Can't use baseUrl to have absolute imports in a library

Type of Issue

[x] Bug Report
[ ] Feature Request

Description

I generated a lib with angular-cli, the sources are directly under the src directory.

If I set the baseUrl in the tsconfig of my lib to ./src and use absolute import in my lib (e.g., import { FormatService } from 'locale/format.service'; instead of import { FormatService } from './format.service'; in a file in the locale directory), the lib build fine, but then when angular tries to use it (it is configured via the paths in tsconfig.json), it fails with the following kind of error:

ERROR in Error during template compile of 'AppModule'
  Could not resolve locale/format.service relative to /home/victor/Codebases/frontend/target/dist-lib/my-lib.d.ts. in 'LocalizationModule'
    'LocalizationModule' contains the error at ../target/dist-lib/my-lib.ts(55,20).
target/dist-lib/locale/localization.module.d.ts(2,51): error TS2307: Cannot find module 'locale/format.service'.

How To Reproduce

Simply set a baseUrl pointing to the source directory and use absolute import instead of a relative one and use the lib in another app.

Expected Behaviour

This should work.

Version Information

$ node_modules/.bin/ng-packagr --version
ng-packagr:            3.0.0
@angular/compiler:     6.0.3
rollup:                0.59.4
tsickle:               0.29.0
typescript:            2.7.2

[vvasabi]

Ng-packagr itself doesn’t do code transformation per see

Hmm… why not? I made a proof of concept (https://github.com/vvasabi/ng-packagr/commit/4a9e689224be826f872d9d1d5801fa33f46d2eed) and was able to get absolute paths working in my library. This library, which has 2 entry points, compiles successfully itself and can be consumed correctly by both an application or another library.

I made this POC because TypeScript already said that they wouldn’t fix it and users could achieve that result using a custom transformer. If ng-packagr does not do this when it reads and before it sends source code to downstream tsickle, rollup, etc., where else can the transformation be done?

Granted, my POC has hacks specifically to work around issues in tsickle and may not be suitable for inclusion into ng-packagr itself. However, I wonder if there can be a way to plug in custom code transformations, so those who need absolute paths will simply enable a plugin. (Or, maybe put the rewrite logic behind an experimental flag…)

In my case, I am consolidating common code from applications to shared libraries. Having the ability to use absolute paths, which the applications do use, will make this task a whole lot easier. After all, it makes no sense for one (good) thing to work in applications but not in libraries. (Heck, IntelliJ will even highlight long, ugly relative import paths to suggest the shorter, cleaner and sexier absolute paths!)

I will really appreciate if the ng-packagr team can reconsider supporting absolute paths in libraries!

[alan-agius4]

That is will make a library not valid as TypeScript will not rewire the paths when emitting, and thus the consumer will not be able to build when using the library and will have this issue.

See here: https://github.com/Microsoft/TypeScript/issues/9910#issuecomment-234729007

Paths mappings shouldn’t be used at a library level, at least for a library using the APF format.