Issue 2879 - Restructure existing process script, split it up into multiple modules

lib/child/bootstrap.js

Index: lib/child/bootstrap.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/child/bootstrap.js
@@ -0,0 +1,90 @@
+/*
+ * This Source Code is subject to the terms of the Mozilla Public License
+ * version 2.0 (the "License"). You can obtain a copy of the License at
+ * http://mozilla.org/MPL/2.0/.
+ */
+
+"use strict";

[Wladimir Palant, 2016/11/17 08:42:58]

This is very close to lib/child/bootstrap.js we use in Adblock Plus. The
differences are:

* "use strict"
* messageManager is declared explicitly (we cannot just use `this` within a
function because with "use strict" it won't be defined).
* Function shutdown protects against reentry, won't do anything if we have
onShutdown.done.
* Not expecting the script URL as parameter for shutdown message - I don't
remember what issue this was working around in Adblock Plus but it was working
fine without in EHH.
* Shutdown message is called ElemHideHelper:Shutdown rather than
AdblockPlus:Shutdown.

[saroyanm, 2016/11/22 14:58:31]

Acknowledged.

+
+(function(messageManager)
+{
+  const Cc = Components.classes;
+  const Ci = Components.interfaces;
+  const Cr = Components.results;
+  const Cu = Components.utils;
+
+  let {Loader, main, unload} = Cu.import("resource://gre/modules/commonjs/toolkit/loader.js", {});

[saroyanm, 2016/11/24 17:46:10]

Nit: Exceeding 80 chars.

[Wladimir Palant, 2016/12/01 09:40:49]

Done.

+  let {Services} = Cu.import("resource://gre/modules/Services.jsm", {});
+
+  Cu.importGlobalProperties(["atob", "btoa", "File", "URL", "URLSearchParams",
+      "TextDecoder", "TextEncoder"]);
+
+  let shutdownHandlers = [];
+  let onShutdown =
+  {
+    done: false,
+    add: function(handler)
+    {
+      if (shutdownHandlers.indexOf(handler) < 0)
+        shutdownHandlers.push(handler);
+    },
+    remove: function(handler)
+    {
+      let index = shutdownHandlers.indexOf(handler);
+      if (index >= 0)
+        shutdownHandlers.splice(index, 1);
+    }
+  };
+
+  function init()
+  {
+    let url = new URL(Components.stack.filename);
+    let params = new URLSearchParams(url.search.substr(1));
+    let info = JSON.parse(params.get("info"));
+
+    let loader = Loader({
+      paths: {
+        "": info.addonRoot + "lib/"
+      },
+      globals: {
+        Components, Cc, Ci, Cu, Cr, atob, btoa, File, URL, URLSearchParams,
+        TextDecoder, TextEncoder, onShutdown
+      },
+      modules: {
+        info, messageManager

[saroyanm, 2016/11/22 14:58:31]

In AdblockPlus we are defining the modules:
modules: {"info": info, "messageManager": this}

Should this be defined like:
modules: {"info": info, "messageManager": messageManager} ?

[Wladimir Palant, 2016/11/24 14:16:29]

Why? This short notation is available starting with Firefox 34 and we are
starting to use it. The code in Adblock Plus is simply older.

[saroyanm, 2016/11/24 17:46:10]

Oh, I was referring actually to your initial comment regarding the differences
in bootstrap file. 
Acknowledged.

+      },
+      id: info.addonID
+    });
+    onShutdown.add(() => unload(loader, "disable"))
+
+    main(loader, "child/main");
+  }
+
+  function shutdown(message)

[saroyanm, 2016/11/22 14:58:31]

message parameter is not being used, probably can be omitted.

[Wladimir Palant, 2016/11/24 14:16:29]

It sure can be but it is still being passed in so I'd rather not omit it.

+  {
+    if (onShutdown.done)
+      return;
+
+    onShutdown.done = true;
+    for (let i = shutdownHandlers.length - 1; i >= 0; i --)
+    {
+      try
+      {
+        shutdownHandlers[i]();
+      }
+      catch (e)
+      {
+        Cu.reportError(e);
+      }
+    }
+    shutdownHandlers = null;
+  }
+
+  messageManager.addMessageListener("ElemHideHelper:Shutdown", shutdown);
+  onShutdown.add(() =>
+  {
+    messageManager.removeMessageListener("ElemHideHelper:Shutdown", shutdown);
+  });
+
+  init();
+})(this);