fix: specless global installation should always install latest

src/api/install.ts

@@ -172,7 +172,7 @@ export async function installPkgs (fuzzyDeps: string[] | Dependencies, maybeOpts
   return lock(opts.prefix, async () => {
     const installType = 'named'
     const ctx = await getContext(opts, installType)
-    const existingSpecs = depsFromPackage(ctx.pkg)
+    const existingSpecs = opts.global ? {} : depsFromPackage(ctx.pkg)
     let packagesToInstall = Array.isArray(fuzzyDeps)
       ? argsToSpecs(fuzzyDeps, {
         defaultTag: opts.tag,

test/install/global.ts

@@ -1,7 +1,8 @@
 import tape = require('tape')
 import promisifyTape from 'tape-promise'
 import path = require('path')
-import {prepare, testDefaults} from '../utils'
+import readPkg = require('read-pkg')
+import {prepare, testDefaults, addDistTag} from '../utils'
 import {installPkgs} from '../../src'
 
 const test = promisifyTape(tape)
@@ -22,3 +23,16 @@ test('global installation', async function (t) {
   const isNegative = require(path.join(globalPrefix, 'node_modules', 'is-negative'))
   t.ok(typeof isNegative === 'function', 'isNegative() is available')
 })
+
+test('always install latest when doing global installation without spec', async function (t: tape.Test) {
+  await addDistTag('peer-c', '2.0.0', 'latest')
+
+  const project = prepare(t)
+  const globalPrefix = process.cwd()
+  const opts = testDefaults({global: true, prefix: globalPrefix})
+
+  await installPkgs(['peer-c@1'], opts)
+  await installPkgs(['peer-c'], opts)
+
+  t.equal(project.requireModule('peer-c/package.json').version, '2.0.0')
+})

test/install/updatingPkgJson.ts

@@ -21,6 +21,7 @@ test('save to package.json (rimraf@2.5.1)', async function (t) {
   t.deepEqual(pkgJson.dependencies, {rimraf: '^2.5.1'}, 'rimraf has been added to dependencies')
 })
 
+// NOTE: this works differently for global installations. See similar tests in global.ts
 test("don't override existing spec in package.json on named installation", async function (t: tape.Test) {
   const project = prepare(t, {
     dependencies: {