ES2015 problem since Angular 8

Type of Issue

[x] Bug Report
[ ] Feature Request

Description

I have upgraded my apps to Angular 8, but if I use es2015 as target in tsconfig.json and use a browser with es2015 support, then the lib is not working correctly (see How to reproduce).

How To Reproduce

Take a look at my repo: https://github.com/paulstelzer/ngxs-issue

There are two branches: master and language. The difference between the two: Inside language branch, the source code is directly in the app. In master I am using the lib created with ng-packagr.

If you now build the repo with production (ng build --prod) a ES5 and ES2015 files will be created (the default since Angular 8).

If you now run the master branch (which is using the lib created with ng-packagr) and ES2015 the lib isn’t working anymore. You can see it because the log “LANGUAGE checkLanguage” will not be shown in console. If you remove the es2015 part from index.html, the app is working again.

If you use the language branch (without a lib built with ng-packagr), ES2015 is working.

If you only build ES5, also the master branch with the lib built with ng-packagr will work.

For me it seems that ng-packagr made somehting that it’s not working in ES2015

Expected Behaviour

Lib should work with ES2015 builded application

Version Information

$ node_modules/.bin/ng-packagr --version
ng-packagr:            5.2.0
@angular/compiler:     8.0.0
rollup:                1.12.5
tsickle:               0.35.0
typescript:            3.4.5
node: 10.12.0
npm: 6.9.0

[alan-agius4]

@DenisSemionov, the issue is within build-optimizer. See: https://github.com/angular/angular-cli/issues/14613#issuecomment-498960867

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