Feature request: allow macro to handle compiler files emission

[elsassph]

One recurring discussion is to add an API for the Haxe compiler to function in memory - this is desirable for tooling.

My last idea, to permit it without having any hard-coded protocol in the compiler is to offer macros to register a callback to emit files:

haxe.macro.Context.onEmitFile( callback:String->String->Void );

Register a callback receiving:

• filePath: path of the file to write
• content: body of the file to write

Note: it's probably naïve and would require more options to emit binary files.

Using such API, a macro could freely:

• post-process files before write,
• or implement a custom protocol to transmit output without I/O.

[Simn]

I would be fine with that from an API point of view, but it might be a little tricky to implement because the compiler doesn't hold the output as a plain string in order to avoid OCaml memory limitation problems.

[elsassph]

Oh so output is direct to file? maybe we'd need a stream, which could be either directly to file or to memory. Effectively we need to support situations where the JS output is tens of MBs.

[Simn]

It uses some rope-based buffer. At least on Js. So maybe it's not actually a problem.

[back2dos]

How about fileName:String->haxe.io.Output for the callback? Then you can pull all kinds of fancy tricks, like open a process and return its stdout or what not.