From 35cc3550ea5e4d03806b3317264a2b45534ae568 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Sun, 6 May 2018 23:08:00 +0200
Subject: [PATCH 01/20] string_decoder: lazy loaded

---
 lib/_stream_readable.js       |  4 +++-
 lib/internal/child_process.js |  6 +++++-
 lib/internal/crypto/cipher.js |  6 +++++-
 lib/readline.js               | 10 +++++++++-
 4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
index 8073e174cc586f..8bbddc97274358 100644
--- a/lib/_stream_readable.js
+++ b/lib/_stream_readable.js
@@ -40,7 +40,9 @@ const {
 } = require('internal/errors').codes;
 const ReadableAsyncIterator = require('internal/streams/async_iterator');
 const { emitExperimentalWarning } = require('internal/util');
-var StringDecoder;
+
+// Lazy loaded to improve the startup performance.
+let StringDecoder;
 
 util.inherits(Readable, Stream);
 
diff --git a/lib/internal/child_process.js b/lib/internal/child_process.js
index a630cff717bcad..1ec3f208660910 100644
--- a/lib/internal/child_process.js
+++ b/lib/internal/child_process.js
@@ -14,7 +14,6 @@ const {
     ERR_MISSING_ARGS
   }
 } = require('internal/errors');
-const { StringDecoder } = require('string_decoder');
 const EventEmitter = require('events');
 const net = require('net');
 const dgram = require('dgram');
@@ -47,6 +46,9 @@ const {
 
 const { SocketListSend, SocketListReceive } = SocketList;
 
+// Lazy loaded for startup performance.
+let StringDecoder;
+
 const MAX_HANDLE_RETRANSMISSIONS = 3;
 
 // this object contain function to convert TCP objects to native handle objects
@@ -476,6 +478,8 @@ function setupChannel(target, channel) {
 
   const control = new Control(channel);
 
+  if (StringDecoder === undefined)
+    StringDecoder = require('string_decoder').StringDecoder;
   var decoder = new StringDecoder('utf8');
   var jsonBuffer = '';
   var pendingHandle = null;
diff --git a/lib/internal/crypto/cipher.js b/lib/internal/crypto/cipher.js
index d1c45bfdce0e0d..bd80c19697e70b 100644
--- a/lib/internal/crypto/cipher.js
+++ b/lib/internal/crypto/cipher.js
@@ -28,11 +28,13 @@ const {
 
 const assert = require('assert');
 const LazyTransform = require('internal/streams/lazy_transform');
-const { StringDecoder } = require('string_decoder');
 
 const { inherits } = require('util');
 const { normalizeEncoding } = require('internal/util');
 
+// Lazy loaded for startup performance.
+let StringDecoder;
+
 function rsaFunctionFor(method, defaultPadding) {
   return function(options, buffer) {
     const key = options.key || options;
@@ -49,6 +51,8 @@ const privateDecrypt = rsaFunctionFor(_privateDecrypt, RSA_PKCS1_OAEP_PADDING);
 
 function getDecoder(decoder, encoding) {
   encoding = normalizeEncoding(encoding);
+  if (StringDecoder === undefined)
+    StringDecoder = require('string_decoder').StringDecoder;
   decoder = decoder || new StringDecoder(encoding);
   assert(decoder.encoding === encoding, 'Cannot change encoding');
   return decoder;
diff --git a/lib/readline.js b/lib/readline.js
index 124fc8111b2f09..89dd1b84f2dde0 100644
--- a/lib/readline.js
+++ b/lib/readline.js
@@ -35,7 +35,6 @@ const {
 const { debug, inherits } = require('util');
 const { Buffer } = require('buffer');
 const EventEmitter = require('events');
-const { StringDecoder } = require('string_decoder');
 const {
   CSI,
   emitKeys,
@@ -52,6 +51,9 @@ const {
   kClearScreenDown
 } = CSI;
 
+// Lazy load StringDecoder for startup performance.
+let StringDecoder;
+
 const kHistorySize = 30;
 const kMincrlfDelay = 100;
 // \r\n, \n, or \r followed by something other than \n
@@ -73,6 +75,9 @@ function Interface(input, output, completer, terminal) {
     return new Interface(input, output, completer, terminal);
   }
 
+  if (StringDecoder === undefined)
+    StringDecoder = require('string_decoder').StringDecoder;
+
   this._sawReturnAt = 0;
   this.isCompletionEnabled = true;
   this._sawKeyPress = false;
@@ -987,6 +992,9 @@ Interface.prototype._ttyWrite = function(s, key) {
 
 function emitKeypressEvents(stream, iface) {
   if (stream[KEYPRESS_DECODER]) return;
+
+  if (StringDecoder === undefined)
+    StringDecoder = require('string_decoder').StringDecoder;
   stream[KEYPRESS_DECODER] = new StringDecoder('utf8');
 
   stream[ESCAPE_DECODER] = emitKeys(stream);

From d480b632f9bc4b004f69c530bf6cf47a92b2c004 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Sun, 6 May 2018 23:08:42 +0200
Subject: [PATCH 02/20] querystring: lazy loaded

---
 lib/internal/url.js |  8 ++++++--
 lib/url.js          | 10 ++++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/lib/internal/url.js b/lib/internal/url.js
index d9daef1524787d..5a51e384fc6b1e 100644
--- a/lib/internal/url.js
+++ b/lib/internal/url.js
@@ -27,7 +27,9 @@ const {
   CHAR_LOWERCASE_A,
   CHAR_LOWERCASE_Z,
 } = require('internal/constants');
-const querystring = require('querystring');
+
+// Lazy loaded for startup performance.
+let querystring;
 
 const { platform } = process;
 const isWindows = platform === 'win32';
@@ -770,8 +772,10 @@ function parseParams(qs) {
       } else if (encodeCheck > 0) {
         // eslint-disable-next-line no-extra-boolean-cast
         if (!!isHexTable[code]) {
-          if (++encodeCheck === 3)
+          if (++encodeCheck === 3) {
+            querystring = require('querystring');
             encoded = true;
+          }
         } else {
           encodeCheck = 0;
         }
diff --git a/lib/url.js b/lib/url.js
index e4326e80b5d948..c517ba7ab3dae0 100644
--- a/lib/url.js
+++ b/lib/url.js
@@ -94,7 +94,6 @@ const slashedProtocol = {
   'file': true,
   'file:': true
 };
-const querystring = require('querystring');
 const {
   CHAR_SPACE,
   CHAR_TAB,
@@ -133,6 +132,9 @@ const {
   CHAR_AT,
 } = require('internal/constants');
 
+// Lazy loaded for startup performance.
+let querystring;
+
 function urlParse(url, parseQueryString, slashesDenoteHost) {
   if (url instanceof Url) return url;
 
@@ -233,6 +235,7 @@ Url.prototype.parse = function parse(url, parseQueryString, slashesDenoteHost) {
       if (simplePath[2]) {
         this.search = simplePath[2];
         if (parseQueryString) {
+          if (querystring === undefined) querystring = require('querystring');
           this.query = querystring.parse(this.search.slice(1));
         } else {
           this.query = this.search.slice(1);
@@ -422,6 +425,7 @@ Url.prototype.parse = function parse(url, parseQueryString, slashesDenoteHost) {
       this.query = rest.slice(questionIdx + 1, hashIdx);
     }
     if (parseQueryString) {
+      if (querystring === undefined) querystring = require('querystring');
       this.query = querystring.parse(this.query);
     }
   } else if (parseQueryString) {
@@ -584,8 +588,10 @@ Url.prototype.format = function format() {
     }
   }
 
-  if (this.query !== null && typeof this.query === 'object')
+  if (this.query !== null && typeof this.query === 'object') {
+    if (querystring === undefined) querystring = require('querystring');
     query = querystring.stringify(this.query);
+  }
 
   var search = this.search || (query && ('?' + query)) || '';
 

From 5c144fabf64327c6d5ccd21b0d4f0df0c489d7b8 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Sun, 6 May 2018 23:09:01 +0200
Subject: [PATCH 03/20] readline: lazy loaded

---
 lib/tty.js | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/tty.js b/lib/tty.js
index 4e9023b0eb6114..b36adf2534c326 100644
--- a/lib/tty.js
+++ b/lib/tty.js
@@ -26,9 +26,11 @@ const net = require('net');
 const { TTY, isTTY } = process.binding('tty_wrap');
 const errors = require('internal/errors');
 const { ERR_INVALID_FD, ERR_TTY_INIT_FAILED } = errors.codes;
-const readline = require('readline');
 const { getColorDepth } = require('internal/tty');
 
+// Lazy loaded for startup performance.
+let readline;
+
 function isatty(fd) {
   return Number.isInteger(fd) && fd >= 0 && isTTY(fd);
 }
@@ -122,15 +124,19 @@ WriteStream.prototype._refreshSize = function() {
 
 // Backwards-compat
 WriteStream.prototype.cursorTo = function(x, y) {
+  if (readline === undefined) readline = require('readline');
   readline.cursorTo(this, x, y);
 };
 WriteStream.prototype.moveCursor = function(dx, dy) {
+  if (readline === undefined) readline = require('readline');
   readline.moveCursor(this, dx, dy);
 };
 WriteStream.prototype.clearLine = function(dir) {
+  if (readline === undefined) readline = require('readline');
   readline.clearLine(this, dir);
 };
 WriteStream.prototype.clearScreenDown = function() {
+  if (readline === undefined) readline = require('readline');
   readline.clearScreenDown(this);
 };
 WriteStream.prototype.getWindowSize = function() {

From a18174b123f35d5a1b7eaa1fcc30519c8a12881e Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Sun, 6 May 2018 23:10:23 +0200
Subject: [PATCH 04/20] os: lazy loaded

---
 lib/assert.js             | 2 +-
 lib/internal/constants.js | 4 ++++
 lib/internal/tty.js       | 9 ++++++---
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/assert.js b/lib/assert.js
index 45ddbe5f817d36..91205af09ea88b 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -34,7 +34,7 @@ const { codes: {
 const { AssertionError, errorCache } = require('internal/assert');
 const { openSync, closeSync, readSync } = require('fs');
 const { inspect, types: { isPromise, isRegExp } } = require('util');
-const { EOL } = require('os');
+const { EOL } = require('internal/constants');
 const { NativeModule } = require('internal/bootstrap/loaders');
 
 // Escape control characters but not \n and \t to keep the line breaks and
diff --git a/lib/internal/constants.js b/lib/internal/constants.js
index 5c884ae6bc4a7f..dfa30bea306e65 100644
--- a/lib/internal/constants.js
+++ b/lib/internal/constants.js
@@ -1,5 +1,7 @@
 'use strict';
 
+const isWindows = process.platform === 'win32';
+
 module.exports = {
   // Alphabet chars.
   CHAR_UPPERCASE_A: 65, /* A */
@@ -45,4 +47,6 @@ module.exports = {
   // Digits
   CHAR_0: 48, /* 0 */
   CHAR_9: 57, /* 9 */
+
+  EOL: isWindows ? '\r\n' : '\n'
 };
diff --git a/lib/internal/tty.js b/lib/internal/tty.js
index c4edab24fb87ab..1e60909f66a636 100644
--- a/lib/internal/tty.js
+++ b/lib/internal/tty.js
@@ -22,9 +22,7 @@
 
 'use strict';
 
-const { release } = require('os');
-
-const OSRelease = release().split('.');
+let OSRelease;
 
 const COLORS_2 = 1;
 const COLORS_16 = 4;
@@ -75,6 +73,11 @@ function getColorDepth(env = process.env) {
   }
 
   if (process.platform === 'win32') {
+    // Lazy load for startup performance.
+    if (OSRelease === undefined) {
+      const { release } = require('os');
+      OSRelease = release().split('.');
+    }
     // Windows 10 build 10586 is the first Windows release that supports 256
     // colors. Windows 10 build 14931 is the first release that supports
     // 16m/TrueColor.

From 02c3b4b154e053a262e6fc16083c76089930293c Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Sun, 6 May 2018 23:10:57 +0200
Subject: [PATCH 05/20] dns: lazy loaded

---
 lib/dgram.js | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/dgram.js b/lib/dgram.js
index 0a72834873e8bd..f3454ffc0702c4 100644
--- a/lib/dgram.js
+++ b/lib/dgram.js
@@ -35,7 +35,6 @@ const {
   ERR_SOCKET_DGRAM_NOT_RUNNING
 } = errors.codes;
 const { Buffer } = require('buffer');
-const dns = require('dns');
 const util = require('util');
 const { isUint8Array } = require('internal/util/types');
 const EventEmitter = require('events');
@@ -47,6 +46,9 @@ const { UV_UDP_REUSEADDR } = process.binding('constants').os;
 
 const { UDP, SendWrap } = process.binding('udp_wrap');
 
+// Lazy load for startup performance.
+let dns;
+
 const BIND_STATE_UNBOUND = 0;
 const BIND_STATE_BINDING = 1;
 const BIND_STATE_BOUND = 2;
@@ -72,9 +74,10 @@ function lookup6(lookup, address, callback) {
 
 
 function newHandle(type, lookup) {
-  if (lookup === undefined)
+  if (lookup === undefined) {
+    if (dns === undefined) dns = require('dns');
     lookup = dns.lookup;
-  else if (typeof lookup !== 'function')
+  } else if (typeof lookup !== 'function')
     throw new ERR_INVALID_ARG_TYPE('lookup', 'Function', lookup);
 
   if (type === 'udp4') {

From 9168e1502ff08917822fb4e730a6f2bfdbbb1644 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Sun, 6 May 2018 23:53:33 +0200
Subject: [PATCH 06/20] bootstrap: only load inspector stuff if necessary

---
 lib/internal/bootstrap/node.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/internal/bootstrap/node.js b/lib/internal/bootstrap/node.js
index 5993cc71f7d404..3113aa079dab2e 100644
--- a/lib/internal/bootstrap/node.js
+++ b/lib/internal/bootstrap/node.js
@@ -65,7 +65,10 @@
       NativeModule.require('internal/process/write-coverage').setup();
 
     NativeModule.require('internal/trace_events_async_hooks').setup();
-    NativeModule.require('internal/inspector_async_hook').setup();
+
+    if (process.config.variables.v8_enable_inspector) {
+      NativeModule.require('internal/inspector_async_hook').setup();
+    }
 
     _process.setupChannel();
     _process.setupRawDebug();

From 1dfa4ec6b04a834de2431cca8023e0c53adefca2 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 00:03:12 +0200
Subject: [PATCH 07/20] esm: lazy load necessary loaders

---
 lib/internal/modules/cjs/loader.js | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
index 022f58d27e2868..e471cc013a6531 100644
--- a/lib/internal/modules/cjs/loader.js
+++ b/lib/internal/modules/cjs/loader.js
@@ -23,8 +23,6 @@
 
 const { NativeModule } = require('internal/bootstrap/loaders');
 const util = require('util');
-const { decorateErrorStack } = require('internal/util');
-const { getURLFromFilePath } = require('internal/url');
 const vm = require('vm');
 const assert = require('assert').ok;
 const fs = require('fs');
@@ -53,11 +51,21 @@ const {
 
 module.exports = Module;
 
-// these are below module.exports for the circular reference
-const asyncESM = require('internal/process/esm_loader');
-const ModuleJob = require('internal/modules/esm/module_job');
-const createDynamicModule = require(
-  'internal/modules/esm/create_dynamic_module');
+let asyncESM;
+let ModuleJob;
+let createDynamicModule;
+let getURLFromFilePath;
+let decorateErrorStack;
+
+function lazyLoadESM() {
+  asyncESM = require('internal/process/esm_loader');
+  ModuleJob = require('internal/modules/esm/module_job');
+  createDynamicModule = require(
+    'internal/modules/esm/create_dynamic_module');
+  decorateErrorStack = require('internal/util').decorateErrorStack;
+  getURLFromFilePath = require('internal/url').getURLFromFilePath;
+}
+
 const {
   CHAR_UPPERCASE_A,
   CHAR_LOWERCASE_A,
@@ -497,6 +505,7 @@ Module._load = function(request, parent, isMain) {
   }
 
   if (experimentalModules && isMain) {
+    if (asyncESM === undefined) lazyLoadESM();
     asyncESM.loaderPromise.then((loader) => {
       return loader.import(getURLFromFilePath(request).pathname);
     })
@@ -604,6 +613,7 @@ Module.prototype.load = function(filename) {
   this.loaded = true;
 
   if (experimentalModules) {
+    if (asyncESM === undefined) lazyLoadESM();
     const ESMLoader = asyncESM.ESMLoader;
     const url = getURLFromFilePath(filename);
     const urlString = `${url}`;
@@ -722,6 +732,7 @@ Module._extensions['.node'] = function(module, filename) {
 };
 
 if (experimentalModules) {
+  if (asyncESM === undefined) lazyLoadESM();
   Module._extensions['.mjs'] = function(module, filename) {
     throw new ERR_REQUIRE_ESM(filename);
   };
@@ -797,5 +808,5 @@ Module._preloadModules = function(requests) {
 
 Module._initPaths();
 
-// backwards compatibility
+// Backwards compatibility
 Module.Module = Module;

From 246ab388814df5a2e046d2703530ee52e2c48c30 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 00:04:19 +0200
Subject: [PATCH 08/20] cluster: remove obsolete array allocation

The array was only used to create a key. Instead of allocating that
first, just directly create the necessary string.
---
 lib/internal/cluster/master.js | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/lib/internal/cluster/master.js b/lib/internal/cluster/master.js
index 8e4f9395da6643..457b3579b12c1c 100644
--- a/lib/internal/cluster/master.js
+++ b/lib/internal/cluster/master.js
@@ -275,12 +275,8 @@ function queryServer(worker, message) {
   if (worker.exitedAfterDisconnect)
     return;
 
-  const args = [message.address,
-                message.port,
-                message.addressType,
-                message.fd,
-                message.index];
-  const key = args.join(':');
+  const key = `${message.address}:${message.port}:${message.addressType}:` +
+              `${message.fd}:${message.index}`;
   var handle = handles[key];
 
   if (handle === undefined) {

From e8ae9a4fa9683919b2a1e1ab03afff1db7121937 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 00:15:00 +0200
Subject: [PATCH 09/20] trace_events: lazy loaded

This makes sure the async hooks and more is only loaded in case it
is actually necessary.
---
 lib/internal/bootstrap/node.js           |  12 ++-
 lib/internal/trace_events_async_hooks.js | 128 +++++++++++------------
 2 files changed, 71 insertions(+), 69 deletions(-)

diff --git a/lib/internal/bootstrap/node.js b/lib/internal/bootstrap/node.js
index 3113aa079dab2e..5d509e4e37b6c9 100644
--- a/lib/internal/bootstrap/node.js
+++ b/lib/internal/bootstrap/node.js
@@ -64,7 +64,17 @@
     if (global.__coverage__)
       NativeModule.require('internal/process/write-coverage').setup();
 
-    NativeModule.require('internal/trace_events_async_hooks').setup();
+
+    {
+      const traceEvents = process.binding('trace_events');
+      const traceEventCategory = 'node,node.async_hooks';
+
+      if (traceEvents.categoryGroupEnabled(traceEventCategory)) {
+        NativeModule.require('internal/trace_events_async_hooks')
+          .setup(traceEvents, traceEventCategory);
+      }
+    }
+
 
     if (process.config.variables.v8_enable_inspector) {
       NativeModule.require('internal/inspector_async_hook').setup();
diff --git a/lib/internal/trace_events_async_hooks.js b/lib/internal/trace_events_async_hooks.js
index db38fe99adcc9c..011dc6bbead187 100644
--- a/lib/internal/trace_events_async_hooks.js
+++ b/lib/internal/trace_events_async_hooks.js
@@ -1,71 +1,63 @@
 'use strict';
 
-const trace_events = process.binding('trace_events');
-const async_wrap = process.binding('async_wrap');
-const async_hooks = require('async_hooks');
-
-// Use small letters such that chrome://tracing groups by the name.
-// The behavior is not only useful but the same as the events emitted using
-// the specific C++ macros.
-const BEFORE_EVENT = 'b'.charCodeAt(0);
-const END_EVENT = 'e'.charCodeAt(0);
-
-// In trace_events it is not only the id but also the name that needs to be
-// repeated. Since async_hooks doesn't expose the provider type in the
-// non-init events, use a map to manually map the asyncId to the type name.
-const typeMemory = new Map();
-
-const trace_event_category = 'node,node.async_hooks';
-
-// It is faster to emit trace_events directly from C++. Thus, this happens in
-// async_wrap.cc. However, events emitted from the JavaScript API or the
-// Embedder C++ API can't be emitted from async_wrap.cc. Thus they are
-// emitted using the JavaScript API. To prevent emitting the same event
-// twice the async_wrap.Providers list is used to filter the events.
-const nativeProviders = new Set(Object.keys(async_wrap.Providers));
-
-const hook = async_hooks.createHook({
-  init(asyncId, type, triggerAsyncId, resource) {
-    if (nativeProviders.has(type)) return;
-
-    typeMemory.set(asyncId, type);
-    trace_events.emit(BEFORE_EVENT, trace_event_category,
-                      type, asyncId,
-                      'triggerAsyncId', triggerAsyncId,
-                      'executionAsyncId', async_hooks.executionAsyncId());
-  },
-
-  before(asyncId) {
-    const type = typeMemory.get(asyncId);
-    if (type === undefined) return;
-
-    trace_events.emit(BEFORE_EVENT, trace_event_category,
-                      type + '_CALLBACK', asyncId);
-  },
-
-  after(asyncId) {
-    const type = typeMemory.get(asyncId);
-    if (type === undefined) return;
-
-    trace_events.emit(END_EVENT, trace_event_category,
-                      type + '_CALLBACK', asyncId);
-  },
-
-  destroy(asyncId) {
-    const type = typeMemory.get(asyncId);
-    if (type === undefined) return;
-
-    trace_events.emit(END_EVENT, trace_event_category,
-                      type, asyncId);
-
-    // cleanup asyncId to type map
-    typeMemory.delete(asyncId);
-  }
-});
-
-
-exports.setup = function() {
-  if (trace_events.categoryGroupEnabled(trace_event_category)) {
-    hook.enable();
-  }
+exports.setup = function(traceEvents, traceEventCategory) {
+  const async_wrap = process.binding('async_wrap');
+  const async_hooks = require('async_hooks');
+
+  // Use small letters such that chrome://tracing groups by the name.
+  // The behavior is not only useful but the same as the events emitted using
+  // the specific C++ macros.
+  const BEFORE_EVENT = 'b'.charCodeAt(0);
+  const END_EVENT = 'e'.charCodeAt(0);
+
+  // In traceEvents it is not only the id but also the name that needs to be
+  // repeated. Since async_hooks doesn't expose the provider type in the
+  // non-init events, use a map to manually map the asyncId to the type name.
+  const typeMemory = new Map();
+
+  // It is faster to emit traceEvents directly from C++. Thus, this happens
+  // in async_wrap.cc. However, events emitted from the JavaScript API or the
+  // Embedder C++ API can't be emitted from async_wrap.cc. Thus they are
+  // emitted using the JavaScript API. To prevent emitting the same event
+  // twice the async_wrap.Providers list is used to filter the events.
+  const nativeProviders = new Set(Object.keys(async_wrap.Providers));
+
+  async_hooks.createHook({
+    init(asyncId, type, triggerAsyncId, resource) {
+      if (nativeProviders.has(type)) return;
+
+      typeMemory.set(asyncId, type);
+      traceEvents.emit(BEFORE_EVENT, traceEventCategory,
+                       type, asyncId,
+                       'triggerAsyncId', triggerAsyncId,
+                       'executionAsyncId', async_hooks.executionAsyncId());
+    },
+
+    before(asyncId) {
+      const type = typeMemory.get(asyncId);
+      if (type === undefined) return;
+
+      traceEvents.emit(BEFORE_EVENT, traceEventCategory,
+                       type + '_CALLBACK', asyncId);
+    },
+
+    after(asyncId) {
+      const type = typeMemory.get(asyncId);
+      if (type === undefined) return;
+
+      traceEvents.emit(END_EVENT, traceEventCategory,
+                       type + '_CALLBACK', asyncId);
+    },
+
+    destroy(asyncId) {
+      const type = typeMemory.get(asyncId);
+      if (type === undefined) return;
+
+      traceEvents.emit(END_EVENT, traceEventCategory,
+                       type, asyncId);
+
+      // cleanup asyncId to type map
+      typeMemory.delete(asyncId);
+    }
+  }).enable();
 };

From ce21afdda47dda04d6840835c3718c2f5b60fbc6 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 02:16:04 +0200
Subject: [PATCH 10/20] lib: use capital letters in comments

---
 lib/internal/bootstrap/node.js | 38 +++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/lib/internal/bootstrap/node.js b/lib/internal/bootstrap/node.js
index 5d509e4e37b6c9..96d07331985762 100644
--- a/lib/internal/bootstrap/node.js
+++ b/lib/internal/bootstrap/node.js
@@ -26,7 +26,7 @@
 
     setupProcessObject();
 
-    // do this good and early, since it handles errors.
+    // Do this good and early, since it handles errors.
     setupProcessFatal();
 
     setupV8();
@@ -108,7 +108,7 @@
     });
     process.argv[0] = process.execPath;
 
-    // Handle `--debug*` deprecation and invalidation
+    // Handle `--debug*` deprecation and invalidation.
     if (process._invalidDebug) {
       process.emitWarning(
         '`node --debug` and `node --debug-brk` are invalid. ' +
@@ -177,7 +177,7 @@
           'DeprecationWarning', 'DEP0068');
       }
 
-      // Start the debugger agent
+      // Start the debugger agent.
       process.nextTick(function() {
         NativeModule.require('internal/deps/node-inspect/lib/_inspect').start();
       });
@@ -186,7 +186,7 @@
       NativeModule.require('internal/v8_prof_processor');
 
     } else {
-      // There is user code to be run
+      // There is user code to be run.
 
       // If this is a worker in cluster mode, start up the communication
       // channel. This needs to be done before any user code gets executed
@@ -204,7 +204,7 @@
         perf.markMilestone(NODE_PERFORMANCE_MILESTONE_MODULE_LOAD_START);
         perf.markMilestone(NODE_PERFORMANCE_MILESTONE_MODULE_LOAD_END);
         // User passed '-e' or '--eval' arguments to Node without '-i' or
-        // '--interactive'
+        // '--interactive'.
 
         perf.markMilestone(
           NODE_PERFORMANCE_MILESTONE_PRELOAD_MODULE_LOAD_START);
@@ -218,7 +218,7 @@
         evalScript('[eval]');
       } else if (process.argv[1] && process.argv[1] !== '-') {
         perf.markMilestone(NODE_PERFORMANCE_MILESTONE_MODULE_LOAD_START);
-        // make process.argv[1] into a full path
+        // Make process.argv[1] into a full path.
         const path = NativeModule.require('path');
         process.argv[1] = path.resolve(process.argv[1]);
 
@@ -230,10 +230,10 @@
         preloadModules();
         perf.markMilestone(
           NODE_PERFORMANCE_MILESTONE_PRELOAD_MODULE_LOAD_END);
-        // check if user passed `-c` or `--check` arguments to Node.
+        // Check if user passed `-c` or `--check` arguments to Node.
         if (process._syntax_check_only != null) {
           const fs = NativeModule.require('fs');
-          // read the source
+          // Read the source.
           const filename = CJSModule._resolveFilename(process.argv[1]);
           const source = fs.readFileSync(filename, 'utf-8');
           checkScriptSyntax(source, filename);
@@ -365,7 +365,7 @@
   function setupGlobalConsole() {
     const originalConsole = global.console;
     const CJSModule = NativeModule.require('internal/modules/cjs/loader');
-    // Setup Node.js global.console
+    // Setup Node.js global.console.
     const wrappedConsole = NativeModule.require('console');
     Object.defineProperty(global, 'console', {
       configurable: true,
@@ -399,7 +399,7 @@
       return;
     }
     const { addCommandLineAPI, consoleCall } = process.binding('inspector');
-    // Setup inspector command line API
+    // Setup inspector command line API.
     const { makeRequireFunction } =
       NativeModule.require('internal/modules/cjs/helpers');
     const path = NativeModule.require('path');
@@ -449,14 +449,14 @@
         exceptionHandlerState.captureFn(er);
       } else if (!process.emit('uncaughtException', er)) {
         // If someone handled it, then great.  otherwise, die in C++ land
-        // since that means that we'll exit the process, emit the 'exit' event
+        // since that means that we'll exit the process, emit the 'exit' event.
         try {
           if (!process._exiting) {
             process._exiting = true;
             process.emit('exit', 1);
           }
-        } catch (er) {
-          // nothing to be done about it at this point.
+        } catch {
+          // Nothing to be done about it at this point.
         }
         try {
           const { kExpandStackSymbol } = NativeModule.require('internal/util');
@@ -467,7 +467,7 @@
       }
 
       // If we handled an error, then make sure any ticks get processed
-      // by ensuring that the next Immediate cycle isn't empty
+      // by ensuring that the next Immediate cycle isn't empty.
       NativeModule.require('timers').setImmediate(noop);
 
       // Emit the after() hooks now that the exception has been handled.
@@ -560,7 +560,7 @@
     process._tickCallback();
   }
 
-  // Load preload modules
+  // Load preload modules.
   function preloadModules() {
     if (process._preload_modules) {
       const {
@@ -577,13 +577,13 @@
       stripShebang, stripBOM
     } = NativeModule.require('internal/modules/cjs/helpers');
 
-    // remove Shebang
+    // Remove Shebang.
     source = stripShebang(source);
-    // remove BOM
+    // Remove BOM.
     source = stripBOM(source);
-    // wrap it
+    // Wrap it.
     source = CJSModule.wrap(source);
-    // compile the script, this will throw if it fails
+    // Compile the script, this will throw if it fails.
     new vm.Script(source, { displayErrors: true, filename });
   }
 

From a093ed32adf24e8bba127d15b878cf3df22caf35 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 02:18:14 +0200
Subject: [PATCH 11/20] bootstrap: remove unnecessary require

The call to url was not necessary since the `url` module itself was
already taking care of this.
---
 lib/internal/bootstrap/node.js | 4 ----
 lib/url.js                     | 2 ++
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/lib/internal/bootstrap/node.js b/lib/internal/bootstrap/node.js
index 96d07331985762..bdd2edce8668dc 100644
--- a/lib/internal/bootstrap/node.js
+++ b/lib/internal/bootstrap/node.js
@@ -90,10 +90,6 @@
       setupGlobalURL();
     }
 
-    // Ensure setURLConstructor() is called before the native
-    // URL::ToObject() method is used.
-    NativeModule.require('internal/url');
-
     // On OpenBSD process.execPath will be relative unless we
     // get the full path before process.execPath is used.
     if (process.platform === 'openbsd') {
diff --git a/lib/url.js b/lib/url.js
index c517ba7ab3dae0..3a2c3c01ea1f30 100644
--- a/lib/url.js
+++ b/lib/url.js
@@ -30,6 +30,8 @@ const {
   ERR_INVALID_ARG_TYPE
 } = require('internal/errors').codes;
 
+// This ensures setURLConstructor() is called before the native
+// URL::ToObject() method is used.
 const { spliceOne } = require('internal/util');
 
 // WHATWG URL implementation provided by internal/url

From 4733c2ae632b4239803cefe827406080a1c4026d Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 02:18:23 +0200
Subject: [PATCH 12/20] tools: stricter eslint rule for globals

---
 lib/.eslintrc.yaml                          |  2 +-
 test/parallel/test-eslint-require-buffer.js |  4 +-
 tools/eslint-rules/require-buffer.js        | 35 ---------------
 tools/eslint-rules/require-globals.js       | 50 +++++++++++++++++++++
 4 files changed, 53 insertions(+), 38 deletions(-)
 delete mode 100644 tools/eslint-rules/require-buffer.js
 create mode 100644 tools/eslint-rules/require-globals.js

diff --git a/lib/.eslintrc.yaml b/lib/.eslintrc.yaml
index 80cada0b8c9ecc..e7cab0ad931b4d 100644
--- a/lib/.eslintrc.yaml
+++ b/lib/.eslintrc.yaml
@@ -20,7 +20,7 @@ rules:
     - selector: "NewExpression[callee.name=/Error$/]:not([callee.name=/^(AssertionError|NghttpError)$/])"
       message: "Use an error exported by the internal/errors module."
   # Custom rules in tools/eslint-rules
-  node-core/require-buffer: error
+  node-core/require-globals: error
   node-core/buffer-constructor: error
   node-core/no-let-in-for-declaration: error
   node-core/lowercase-name-for-primitive: error
diff --git a/test/parallel/test-eslint-require-buffer.js b/test/parallel/test-eslint-require-buffer.js
index da17d44c7f600d..d928c435480e5e 100644
--- a/test/parallel/test-eslint-require-buffer.js
+++ b/test/parallel/test-eslint-require-buffer.js
@@ -5,7 +5,7 @@ const common = require('../common');
 common.skipIfEslintMissing();
 
 const RuleTester = require('../../tools/node_modules/eslint').RuleTester;
-const rule = require('../../tools/eslint-rules/require-buffer');
+const rule = require('../../tools/eslint-rules/require-globals');
 const ruleTester = new RuleTester({
   parserOptions: { ecmaVersion: 6 },
   env: { node: true }
@@ -18,7 +18,7 @@ const useStrict = '\'use strict\';\n\n';
 const bufferModule = 'const { Buffer } = require(\'buffer\');\n';
 const mockComment = '// Some Comment\n//\n// Another Comment\n\n';
 const useBuffer = 'Buffer;';
-ruleTester.run('require-buffer', rule, {
+ruleTester.run('require-globals', rule, {
   valid: [
     'foo',
     'const Buffer = require("Buffer"); Buffer;',
diff --git a/tools/eslint-rules/require-buffer.js b/tools/eslint-rules/require-buffer.js
deleted file mode 100644
index b12b9ce04e7cfc..00000000000000
--- a/tools/eslint-rules/require-buffer.js
+++ /dev/null
@@ -1,35 +0,0 @@
-'use strict';
-const BUFFER_REQUIRE = 'const { Buffer } = require(\'buffer\');';
-
-module.exports = function(context) {
-
-  function flagIt(reference) {
-    const msg = `Use ${BUFFER_REQUIRE} at the beginning of this file`;
-
-    context.report({
-      node: reference.identifier,
-      message: msg,
-      fix: (fixer) => {
-        const sourceCode = context.getSourceCode();
-
-        const useStrict = /'use strict';\n\n?/g;
-        const hasUseStrict = !!useStrict.exec(sourceCode.text);
-        const firstLOC = sourceCode.ast.range[0];
-        const rangeNeedle = hasUseStrict ? useStrict.lastIndex : firstLOC;
-
-        return fixer.insertTextBeforeRange([rangeNeedle],
-                                           `${BUFFER_REQUIRE}\n`);
-      }
-    });
-  }
-
-  return {
-    'Program:exit': function() {
-      const globalScope = context.getScope();
-      const variable = globalScope.set.get('Buffer');
-      if (variable) {
-        variable.references.forEach(flagIt);
-      }
-    }
-  };
-};
diff --git a/tools/eslint-rules/require-globals.js b/tools/eslint-rules/require-globals.js
new file mode 100644
index 00000000000000..bc49ff6c8746ed
--- /dev/null
+++ b/tools/eslint-rules/require-globals.js
@@ -0,0 +1,50 @@
+'use strict';
+
+// This rule makes sure that no Globals are going to be used in /lib.
+// That could otherwise result in problems with the repl.
+
+module.exports = function(context) {
+
+  function flagIt(msg, fix) {
+    return (reference) => {
+      context.report({
+        node: reference.identifier,
+        message: msg,
+        fix: (fixer) => {
+          const sourceCode = context.getSourceCode();
+
+          const useStrict = /'use strict';\n\n?/g;
+          const hasUseStrict = !!useStrict.exec(sourceCode.text);
+          const firstLOC = sourceCode.ast.range[0];
+          const rangeNeedle = hasUseStrict ? useStrict.lastIndex : firstLOC;
+
+          return fixer.insertTextBeforeRange([rangeNeedle], `${fix}\n`);
+        }
+      });
+    };
+  }
+
+  return {
+    'Program:exit': function() {
+      const globalScope = context.getScope();
+      let variable = globalScope.set.get('Buffer');
+      if (variable) {
+        const fix = "const { Buffer } = require('buffer');";
+        const msg = `Use ${fix} at the beginning of this file`;
+        variable.references.forEach(flagIt(msg, fix));
+      }
+      variable = globalScope.set.get('URL');
+      if (variable) {
+        const fix = "const { URL } = require('url');";
+        const msg = `Use ${fix} at the beginning of this file`;
+        variable.references.forEach(flagIt(msg, fix));
+      }
+      variable = globalScope.set.get('URLSearchParams');
+      if (variable) {
+        const fix = "const { URLSearchParams } = require('url');";
+        const msg = `Use ${fix} at the beginning of this file`;
+        variable.references.forEach(flagIt(msg, fix));
+      }
+    }
+  };
+};

From e0080ce2ac48226ac58b84b9fa79635791a0ed9b Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 03:53:02 +0200
Subject: [PATCH 13/20] assert,util: lazy load comparison functions

---
 lib/assert.js | 18 ++++++++++++++----
 lib/util.js   | 13 ++++++++-----
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/lib/assert.js b/lib/assert.js
index 91205af09ea88b..4dafdd2bf04a54 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -21,10 +21,6 @@
 'use strict';
 
 const { Buffer } = require('buffer');
-const {
-  isDeepEqual,
-  isDeepStrictEqual
-} = require('internal/util/comparisons');
 const { codes: {
   ERR_AMBIGUOUS_ARGUMENT,
   ERR_INVALID_ARG_TYPE,
@@ -37,6 +33,15 @@ const { inspect, types: { isPromise, isRegExp } } = require('util');
 const { EOL } = require('internal/constants');
 const { NativeModule } = require('internal/bootstrap/loaders');
 
+let isDeepEqual;
+let isDeepStrictEqual;
+
+function lazyLoadComparison() {
+  const comparison = require('internal/util/comparisons');
+  isDeepEqual = comparison.isDeepEqual;
+  isDeepStrictEqual = comparison.isDeepStrictEqual;
+}
+
 // Escape control characters but not \n and \t to keep the line breaks and
 // indentation intact.
 // eslint-disable-next-line no-control-regex
@@ -285,6 +290,7 @@ assert.notEqual = function notEqual(actual, expected, message) {
 
 // The equivalence assertion tests a deep equality relation.
 assert.deepEqual = function deepEqual(actual, expected, message) {
+  if (isDeepEqual === undefined) lazyLoadComparison();
   if (!isDeepEqual(actual, expected)) {
     innerFail({
       actual,
@@ -298,6 +304,7 @@ assert.deepEqual = function deepEqual(actual, expected, message) {
 
 // The non-equivalence assertion tests for any deep inequality.
 assert.notDeepEqual = function notDeepEqual(actual, expected, message) {
+  if (isDeepEqual === undefined) lazyLoadComparison();
   if (isDeepEqual(actual, expected)) {
     innerFail({
       actual,
@@ -311,6 +318,7 @@ assert.notDeepEqual = function notDeepEqual(actual, expected, message) {
 /* eslint-enable */
 
 assert.deepStrictEqual = function deepStrictEqual(actual, expected, message) {
+  if (isDeepEqual === undefined) lazyLoadComparison();
   if (!isDeepStrictEqual(actual, expected)) {
     innerFail({
       actual,
@@ -324,6 +332,7 @@ assert.deepStrictEqual = function deepStrictEqual(actual, expected, message) {
 
 assert.notDeepStrictEqual = notDeepStrictEqual;
 function notDeepStrictEqual(actual, expected, message) {
+  if (isDeepEqual === undefined) lazyLoadComparison();
   if (isDeepStrictEqual(actual, expected)) {
     innerFail({
       actual,
@@ -437,6 +446,7 @@ function expectedException(actual, expected, msg) {
       throw new ERR_INVALID_ARG_VALUE('error',
                                       expected, 'may not be an empty object');
     }
+    if (isDeepEqual === undefined) lazyLoadComparison();
     for (const key of keys) {
       if (typeof actual[key] === 'string' &&
           isRegExp(expected[key]) &&
diff --git a/lib/util.js b/lib/util.js
index 45d98de194c836..bd7a98694b91a9 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -64,10 +64,6 @@ const {
   isTypedArray
 } = types;
 
-const {
-  isDeepStrictEqual
-} = require('internal/util/comparisons');
-
 const {
   customInspectSymbol,
   deprecate,
@@ -95,6 +91,7 @@ const dateToISOString = Date.prototype.toISOString;
 const errorToString = Error.prototype.toString;
 
 let CIRCULAR_ERROR_MESSAGE;
+let internalDeepEqual;
 
 /* eslint-disable */
 const strEscapeSequencesRegExp = /[\x00-\x1f\x27\x5c]/;
@@ -1261,7 +1258,13 @@ module.exports = exports = {
   isArray: Array.isArray,
   isBoolean,
   isBuffer,
-  isDeepStrictEqual,
+  isDeepStrictEqual(a, b) {
+    if (internalDeepEqual === undefined) {
+      internalDeepEqual = require('internal/util/comparisons')
+        .isDeepStrictEqual;
+    }
+    return internalDeepEqual(a, b);
+  },
   isNull,
   isNullOrUndefined,
   isNumber,

From bd96a9d5f333e06b0834d241ff6a25f2e06bb0ec Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 04:25:26 +0200
Subject: [PATCH 14/20] async_hook: lazy loading for startup performance

---
 lib/internal/inspector_async_hook.js | 62 ++++++++++++++++------------
 1 file changed, 35 insertions(+), 27 deletions(-)

diff --git a/lib/internal/inspector_async_hook.js b/lib/internal/inspector_async_hook.js
index b190ff90b8ea2c..6a7489af974a40 100644
--- a/lib/internal/inspector_async_hook.js
+++ b/lib/internal/inspector_async_hook.js
@@ -1,49 +1,56 @@
 'use strict';
 
-const { createHook } = require('async_hooks');
 const inspector = process.binding('inspector');
-const config = process.binding('config');
 
 if (!inspector || !inspector.asyncTaskScheduled) {
   exports.setup = function() {};
   return;
 }
 
-const hook = createHook({
-  init(asyncId, type, triggerAsyncId, resource) {
+let hook;
+let config;
+
+function lazyHookCreation() {
+  const { createHook } = require('async_hooks');
+  config = process.binding('config');
+
+  hook = createHook({
+    init(asyncId, type, triggerAsyncId, resource) {
     // It's difficult to tell which tasks will be recurring and which won't,
     // therefore we mark all tasks as recurring. Based on the discussion
     // in https://github.com/nodejs/node/pull/13870#discussion_r124515293,
     // this should be fine as long as we call asyncTaskCanceled() too.
-    const recurring = true;
-    if (type === 'PROMISE')
-      this.promiseIds.add(asyncId);
-    else
-      inspector.asyncTaskScheduled(type, asyncId, recurring);
-  },
+      const recurring = true;
+      if (type === 'PROMISE')
+        this.promiseIds.add(asyncId);
+      else
+        inspector.asyncTaskScheduled(type, asyncId, recurring);
+    },
 
-  before(asyncId) {
-    if (this.promiseIds.has(asyncId))
-      return;
-    inspector.asyncTaskStarted(asyncId);
-  },
+    before(asyncId) {
+      if (this.promiseIds.has(asyncId))
+        return;
+      inspector.asyncTaskStarted(asyncId);
+    },
 
-  after(asyncId) {
-    if (this.promiseIds.has(asyncId))
-      return;
-    inspector.asyncTaskFinished(asyncId);
-  },
+    after(asyncId) {
+      if (this.promiseIds.has(asyncId))
+        return;
+      inspector.asyncTaskFinished(asyncId);
+    },
 
-  destroy(asyncId) {
-    if (this.promiseIds.has(asyncId))
-      return this.promiseIds.delete(asyncId);
-    inspector.asyncTaskCanceled(asyncId);
-  },
-});
+    destroy(asyncId) {
+      if (this.promiseIds.has(asyncId))
+        return this.promiseIds.delete(asyncId);
+      inspector.asyncTaskCanceled(asyncId);
+    },
+  });
 
-hook.promiseIds = new Set();
+  hook.promiseIds = new Set();
+}
 
 function enable() {
+  if (hook === undefined) lazyHookCreation();
   if (config.bits < 64) {
     // V8 Inspector stores task ids as (void*) pointers.
     // async_hooks store ids as 64bit numbers.
@@ -61,6 +68,7 @@ function enable() {
 }
 
 function disable() {
+  if (hook === undefined) lazyHookCreation();
   hook.disable();
 }
 

From d31581f61d0952066be406031889d4a6f0cd0c94 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 04:25:54 +0200
Subject: [PATCH 15/20] bootstrap: do not call performance hooks

---
 lib/internal/bootstrap/node.js | 1 -
 lib/internal/process.js        | 5 -----
 2 files changed, 6 deletions(-)

diff --git a/lib/internal/bootstrap/node.js b/lib/internal/bootstrap/node.js
index bdd2edce8668dc..e23ec858f33cc8 100644
--- a/lib/internal/bootstrap/node.js
+++ b/lib/internal/bootstrap/node.js
@@ -57,7 +57,6 @@
     } = perf.constants;
 
     _process.setup_hrtime();
-    _process.setup_performance();
     _process.setup_cpuUsage();
     _process.setupMemoryUsage();
     _process.setupKillAndExit();
diff --git a/lib/internal/process.js b/lib/internal/process.js
index cc8318cbe3ce53..3d02e6eb87cc6a 100644
--- a/lib/internal/process.js
+++ b/lib/internal/process.js
@@ -24,10 +24,6 @@ process.assert = deprecate(
   'process.assert() is deprecated. Please use the `assert` module instead.',
   'DEP0100');
 
-function setup_performance() {
-  require('perf_hooks');
-}
-
 // Set up the process.cpuUsage() function.
 function setup_cpuUsage() {
   // Get the native function, which will be replaced with a JS version.
@@ -284,7 +280,6 @@ function setupUncaughtExceptionCapture(exceptionHandlerState) {
 }
 
 module.exports = {
-  setup_performance,
   setup_cpuUsage,
   setup_hrtime,
   setupMemoryUsage,

From 0093e0d173a4e795aa8a5ef6151d7db078a0b744 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 05:11:55 +0200
Subject: [PATCH 16/20] stream: lazy load ReadableAsyncIterator

---
 lib/_stream_readable.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
index 8bbddc97274358..74cba547f6b773 100644
--- a/lib/_stream_readable.js
+++ b/lib/_stream_readable.js
@@ -38,11 +38,11 @@ const {
   ERR_METHOD_NOT_IMPLEMENTED,
   ERR_STREAM_UNSHIFT_AFTER_END_EVENT
 } = require('internal/errors').codes;
-const ReadableAsyncIterator = require('internal/streams/async_iterator');
 const { emitExperimentalWarning } = require('internal/util');
 
 // Lazy loaded to improve the startup performance.
 let StringDecoder;
+let ReadableAsyncIterator;
 
 util.inherits(Readable, Stream);
 
@@ -987,7 +987,8 @@ Readable.prototype.wrap = function(stream) {
 
 Readable.prototype[Symbol.asyncIterator] = function() {
   emitExperimentalWarning('Readable[Symbol.asyncIterator]');
-
+  if (ReadableAsyncIterator === undefined)
+    ReadableAsyncIterator = require('internal/streams/async_iterator');
   return new ReadableAsyncIterator(this);
 };
 

From 0b31adca20ade1801825b03aa782cf2458705b69 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 05:12:10 +0200
Subject: [PATCH 17/20] console: lazy load cli

---
 lib/console.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/console.js b/lib/console.js
index 46b7f7627eddae..868b2f286bedf4 100644
--- a/lib/console.js
+++ b/lib/console.js
@@ -31,7 +31,6 @@ const {
 } = require('internal/errors');
 const { previewMapIterator, previewSetIterator } = require('internal/v8');
 const { Buffer: { isBuffer } } = require('buffer');
-const cliTable = require('internal/cli_table');
 const util = require('util');
 const {
   isTypedArray, isSet, isMap, isSetIterator, isMapIterator,
@@ -49,6 +48,9 @@ const {
   from: ArrayFrom,
 } = Array;
 
+// Lazy loaded for startup performance.
+let cliTable;
+
 // Track amount of indentation required via `console.group()`.
 const kGroupIndent = Symbol('kGroupIndent');
 
@@ -329,6 +331,7 @@ Console.prototype.table = function(tabularData, properties) {
       (typeof tabularData !== 'object' && typeof tabularData !== 'function'))
     return this.log(tabularData);
 
+  if (cliTable === undefined) cliTable = require('internal/cli_table');
   const final = (k, v) => this.log(cliTable(k, v));
 
   const inspect = (v) => {

From 5c3a245603e8f4de7dea33bdb8d4d70faac6d736 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 05:12:32 +0200
Subject: [PATCH 18/20] stream: lazy load end-of-stream

---
 lib/internal/streams/pipeline.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/internal/streams/pipeline.js b/lib/internal/streams/pipeline.js
index 7e87210a774c5f..1178108842be61 100644
--- a/lib/internal/streams/pipeline.js
+++ b/lib/internal/streams/pipeline.js
@@ -3,7 +3,7 @@
 
 'use strict';
 
-const eos = require('internal/streams/end-of-stream');
+let eos;
 
 const {
   ERR_MISSING_ARGS,
@@ -33,6 +33,7 @@ function destroyer(stream, reading, writing, callback) {
     closed = true;
   });
 
+  if (eos === undefined) eos = require('internal/streams/end-of-stream');
   eos(stream, { readable: reading, writable: writing }, (err) => {
     if (err) return callback(err);
     closed = true;

From b0bbbba97e558fc92b0dc229be03dddd9b544a8c Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 05:12:47 +0200
Subject: [PATCH 19/20] net: lazy load dns

---
 lib/net.js | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/lib/net.js b/lib/net.js
index 5537c472fe05e3..7d0a4a0e54a255 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -75,13 +75,12 @@ const {
   ERR_SOCKET_BAD_PORT,
   ERR_SOCKET_CLOSED
 } = errors.codes;
-const dns = require('dns');
 
 const kLastWriteQueueSize = Symbol('lastWriteQueueSize');
 
-// `cluster` is only used by `listenInCluster` so for startup performance
-// reasons it's lazy loaded.
-var cluster = null;
+// Lazy loaded to improve startup performance.
+let cluster;
+let dns;
 
 const errnoException = errors.errnoException;
 const exceptionWithHostPort = errors.exceptionWithHostPort;
@@ -1034,6 +1033,8 @@ function lookupAndConnect(self, options) {
     throw new ERR_INVALID_ARG_TYPE('options.lookup',
                                    'Function', options.lookup);
 
+
+  if (dns === undefined) dns = require('dns');
   var dnsopts = {
     family: options.family,
     hints: options.hints || 0
@@ -1368,7 +1369,7 @@ function listenInCluster(server, address, port, addressType,
                          backlog, fd, exclusive) {
   exclusive = !!exclusive;
 
-  if (cluster === null) cluster = require('cluster');
+  if (cluster === undefined) cluster = require('cluster');
 
   if (cluster.isMaster || exclusive) {
     // Will create a new handle
@@ -1482,6 +1483,7 @@ Server.prototype.listen = function(...args) {
 };
 
 function lookupAndListen(self, port, address, backlog, exclusive) {
+  if (dns === undefined) dns = require('dns');
   dns.lookup(address, function doListen(err, ip, addressType) {
     if (err) {
       self.emit('error', err);

From 3ca0b58759baa4bb2a25e76111fe75781f122373 Mon Sep 17 00:00:00 2001
From: Ruben Bridgewater <ruben@bridgewater.de>
Date: Mon, 7 May 2018 06:04:07 +0200
Subject: [PATCH 20/20] test: add loaded modules test

This makes sure there is no regression by switching to loading
eagerly.
---
 test/parallel/test-bootstrap-modules.js | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 test/parallel/test-bootstrap-modules.js

diff --git a/test/parallel/test-bootstrap-modules.js b/test/parallel/test-bootstrap-modules.js
new file mode 100644
index 00000000000000..4a46ac905b8161
--- /dev/null
+++ b/test/parallel/test-bootstrap-modules.js
@@ -0,0 +1,14 @@
+/* eslint-disable node-core/required-modules */
+
+'use strict';
+
+// Ordinarily test files must require('common') but that action causes
+// the global console to be compiled, defeating the purpose of this test.
+// This makes sure no additional files are added without carefully considering
+// lazy loading. Please adjust the value if necessary.
+
+const list = process.moduleLoadList.slice();
+
+const assert = require('assert');
+
+assert(list.length <= 73, list);