feat: add user-specified registry support (from npmrc)

src/commands/module/add.ts

@@ -1,3 +1,7 @@
+import * as fs from 'node:fs'
+import { homedir } from 'node:os'
+import { join } from 'node:path'
+import type { FileHandle } from 'node:fs/promises'
 import { defineCommand } from 'citty'
 import { resolve } from 'pathe'
 import consola from 'consola'
@@ -216,9 +220,8 @@ async function resolveModule(
 
   // Fetch package on npm
   pkgVersion = pkgVersion || 'latest'
-  const pkg = await $fetch(
-    `https://registry.npmjs.org/${pkgName}/${pkgVersion}`,
-  )
+  const registry = await detectNpmRegistry()
+  const pkg = await $fetch(`${registry}/${pkgName}/${pkgVersion}`)
   const pkgDependencies = Object.assign(
     pkg.dependencies || {},
     pkg.devDependencies || {},
@@ -248,3 +251,39 @@ async function resolveModule(
     pkgVersion,
   }
 }
+
+async function detectNpmRegistry() {
+  if (process.env.COREPACK_NPM_REGISTRY) {
+    return process.env.COREPACK_NPM_REGISTRY
+  }
+  const userNpmrcPath = join(homedir(), '.npmrc')
+  const cwdNpmrcPath = join(process.cwd(), '.npmrc')
+  const registry = await getRegistryFromFile([cwdNpmrcPath, userNpmrcPath])
+  if (registry) {
+    process.env.COREPACK_NPM_REGISTRY = registry
+  }
+  return registry || 'https://registry.npmjs.org'
+}
+
+async function getRegistryFromFile(paths: string[]) {
+  for (const npmrcPath of paths) {
+    let fd: FileHandle | undefined
+    try {
+      fd = await fs.promises.open(npmrcPath, 'r')
+      if (await fd.stat().then(r => r.isFile())) {
+        const npmrcContent = await fd.readFile('utf-8')
+        const registryMatch = npmrcContent.match(/registry=(.*)/)
+        if (registryMatch) {
+          return registryMatch[1].trim()
+        }
+      }
+    }
+    catch {
+    // swallow errors as file does not exist
+    }
+    finally {
+      await fd?.close()
+    }
+  }
+  return null
+}