New emit pipeline and API/CLI refactor

[ark120202]

• API was refactored (closes CLI/Lib Refactor #393):

  • BREAKING CHANGE: LuaTranspiler was removed
  • Added a new function transpile, that runs program.emit with custom transformers and collects emitted results
  • Added emitTranspiledFiles function, that writes results to disk. Later it would be replaced by Compilation class (New module resolution and Compilation structure #432).
  • All public transformation APIs now return ts.Diagnostic[] instead of throwing/logging/exiting (Return ts diagnostics instead of throwing errors from transformer #412 still isn't completely resolved, since for now it just catches TranspileError thrown from transformer).
  • All public APIs now are exported from package index file
  • Added 3 new high-level API functions - transpileFiles, transpileProject, and transpileVirtualProject
  • BREAKING CHANGE: Changed signature of transpileString to receive only a string and options. Old features may be done with transpileVirtualProject.
  • BREAKING CHANGE: CompilerOptions aren't case-insensitive anymore. It should be normalized before using from the API.
  • BREAKING CHANGE: CLI-related functions aren't exported anymore.

• CLI was refactored:

  • Internal structure now is more similar to tsc
  • Diagnostics are formatted like in tsc now, with a support of pretty reporter
  • Since transformation pipeline now returns diagnostics, transpilation errors are reported just like any other diagnostics. Resolves Improve error reporting #368.
  • Watch mode now supports reloading of config file
  • Running CLI without a project or files now searches for tsconfig.json (like tsc)
  • Option names in CLI are case-insensitive now
  • Root-level options are deprecated
  • BREAKING CHANGE: Boolean options as strings ("true" and "false") are no longer allowed
  • BREAKING CHANGE: Unknown options in tstl config object are considered as errors now

• Added support for some emit-related flags:

  • declaration
  • declarationMap
  • emitDeclarationOnly
  • noEmit
  • noEmitOnError (it's not default anymore)

[lolleko]

Is there no way to retrieve the transpiled AST anymore?
Also would be nice to know if this can run in a browser.

This is relevant for the website.

[ark120202]

Ah, so that's where it was used.
I don't really like exposing ast as a part of TranspiledFile interface, as it's an implementation detail, but I guess it's okay if there are use cases.

transpile doesn't use any node-specific API so it should work fine.
emitTranspiledFiles probably would would work, but it won't after module resolution would be implemented. Though it's not relevant for single-file use case anyway.