fix: shrinkwrap setting incorrect lockfileVersion

lib/commands/shrinkwrap.js

@@ -1,7 +1,5 @@
 const { resolve, basename } = require('path')
-const util = require('util')
-const fs = require('fs')
-const { unlink } = fs.promises || { unlink: util.promisify(fs.unlink) }
+const { unlink } = require('fs').promises
 const Arborist = require('@npmcli/arborist')
 const log = require('npmlog')
 
@@ -21,7 +19,6 @@ class Shrinkwrap extends BaseCommand {
     // if has a npm-shrinkwrap.json, nothing to do
     // if has a package-lock.json, rename to npm-shrinkwrap.json
     // if has neither, load the actual tree and save that as npm-shrinkwrap.json
-    // in all cases, re-cast to current lockfile version
     //
     // loadVirtual, fall back to loadActual
     // rename shrinkwrap file type, and tree.meta.save()
@@ -40,17 +37,37 @@ class Shrinkwrap extends BaseCommand {
     const oldFilename = meta.filename
     const notSW = !newFile && basename(oldFilename) !== 'npm-shrinkwrap.json'
 
+    // The computed lockfile version of a hidden lockfile is always 3
+    // even if the actual value of the property is a different.
+    // When shrinkwrap is run with only a hidden lockfile we want to
+    // set the shrinkwrap lockfile version as whatever was explicitly
+    // requested with a fallback to the actual value from the hidden
+    // lockfile.
+    if (meta.hiddenLockfile) {
+      meta.lockfileVersion = arb.options.lockfileVersion ||
+        meta.originalLockfileVersion
+    }
     meta.hiddenLockfile = false
     meta.filename = sw
     await meta.save()
 
-    if (newFile)
-      log.notice('', 'created a lockfile as npm-shrinkwrap.json')
-    else if (notSW) {
+    const updatedVersion = meta.originalLockfileVersion !== meta.lockfileVersion
+      ? meta.lockfileVersion
+      : null
+
+    if (newFile) {
+      let message = 'created a lockfile as npm-shrinkwrap.json'
+      if (updatedVersion)
+        message += ` with version ${updatedVersion}`
+      log.notice('', message)
+    } else if (notSW) {
       await unlink(oldFilename)
-      log.notice('', 'package-lock.json has been renamed to npm-shrinkwrap.json')
-    } else if (meta.originalLockfileVersion !== this.npm.lockfileVersion)
-      log.notice('', `npm-shrinkwrap.json updated to version ${this.npm.lockfileVersion}`)
+      let message = 'package-lock.json has been renamed to npm-shrinkwrap.json'
+      if (updatedVersion)
+        message += ` and updated to version ${updatedVersion}`
+      log.notice('', message)
+    } else if (updatedVersion)
+      log.notice('', `npm-shrinkwrap.json updated to version ${updatedVersion}`)
     else
       log.notice('', 'npm-shrinkwrap.json up to date')
   }