fix: bin_dest output points to self-updated pnpm, not bootstrap (#247)

`pnpm self-update <version>` writes the target binary to
`${PNPM_HOME}/bin/`, leaving the bootstrap symlink at `${PNPM_HOME}/pnpm`
untouched. The `bin_dest` output was set to `${PNPM_HOME}`, so consumers
invoking `${{ steps.pnpm.outputs.bin_dest }}/pnpm` got the bootstrap
version (currently 11.0.4) instead of the version they requested.

PATH lookup hid the bug: `${PNPM_HOME}/bin` was prepended ahead of
`${PNPM_HOME}`, so `pnpm` resolved from PATH was the right one. Existing
version-respect tests only checked `pnpm --version`, not `bin_dest`.

Resolve `binDest` inside `runSelfInstaller` (target lives in
`${PNPM_HOME}/bin` after self-update, otherwise stays at `${PNPM_HOME}`)
and plumb it through to `setOutputs`. Add a regression test that invokes
`${bin_dest}/pnpm --version` directly across Linux/macOS/Windows.

.github/workflows/test.yaml

@@ -166,6 +166,45 @@ jobs:
           fi
         shell: bash
 
+  test_bin_dest_output:
+    name: 'Test bin_dest output points to requested version (${{ matrix.version }}, ${{ matrix.os }})'
+    # Regression test for #247: invoking pnpm via the `bin_dest` output returned the
+    # bootstrap version because self-update writes the target to `${bin_dest}/bin/`,
+    # not directly into `${bin_dest}/`.
+
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          - macos-latest
+          - windows-latest
+        version:
+          - '9.15.5'
+          - '10.33.2'
+
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+
+      - id: pnpm
+        name: Run the action
+        uses: ./
+        with:
+          version: ${{ matrix.version }}
+
+      - name: 'Test: bin_dest/pnpm reports requested version'
+        run: |
+          required='${{ matrix.version }}'
+          actual="$(${{ steps.pnpm.outputs.bin_dest }}/pnpm --version)"
+          echo "pnpm version via bin_dest: ${actual}"
+          if [ "${actual}" != "${required}" ]; then
+            echo "Expected pnpm version ${required}, but got ${actual}"
+            exit 1
+          fi
+        shell: bash
+
   test_package_manager_field:
     name: 'Test packageManager field is respected (${{ matrix.version }}, ${{ matrix.os }})'
     # Reproduces #227: when `packageManager` is set in package.json and no `version:` input is given,

src/index.ts

@@ -20,9 +20,10 @@ async function main() {
 async function runMain(inputs: Inputs) {
   saveState('is_post', 'true')
 
-  await installPnpm(inputs)
+  const binDest = await installPnpm(inputs)
+  if (binDest === undefined) return
   console.log('Installation Completed!')
-  setOutputs(inputs)
+  setOutputs(inputs, binDest)
 
   await restoreCache(inputs)
 

src/install-pnpm/index.ts

@@ -4,13 +4,15 @@ import runSelfInstaller from './run'
 
 export { runSelfInstaller }
 
-export async function install(inputs: Inputs) {
+export async function install(inputs: Inputs): Promise<string | undefined> {
   startGroup('Running self-installer...')
-  const status = await runSelfInstaller(inputs)
+  const { exitCode, binDest } = await runSelfInstaller(inputs)
   endGroup()
-  if (status) {
-    return setFailed(`Something went wrong, self-installer exits with code ${status}`)
+  if (exitCode) {
+    setFailed(`Something went wrong, self-installer exits with code ${exitCode}`)
+    return undefined
   }
+  return binDest
 }
 
 export default install

src/install-pnpm/run.ts

@@ -12,7 +12,12 @@ import exeLock from './bootstrap/exe-lock.json'
 const BOOTSTRAP_PNPM_PACKAGE_JSON = JSON.stringify({ private: true, dependencies: { pnpm: pnpmLock.packages['node_modules/pnpm'].version } })
 const BOOTSTRAP_EXE_PACKAGE_JSON = JSON.stringify({ private: true, dependencies: { '@pnpm/exe': exeLock.packages['node_modules/@pnpm/exe'].version } })
 
-export async function runSelfInstaller(inputs: Inputs): Promise<number> {
+export interface SelfInstallerResult {
+  exitCode: number
+  binDest: string
+}
+
+export async function runSelfInstaller(inputs: Inputs): Promise<SelfInstallerResult> {
   const { version, dest, packageJsonFile } = inputs
 
   // pnpm v11 requires Node >= 22.13; use standalone (exe) bootstrap which
@@ -45,7 +50,7 @@ export async function runSelfInstaller(inputs: Inputs): Promise<number> {
   const npmEnv = { ...process.env, [pathKey]: currentPath ? currentPath + path.delimiter + nodeDir : nodeDir }
   const npmExitCode = await runCommand('npm', ['ci'], { cwd: dest, env: npmEnv })
   if (npmExitCode !== 0) {
-    return npmExitCode
+    return { exitCode: npmExitCode, binDest: path.join(dest, 'node_modules', '.bin') }
   }
 
   // On Windows with standalone mode, npm's .bin shims can't properly
@@ -87,11 +92,18 @@ export async function runSelfInstaller(inputs: Inputs): Promise<number> {
     const args = standalone ? ['self-update', targetVersion] : [bootstrapPnpm, 'self-update', targetVersion]
     const exitCode = await runCommand(cmd, args, { cwd: dest })
     if (exitCode !== 0) {
-      return exitCode
+      return { exitCode, binDest: pnpmHome }
     }
+    // self-update writes the target pnpm/pnpx into PNPM_HOME/bin, leaving
+    // the bootstrap symlinks in pnpmHome pointing at the old version. Use
+    // PNPM_HOME/bin so consumers of the bin_dest output (e.g.
+    // `${steps.pnpm.outputs.bin_dest}/pnpm`) invoke the requested version.
+    return { exitCode: 0, binDest: path.join(pnpmHome, 'bin') }
   }
 
-  return 0
+  // No explicit target version: rely on the bootstrap pnpm to switch to
+  // the version declared in packageManager/devEngines at runtime.
+  return { exitCode: 0, binDest: pnpmHome }
 }
 
 function readTargetVersion(opts: {

src/outputs/index.ts

@@ -1,9 +1,7 @@
 import { setOutput } from '@actions/core'
 import { Inputs } from '../inputs'
-import { getBinDest } from '../utils'
 
-export function setOutputs(inputs: Inputs) {
-  const binDest = getBinDest(inputs)
+export function setOutputs(inputs: Inputs, binDest: string) {
   // NOTE: addPath is already called in installPnpm — do not call it again
   // here, as a second addPath would shadow the correct entry on Windows.
   setOutput('dest', inputs.dest)