[Enhancement] Support TS for indexTransform

packages/custom-webpack/README.md

@@ -362,7 +362,7 @@ module.exports = async config => {
 **_Requires `@angular-devkit/[email protected]` and `@angular-builders/[email protected]`._**
 
 Since Angular 8 `index.html` is not generated as part of the Webpack build. If you want to modify your `index.html` you should use `indexTransform` option.  
-`indexTransform` is a path (relative to workspace root) to a `.js` file that exports transformation function for `index.html`.  
+`indexTransform` is a path (relative to workspace root) to a `.js` or `.ts` file that exports transformation function for `index.html`.  
 Function signature is as following:
 
 ```typescript

packages/custom-webpack/src/common.ts

@@ -23,6 +23,14 @@ export const indexHtmlTransformFactory: (
   context: BuilderContext
 ) => IndexHtmlTransform = ({ indexTransform }, { workspaceRoot, target }) => {
   if (!indexTransform) return null;
+  if (indexTransform.endsWith('.ts')) {
+    // Register TS compiler lazily
+    require('ts-node').register({
+      compilerOptions: {
+        module: 'commonjs',
+      },
+    });
+  }
   const transform = require(`${getSystemPath(normalize(workspaceRoot))}/${indexTransform}`);
   return async (indexHtml: string) => transform(target, indexHtml);
 };