Recently, I have been motivated to upgrade the currently application I am writing from Angular 5 to Angular 6. Since there was going to be a rewrite of the application any way, I thought this is a good opportunity to upgrade.
First error: #
in tsconfig.json, only include '.ts' as resolve.extension. as a result, rxjs kept on throwing error during bundling
ERROR in ./node_modules/rxjs/_esm5/index.js Module not found: Error: Can't resolve './internal/util/pipe' in '/PATH-TO-PROJECT/node_modules/rxjs/_esm5'
Second error: #
I changed the target from es5 to es2015 in lieu for supporting angular elements. But the bundler throws error on failing to find module @angular/core. changing target back to es5 circumvents the problem. Turns out, with the increased support for dynamic import, one will need to specify moduleResolution as node in tsconfig.json to explicitly tell the typescript compiler that imports are node modules.