Usage With Angular

Because Angular CLI does not support custom TypeScript transformers/plugins (there is still an open feature request, more than 4 years), custom transformers must be configured manually by tampering with the Webpack configuration file.

For this purpose the ng-custom-transformers package was created which simplifies the usage.

Because this solution is not "native" there can be some problems with some Angular's utilities, eg. packgr.

1. Install packages,

npm i tst-reflect && npm i tst-reflect-transformer -D

2. add transformer to tsconfig.json,

{
    "compilerOptions": {
        // your options...

        // ADD THIS!
        "plugins": [
            {
                "transform": "tst-reflect-transformer"
            }
        ]
    }
}

3. npm i ng-custom-transformers -D,
4. continue by A or B.

A. @angular-builders/custom-webpack

5. npm i @angular-builders/custom-webpack -D,
6. create file mod.webpack.config.js,

const {AngularCustomTransformers} = require("ng-custom-transformers");

module.exports = (config, options, targetOptions) => {
    // Your transformations of "config" ....

    // And the important part here: modifyConfig()
    return AngularCustomTransformers.modifyConfig(config);
};

7. modify angular.json,

{
    "architect": {
        // ...
        "build": {
            "builder": "@angular-builders/custom-webpack:browser",
            // use @angular-builders/custom-webpack builder
            "options": {
                "customWebpackConfig": {
                    "path": "./mod.webpack.config.js"
                }
                // ...
            }
        },
        "serve": {
            "builder": "@angular-builders/custom-webpack:dev-server",
            // use @angular-builders/custom-webpack builder
            // ...
        },
    }
}

8. ng build or ng serve done.

B. ngx-build-plus

5. ng add ngx-build-plus
6. ng build --plugin ng-custom-transformers or ng serve --plugin ng-custom-transformers

ngx-build-plus overrides angular.json automatically.

Demo

Demo project on StackBlitz here.