[service] Use service to discover and parse tsconfig and discover matched source files

[cspotcode]

This is a situation I've encountered that actually has an easy workaround, but I thought I'd share it in case anyone else is trying to do the same.

Use-case

I want to discover the tsconfig for a directory, get the parsed compiler options, and get a list of source files.

Right now, the API leads one to believe that they must know the name of a source file first, rather than discovering the source files from the tsconfig.

Workaround

Try to parse a .ts file that you know does not exist. This will trigger tsconfig discovery and the creation of a language service.

import { TypeScriptService } from '@ts-tools/service';
const service = new TypeScriptService();
service.transpileFile('DOES NOT EXIST.ts', {
  tsconfigFileName : 'tsconfig.json',
  getCompilerOptions = (baseHost, tsconfigOptions) =>tsconfigOptions
});
const runningService = service.runningServices.get('tsconfig.json')!;
// Grab parsed compilerOptions
console.dir(runningService.languageService.getProgram()!.getCompilerOptions());
// Grab parsed set of source files
console.dir(runningService.rootFileNames);

[AviVahl]

The service provides on-demand transpilation capabilities. Meaning, upon needing to transpile some .ts/x file, it will do the necessary work.

Loading config explicitly can be easier using createBaseHost yourself (also exported from the package) and parsing the config using typescript. I did something similar in @ts-tools/build: https://github.com/AviVahl/ts-tools/blob/%40ts-tools/build%400.1.8/packages/build/src/build.ts#L63

I may provide a config loading API as a warmup for the service. Could save config lookup work for the files already included in the pre-loaded config.

[AviVahl]

check out the new APIs in the upcoming service@2.0.0.