"delay" handler for definitions with async calls

[demurgos]

Some modules do need to perform asynchronous calls to be fully initialized.
In example :
IndexDB calls https://developer.mozilla.org/en/docs/IndexedDB
Ajax requests
Blob builders
Custom methods with asynchronous tasks

To get sure that the asynchronous calls are performed before the defined events are triggered, it is possible to use a plugin that will manually handle those special cases. The problem is that to delay the "define" event, the plugin has to used for each require which creates redundancy across secondary modules depending on the first module requiring async calls. It would be more logical if the async nature of a module was in its definition.
The idea would be to not only load modules asynchronously but also to get their value asynchronously.
The best idea I found was to create a new special handler ( like "require", "exports" or "module" ) called "delay" and being a callback function for the return value.
For example it would look this way :

define(["delay"], function ( delay ) { // depends on the "delay" handler : the value will be returned asynchronously
var Module = ... ;
setTimeout(function(){ //Some asynchronous actions
delay(Module) ; //This does actually returns the Module's value and triggers the "defined" event.
//It's transparent, just as if the loading time over the network was a bit longer.
},1000);
return Module ; //This does not do anything because delay is active
});

This was achieved with only a few lines of code (check the diff) and could offer a useful feature to get a better structured module when its initialization does not simple rely on the load of the file.

PS : I do have a CLA with Dojo

[jrburke]

See notes on #1075

[ghost]

@demurgos. As I see I'm not not only one who think about async/delayed exports in AMD.
With your pull request we have already a second way to implement it, see also my implementation #1075. So we should open an issue on the amdjs-api repo to discuss it.

[demurgos]

Thanks, I have seen your interesting implementation too.
This was my first pull request I made so sorry, I see it was not complete : I just wanted to propose a way to deal with some rare but existing cases because what you have done is just great.

I'll try to improve my solution because it's still has its issue that it requires a handler name - personnally that's already the reason why I did not named that "async". Could it be usefull to provide some concrete examples or situations when this async definition is helpfull?

An other thing that bugged me : should the Module offer a synchronous AND an asynchronous export ? I feel like its getting to over-complicate it, could this be usefull ?

[ghost]

I opened an issue on the amdjs-api repo, I quoted your comment there as well. So let's move the discussion to the issue, to get an async/delayed AMD standard implementation soon.