Throw error when multiple versions specified

src/install-pnpm/run.ts

@@ -41,18 +41,32 @@ async function readTarget(opts: {
   readonly standalone: boolean
 }) {
   const { version, packageJsonFile, standalone } = opts
+  const { GITHUB_WORKSPACE } = process.env
 
-  if (version) return `${ standalone ? '@pnpm/exe' : 'pnpm' }@${version}`
+  let packageManager
+
+  if (GITHUB_WORKSPACE) {
+    ({ packageManager } = JSON.parse(await readFile(path.join(GITHUB_WORKSPACE, packageJsonFile), 'utf8')))
+  }
+
+  if (version) {
+    if (typeof packageManager === 'string') {
+      throw new Error(`Multiple versions of pnpm specified:
+  - version ${version} in the GitHub Action config with the key "version"
+  - version ${packageManager} in the package.json with the key "packageManager"
+Remove one of these versions to avoid version mismatch errors like ERR_PNPM_BAD_PM_VERSION`)
+    }
+
+    return `${ standalone ? '@pnpm/exe' : 'pnpm' }@${version}`
+  }
 
-  const { GITHUB_WORKSPACE } = process.env
   if (!GITHUB_WORKSPACE) {
     throw new Error(`No workspace is found.
 If you're intended to let pnpm/action-setup read preferred pnpm version from the "packageManager" field in the package.json file,
 please run the actions/checkout before pnpm/action-setup.
 Otherwise, please specify the pnpm version in the action configuration.`)
   }
 
-  const { packageManager } = JSON.parse(await readFile(path.join(GITHUB_WORKSPACE, packageJsonFile), 'utf8'))
   if (typeof packageManager !== 'string') {
     throw new Error(`No pnpm version is specified.
 Please specify it by one of the following ways:
@@ -64,7 +78,7 @@ 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@')
   }