fix: pnpm doesn't respect save-prefix (#3420)

When save-prefix in .npmrc is set to an empty string,
 pnpm does not honor it and sets the package version with the default ^ as a prefix.

Close #3414

Co-authored-by: amit <amit@enso.security>

.changeset/spicy-eggs-collect.md

@@ -0,0 +1,5 @@
+---
+"@pnpm/plugin-commands-installation": patch
+---
+
+Fix: align pnpm save-prefix behavior when a range is not specified explicitly.

packages/plugin-commands-installation/src/getPinnedVersion.ts

@@ -1,4 +1,4 @@
 export default function getPinnedVersion (opts: { saveExact?: boolean, savePrefix?: string }) {
-  if (opts.saveExact === true) return 'patch'
+  if (opts.saveExact === true || opts.savePrefix === '') return 'patch'
   return opts.savePrefix === '~' ? 'minor' : 'major'
 }

packages/plugin-commands-installation/test/add.ts

@@ -243,3 +243,45 @@ test('pnpm add --save-peer', async () => {
     )
   }
 })
+
+test('pnpm add - with save-prefix set to empty string should save package version without prefix', async () => {
+  prepare()
+  await add.handler({
+    ...DEFAULT_OPTIONS,
+    dir: process.cwd(),
+    linkWorkspacePackages: false,
+    savePrefix: '',
+  }, ['is-positive@1.0.0'])
+
+  {
+    const manifest = await loadJsonFile(path.resolve('package.json'))
+
+    expect(
+      manifest
+    ).toStrictEqual(
+      {
+        name: 'project',
+        version: '0.0.0',
+        dependencies: { 'is-positive': '1.0.0' },
+      }
+    )
+  }
+})
+
+test('pnpm add - should add prefix when set in .npmrc when a range is not specified explicitly', async () => {
+  prepare()
+  await add.handler({
+    ...DEFAULT_OPTIONS,
+    dir: process.cwd(),
+    linkWorkspacePackages: false,
+    savePrefix: '~',
+  }, ['is-positive'])
+
+  {
+    const manifest = (await import(path.resolve('package.json')))
+
+    expect(
+      manifest.dependencies['is-positive']
+    ).toMatch(/~([0-9]+)\.([0-9]+)\.([0-9]+)(?:-([0-9A-Za-z-]+(?:\.[0-9A-Za-z-]+)*))?(?:\+[0-9A-Za-z-]+)?$/)
+  }
+})