qapi: Fix code generation for empty modules

When a sub-module doesn't contain any definitions, we don't generate
code for it, but we do generate the #include.

We generate code only for modules that get visited.
QAPISchema.visit() visits only modules that have definitions.  It can
visit modules multiple times.

Clean this up as follows.  Collect entities in their QAPISchemaModule.
Have QAPISchema.visit() call QAPISchemaModule.visit() for each module.
Have QAPISchemaModule.visit() call .visit_module() for itself, and
QAPISchemaEntity.visit() for each of its entities.  This way, we visit
each module exactly once.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20191120182551.23795-6-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 13 insertions, 11 deletions

diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 0f2e0dcfce..0bfc5256fb 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -68,6 +68,7 @@ class QAPISchemaEntity(object):
     def _set_module(self, schema, info):
         assert self._checked
         self._module = schema.module_by_fname(info and info.fname)
+        self._module.add_entity(self)
 
     def set_module(self, schema):
         self._set_module(schema, self.info)
@@ -77,11 +78,6 @@ class QAPISchemaEntity(object):
         assert self._checked
         return self._ifcond
 
-    @property
-    def module(self):
-        assert self._module or not self.info
-        return self._module
-
     def is_implicit(self):
         return not self.info
 
@@ -142,6 +138,16 @@ class QAPISchemaVisitor(object):
 class QAPISchemaModule(object):
     def __init__(self, name):
         self.name = name
+        self._entity_list = []
+
+    def add_entity(self, ent):
+        self._entity_list.append(ent)
+
+    def visit(self, visitor):
+        visitor.visit_module(self.name)
+        for entity in self._entity_list:
+            if visitor.visit_needed(entity):
+                entity.visit(visitor)
 
 
 class QAPISchemaInclude(QAPISchemaEntity):
@@ -1093,10 +1099,6 @@ class QAPISchema(object):
     def visit(self, visitor):
         visitor.visit_begin(self)
         module = None
-        for entity in self._entity_list:
-            if visitor.visit_needed(entity):
-                if entity.module != module:
-                    module = entity.module
-                    visitor.visit_module(module.name)
-                entity.visit(visitor)
+        for mod in self._module_dict.values():
+            mod.visit(visitor)
         visitor.visit_end()