All TypeScript files have been updated to pass the new eslint-based linting checks. eslint compatible disabling comments have also been added in place of the previous tslint comments.
Library code inside fesm2015/esm2015/_esm2015 directories has been downlevelled to ES2015 which will not have native async/await. As a result, code from those directories can be skipped from the additional checks as well as the downlevel processing. RxJS uses the `_esm2015` directory naming convention.
With this change we configure `webpack-dev-middleware` and `webpack-dev-server` to print errors to the console, which previously were not displayed. This is because both of these libraries log/emit errors using the logger and the compilation API.
Certain errors such as the one below, were being swallowed during `ng serve`.
```
An unhandled exception occurred: Prevent writing to file that only differs in casing or query string from already written file.
This will lead to a race-condition and corrupted files on case-insensitive file systems.
/home/circleci/ng/aio/dist/generated/docs/api/router/Routes.json
/home/circleci/ng/aio/dist/generated/docs/api/router/ROUTES.json
```
Tailwind now suppports an environment variable named `TAILWIND_MODE` with possible values of `build` and `watch`. If the variable has not been set, the tooling will now set the variable based on the builder's `watch` option.
The current stable version of `webpack-dev-server` does not fully handle Webpack 5's configuration options. In this case, the `target` option can now be an array. However, the array form is ignored by the dev server which can cause the live reload client code to not be included in the output bundles. To remedy this, the `injectClient` option is used when live reload is enabled which forces the client code to be included regardless of the `target` option.
The GC caching mode will remove any unused cache entries after each rebuild. This prevents old modules from being retained indefinitely during long-lived development sessions.
The Webpack 5 automatic public path support can cause an incorrect public path to be used to load assets and lazy loaded routes. The current logic relies on the last script element found at runtime in the application's index HTML which may not be related to the application scripts. Now if a `deployUrl` is not specified, the Webpack `publicPath` option is defaulted to an empty string which provides equivalent behavior to Webpack 4.
In Webpack 5, the Webpack callback must be used when Webpack is running in watch mode.
Related warning
```
.(node:6565) [DEP_WEBPACK_WATCH_WITHOUT_CALLBACK] DeprecationWarning: A 'callback' argument need to be provided to the 'webpack(options, callback)' function when the 'watch' option is set. There is no way to handle the 'watch' option without a callback.
```
Webpack 5 now uses a `chunkHash` hook that is accessible from `JavascriptModulesPlugin.getCompilationHooks()`. The `hashForChunk` hooks have been deprecated in Webpack 5.
TypeScript files had the potential to be processed twice by the build optimizer. This did not affect the output code but could lead to longer production build times. The build optimizer is now configured in one centralized location for both TypeScript and JavaScript files. The Webpack configuration partial for TypeScript support is also reduced to one common function for both AOT and JIT as a result.
