allow empty sub-protocols

ipc/ipdl/ipdl/parser.py

@@ -269,7 +269,7 @@ def p_NamespacedProtocolDefn(p):
         p[0] = protocol
 
 def p_ProtocolDefn(p):
-    """ProtocolDefn : OptionalSendSemanticsQual PROTOCOL ID '{' ManagerStmtOpt ManagesStmts MessageDecls TransitionStmts '}' ';'"""
+    """ProtocolDefn : OptionalSendSemanticsQual PROTOCOL ID '{' ManagerStmtOpt ManagesStmts OptionalMessageDecls TransitionStmts '}' ';'"""
     protocol = Protocol(locFromTok(p, 2))
     protocol.name = p[3]
     protocol.sendSemantics = p[1]
@@ -300,6 +300,14 @@ def p_ManagesStmt(p):
     """ManagesStmt : MANAGES ID ';'"""
     p[0] = ManagesStmt(locFromTok(p, 1), p[2])
 
+def p_OptionalMessageDecls(p):
+    """OptionalMessageDecls : MessageDecls
+                            | """
+    if 2 == len(p):
+        p[0] = p[1]
+    else:
+        p[0] = [ ]
+
 def p_MessageDecls(p):
     """MessageDecls : MessageDecls MessageDeclThing
                     | MessageDeclThing"""

ipc/ipdl/ipdl/type.py

@@ -437,6 +437,11 @@ class GatherDecls(TcheckVisitor):
             managed.manager = p
             managed.accept(self)
 
+        if p.manager is None and 0 == len(p.messageDecls):
+            self.error(p.loc,
+                       "top-level protocol `%s' cannot be empty",
+                       p.name)
+
         setattr(self, 'currentProtocolDecl', p.decl)
         for msg in p.messageDecls:
             msg.accept(self)