module_resolution=none or =explicit

Discussed in-person with @DanielRosenwasser

In google we have performance issues with tsc and with editor plugins. We have tracked this down to the node moduleResolutionKind looking in many locations on a network-mounted disk.

We don't actually want the node moduleResolution, we only want the baseUrl/paths/rootDirs feature known as "path mapping". Put another way, we explicitly list locations for all inputs, and we never want the compiler to stat a file outside of the explicit input locations.

For tsc, we provide a custom CompilerHost that avoids touching the disk, we implement fileExists and directoryExists purely by consulting our file manifest. However, we can't do this trick for editors, which are becoming increasingly unusable.

As an example, we provide interop with Closure Compiler code that declares goog.module, by naming these goog:some.module. This results in the language services looking for a file like goog:some.module.d.ts all over the network-mounted filesystem, even though a later sourceFile in the program has declare module 'goog:some.module'

cc @vikerman @rkirov

Comienza con el comportamiento de resolución de módulos de tsc y los servicios de lenguaje utilizados por los plugins del editor. Revisa cómo se consultan CompilerHost fileExists y directoryExists durante la búsqueda de módulos y, después, define qué debería hacer un modo de resolución de módulos explícito o deshabilitado con baseUrl, paths, rootDirs y los módulos declarados. Se considera terminado cuando las búsquedas evitan ubicaciones fuera de las entradas explícitas sin romper el mapeo de rutas.