qapi: Require boxed for conditional command and event arguments

The C code generator fails to honor 'if' conditions of command and
event arguments.

For instance, tests/qapi-schema/qapi-schema-test.json has

    { 'event': 'TEST_IF_EVENT',
      'data': { 'foo': 'TestIfStruct',
		'bar': { 'type': ['str'], 'if': 'TEST_IF_EVT_ARG' } },
      'if': { 'all': ['TEST_IF_EVT', 'TEST_IF_STRUCT'] } }

Generated tests/test-qapi-events.h fails to honor the TEST_IF_EVT_ARG
condition:

    #if defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT)
    void qapi_event_send_test_if_event(TestIfStruct *foo, strList *bar);
    #endif /* defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT) */

Only uses so far are in tests/.

We could fix the generator to emit something like

    #if defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT)
    void qapi_event_send_test_if_event(TestIfStruct *foo
    #if defined(TEST_IF_EVT_ARG)
                    , strList *bar
    #endif
                    );
    #endif /* defined(TEST_IF_EVT) && defined(TEST_IF_STRUCT) */

Ugly.  Calls become similarly ugly.  Not worth fixing.

Conditional arguments work fine with 'boxed': true, simply because
complex types with conditional members work fine.  Not worth breaking.

Reject conditional arguments unless boxed.

Move the tests cases covering unboxed conditional arguments out of
tests/qapi-schema/qapi-schema-test.json.  Cover boxed conditional
arguments there instead.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230316071325.492471-15-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

docs/devel/qapi-code-gen.rst

@@ -805,9 +805,8 @@ gets its generated code guarded like this::
  ... generated code ...
  #endif /* defined(HAVE_BAR) && defined(CONFIG_FOO) */
 
-Individual members of complex types, commands arguments, and
+Individual members of complex types can also be made conditional.
-event-specific data can also be made conditional.  This requires the
+This requires the longhand form of MEMBER.
-longhand form of MEMBER.
 
 Example: a struct type with unconditional member 'foo' and conditional
 member 'bar' ::

scripts/qapi/commands.py

@@ -66,6 +66,7 @@ def gen_call(name: str,
     elif arg_type:
         assert not arg_type.variants
         for memb in arg_type.members:
+            assert not memb.ifcond.is_present()
             if memb.need_has():
                 argstr += 'arg.has_%s, ' % c_name(memb.name)
             argstr += 'arg.%s, ' % c_name(memb.name)

scripts/qapi/gen.py

@@ -119,6 +119,7 @@ def build_params(arg_type: Optional[QAPISchemaObjectType],
     elif arg_type:
         assert not arg_type.variants
         for memb in arg_type.members:
+            assert not memb.ifcond.is_present()
             ret += sep
             sep = ', '
             if memb.need_has():

scripts/qapi/schema.py

@@ -486,6 +486,10 @@ class QAPISchemaObjectType(QAPISchemaType):
         assert self.members is not None
         return not self.members and not self.variants
 
+    def has_conditional_members(self):
+        assert self.members is not None
+        return any(m.ifcond.is_present() for m in self.members)
+
     def c_name(self):
         assert self.name != 'q_empty'
         return super().c_name()
@@ -817,6 +821,11 @@ class QAPISchemaCommand(QAPISchemaEntity):
                     self.info,
                     "command's 'data' can take %s only with 'boxed': true"
                     % self.arg_type.describe())
+            self.arg_type.check(schema)
+            if self.arg_type.has_conditional_members() and not self.boxed:
+                raise QAPISemError(
+                    self.info,
+                    "conditional command arguments require 'boxed': true")
         if self._ret_type_name:
             self.ret_type = schema.resolve_type(
                 self._ret_type_name, self.info, "command's 'returns'")
@@ -872,6 +881,11 @@ class QAPISchemaEvent(QAPISchemaEntity):
                     self.info,
                     "event's 'data' can take %s only with 'boxed': true"
                     % self.arg_type.describe())
+            self.arg_type.check(schema)
+            if self.arg_type.has_conditional_members() and not self.boxed:
+                raise QAPISemError(
+                    self.info,
+                    "conditional event arguments require 'boxed': true")
 
     def connect_doc(self, doc=None):
         super().connect_doc(doc)

tests/qapi-schema/args-if-implicit.err

@@ -0,0 +1,2 @@
+args-if-implicit.json: In command 'test-if-cmd':
+args-if-implicit.json:1: conditional command arguments require 'boxed': true

tests/qapi-schema/args-if-implicit.json

@@ -0,0 +1,4 @@
+{ 'command': 'test-if-cmd',
+  'data': {
+    'foo': 'int',
+    'bar': { 'type': 'str', 'if': 'TEST_IF_CMD_ARG' } } }

tests/qapi-schema/args-if-unboxed.err

@@ -0,0 +1,2 @@
+args-if-unboxed.json: In command 'test-if-cmd':
+args-if-unboxed.json:5: conditional command arguments require 'boxed': true

tests/qapi-schema/args-if-unboxed.json

@@ -0,0 +1,6 @@
+{ 'struct': 'TestIfCmdArgs',
+  'data': {
+    'foo': 'int',
+    'bar': { 'type': 'str', 'if': 'TEST_IF_CMD_ARG' } } }
+{ 'command': 'test-if-cmd',
+  'data': 'TestIfCmdArgs' }

tests/qapi-schema/event-args-if-unboxed.err

@@ -0,0 +1,2 @@
+tests/qapi-schema/event-args-if-unboxed.json: In event 'TEST_IF_EVENT':
+tests/qapi-schema/event-args-if-unboxed.json:1: event's 'data' members may have 'if' conditions only with 'boxed': true

tests/qapi-schema/event-args-if-unboxed.json

@@ -0,0 +1,4 @@
+ { 'event': 'TEST_IF_EVENT',
+  'data': {
+    'foo': 'int',
+    'bar': { 'type': 'str', 'if': 'TEST_IF_CMD_ARG' } } }

tests/qapi-schema/meson.build

@@ -27,6 +27,8 @@ schemas = [
   'args-bad-boxed.json',
   'args-boxed-anon.json',
   'args-boxed-string.json',
+  'args-if-implicit.json',
+  'args-if-unboxed.json',
   'args-int.json',
   'args-invalid.json',
   'args-member-array-bad.json',

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

@@ -249,17 +249,16 @@
   'if': { 'all': ['TEST_IF_ALT', 'TEST_IF_STRUCT'] } }
 
 { 'command': 'test-if-cmd',
-  'data': {
+  'boxed': true,
-    'foo': 'TestIfStruct',
+  'data': 'TestIfStruct',
-    'bar': { 'type': 'str', 'if': 'TEST_IF_CMD_ARG' } },
   'returns': 'UserDefThree',
   'if': { 'all': ['TEST_IF_CMD', 'TEST_IF_STRUCT'] } }
 
 { 'command': 'test-cmd-return-def-three', 'returns': 'UserDefThree' }
 
 { 'event': 'TEST_IF_EVENT',
-  'data': { 'foo': 'TestIfStruct',
+  'boxed': true,
-            'bar': { 'type': ['str'], 'if': 'TEST_IF_EVT_ARG' } },
+  'data': 'TestIfStruct',
   'if': { 'all': ['TEST_IF_EVT', 'TEST_IF_STRUCT'] } }
 
 { 'event': 'TEST_IF_EVENT2', 'data': {},

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

@@ -283,23 +283,13 @@ object q_obj_test-if-alternate-cmd-arg
 command test-if-alternate-cmd q_obj_test-if-alternate-cmd-arg -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
     if {'all': ['TEST_IF_ALT', 'TEST_IF_STRUCT']}
-object q_obj_test-if-cmd-arg
+command test-if-cmd TestIfStruct -> UserDefThree
-    member foo: TestIfStruct optional=False
+    gen=True success_response=True boxed=True oob=False preconfig=False
-    member bar: str optional=False
-        if TEST_IF_CMD_ARG
-    if {'all': ['TEST_IF_CMD', 'TEST_IF_STRUCT']}
-command test-if-cmd q_obj_test-if-cmd-arg -> UserDefThree
-    gen=True success_response=True boxed=False oob=False preconfig=False
     if {'all': ['TEST_IF_CMD', 'TEST_IF_STRUCT']}
 command test-cmd-return-def-three None -> UserDefThree
     gen=True success_response=True boxed=False oob=False preconfig=False
-object q_obj_TEST_IF_EVENT-arg
+event TEST_IF_EVENT TestIfStruct
-    member foo: TestIfStruct optional=False
+    boxed=True
-    member bar: strList optional=False
-        if TEST_IF_EVT_ARG
-    if {'all': ['TEST_IF_EVT', 'TEST_IF_STRUCT']}
-event TEST_IF_EVENT q_obj_TEST_IF_EVENT-arg
-    boxed=False
     if {'all': ['TEST_IF_EVT', 'TEST_IF_STRUCT']}
 event TEST_IF_EVENT2 None
     boxed=False