Is there any way to implement nsICommandLineHandler in a restartless add-on?

Question

Is there any way to implement nsICommandLineHandler in a restartless add-on?

It seems possible from https://addons.mozilla.org/en-US/developers/docs/sdk/latest/modules/sdk/platform/xpcom.html , but this code (run from within exports.main) is not working for me:

var { Class } = require('sdk/core/heritage');
var { Unknown, Factory } = require('sdk/platform/xpcom');
var { Cc, Ci } = require('chrome');

var contractId = '@mozilla.org/commandlinehandler/general-startup;1?type=webappfind';

// Define a component
var CommandLineHandler = Class({
  extends: Unknown,
  get wrappedJSObject() this,

  classDescription: "webAppFinder",
  /* Not used by SDK, so commenting out
  _xpcom_categories: [{  
    category: "command-line-handler",  
    // category names are sorted alphabetically. Typical command-line handlers use a  
    // category that begins with the letter "m".  
    entry: "m-webappfind"  
  }],
  */
  helpInfo : "  -webappfind               Open My Application\n",
  // nsICommandLineHandler
  handle : function clh_handle(cmdLine) {
    try {
        console.log('good so far'); // Doesn't actually reach here
        var fileStr = cmdLine.handleFlagWithParam("webappfind", false);
        if (fileStr) {
          console.log('made it');
        }
    }
    catch (e) {
        Cu.reportError("incorrect parameter passed to -webappfind on the command line.");
    }

    if (cmdLine.handleFlag("webappfind", false)) { // no argument
        cmdLine.preventDefault = true;
        throw 'A valid ID must be provided to webappfind';
    }
  },
  hello: function() {return 'Hello World';}
});

// Create and register the factory
var factory = Factory({
  contract: contractId,
//  id: '{7f397cba-7a9a-4a05-9ca7-a5b8d7438c6c}', // Despite the docs saying one can add both, this doesn't work
  Component: CommandLineHandler
});

I have the following code afterward which works...

// XPCOM clients can retrieve and use this new
// component in the normal way
var wrapper = Cc[contractId].createInstance(Ci.nsISupports);
var helloWorld = wrapper.wrappedJSObject;
console.log(helloWorld.hello());

...but Firefox is not accepting command line args as per this error:

Error: Warning: unrecognized command line flag -webappfind

Source file: resource://app/components/nsBrowserContentHandler.js Line: 765

UPDATE

I've now taken @nmaier's advice to add categories and therefore added these lines afterward:

var catMan = Cc['@mozilla.org/categorymanager;1'].getService(Ci.nsICategoryManager); //
catMan.addCategoryEntry('command-line-handler', 'm-webappfind' /*contractId*/, contractId, false, true);

But I'm getting these 3 errors when invoking from the command line:

Error: [Exception... "'Failure' when calling method: [nsIFactory::createInstance]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "native frame :: :: :: line 0" data: no]

Contract ID '@mozilla.org/commandlinehandler/general-startup;1?type=webappfind' was registered as a command line handler for entry 'm-webappfind', but could not be created.

Error: Warning: unrecognized command line flag -webappfind

Source file: resource://app/components/nsBrowserContentHandler.js Line: 765

Answer 1

The SDK will not register categories for you.

Some remarks regarding categories can be found here: https://stackoverflow.com/a/18366485/484441

But still, I'm not sure if bootstrapped extensions are actually started before the initial command line is processed. Trial and error, I guess...

Edit: Your component does not specify any interfaces, hence it does only support nsISupports. The SDK module docs state that you should add an interfaces: [ 'nsICommandLineHandler' ] property.