Using input/output facade

[SparshithNR]

Using input/output facade inside the broccoli-persistent filter.

[stefanpenner]

Although functionally correct, this fallback should most likely be removed. Under what circumstances should we allow native fs to be used now?

My feeling is that, allowing for this fallback may hide bugs. Specifically bugs where some future PR accidentally causes options.fs to be falsy causing an erroneous fallback to fs. The resulting issues would likely be hard to diagnose.

Since this is an internal private object, I would prefer if we make it exactly what we need, and make options.fs mandatory, with no graceful fallback

[SparshithNR]

This was done to provide backward compatibility for those who extended the Filter class.

[SparshithNR]

I am not sure if there is a real use case for this.
an example will be

class awk extends Filter {
build () {
// we can won't break this implementation.
let srcDir = this.inputPaths[0];
 this.dependencies = this.processor.initialDependencies(srcDir);
 // .... do build related stuffs.
}
processString(content) {
 return content;
}
}

The current implementation need to make a slight change where I assume srcDirs in new Dependency(srcDirs) always receives array, I have to make a change to convert if the argument is not an array change to an array.

[stefanpenner]

@SparshithNR that would suggest to me, that we have just changed the signature of initializeDependencies in a breaking way, that is unexpected. Users having to remember to pass this.input if they invoke the initialDependencies stuff seems very unfortunate.

Can we pass the needed details to the processor when it is initialized? That would ensure no breaking changes occurs.

[SparshithNR]

Unfortunately no, we cannot pass it while initializing the processor. The processor gets initialized at the constructor and this.input is accessible only at the build time.

[SparshithNR]

Closing this as #191 addressed this.