docs: bump action-setup version in README

* Throw error when multiple versions specified

* fix: fmt

* fix: fmt

* Swallow error on ENOENT

* Match versions

* refactor: install pnpm

---------

Co-authored-by: Khải <hvksmr1996@gmail.com>
Co-authored-by: Zoltan Kochan <z@kochan.io>

README.md

@@ -72,7 +72,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         with:
           version: 8
 ```
@@ -91,7 +91,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         with:
           version: 8
           run_install: |
@@ -120,7 +120,7 @@ jobs:
         with:
           node-version: 20
 
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         name: Install pnpm
         with:
           version: 8

src/install-pnpm/run.ts

@@ -1,8 +1,10 @@
 import { addPath, exportVariable } from '@actions/core'
 import { spawn } from 'child_process'
-import { rm, writeFile, readFile, mkdir } from 'fs/promises'
+import { rm, writeFile, mkdir } from 'fs/promises'
+import { readFileSync } from 'fs'
 import path from 'path'
 import { execPath } from 'process'
+import util from 'util'
 import { Inputs } from '../inputs'
 
 export async function runSelfInstaller(inputs: Inputs): Promise<number> {
@@ -43,14 +45,22 @@ async function readTarget(opts: {
   const { version, packageJsonFile, standalone } = opts
   const { GITHUB_WORKSPACE } = process.env
 
-  let packageManager;
+  let packageManager
 
   if (GITHUB_WORKSPACE) {
-    ({ packageManager } = JSON.parse(await readFile(path.join(GITHUB_WORKSPACE, packageJsonFile), 'utf8')))
+    try {
+      ({ packageManager } = JSON.parse(readFileSync(path.join(GITHUB_WORKSPACE, packageJsonFile), 'utf8')))
+    } catch (error: unknown) {
+      // Swallow error if package.json doesn't exist in root
+      if (!util.types.isNativeError(error) || !('code' in error) || error.code !== 'ENOENT') throw error
+    }
   }
 
   if (version) {
-    if (typeof packageManager === 'string') {
+    if (
+      typeof packageManager === 'string' &&
+      packageManager.replace('pnpm@', '') !== version
+    ) {
       throw new Error(`Multiple versions of pnpm specified:
   - version ${version} in the GitHub Action config with the key "version"
   - version ${packageManager} in the package.json with the key "packageManager"
@@ -78,7 +88,7 @@ Please specify it by one of the following ways:
     throw new Error('Invalid packageManager field in package.json')
   }
 
-  if (standalone){
+  if (standalone) {
     return packageManager.replace('pnpm@', '@pnpm/exe@')
   }