[Spike] How to migrate Angular 1.x and 2+ LB3 client

[dhmlau]

Originated from epic: #3954

A spike on migrating Angular 1.x and 2+ LB3 client.

Acceptance Criteria

• Find out whether OpenAPI generator a good solution
  • If yes, how to migrate?
  • If no, what would be our recommended solution in the context of migration guide?
• Expected outcome:
  • our recommended approach and description on how to do it.
  • create a follow up task, if needed, to add the instruction as part of the migration guide

[derdeka]

@dhmlau I did POCs for OpenAPI generator and ng-openapi-gen in the last weeks and can share some stuff. Both of them have their upsides and downsides, but are very different to loopback-sdk-builder. My hope was to find a kind of drop-in-replacement for loopback-sdk-builder to limit the required refactorings to my frontend application to a minimum in the first step, but both of them need big changes.

How do you want to run the spike? I suggest to create two alternative frontends for loopback4-example-shopping to test both sdks. How to start?

[dhmlau]

@derdeka, it would be great if you could share the information between OpenAPI generator and ng-openapi-gen. Thanks!

I just discussed with @bajtos, it might be good to:

• take the CoffeeShop application as the starting point - it's a smaller app than the shopping app
• generate the client using LB3 SDK client and OpenAPI generator (or ng-openapi-gen).
• compare the differences
  WDYT?

Also, we're not sure if we should only investigate the Angular 2+ client route, perhaps there are much fewer users on Angular 1.x?

[derdeka]

• take the CoffeeShop application as the starting point - it's a smaller app than the shopping app

@dhmlau AFAIK there is no coffeeshop app written in lb4 yet. Correct?