perf(util): load npm config lazily (#42458)

packages/util/src/npm-config.ts

@@ -1,15 +1,16 @@
 export * as NpmConfig from "./npm-config.js"
 
 import { fileURLToPath } from "url"
-// @ts-expect-error npm does not publish types for this internal config API.
-import Config from "@npmcli/config"
-// @ts-expect-error npm does not publish types for this internal config API.
-import { definitions, flatten, nerfDarts, shorthands } from "@npmcli/config/lib/definitions/index.js"
 import { Effect } from "effect"
 
 export const load = (dir: string) =>
   Effect.tryPromise({
     try: async () => {
+      // @ts-expect-error npm does not publish types for this internal config API.
+      const { default: Config } = await import("@npmcli/config")
+      // @ts-expect-error npm does not publish types for this internal config API.
+      const { default: npmDefinitions } = await import("@npmcli/config/lib/definitions/index.js")
+      const { definitions, flatten, nerfDarts, shorthands } = npmDefinitions
       const config = new Config({
         // Resolved per call: on workerd import.meta.url is undefined and building
         // this URL at module scope fails startup validation; npm config never runs there.

packages/workerd-spike/vitest.config.ts

@@ -51,10 +51,8 @@ export default defineWorkersConfig({
       // mime-types requires mime-db's JSON database at require time; keep the
       // lookup surface but back it with a static shim.
       { find: /^mime-types$/, replacement: new URL("./test/shims/mime-types.mjs", import.meta.url).pathname },
-      // util/npm.ts imports the npm toolchain at module scope; plugin installs
-      // never happen in the workerd profile (plugin discovery is precompiled-only),
-      // and @npmcli/config touches process.stdout.isTTY during module init.
-      { find: /^@npmcli\/config(\/.*)?$/, replacement: mockProxy },
+      // Plugin installs never happen in the workerd profile (plugin discovery
+      // is precompiled-only), so mock the package installation toolchain.
       { find: /^@npmcli\/arborist(\/.*)?$/, replacement: mockProxy },
       { find: /^pacote(\/.*)?$/, replacement: mockProxy },
     ],