[fix] node v10.0 lacks fs.promises

In this node version, fall back to `util.promisify` of the callback version.

Maybe fixes npm/cli#2623. Maybe fixes npm/cli#2652. Maybe fixes npm/cli#2625.

PR-URL: #21
Credit: @ljharb
Close: #21
Reviewed-by: @ruyadorno

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ jobs:
   build:
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x]
+        node-version: ['10.0', 10.x, '12.0', 12.x, '14.0', 14.x]
         platform:
         - os: ubuntu-latest
           shell: bash

lib/is-server-package.js

@@ -1,4 +1,6 @@
-const { stat } = require('fs').promises
+const util = require('util')
+const fs = require('fs')
+const { stat } = fs.promises || { stat: util.promisify(fs.stat) }
 const { resolve } = require('path')
 module.exports = async path => {
   try {

test/is-server-package.js

@@ -1,4 +1,5 @@
 const t = require('tap')
+const requireInject = require('require-inject')
 const isServerPackage = require('../lib/is-server-package.js')
 
 t.test('returns true if server.js present', async t => {
@@ -19,3 +20,7 @@ t.test('returns false if server.js not a file', async t => {
   })
   t.equal(await isServerPackage(path), false)
 })
+
+t.test('works without fs.promises', async t => {
+  t.doesNotThrow(() => requireInject('../lib/is-server-package', { fs: { ...require('fs'), promises: null }}))
+})