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, 10 insertions, 7 deletions

diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index d7f51ee250..b7a647076d 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -335,6 +335,10 @@ class QAPISchemaGenVisitVisitor(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 visit_enum_type(self, name, info, values, prefix):
         self.decl += gen_visit_decl(name, scalar=True)
         self.defn += gen_visit_enum(name)
@@ -351,13 +355,12 @@ class QAPISchemaGenVisitVisitor(QAPISchemaVisitor):
             self.defn += defn
 
     def visit_object_type(self, name, info, base, members, variants):
-        if info:
-            self.decl += gen_visit_decl(name)
-            if variants:
-                assert not members      # not implemented
-                self.defn += gen_visit_union(name, base, variants)
-            else:
-                self.defn += gen_visit_struct(name, base, members)
+        self.decl += gen_visit_decl(name)
+        if variants:
+            assert not members      # not implemented
+            self.defn += gen_visit_union(name, base, variants)
+        else:
+            self.defn += gen_visit_struct(name, base, members)
 
     def visit_alternate_type(self, name, info, variants):
         self.decl += gen_visit_decl(name)