Provide definition maps during application development

[tobi-or-not-tobi]

Customers who use Spartacus (libraries) might have a disadvantage of not having sources available during development. We like to make the Spartacus sources available in the customers IDE to improve the developer experience.

The typescript compiler made an option available to generate declaration maps (--declarationMap), which is solving this problem:

hitting go-to-definition on a declaration from a .d.ts file generated with --declarationMap will take you to the source file (.ts) location where that declaration was defined, and not to the .d.ts.
(https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-9.html#new---declarationmap)

These map files should be generated and published in as part of the Spartacus packages.

I've done a quick test on this, and so far I've not been able to generate the declaration maps. We're getting complains when specifying the declarationMap in the tsconfig about missing declaration or composite. If we try to set these flags, we're getting into other issues. Long story short, we need a dev who can investigate.

[tobi-or-not-tobi]

Issue logged at ng-packagr/ng-packagr#1464

[tobi-or-not-tobi]

The ng-packagr issue has been closed with release 10.0.0-rc.2. We need to confirm if this enables declaration maps for Spartacus libs.

@dunqan would you mind checking if we already can enable this? i'm not sure if it can be used as the ng-packagr lib is not made final yet. There's a angular-cli ticket as well though.