From cf8555bd1235d6f037c59c86db8e921cceec2475 Mon Sep 17 00:00:00 2001
From: Zoltan Kochan <z@kochan.io>
Date: Mon, 16 Mar 2026 01:06:54 +0100
Subject: [PATCH] feat: read pnpm version from devEngines.packageManager field

When no version is specified in the action config or the packageManager
field of package.json, fall back to devEngines.packageManager.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 dist/index.js           | Bin 1427908 -> 1428109 bytes
 src/install-pnpm/run.ts |  16 ++++++++++++----
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/dist/index.js b/dist/index.js
index 885a0c2fab92195032967742fa2eade0516baac2..73fbf803e6419f0ab32c99107e675330c3c68436 100644
GIT binary patch
delta 363
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spi+%XRc(T%PO4`0^ap!Ib+#|uBbvoD{pvnZb#8>8^tS)mCwhVl0KNEtssI20

delta 214
zcmeC38h&JQctZ<g3sVbo3rh=Y3tJ0&3r7oQ3s(zw3r`Dg3ttO=i$IHDi%^Sji^vwy
z=H2|(nQ0n%nk7Y*)j6pp3dPf>>=rc?vDT<ANKDR7Oi%Sq%mb1|R++WakM9;$QYqG{
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zGfx4;E!G3^6m4ylT>boA{X&#9OEQY`%N2@ifsRPkte*Zplu>kg?LJZQ?V5W<vzWGD
J*)O`23jojmN@)N9

diff --git a/src/install-pnpm/run.ts b/src/install-pnpm/run.ts
index 6499130..4221555 100644
--- a/src/install-pnpm/run.ts
+++ b/src/install-pnpm/run.ts
@@ -70,21 +70,28 @@ function readTargetVersion(opts: {
   const { version, packageJsonFile } = opts
   const { GITHUB_WORKSPACE } = process.env
 
-  let packageManager: unknown
+  let packageManager: string | undefined
+  let devEngines: { packageManager?: { name?: string; version?: string } } | undefined
 
   if (GITHUB_WORKSPACE) {
     try {
       const content = readFileSync(path.join(GITHUB_WORKSPACE, packageJsonFile), 'utf8');
-      ({ packageManager } = packageJsonFile.endsWith(".yaml")
+      const manifest = packageJsonFile.endsWith(".yaml")
         ? parseYaml(content, { merge: true })
         : JSON.parse(content)
-      )
+      packageManager = manifest.packageManager
+      devEngines = manifest.devEngines
     } 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 packageManager field is not set, try devEngines.packageManager
+  if (typeof packageManager !== 'string' && devEngines?.packageManager?.name === 'pnpm' && devEngines.packageManager.version) {
+    packageManager = `pnpm@${devEngines.packageManager.version}`
+  }
+
   if (version) {
     if (
       typeof packageManager === 'string' &&
@@ -115,7 +122,8 @@ Otherwise, please specify the pnpm version in the action configuration.`)
   throw new Error(`No pnpm version is specified.
 Please specify it by one of the following ways:
   - in the GitHub Action config with the key "version"
-  - in the package.json with the key "packageManager"`)
+  - in the package.json with the key "packageManager"
+  - in the package.json with the key "devEngines.packageManager"`)
 }
 
 function runCommand(cmd: string, args: string[], opts: { cwd: string }): Promise<number> {