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>

3 files changed, 16 insertions, 0 deletions

diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index a079378d1b..d1fdf4182c 100644
--- a/scripts/qapi/commands.py
+++ b/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)
diff --git a/scripts/qapi/gen.py b/scripts/qapi/gen.py
index b5a8d03e8e..8f8f784f4a 100644
--- a/scripts/qapi/gen.py
+++ b/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():
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 719152fe49..8f31f8832f 100644
--- a/scripts/qapi/schema.py
+++ b/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)