[build-utils] log pnpm lockfile selection (#11591)

Both `pnpm@6` and `pnpm@7` can parse lockfile versions `5.3` and `5.4`, but if there's a mismatch, `pnpm` will output a warning saying so. In order to prevent confusing warnings from being displayed to the user, this PR aligns the pnpm version with the exact lockfile verison.

It also adds a debug log to show which package manager version was determined based on the lockfile version.

.changeset/smooth-zoos-drop.md

@@ -0,0 +1,5 @@
+---
+"@vercel/build-utils": patch
+---
+
+[build-utils] pnpm lockfile testing and fixing

packages/build-utils/src/fs/run-user-scripts.ts

@@ -594,6 +594,7 @@ export function getEnvForPackageManager({
 
 type DetectedPnpmVersion =
   | 'not found'
+  | 'pnpm 6'
   | 'pnpm 7'
   | 'pnpm 8'
   | 'pnpm 9'
@@ -608,7 +609,9 @@ function detectPnpmVersion(
       return 'corepack_enabled';
     case lockfileVersion === undefined:
       return 'not found';
-    case lockfileVersion === 5.3 || lockfileVersion === 5.4:
+    case lockfileVersion === 5.3:
+      return 'pnpm 6';
+    case lockfileVersion === 5.4:
       return 'pnpm 7';
     case lockfileVersion === 6.0 || lockfileVersion === 6.1:
       return 'pnpm 8';
@@ -703,6 +706,7 @@ export function getPathOverrideForPackageManager({
             detectedLockfile: 'pnpm-lock.yaml',
             detectedPackageManager: 'pnpm 9',
           };
+        case 'pnpm 6':
         default:
           return no_override;
       }
@@ -764,6 +768,14 @@ export function getPathForPackageManager({
     env,
   });
 
+  debug(
+    `Detected ${
+      overrides.detectedPackageManager
+    } with lockfileVersion ${lockfileVersion} (${typeof lockfileVersion}): ${
+      overrides.path
+    }`
+  );
+
   const alreadyInPath = (newPath: string) => {
     const oldPath = env.PATH ?? '';
     return oldPath.split(path.delimiter).includes(newPath);

packages/build-utils/test/unit.get-env-for-package-manager.test.ts

@@ -365,6 +365,23 @@ describe('Test `getPathOverrideForPackageManager()`', () => {
         path: undefined,
       },
     },
+    {
+      name: 'should not set path if pnpm 6 is detected',
+      args: {
+        cliType: 'pnpm',
+        nodeVersion: { major: 16, range: '16.x', runtime: 'nodejs16.x' },
+        lockfileVersion: 5.3, // detects as pnpm@6, which is the default
+        env: {
+          FOO: 'bar',
+          PATH: 'foo',
+        },
+      },
+      want: {
+        detectedLockfile: undefined,
+        detectedPackageManager: undefined,
+        path: undefined,
+      },
+    },
     {
       name: 'should set path if pnpm 7+ is detected',
       args: {