custom-webpack:server errors with Cannot read properties of undefined (reading 'colors')

Describe the Bug

When using the @angular-builders/custom-webpack:server builder, it is erroring with the following error.

TypeError: Cannot read properties of undefined (reading 'colors')
    at statsToString (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-angular/src/webpack/utils/stats.js:193:32)
    at webpackStatsLogger (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-angular/src/webpack/utils/stats.js:374:17)
    at MergeMapSubscriber.project (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-angular/src/builders/server/index.js:93:44)
    at MergeMapSubscriber._tryNext (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-angular/node_modules/rxjs/internal/operators/mergeMap.js:67:27)
    at MergeMapSubscriber._next (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-angular/node_modules/rxjs/internal/operators/mergeMap.js:57:18)
    at MergeMapSubscriber.Subscriber.next (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-angular/node_modules/rxjs/internal/Subscriber.js:66:18)
    at SafeSubscriber.__tryOrUnsub (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/node_modules/rxjs/internal/Subscriber.js:205:16)
    at SafeSubscriber.next (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/node_modules/rxjs/internal/Subscriber.js:143:22)
    at Subscriber._next (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/node_modules/rxjs/internal/Subscriber.js:89:26)
    at Subscriber.next (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/node_modules/rxjs/internal/Subscriber.js:66:18)
    at SwitchMapSubscriber.notifyNext (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/node_modules/rxjs/internal/operators/switchMap.js:85:26)
    at SimpleInnerSubscriber._next (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/node_modules/rxjs/internal/innerSubscribe.js:27:21)
    at SimpleInnerSubscriber.Subscriber.next (/Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/node_modules/rxjs/internal/Subscriber.js:66:18)
    at /Users/zach.morgan/Development/mfe-universal/node_modules/@angular-devkit/build-webpack/src/webpack/index.js:58:25
    at /Users/zach.morgan/Development/mfe-universal/node_modules/webpack/lib/HookWebpackError.js:68:3
    at Hook.eval [as callAsync] (eval at create (/Users/zach.morgan/Development/mfe-universal/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:6:1)

If I dont specify a customWebpackConfig, it works fine. However, as soon as I specify one, it errors. Even if the custom webpack config is essentially empty.

Minimal Reproduction

I kept the original server target and created a server-custom target for the repro.

https://github.com/sir-captainmorgan21/angular-builders-custom-webpack-sever-repro

Expected Behavior

I’d expect this to run without errors.

Environment

Libs
- @angular/core version: ~14.2.0
- @angular-devkit/build-angular version: ~14.2.0
- @angular-builders/custom-webpack version: ^14.0.1

[arturovt]

It merges when it exports an object, but it doesn’t merge when it exports a factory function:

If customWebpackConfig.path file exports a function, the behaviour of the builder changes : no more automatic merge is applied, instead the function is called with the base Webpack configuration and must return the new configuration.

[sir-captainmorgan21]

@just-jeb that was it. Thanks! I actually re-read through your docs, and was able to find that. May be a good place for a trouble shooting section though.