feat(core): use corepack to infer package manager

packages/cli/src/utils/commands.ts

@@ -1,13 +1,48 @@
-import { spawnSync } from 'node:child_process'
+import { existsSync, readFileSync } from 'node:fs'
+import path from 'node:path'
+
+const DEFAULT_PACKAGE_MANAGER = 'yarn'
+
+const supportedPackageManagers = {
+  yarn: true,
+  pnpm: true,
+  bun: true,
+  npm: true,
+}
 
 // Retrieves the package manager based on the developer lockfile, using `ni`.
 export function getPreferredPackageManager() {
-  const agent = spawnSync('na', ['?'], {
-    encoding: 'utf8',
-    shell: true,
-  }).stdout.trim()
+  const packageJsonPath = path.resolve(process.cwd(), 'package.json')
+
+  if (!existsSync(packageJsonPath)) {
+    console.warn(
+      `package.json not found! Using default package manager: ${DEFAULT_PACKAGE_MANAGER}.`
+    )
+    return DEFAULT_PACKAGE_MANAGER // TODO threat errors
+  }
+
+  const fileContent = readFileSync(packageJsonPath)
+  const { packageManager } = JSON.parse(fileContent.toString())
+
+  if (!packageManager) {
+    console.warn(
+      `Corepack not enabled! Using default package manager: ${DEFAULT_PACKAGE_MANAGER}.`
+    )
+    return DEFAULT_PACKAGE_MANAGER // corepack not enabled
+  }
+
+  const [packageManagerName] = packageManager.split('@')
 
-  if (agent === '') return 'yarn' // Default to Yarn
+  if (
+    !supportedPackageManagers[
+      packageManagerName as keyof typeof supportedPackageManagers
+    ]
+  ) {
+    console.warn(
+      `${packageManagerName} is not supported: Use one of ${Object.keys(supportedPackageManagers).join(',')}.`
+    )
+    return DEFAULT_PACKAGE_MANAGER // TODO threat errors
+  }
 
-  return agent
+  return packageManagerName
 }