feat(@schematics/angular): add configuration files generation schematic

[alan-agius4]

This commits add a schematic to generate Karma and Browserlist files which since version 15 are no longer generated by default. This schematic should be used to generate these files when further customisation is needed.

Usage

ng generate config karma
ng generate config browserlist

Closes #24294

[nicojs]

As far as I can see, this doesn't close #24294. Tools like the IntelliJ karma plugin and StrykerJS are still unable to auto-discover the config. 🤷‍♀️

[alan-agius4]

As far as I can see, this doesn't close #24294. Tools like the IntelliJ karma plugin and StrykerJS are still unable to auto-discover the config. 🤷‍♀️

How would these plugins auto discover the config if present in node_modules? You would still need to create a karma.conf.js in the project.

[nicojs]

With my change, a tool could use require('@angular-devkit/build-angular/src/builders/karma/karma.conf.js') to import the karma config and use that to configure karma from their own config file.

[nicojs]

Could we at least export a factory method for configuring karma?

[alan-agius4]

Could we at least export a factory method for configuring karma?

You can use the builder API to transform the built in option

angular-cli/packages/angular_devkit/build_angular/src/builders/karma/index.ts

Line 78 in fbfbca5

karmaOptions?: (options: KarmaConfigOptions) => KarmaConfigOptions;

A karma config on its own without the builder is not that useful as karma requires the output of the webpack builder which is done when running ng test in addition some of the karma plugins requires to run with an Angular CLI context.

[nicojs]

Ah, I understand the confusion. Please let me elaborate.

StrykerJS (and the IntelliJ plugin) discover whether the current project is an Angular or a regular Karma project. If it is an Angular project, it uses ng test --karma-config=/path/to/stryker/karma.conf.js to start karma. This makes sure that webpack and such are correctly started.

The karma config file ("/path/to/stryker/karma.conf.js") provided is a custom karma config file crafted in StrykerJS. From that config file, we load your local karma.conf.js. Since Angular 15, this file is no longer generated; thus, we need a new way to load the angular karma config. I was hoping something like this: #24458 (comment)

This is the part of the StrykerJS code that uses ng test:
https://github.com/stryker-mutator/stryker-js/blob/8bf885f490de6625466a011dc79cf04d53aeb698/packages/karma-runner/src/starters/angular-starter.ts#L30-L51

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