qapi: Drop support for boxed alternate arguments

Commands and events can define their argument type inline (default) or
by referring to another type ('boxed': true, since commit c818408e44
"qapi: Implement boxed types for commands/events", v2.7.0).  The
unboxed inline definition is an (anonymous) struct type.  The boxed
type may be a struct, union, or alternate type.

The latter is problematic: docs/interop/qemu-spec.txt requires the
value of the 'data' key to be a json-object, but any non-degenerate
alternate type has at least one branch that isn't.

Fortunately, we haven't made use of alternates in this context outside
tests/.  Drop support for them.

QAPISchemaAlternateType.is_empty() is now unused.  Drop it, too.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190913201349.24332-4-armbru@redhat.com>

1 files changed, 4 insertions, 11 deletions

diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index 9aefcfe015..54d02458b5 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -840,7 +840,7 @@ def check_command(expr, info):
 
     args_meta = ['struct']
     if boxed:
-        args_meta += ['union', 'alternate']
+        args_meta += ['union']
     check_type(info, "'data' for command '%s'" % name,
                expr.get('data'), allow_dict=not boxed,
                allow_metas=args_meta)
@@ -858,7 +858,7 @@ def check_event(expr, info):
 
     meta = ['struct']
     if boxed:
-        meta += ['union', 'alternate']
+        meta += ['union']
     check_type(info, "'data' for event '%s'" % name,
                expr.get('data'), allow_dict=not boxed,
                allow_metas=meta)
@@ -1690,9 +1690,6 @@ class QAPISchemaAlternateType(QAPISchemaType):
         visitor.visit_alternate_type(self.name, self.info, self.ifcond,
                                      self.variants)
 
-    def is_empty(self):
-        return False
-
 
 class QAPISchemaCommand(QAPISchemaEntity):
     def __init__(self, name, info, doc, ifcond, arg_type, ret_type,
@@ -1714,15 +1711,13 @@ class QAPISchemaCommand(QAPISchemaEntity):
         QAPISchemaEntity.check(self, schema)
         if self._arg_type_name:
             self.arg_type = schema.lookup_type(self._arg_type_name)
-            assert (isinstance(self.arg_type, QAPISchemaObjectType) or
-                    isinstance(self.arg_type, QAPISchemaAlternateType))
+            assert isinstance(self.arg_type, QAPISchemaObjectType)
             self.arg_type.check(schema)
             if self.boxed:
                 if self.arg_type.is_empty():
                     raise QAPISemError(self.info,
                                        "Cannot use 'boxed' with empty type")
             else:
-                assert not isinstance(self.arg_type, QAPISchemaAlternateType)
                 assert not self.arg_type.variants
         elif self.boxed:
             raise QAPISemError(self.info, "Use of 'boxed' requires 'data'")
@@ -1750,15 +1745,13 @@ class QAPISchemaEvent(QAPISchemaEntity):
         QAPISchemaEntity.check(self, schema)
         if self._arg_type_name:
             self.arg_type = schema.lookup_type(self._arg_type_name)
-            assert (isinstance(self.arg_type, QAPISchemaObjectType) or
-                    isinstance(self.arg_type, QAPISchemaAlternateType))
+            assert isinstance(self.arg_type, QAPISchemaObjectType)
             self.arg_type.check(schema)
             if self.boxed:
                 if self.arg_type.is_empty():
                     raise QAPISemError(self.info,
                                        "Cannot use 'boxed' with empty type")
             else:
-                assert not isinstance(self.arg_type, QAPISchemaAlternateType)
                 assert not self.arg_type.variants
         elif self.boxed:
             raise QAPISemError(self.info, "Use of 'boxed' requires 'data'")