[CLI] Generating index.ts in each models/repositories/controllers automatically

[dhmlau]

Description / Steps to reproduce / Feature proposal

In an LB4 app (e.g. in example-getting-started example), it seems like the general pattern is to have the export statements in the index.ts file in each folders (models/repositories/controllers), so that the classes in those folders can simply be imported by
import {SomeClass} from "../models";

Acceptance Criteria

I wonder if this is a good idea to:

• generate those index.ts automatically as part of lb4 app command
• for any artifacts created by CLI (currently we only have lb4 controller), add the export in index.ts
  e.g. export * from './someclass.repository';

[virkt25]

Do we still want this with pattern with @loopback/boot in place which can just discover and bind the classes.

That said someone might still want to import a class for type information

[shimks]

I'd say we still want this so that users can easily import them to unit/integration test. That being said, I'm not sure if this is something we NEED to have.

[dhmlau]

Currently if I want to reference some model in models folder in a controller, i think we still need to import it even with boot. right?
IMO, it's just nice-to-have, because when I was creating my own app, I had to create the index.ts for each folder. It would be nice if the tooling can do it for me. But we don't have the generator for models and repositories (which might have bigger need).

[virkt25]

If we are generating the artifacts, this part should be easy. +1 for it.

[raymondfeng]

The complexity comes into play when we add the 2nd controller. To maintain controllers/index.ts, the cli needs to know to how to add new entries to the existing index.ts.

[shimks]

That sounds easy enough for me; check the content of index.ts if it exists. If the import is already there, leave it alone. If it isn't, then add it.

[dhmlau]

i thought we are going to have a separate export statement for each class? then if it exists, then we have to append from what's existing.

export * from './test1.controller';
export * from './test2.controller';

[virkt25]

Well, when a new artifact is generated using lb4 it should generate a index.ts in the artifact folder if not present and if present, it should append the new file as an import.

[dhmlau]

Discussed with @bajtos , what's in scope for DP3 is to decide as a team on what to do with this.

[virkt25]

This isn't anything particularly difficult about implementing this IMO. Here's some modules we can leverage to accomplish this task:

• https://www.npmjs.com/package/make-index
• https://www.npmjs.com/package/ts-indexer
• https://www.npmjs.com/package/create-ts-index

[bajtos]

@virkt25 nice! I'd rather avoid using modules in 0.x version, that leaves only one candidate: https://www.npmjs.com/package/create-ts-index

Originally, I was thinking about editing index.ts files manually in our lb4 CLI. If create-ts-index works well enough, then I am all for using it.

[bajtos]

Assigned to @virkt25, looks like he is already working on something related in #1363