[Vite] When NX target is build, build libs from dist folder instead of from source

[tpucci]

Context

A Monorepo with vite buildable libs.

Goal

When building (target === 'build') a vite application, use NX dependency graph to use buildable libs dist output instead of building from source (current default).

Consequences

With tens of libs, the application build time could benefit from previous built tasks (which are cached). Currently, those dependencies are built but are not used by the application build target.

Explanation

When using NX to generate a vite lib, the generated vite.config.ts file includes this plugin:

nxViteTsPaths()

Without any option, this plugin builds libs from source.
More over, there is a bug with tsconfig-paths which looks for an export field in package.json. However the default generated package.json does not include an export field:

{
  "name": "@org/lib",
  "version": "0.0.1",
  "private": true,
  "type": "module",
  "main": "./index.js",
  "types": "./index.d.ts",
  "dependencies": {}
}

I think a better vite.config.ts generated default would be this instead:

    nxViteTsPaths({
      mainFields: ["module", "main"],
	// 👇 Uses the NX dependency graph 🎉
      buildLibsFromSource: process.env.NX_TASK_TARGET_TARGET !== "build",
    }),

Or, option B, we could change the plugin:

export function nxViteTsPaths(options: nxViteTsPathsOptions = {}) {
...

-  options.mainFields ??= [['exports', '.', 'import'], 'module', 'main'];
+  options.mainFields ??= ['module', 'main'];

-  options.buildLibsFromSource ??= true;
+  options.buildLibsFromSource ??= (process.env.NX_TASK_TARGET_TARGET !== "build");

...