perf(@angular-devkit/build-angular): enable opt-in usage of file system cache

[alan-agius4]

With this change we enable Webpack's filesystem cache, this important because terser-webpack-plugin, css-minimizer-webpack-plugin and copy-webpack-plugin all use Webpacks' caching API to avoid additional processing during the 2nd build.

This changes causes node_modules to be treated as immutable. Webpack will avoid hashing and timestamping them, assume the version is unique and will use it as a snapshot.

To opt-in using the experimental persistent build cache use theNG_PERSISTENT_BUILD_CACHE environment variable.

NG_PERSISTENT_BUILD_CACHE=1 ng serve

[splincode]

@alan-agius4 hi!, what do you think about support additional property in angularCompilerOptions?

so that caching can be easily configured

tsconfig.json

{
  "angularCompilerOptions": {
     // ...
     persistentBuildCache: true
  }
}

[alan-agius4]

Hi @splincode,

This is not really a compiler option, so angular.json would be a better place. That said, we did discuss this and for the time being we don't want to add this to the API for a number of reasons.

• Having this in an file will make it harder to opt-in/opt-out in different environments
• This is a still experimental. We want to understand the impact of this and if in v13 we should abandon, turn it on by default, or leave it as opt-in.

[AFDevMike]

Can anyone confirm this will (potentially) improve --prod / --configuration production as well?

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