Ionic library with component templateUrl not working

Issue

I've Created a Ionic 5 solution and added a Library to my multi-solution project with a component "landing", but when I try and use the templateUrl in my landing.component.ts I get

ERROR Error: Uncaught (in promise): Failed to load landing.component.html

Using template with the html works fine. Any idea why?

Doesn't work at all

 templateUrl: './landing.component.html',

Works fine

template: `
  <p>
    core-LANDING workss!
  </p>`,

I've tried using "require('./landing.component.html')" but then my library won't build with exception

The class 'LandingComponent' is listed in the declarations of the NgModule 'CoreLibModule', but is not a directive, a component, or a pipe. Either remove it from the NgModule's declarations, or add an appropriate Angular decorator.

Edit

1. Yes Landing.component.html (templateUrl:) does exist. My library does not compile if it doesn't exist.
2. Structure of solution below.

Solution

Found the issue. Man, that's 3 days down the toilet for something simple

*Do not use the ng-package.json to build your solution (ie. don't bet on npm run build work using the default ng-package.json). Add the ngPackage tag to your library package.json and include the assets you want to import. Build it using the script command to reference the library package.json file specifically. Something to do with having to load the peer dependencies to resolve the paths

Your library library package.json

{
  "$schema": "../../node_modules/ng-packagr/package.schema.json",
  "name": "core-lib",
  "version": "0.0.1",
  "ngPackage": {
    "dest": "../../dist/core-lib",
    "assets": [
      "src/lib/components/**/*.html",
      "src/lib/components/**/*.css"
    ],
    "lib": {
      "entryFile": "src/public-api.ts"
    }
  },
  "peerDependencies": {
    "@angular/common": "^10.2.4",
    "@angular/core": "^10.2.4"
  },
  "dependencies": {
    "tslib": "^2.0.0"
  }
}

Your base project package.json (add this into the scripts tag)

"build:coreLib": "ng-packagr -p projects/core-lib/package.json"

Then build your library running

npm run build:coreLib

What an undocumented headache.

Answered By - Ruan