Issue 3251 - Simplify messaging from child scripts to parent

lib/child/bootstrap.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 39 matching lines @@
   function init(message)
   {
     removeMessageListener("AdblockPlus:Info", init);
 
     let callbackPrefix = Services.appinfo.processID + " ";
     let maxCallbackID = 0;
     let callbacks = new Map();
 
     function sendSyncMessageSingleResponse(messageName, data)
     {
-      let response = sendSyncMessage(messageName, {data})[0];
-      return typeof response == "string" ? JSON.parse(response) : response;
+      return sendSyncMessage(messageName, {data})[0];
     }
 
     function sendAsyncMessageWithResponse(messageName, data, callback)

[Wladimir Palant, 2015/11/04 15:04:09]

Note that normally the third parameter for both sendSyncMessage and
sendAsyncMessage is objects. I think that explicitly disallowing it is a good
idea - with these objects being accessed via CPOWs it's a serious footgun.

     {
       data = {data};
       if (callback)
       {
         let callbackID = callbackPrefix + (++maxCallbackID);
         callbacks.set(callbackID, callback);
         data.callbackID = callbackID;
       }
       sendAsyncMessage(messageName, data);
     }
@@ skipping 12 matching lines @@
     onShutdown.add(() => removeMessageListener("AdblockPlus:Response", onResponse));
 
     let info = message.data;
     loader = Loader({
       paths: {
         "": info.addonRoot + "lib/"
       },
       globals: {
         Components, Cc, Ci, Cu, Cr, atob, btoa, onShutdown,
         addMessageListener, removeMessageListener,
         sendAsyncMessage: sendAsyncMessageWithResponse,

[tschuster, 2015/11/14 21:26:07]

I don't think it's great that we use the same name for those as the standard
functions, but I don't have good name suggestion now either.

[Wladimir Palant, 2015/11/16 12:54:24]

I don't think these will stay like that. My idea is to implement a proper
messaging module and then merge the messaging functionality currently in
ext/common into it as well. But - enough changes for now, that refactoring will
happen along with the CSS Property Filters implementation.

         sendSyncMessage: sendSyncMessageSingleResponse
       },
       modules: {"info": info},
       id: info.addonID
     });
     onShutdown.add(() => unload(loader, "disable"))
 
     main(loader, "child/main");
   }
 
@@ skipping 13 matching lines @@
         catch (e)
         {
           Cu.reportError(e);
         }
       }
       shutdownHandlers = null;
     }
   }
 })();