fix: npm link <pkg> should not save package.json

When running `npm link <pkg>` it should not save the new item to the
currrent dependencies of that package.json file.

Fixes: #2034

Co-authored-by: Darcy Clarke <darcy@darcyclarke.me>

PR-URL: #2245
Credit: @ruyadorno
Close: #2245
Reviewed-by: @darcyclarke

lib/link.js

@@ -112,14 +112,23 @@ const linkInstall = async args => {
     )
   }
 
+  // npm link should not save=true by default unless you're
+  // using any of --save-dev or other types
+  const save =
+    Boolean(npm.config.find('save') !== 'default' || npm.flatOptions.saveType)
+
   // create a new arborist instance for the local prefix and
   // reify all the pending names as symlinks there
   const localArb = new Arborist({
     ...npm.flatOptions,
     path: npm.prefix,
+    save,
   })
   await localArb.reify({
+    ...npm.flatOptions,
+    path: npm.prefix,
     add: names.map(l => `file:${resolve(globalTop, 'node_modules', l)}`),
+    save,
   })
 
   await reifyFinish(localArb)

test/lib/link.js

@@ -23,6 +23,7 @@ const npm = {
     get () {
       return false
     },
+    find () {},
   },
 }
 const printLinks = async (opts) => {
@@ -196,7 +197,7 @@ t.test('link global linked pkg to local nm when using args', (t) => {
 })
 
 t.test('link pkg already in global space', (t) => {
-  t.plan(2)
+  t.plan(3)
 
   const testdir = t.testdir({
     'global-prefix': {
@@ -224,17 +225,26 @@ t.test('link pkg already in global space', (t) => {
   npm.globalDir = resolve(testdir, 'global-prefix', 'lib', 'node_modules')
   npm.prefix = resolve(testdir, 'my-project')
 
+  npm.config.find = () => 'default'
+
   const _cwd = process.cwd()
   process.chdir(npm.prefix)
 
   reifyOutput = async () => {
     reifyOutput = undefined
     process.chdir(_cwd)
+    npm.config.find = () => null
 
     const links = await printLinks({
       path: npm.prefix,
     })
 
+    t.equal(
+      require(resolve(testdir, 'my-project', 'package.json')).dependencies,
+      undefined,
+      'should not save to package.json upon linking'
+    )
+
     t.matchSnapshot(links, 'should create a local symlink to global pkg')
   }