update README

README.md

@@ -1,27 +1,28 @@
-# AngularSvgSpriteLoaderBug
+# angular-svg-sprite-issue
 
-This project was generated with [Angular CLI](https://github.com/angular/angular-cli) version 8.3.17.
+This project reproduces a bug with [svg-sprite-loader](https://github.com/kisenka/svg-sprite-loader) in extract mode when integrating with [Angular CLI](https://github.com/angular/angular-cli).
 
-## Development server
+## Background to the integration
 
-Run `ng serve` for a dev server. Navigate to `http://localhost:4200/`. The app will automatically reload if you change any of the source files.
+Angular CLI uses internally [webpack](https://github.com/webpack/webpack) to build an Angular app and handles in general the whole webpack configuration for you. But it also provides an extension point - called [Builders](https://angular.io/guide/cli-builder). With the builder [@angular-builders/custom-webpack](https://www.npmjs.com/package/@angular-builders/custom-webpack) you get access to the webpack configuration that was created by Angular CLI and you can adjust it to your needs. At this point you can integrate the svg-sprite-loader how it is shown by this minimal repository.
 
-## Code scaffolding
+## The issue
 
-Run `ng generate component component-name` to generate a new component. You can also use `ng generate directive|pipe|service|class|guard|interface|enum|module`.
+In development everthing works as expected, but when you build for production the following error is thrown:
+```
+angular-svg-sprite-issue\node_modules\@angular-devkit\build-webpack\src\utils.js:17
+                id: chunk.id.toString(),
+                             ^
 
-## Build
+TypeError: Cannot read property 'toString' of null
+```
+Although the error is thrown in the package [@angular-devkit/build-webpack](https://www.npmjs.com/package/@angular-devkit/build-webpack) the root cause lies in the plug-in of svg-sprite-loader. In the plug-in a new chunk for the SVG sprite is added to the webpack compilation without setting its `id` ([see code](https://github.com/kisenka/svg-sprite-loader/blob/85f07caed508403ab259b5b13eabc97704e0261b/lib/plugin.js#L165-L179)).
 
-Run `ng build` to build the project. The build artifacts will be stored in the `dist/` directory. Use the `--prod` flag for a production build.
+## Reproduction steps
 
-## Running unit tests
+1. `npm install`
+2. `npm run build`
 
-Run `ng test` to execute the unit tests via [Karma](https://karma-runner.github.io).
+## Debugging with VS Code
 
-## Running end-to-end tests
-
-Run `ng e2e` to execute the end-to-end tests via [Protractor](http://www.protractortest.org/).
-
-## Further help
-
-To get more help on the Angular CLI use `ng help` or go check out the [Angular CLI README](https://github.com/angular/angular-cli/blob/master/README.md).
+In the repository a debug configuration "ng build --prod" is included to debug the compilation process with VS Code.