fix: wrap 'fs.realpath.native' when configured with asyncHooks=false (#…

…2403)

Before this `fs.realpath.native` would be undefined after wrapping
of `fs.realpath`.

Fixes: #2401

CHANGELOG.asciidoc

@@ -39,6 +39,10 @@ Notes:
 [float]
 ===== Bug fixes
 
+* Wrap `fs.realpath.native` when configured with `asyncHooks=false`. This
+  fixes using that function (which was undefined before this fix) and a
+  crash when importing fs-extra@10. ({issues}2401[#2401])
+
 * A significant change was made to internal run context tracking (a.k.a. async
   context tracking). There are no configuration changes or API changes for
   custom instrumentation. ({pull}2181[#2181])

lib/instrumentation/patch-async.js

@@ -249,6 +249,11 @@ module.exports = function (ins) {
   if (dns.resolveNaptr) wrap(dns, 'resolveNaptr', activator)
 
   var fs = require('fs')
+  var wrappedFsRealpathNative
+  if (fs.realpath.native) {
+    wrappedFsRealpathNative = wrap(fs.realpath, 'native', activator)
+  }
+
   massWrap(
     fs,
     [
@@ -287,6 +292,10 @@ module.exports = function (ins) {
     activator
   )
 
+  if (wrappedFsRealpathNative) {
+    fs.realpath.native = wrappedFsRealpathNative
+  }
+
   // only wrap lchown and lchmod on systems that have them.
   if (fs.lchown) wrap(fs, 'lchown', activator) // eslint-disable-line node/no-deprecated-api
   if (fs.lchmod) wrap(fs, 'lchmod', activator) // eslint-disable-line node/no-deprecated-api

test/instrumentation/fs.test.js

@@ -0,0 +1,33 @@
+'use strict'
+
+// Some testing of run-context tracking through 'fs' methods.
+
+const apm = require('../..').start({
+  serviceName: 'test-fs',
+  captureExceptions: false,
+  metricsInterval: '0s',
+  centralConfig: false,
+  cloudProvider: 'none',
+  disableSend: true,
+  asyncHooks: false
+})
+
+const fs = require('fs')
+
+const tape = require('tape')
+
+if (typeof fs.realpath.native === 'function') {
+  // Before https://github.com/elastic/apm-agent-nodejs/issues/2401 this test
+  // would crash with asyncHooks=false
+  tape.test('fs.realpath.native', function (t) {
+    var trans = apm.startTransaction('t0')
+    var span = apm.startSpan('s1')
+    fs.realpath.native(__filename, function (err, resolvedPath) {
+      t.error(err, 'no error from fs.realpath.native')
+      t.equal(apm.currentSpan, span, 'apm.currentSpan is as expected')
+      span.end()
+      trans.end()
+      t.end()
+    })
+  })
+}