Inject module dynamically, only if required

Question

I'm using Require.js in combination with Angular.js.

Some controllers need huge external dependencies which others don't need, for example, FirstController requires Angular UI Codemirror. That's a extra 135 kb, at least:

require([
  "angular",
  "angular.ui.codemirror" // requires codemirror itself
], function(angular) {
  angular.module("app", [ ..., "ui.codemirror" ]).controller("FirstController", [ ... ]);
});

I don't want to have to include the directive and the Codemirror lib everytime my page loads just to make Angular happy.
That's why I'm right now loading the controller only when the route is hit, like what's done here.

However, when I need something like

define([
  "app",
  "angular.ui.codemirror"
], function(app) {
  // ui-codemirror directive MUST be available to the view of this controller as of now
  app.lazy.controller("FirstController", [
    "$scope",
    function($scope) {
      // ...
    }
  ]);
});

How can I tell Angular to inject ui.codemirror module (or any other module) in the app module aswell?
I don't care if it's a hackish way to accomplish this, unless it involves modifying the code of external dependencies.

If it's useful: I'm running Angular 1.2.0.

Answer 1

I have been trying to mix requirejs+Angular for some time now. I published a little project in Github (angular-require-lazy) with my effort so far, since the scope is too large for inline code or fiddles. The project demonstrates the following points:

• AngularJS modules are lazy loaded.
• Directives can be lazy loaded too.
• There is a "module" discovery and metadata mechanism (see my other pet project: require-lazy)
• The application is split into bundles automatically (i.e. building with r.js works)

How is it done:

• The providers (e.g. $controllerProvider, $compileProvider) are captured from a config function (technique I first saw in angularjs-requirejs-lazy-controllers).
• After bootstraping, angular is replaced by our own wrapper that can handle lazy loaded modules.
• The injector is captured and provided as a promise.
• AMD modules can be converted to Angular modules.

This implementation satisfies your needs: it can lazy-load Angular modules (at least the ng-grid I am using), is definitely hackish :) and does not modify external libraries.

Comments/opinions are more than welcome.

---

(EDIT) The differentiation of this solution from others is that it does not do dynamic require() calls, thus can be built with r.js (and my require-lazy project). Other than that the ideas are more or less convergent across the various solutions.

Good luck to all!

Answer 2

Attention: use the solution by Nikos Paraskevopoulos, as it's more reliable (I'm using it), and has way more examples.

---

Okay, I have finally found out how to achieve this with a brief help with this answer.

As I said in my question, this has come to be a very hacky way. It envolves applying each function in the _invokeQueue array of the depended module in the context of the app module.

It's something like this (pay more attention in the moduleExtender function please):

define([ "angular" ], function( angular ) {
    // Returns a angular module, searching for its name, if it's a string
    function get( name ) {
        if ( typeof name === "string" ) {
            return angular.module( name );
        }

        return name;
    };

    var moduleExtender = function( sourceModule ) {
        var modules = Array.prototype.slice.call( arguments );

        // Take sourceModule out of the array
        modules.shift();

        // Parse the source module
        sourceModule = get( sourceModule );
        if ( !sourceModule._amdDecorated ) {
            throw new Error( "Can't extend a module which hasn't been decorated." );
        }

        // Merge all modules into the source module
        modules.forEach(function( module ) {
            module = get( module );
            module._invokeQueue.reverse().forEach(function( call ) {
                // call is in format [ provider, function, args ]
                var provider = sourceModule._lazyProviders[ call[ 0 ] ];

                // Same as for example $controllerProvider.register("Ctrl", function() { ... })
                provider && provider[ call[ 1 ] ].apply( provider, call[ 2 ] );
            });
        });
    };

    var moduleDecorator = function( module ) {
        module = get( module );
        module.extend = moduleExtender.bind( null, module );

        // Add config to decorate with lazy providers
        module.config([
            "$compileProvider",
            "$controllerProvider",
            "$filterProvider",
            "$provide",
            function( $compileProvider, $controllerProvider, $filterProvider, $provide ) {
                module._lazyProviders = {
                    $compileProvider: $compileProvider,
                    $controllerProvider: $controllerProvider,
                    $filterProvider: $filterProvider,
                    $provide: $provide
                };

                module.lazy = {
                    // ...controller, directive, etc, all functions to define something in angular are here, just like the project mentioned in the question
                };
                module._amdDecorated = true;
            }
        ]);
    };

    // Tadaaa, all done!
    return {
        decorate: moduleDecorator
    };
});

After this has been done, I just need, for example, to do this:

app.extend( "ui.codemirror" ); // ui.codemirror module will now be available in my application
app.controller( "FirstController", [ ..., function() { });

Answer 3

The key to this is that any modules your app module depends on also needs to be a lazy loading module as well. This is because the provider and instance caches that angular uses for its $injector service are private and they do not expose a method to register new modules after initialization is completed.

So the 'hacky' way to do this would be to edit each of the modules you wish to lazy load to require a lazy loading module object (In the example you linked, the module is located in the file 'appModules.js'), then edit each of the controller, directive, factory etc calls to use app.lazy.{same call} instead.

After that, you can continue to follow the sample project you've linked to by looking at how app routes are lazily loaded (the 'appRoutes.js' file shows how to do this).

Not too sure if this helps, but good luck.