fix: run @pnpm/exe setup logic in-process to fix version switching without Node.js (#10696)

When pnpm is installed as a standalone executable in environments without
a system Node.js (e.g. Docker containers), the `@pnpm/exe` preinstall
script (`node setup.js`) fails because `node` is not on PATH. This broke
version switching via the `packageManager` field in package.json since
v10.30.2, which changed `getCurrentPackageName()` to return `@pnpm/exe`
instead of platform-specific package names like `@pnpm/linux-x64`.

Install with `--ignore-scripts` and link the platform-specific binary
in-process instead. The setup logic is inlined because setup.js can't
be loaded at runtime: `require()` fails on ESM (pnpm v11+) and
`import()` is intercepted by pkg's virtual filesystem in standalone
executables.

Closes #10687

.changeset/fix-exe-version-switch-no-nodejs.md

@@ -0,0 +1,6 @@
+---
+"@pnpm/tools.plugin-commands-self-updater": patch
+"pnpm": patch
+---
+
+Fixed version switching via `packageManager` field failing when pnpm is installed as a standalone executable in environments without a system Node.js [#10687](https://github.com/pnpm/pnpm/issues/10687).

tools/plugin-commands-self-updater/src/installPnpmToTools.ts

@@ -39,17 +39,23 @@ export async function installPnpmToTools (pnpmVersion: string, opts: SelfUpdateC
   try {
     // The reason we don't just run add.handler is that at this point we might have settings from local config files
     // that we don't want to use while installing the pnpm CLI.
+    // We use --ignore-scripts because `@pnpm/exe` has a `preinstall` script that runs `node setup.js`,
+    // which fails in environments without a system Node.js (e.g. when pnpm is installed as a standalone executable).
+    // Instead, we link the platform-specific binary in-process after install.
     runPnpmCli([
       'add',
       `${currentPkgName}@${pnpmVersion}`,
       '--loglevel=error',
-      '--allow-build=@pnpm/exe',
-      '--no-dangerously-allow-all-builds',
+      '--ignore-scripts',
+      '--config.strict-dep-builds=false',
       // We want to avoid symlinks because of the rename step,
       // which breaks the junctions on Windows.
       '--config.node-linker=hoisted',
       '--config.bin=bin',
     ], { cwd: stage })
+    if (currentPkgName === '@pnpm/exe') {
+      linkExePlatformBinary(stage)
+    }
     // We need the operation of installing pnpm to be atomic.
     // However, we cannot use a rename as that breaks the command shim created for pnpm.
     // Hence, we use a symlink.
@@ -67,3 +73,40 @@ export async function installPnpmToTools (pnpmVersion: string, opts: SelfUpdateC
     binDir,
   }
 }
+
+// This replicates the logic from @pnpm/exe's setup.js (pnpm/artifacts/exe/setup.js).
+// We can't run setup.js via require() or import() because:
+// - require() fails when setup.js is ESM (pnpm v11+)
+// - import() is intercepted by pkg's virtual filesystem in standalone executables
+// So we inline the logic: find the platform-specific binary and hard-link it
+// into the @pnpm/exe package directory.
+function linkExePlatformBinary (stageDir: string): void {
+  const platform = process.platform === 'win32'
+    ? 'win'
+    : process.platform === 'darwin'
+      ? 'macos'
+      : process.platform
+  const arch = platform === 'win' && process.arch === 'ia32' ? 'x86' : process.arch
+  const executable = platform === 'win' ? 'pnpm.exe' : 'pnpm'
+  const platformPkgDir = path.join(stageDir, 'node_modules', '@pnpm', `${platform}-${arch}`)
+  const src = path.join(platformPkgDir, executable)
+  if (!fs.existsSync(src)) return
+  const exePkgDir = path.join(stageDir, 'node_modules', '@pnpm', 'exe')
+  const dest = path.join(exePkgDir, executable)
+  try {
+    fs.unlinkSync(dest)
+  } catch (err: unknown) {
+    if ((err as NodeJS.ErrnoException).code !== 'ENOENT') {
+      throw err
+    }
+  }
+  fs.linkSync(src, dest)
+  fs.chmodSync(dest, 0o755)
+  if (platform === 'win') {
+    const exePkgJsonPath = path.join(exePkgDir, 'package.json')
+    const exePkg = JSON.parse(fs.readFileSync(exePkgJsonPath, 'utf8'))
+    fs.writeFileSync(path.join(exePkgDir, 'pnpm'), 'This file intentionally left blank')
+    exePkg.bin.pnpm = 'pnpm.exe'
+    fs.writeFileSync(exePkgJsonPath, JSON.stringify(exePkg, null, 2))
+  }
+}