feat(child): add opts.installerStdio (#126)

This is needed because pnpm prints its logging to stdout.

Fixes:  #121

index.js

@@ -235,7 +235,9 @@ function installPackages (specs, prefix, opts) {
     return process.platform === 'win32' ? child.escapeArg(npmPath, true) : npmPath
   }).then(npmPath => {
     return child.spawn(npmPath, args, {
-      stdio: [0, 'pipe', opts.q ? 'ignore' : 2]
+      stdio: opts.installerStdio
+        ? opts.installerStdio
+        : [0, 'pipe', opts.q ? 'ignore' : 2]
     }).then(deets => {
       try {
         return deets.stdout ? JSON.parse(deets.stdout) : null

test/index.js

@@ -255,3 +255,18 @@ test('findNodeScript', t => {
     })
   })
 })
+
+test('npx with custom installer stdio', t => {
+  const NPX_PATH = path.resolve(__dirname, 'util', 'npx-bin-inherit-stdio.js')
+  const NPX_ESC = isWindows ? child.escapeArg(NPX_PATH) : NPX_PATH
+
+  return child.spawn('node', [
+    NPX_ESC, '[email protected]'
+  ], {stdio: 'pipe'}).then(res => {
+    t.equal(res.code, 0, 'command succeeded')
+    t.match(
+      res.stdout.toString(), /"added":/, 'installer output printed directly to console'
+    )
+    t.end()
+  })
+})

test/util/npx-bin-inherit-stdio.js

@@ -0,0 +1,11 @@
+#!/usr/bin/env node
+
+const npx = require('../../index.js')
+const path = require('path')
+
+const NPM_PATH = path.join(__dirname, '../..', 'node_modules', 'npm', 'bin', 'npm-cli.js')
+
+const npxOpts = Object.assign({}, npx.parseArgs(process.argv, NPM_PATH), {
+  installerStdio: 'inherit'
+})
+npx(npxOpts)