Revert check for fs.realpath.native (#887)

lib/fs/__tests__/realpath.test.js

@@ -1,11 +1,75 @@
 'use strict'
 
-const fse = require('../..')
+const fs = require('fs')
+const path = require('path')
 const assert = require('assert')
 
 /* eslint-env mocha */
 
+describe('realpath.native does not exist', () => {
+  let warning
+  const originalListener = process.listeners('warning')[process.listeners('warning').length - 1]
+  const warningListener = error => {
+    if (error.name === 'Warning') {
+      if (error.code.startsWith('fs-extra-WARN0003')) {
+        warning = error
+        return
+      }
+    }
+    originalListener(error)
+  }
+
+  const realpathNativeBackup = fs.realpath.native
+  const clearFseCache = () => {
+    const fsePath = path.dirname(require.resolve('../../..'))
+    for (const entry in require.cache) {
+      if (entry.startsWith(fsePath)) {
+        delete require.cache[entry]
+      }
+    }
+  }
+
+  before(() => {
+    process.off('warning', originalListener)
+    process.on('warning', warningListener)
+
+    // clear existing require.cache
+    clearFseCache()
+
+    // mock stub
+    delete fs.realpath.native
+  })
+
+  after(() => {
+    process.off('warning', warningListener)
+    process.on('warning', originalListener)
+
+    // clear stubbed require.cache
+    clearFseCache()
+
+    // reinstate
+    fs.realpath.native = realpathNativeBackup
+    require('../..')
+  })
+
+  it('fse fallback to realpath internally', () => {
+    const fse = require(require.resolve('../..'))
+
+    // next event loop to allow event emitter/listener to happen
+    setImmediate(() => {
+      assert(warning, 'fs-extra-WARN0003 should be emitted')
+    })
+
+    fse.realpath.native(__dirname, (err, path) => {
+      assert.ifError(err)
+      assert.strictEqual(path, __dirname)
+    })
+  })
+})
+
 describe('realpath.native', () => {
+  const fse = require('../..')
+
   it('works with callbacks', () => {
     fse.realpath.native(__dirname, (err, path) => {
       assert.ifError(err)

lib/fs/index.js

@@ -54,7 +54,6 @@ Object.assign(exports, fs)
 api.forEach(method => {
   exports[method] = u(fs[method])
 })
-exports.realpath.native = u(fs.realpath.native)
 
 // We differ from mz/fs in that we still ship the old, broken, fs.exists()
 // since we are a drop-in replacement for the native module
@@ -117,3 +116,25 @@ if (typeof fs.writev === 'function') {
     })
   }
 }
+
+// fs.realpath.native only available in Node v9.2+
+if (typeof fs.realpath.native === 'function') {
+  exports.realpath.native = u(fs.realpath.native)
+} else {
+  // fallback to a similar method signature that is present before Node v9.2
+  exports.realpath.native = u(fs.realpath)
+
+  // emit warning that fs.realpath.native is not a function (or undefined)
+  const nodeVer = process.version.match(/(\d+)\.(\d+)\.(\d+)/)
+  const [major, minor] = nodeVer.slice(1).map(_ => parseInt(_))
+  process.emitWarning(
+    `fs.realpath.native is not a function: ${fs.realpath.native}.\n` +
+    '\tfs.realpath.native is now redirected to fs.realpath as a fallback measure.\n\n' +
+    (
+      (major <= 9 || (major === 9 && minor < 2))
+        ? `\tEnsure that NodeJS is at least v9.2.0. Detected: ${process.version}.`
+        : '\tEnsure that fs-extra is imported before other dependencies that can change fs.\n\n' +
+          '\tsee https://github.com/jprichardson/node-fs-extra/pull/953'
+    ),
+    'Warning', 'fs-extra-WARN0003')
+}