How do I prevent Firefox SDK content scripts from

Question

How do I prevent Firefox SDK content scripts from loading multiple times? The docs and a bug report I found suggest the contentScriptWhen property should limit the number of times my content scripts are executed, yet I see them running anywhere from twice to 15 times in a page load.

Here's what's in my main.js:

var data = require("sdk/self").data;
var tabs = require('sdk/tabs');

var pageMod = require('sdk/page-mod');
pageMod.PageMod({
    include: ['*'],
    contentScriptWhen: "ready",
    contentScriptFile: [data.url("extBootstrapper.js"), data.url("extContent.js")],
    onAttach: function(worker) {
       //handlers for AJAX and changing preferences, etc
       ...
});

I've tried controlling this behavior with the contentScriptWhen property, as well as by having an 'isLoaded' flag on each script - neither prevents the scripts from executing multiple times.

Answer 1

Turns out this was a duplicate of this question, which, naturally, only turned up in search results a couple of hours after I had posted its duplicate. Go figure.

It lead me to this question in which the author was attempting to prevent his addon from running in iFrames. Eureka! Turns out my addon wasn't "initializing" multiple times for the same page, but page-mod doesn't make distinctions between pages and iFrames.

The solution I used was to use the tabs API to inject my content onto the page, like so:

var data = require("sdk/self").data;
var tabs = require('sdk/tabs');

tabs.on('ready', function(tab) {
     var worker = tab.attach({
          contentScriptOptions: {},
          contentScriptFile: [data.url('myScript.js')]
     });

     // now set up your hooks:        
     worker.port.on('someKey', function(data) {
          //do whatever with your data
     });

});

Turns out another version of this question also existed, in which the attachTo property is used to specify that pageMod.onAttach should only be fired on the top window, rather than iframes:

var data = require("sdk/self").data;
var page = require('sdk/page-mod');

page.PageMod({
     match:['*'],
     contentScriptOptions: {},
     contentScriptFile: [data.url('myScript.js')],
     attachTo: 'top',
     onAttach: function(worker) {
         //set up hooks or other background behavior
     },
});