WIP: Recompile Less when dependent files (@imports) change

[mnquintana]

⚠️ Work in progress ⚠️

Part of https://github.com/electron/electron-compile/issues/27

This PR implements determineDependentFiles for Less, which should give electron-compile everything it needs to know to properly recompile a Less file's dependencies. ✨

TODO

• [ ] Figure out how best to express the dependency between compile and determineDependentFiles (ie. determineDependentFiles must be called before compile)
  • Right now it's handled in CompilerHost, BUT it's possible for a compiler to require other compilers directly, like InlineHtml does, in which case we currently have to duplicate the logic
  • Maybe CompilerBase should call determineDependentFiles in its base compile methods, and then we just call the superclass methods from the subclasses? I dunno
• [ ] Figure out how error handling should work
  • Right now I'm just passing errors along in the compilerContext from determineDependentFiles and throwing them on compile, but I dunno how I feel about that 😕

[anaisbetts]

Figure out how best to express the dependency between compile and determineDependentFiles (ie. determineDependentFiles must be called before compile)

The order methods are called during compilation are guaranteed by electron-compile, you don't have to worry about compile being called before determineDependentFiles

[mnquintana]

@paulcbetts Not in this second case:

Right now it's handled in CompilerHost, BUT it's possible for a compiler to require other compilers directly, like InlineHtml does, in which case we currently have to duplicate the logic

[anaisbetts]

✨