run ngcc when using ng test to run test with ivy

Describe the solution you’d like When running ng test with

"test": {
          "builder": "@angular-builders/jest:run",
          "options": {
          }

inside angular.json, it should run ngcc beforehand as angular-cli already does (see: https://github.com/angular/angular-cli/pull/15044#issue-296489062). Otherwise, tests are not running with ivy, which should be the default for angular 9. As this might break existing tests, an options flag like "enableIvy": false could still be added in order to run them the old way. Or just use the configuration that’s already existing in tsconfig.spec.ts which usually points to tsconfig.ts that has "enableIvy": false already defined.

Describe alternatives you’ve considered The only way I could make it work is by defining a scripts inside package.json.

{
  "scripts": {
    "test": "ngcc && ng test"
  }
}

and then execute it with npm run test. It would still be great to just run it with ng test

[just-jeb]

Here are my findings:

• ngcc transforms libraries, typically node_modules (js files and dts), to make them Ivy compatible. It is necessary, especially if you want to have meaningful error messages when your test fails.
• For node_modules it’s enough to run ngcc only once, for example in postinstall hook to ensure compatibility.
• There is a very specific use case when you need to run ngcc on modules other than node_modules - when you have a monorepo with libraries and you reference the production bundles of these libraries (dist folders) from your app’s tsconfig.
• Angular CLI commands (build, serve, karma) use ngtools/webpack and as part of Webpack compilation they run ngcc_processor on each non-relative module, which essentially handles the case of monorepo with libraries. It also eliminates the need to run ngcc for the whole node_modules and only runs it for the files that are part of the compilation.

Conclusion: Running ngcc as a postinstall hook might be a viable workaround for 95% of projects, so we have to include it in the documentation and the migration guide.
However, the only solution that will handle all the use cases properly is adding a custom Jest transformer that will apply ngcc_processor from ngtools/webpack to all the non-relative modules similarly to Angular CLI.
I seriously doubt though that this transformer should be implemented here and not in jest-preset-angular.

[just-jeb]

Unfortunately, currently this is the only way. A few things you can do:

1. Cache node_modules on CI workers
2. Identify the modules that require ngcc run and run it on them specifically (instead of the whole node_modules folder).
3. Watch this issue to see whether there will be some solution. Here is some more info.