I would like to propose a new feature for the ActionScript language in the Apache Flex "Falcon" compiler. It would be nice if developers could (optionally) rename an import.
Background ========== Normally when you import a class, you can reference the name of the class, without the package (unless there is another class with the same name): // begin example import com.example.ImportedClass; var example:ImportedClass; //end example I would like to make it possible to optionally rename the shortened version, like this: // begin example import NewName = com.example.ImportedClass; var test:NewName; //end example This would make it possible to resolve ambiguities without using the fully-qualified class name. Consider the following situation that commonly comes up when developing Starling apps where the fully-qualified name is required for different types of events: // begin example import flash.events.Event; import starling.events.Event; var one:flash.events.Event; var two:starling.events.Event; // end example If we could rename imports, our code wouldn't require cumbersome fully-qualified names. Consider the following example, references to FlashEvent will resolve to flash.events.Event and StarlingEvent will resolve to starling.events.Event: // begin example import FlashEvent = flash.events.Event; import StarlingEvent = starling.events.Event; var one:FlashEvent; var two:StarlingEvent; // end example In the next example, references to FlashEvent will resolve to flash.events.Event, similar to the previous example. References to Event can resolve to starling.events.Event without ambiguity because flash.events.Event has been given a different name. // begin example import FlashEvent = flash.events.Event; import starling.events.Event; var one:FlashEvent; var two:Event; // end example This would also be useful for transpile-to-JS workflow where the top-level package is littered with a ton of HTML classes that may conflict with names user-defined classes. For instance, there's a top-level Event class. There is no way to specify a different fully-qualified name for things in the top-level package, so it's hard to resolve ambiguity when using these classes. We have a bit of a workaround in Falcon by supporting a fake "window." package, but that's not ideal. Especially if you consider Node.js, which doesn't actually have a global window object. Risks and Challenges =================== * Renaming imports is a completely optional feature. Anyone can continue to code in ActionScript without ever using renamed imports. * Existing code won't be broken by this new feature. Regular imports that don't do any renaming will continue to work the same as they always have. * Runtimes like Adobe Flash Player will not need to be modified to support renaming imports. Imports are completely resolved at compile-time. * A SWC compiled from code with renamed imports will work with compilers that don't support renaming imports. Again, a SWC contains compiled code, so imports were already resolved. * I have implemented this feature already, in a local branch of flex-falcon on my machine. The code already exists, and it works today. The one tricky thing is that most IDEs probably won't play well with code that uses renamed imports. My NextGenAS extension for VSCode should have no problem because it loads the Falcon compiler from the Apache FlexJS SDK for its code intelligence features. If Falcon supports it, so will the extension. Adobe Flash Builder uses ASC 2.0 in a similar way, as I understand it. With that in mind, Flash Builder won't understand code with renamed imports unless Adobe modifies ASC 2.0 to add the same feature. I think third-party IDEs (like IntelliJ IDEA and FDT) have their own code models (rather than talking to the compiler), so they'd need to make their own changes to support this feature too. I would like to contact the Flash runtimes team at Adobe and ask if they'd be willing to implement this feature in ASC 2.0 too. It's a small change, but useful for developer productivity, so it should be well received by the community. Additionally, since it will affect the compiler and not the runtime, it will be significantly less risky for Adobe than other new language features might be. Finally, considering that the Falcon and ASC 2.0 codebases are probably still extremely similar, I wouldn't be surprised if the changes were exactly the same. To go back to the previous point about IDEs, I'm pretty sure that if ASC 2.0 supports this feature, Flash Builder will get it for free when someone upgrades the AIR SDK used by the FB plugin. There may still be some quirks (I'm curious to see if organizing imports breaks or not), but I think ActionScript developers are used to a few occasional quirks these days. Comments welcome. - Josh
