

@@ -37,10 +37,13 @@
   'base': 'UserDefZero',
   'data': { 'a' : 'UserDefA', 'b' : 'UserDefB' } }
 
+{ 'type': 'UserDefUnionBase',
+  'data': { 'string': 'str', 'enum1': 'EnumOne' } }
+
 { 'union': 'UserDefFlatUnion',
-  'base': 'UserDefOne',
-  'discriminator': 'string',
-  'data': { 'a' : 'UserDefA', 'b' : 'UserDefB' } }
+  'base': 'UserDefUnionBase',
+  'discriminator': 'enum1',
+  'data': { 'value1' : 'UserDefA', 'value2' : 'UserDefB', 'value3' : 'UserDefB' } }
 # FIXME generated struct UserDefFlatUnion has members for direct base
 # UserDefOne, but lacks members for indirect base UserDefZero
 

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

@@ -7,7 +7,8 @@
  OrderedDict([('type', 'UserDefA'), ('data', OrderedDict([('boolean', 'bool')]))]),
  OrderedDict([('type', 'UserDefB'), ('data', OrderedDict([('integer', 'int')]))]),
  OrderedDict([('union', 'UserDefUnion'), ('base', 'UserDefZero'), ('data', OrderedDict([('a', 'UserDefA'), ('b', 'UserDefB')]))]),
- OrderedDict([('union', 'UserDefFlatUnion'), ('base', 'UserDefOne'), ('discriminator', 'string'), ('data', OrderedDict([('a', 'UserDefA'), ('b', 'UserDefB')]))]),
+ OrderedDict([('type', 'UserDefUnionBase'), ('data', OrderedDict([('string', 'str'), ('enum1', 'EnumOne')]))]),
+ OrderedDict([('union', 'UserDefFlatUnion'), ('base', 'UserDefUnionBase'), ('discriminator', 'enum1'), ('data', OrderedDict([('value1', 'UserDefA'), ('value2', 'UserDefB'), ('value3', 'UserDefB')]))]),
  OrderedDict([('union', 'UserDefAnonUnion'), ('discriminator', OrderedDict()), ('data', OrderedDict([('uda', 'UserDefA'), ('s', 'str'), ('i', 'int')]))]),
  OrderedDict([('union', 'UserDefNativeListUnion'), ('data', OrderedDict([('integer', ['int']), ('s8', ['int8']), ('s16', ['int16']), ('s32', ['int32']), ('s64', ['int64']), ('u8', ['uint8']), ('u16', ['uint16']), ('u32', ['uint32']), ('u64', ['uint64']), ('number', ['number']), ('boolean', ['bool']), ('string', ['str'])]))]),
  OrderedDict([('command', 'user_def_cmd'), ('data', OrderedDict())]),
@@ -17,7 +18,6 @@
  OrderedDict([('type', 'UserDefOptions'), ('data', OrderedDict([('*i64', ['int']), ('*u64', ['uint64']), ('*u16', ['uint16']), ('*i64x', 'int'), ('*u64x', 'uint64')]))])]
 [{'enum_name': 'EnumOne', 'enum_values': ['value1', 'value2', 'value3']},
  {'enum_name': 'UserDefUnionKind', 'enum_values': None},
- {'enum_name': 'UserDefFlatUnionKind', 'enum_values': None},
  {'enum_name': 'UserDefAnonUnionKind', 'enum_values': None},
  {'enum_name': 'UserDefNativeListUnionKind', 'enum_values': None}]
 [OrderedDict([('type', 'NestedEnumsOne'), ('data', OrderedDict([('enum1', 'EnumOne'), ('*enum2', 'EnumOne'), ('enum3', 'EnumOne'), ('*enum4', 'EnumOne')]))]),
@@ -27,4 +27,5 @@
  OrderedDict([('type', 'UserDefNested'), ('data', OrderedDict([('string0', 'str'), ('dict1', OrderedDict([('string1', 'str'), ('dict2', OrderedDict([('userdef1', 'UserDefOne'), ('string2', 'str')])), ('*dict3', OrderedDict([('userdef2', 'UserDefOne'), ('string3', 'str')]))]))]))]),
  OrderedDict([('type', 'UserDefA'), ('data', OrderedDict([('boolean', 'bool')]))]),
  OrderedDict([('type', 'UserDefB'), ('data', OrderedDict([('integer', 'int')]))]),
+ OrderedDict([('type', 'UserDefUnionBase'), ('data', OrderedDict([('string', 'str'), ('enum1', 'EnumOne')]))]),
  OrderedDict([('type', 'UserDefOptions'), ('data', OrderedDict([('*i64', ['int']), ('*u64', ['uint64']), ('*u16', ['uint16']), ('*i64x', 'int'), ('*u64x', 'uint64')]))])]

tests/test-qmp-input-strict.c

@@ -146,7 +146,10 @@ static void test_validate_union_flat(TestInputVisitorData *data,
     Visitor *v;
     Error *errp = NULL;
 
-    v = validate_test_init(data, "{ 'string': 'a', 'boolean': true }");
+    v = validate_test_init(data,
+                           "{ 'enum1': 'value1', "
+                           "'string': 'str', "
+                           "'boolean': true }");
     /* TODO when generator bug is fixed, add 'integer': 41 */
 
     visit_type_UserDefFlatUnion(v, &tmp, NULL, &errp);

tests/test-qmp-input-visitor.c

@@ -310,14 +310,18 @@ static void test_visitor_in_union_flat(TestInputVisitorData *data,
     Error *err = NULL;
     UserDefFlatUnion *tmp;
 
-    v = visitor_input_test_init(data, "{ 'string': 'a', 'boolean': true }");
+    v = visitor_input_test_init(data,
+                                "{ 'enum1': 'value1', "
+                                "'string': 'str', "
+                                "'boolean': true }");
     /* TODO when generator bug is fixed, add 'integer': 41 */
 
     visit_type_UserDefFlatUnion(v, &tmp, NULL, &err);
     g_assert(err == NULL);
-    g_assert_cmpint(tmp->kind, ==, USER_DEF_UNION_KIND_A);
+    g_assert_cmpint(tmp->kind, ==, ENUM_ONE_VALUE1);
+    g_assert_cmpstr(tmp->string, ==, "str");
     /* TODO g_assert_cmpint(tmp->integer, ==, 41); */
-    g_assert_cmpint(tmp->a->boolean, ==, true);
+    g_assert_cmpint(tmp->value1->boolean, ==, true);
     qapi_free_UserDefFlatUnion(tmp);
 }
 

tests/test-qmp-output-visitor.c

@@ -449,10 +449,11 @@ static void test_visitor_out_union_flat(TestOutputVisitorData *data,
     Error *err = NULL;
 
     UserDefFlatUnion *tmp = g_malloc0(sizeof(UserDefFlatUnion));
-    tmp->kind = USER_DEF_UNION_KIND_A;
-    tmp->a = g_malloc0(sizeof(UserDefA));
+    tmp->kind = ENUM_ONE_VALUE1;
+    tmp->string = g_strdup("str");
+    tmp->value1 = g_malloc0(sizeof(UserDefA));
     /* TODO when generator bug is fixed: tmp->integer = 41; */
-    tmp->a->boolean = true;
+    tmp->value1->boolean = true;
 
     visit_type_UserDefFlatUnion(data->ov, &tmp, NULL, &err);
     g_assert(err == NULL);
@@ -461,7 +462,8 @@ static void test_visitor_out_union_flat(TestOutputVisitorData *data,
     g_assert(qobject_type(arg) == QTYPE_QDICT);
     qdict = qobject_to_qdict(arg);
 
-    g_assert_cmpstr(qdict_get_str(qdict, "string"), ==, "a");
+    g_assert_cmpstr(qdict_get_str(qdict, "enum1"), ==, "value1");
+    g_assert_cmpstr(qdict_get_str(qdict, "string"), ==, "str");
     /* TODO g_assert_cmpint(qdict_get_int(qdict, "integer"), ==, 41); */
     g_assert_cmpint(qdict_get_bool(qdict, "boolean"), ==, true);