fix: dedupe direct deps when headless install is used

.changeset/loud-lions-remember.md

@@ -0,0 +1,5 @@
+---
+"@pnpm/headless": patch
+---
+
+Dedupe direct dependencies.

pkg-manager/core/test/install/dedupeDirectDeps.ts

@@ -95,4 +95,10 @@ test('dedupe direct dependencies', async () => {
   expect(fs.readdirSync('project-2/node_modules').sort()).toEqual(['is-odd'])
   await projects['project-3'].hasNot('is-negative')
   expect(fs.existsSync('project-3/node_modules')).toBeFalsy()
+
+  // Test the same with headless install
+  await mutateModules(importers, await testDefaults({ allProjects, dedupeDirectDeps: true, frozenLockfile: true }))
+  expect(fs.readdirSync('project-2/node_modules').sort()).toEqual(['is-odd'])
+  await projects['project-3'].hasNot('is-negative')
+  expect(fs.existsSync('project-3/node_modules')).toBeFalsy()
 })

pkg-manager/headless/src/index.ts

@@ -340,7 +340,7 @@ export async function headlessInstall (opts: HeadlessOptions) {
 
     await symlinkDirectDependencies({
       directDependenciesByImporterId: symlinkedDirectDependenciesByImporterId!,
-      dedupe: opts.dedupeDirectDeps,
+      dedupe: Boolean(opts.dedupeDirectDeps),
       filteredLockfile,
       lockfileDir,
       projects: selectedProjects,
@@ -408,6 +408,7 @@ export async function headlessInstall (opts: HeadlessOptions) {
     /** Skip linking and due to no project manifest */
     if (!opts.ignorePackageManifest) {
       await symlinkDirectDependencies({
+        dedupe: Boolean(opts.dedupeDirectDeps),
         directDependenciesByImporterId,
         filteredLockfile,
         lockfileDir,
@@ -564,7 +565,7 @@ export async function headlessInstall (opts: HeadlessOptions) {
 
 type SymlinkDirectDependenciesOpts = Pick<HeadlessOptions, 'registries' | 'symlink' | 'lockfileDir'> & {
   filteredLockfile: Lockfile
-  dedupe?: boolean
+  dedupe: boolean
   directDependenciesByImporterId: DirectDependenciesByImporterId
   projects: Project[]
 }