Adding better-files to the Scala Platform

[mdedetrich]

@lihaoyi

There is no reason we can’t implement a facade for java.nio in scala-native, or for that matter in Scala.js for all the synchronous APIs that exist (in-memory FS, node’s sync FS, …). That’s what we’ve done with Java collections, for example, and the effort required is relatively trivial compared to designing a whole new IO library from scratch.

Java NIO is a very low level library, and it doesn’t really make sense on some platforms (Scala.js) and could be very different on other libraries (scala-native). If Scala.js would add suppor this library via platforms like node.js, I suspect it would be very hard to make a proper interface to Java NIO within Scala.js and for scala-native I suspect that the use case in scala-native (low level accesss to C/C++ libraries) would mean that implementing Java NIO would be less than ideal

The collections analogy isn’t apt, its an apples to oranges comparison. Collections API is designed to be high level, IO access unless its a very high level API isn’t (unless we deliberately design the scope of this SPP to be very small which gets to my earlier point)

@lihaoyi

There are plenty of reasons to want something better than better files (betterer files?) but scala-native/scala-js compatibility is not one of them. I’ve reimplemented a large chunk of java.io.File in Scala.js in-memory to port some Scala-JVM code; took less than an hour to get quite good coverage, and I see no reason that java.nio would be different.

java.io.File is deliberately a high level API, java.nio is not (at least in its entirety of its design, i.e. memory mapping of files and channels). It provides very low level access to filesystem operations, and also its idea of “async” (or non blocking) is quite different to what typical non blacking actions look like in Scala.

I for example do not see how channels would work with Scala.js, and memory mapped files isn’t something thats also official supported with node.js

To be clear, if we wan’t this SPP to just be very high level without async or any other features like that, than the better abstraction would actually be Java’s original java.file and not java.nio.