qapi: Use predicate callback to determine visit filtering

Previously, qapi-types and qapi-visit filtered out implicit
objects during visit_object_type() by using 'info' (works since
implicit objects do not [yet] have associated info); meanwhile
qapi-introspect filtered out all schema types on the first pass
by returning a python type from visit_begin(), which was then
used at a distance in QAPISchema.visit() to do the filtering.

Rather than keeping these ad hoc approaches, add a new visitor
callback visit_needed() which returns False to skip a given
entity, and which defaults to True unless overridden.  Use the
new mechanism to simplify all three filtering visitors.

No change to the generated code.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1444710158-8723-2-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 11 insertions, 8 deletions

diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index d405f8d670..2a29c6e106 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -233,6 +233,10 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor):
         self.decl = self._btin + self.decl
         self._btin = None
 
+    def visit_needed(self, entity):
+        # Visit everything except implicit objects
+        return not isinstance(entity, QAPISchemaObjectType) or entity.info
+
     def _gen_type_cleanup(self, name):
         self.decl += gen_type_cleanup_decl(name)
         self.defn += gen_type_cleanup(name)
@@ -254,14 +258,13 @@ class QAPISchemaGenTypeVisitor(QAPISchemaVisitor):
             self._gen_type_cleanup(name)
 
     def visit_object_type(self, name, info, base, members, variants):
-        if info:
-            self._fwdecl += gen_fwd_object_or_array(name)
-            if variants:
-                assert not members      # not implemented
-                self.decl += gen_union(name, base, variants)
-            else:
-                self.decl += gen_struct(name, base, members)
-            self._gen_type_cleanup(name)
+        self._fwdecl += gen_fwd_object_or_array(name)
+        if variants:
+            assert not members      # not implemented
+            self.decl += gen_union(name, base, variants)
+        else:
+            self.decl += gen_struct(name, base, members)
+        self._gen_type_cleanup(name)
 
     def visit_alternate_type(self, name, info, variants):
         self._fwdecl += gen_fwd_object_or_array(name)