lib: export submodules in parent builtins

lib/stream.js

@@ -22,6 +22,7 @@
 'use strict';
 
 const {
+  ObjectDefineProperties,
   ObjectDefineProperty,
 } = primordials;
 
@@ -51,12 +52,34 @@ Stream.finished = eos;
 Stream.destroy = destroyer;
 Stream.compose = compose;
 
-ObjectDefineProperty(Stream, 'promises', {
-  configurable: true,
-  enumerable: true,
-  get() {
-    return promises;
-  }
+let consumers;
+let web;
+ObjectDefineProperties(Stream, {
+  consumers: {
+    configurable: true,
+    enumerable: true,
+    get() {
+      if (consumers === undefined)
+        consumers = require('stream/consumers');
+      return consumers;
+    }
+  },
+  web: {
+    configurable: true,
+    enumerable: true,
+    get() {
+      if (web === undefined)
+        web = require('stream/web');
+      return web;
+    }
+  },
+  promises: {
+    configurable: true,
+    enumerable: true,
+    get() {
+      return promises;
+    },
+  },
 });
 
 ObjectDefineProperty(pipeline, customPromisify, {

lib/timers.js

@@ -360,3 +360,13 @@ module.exports = {
     'timers.enroll() is deprecated. Please use setTimeout instead.',
     'DEP0095')
 };
+
+ObjectDefineProperty(module.exports, 'promises', {
+  configurable: true,
+  enumerable: true,
+  get() {
+    if (!timersPromises)
+      timersPromises = require('timers/promises');
+    return timersPromises;
+  },
+});

test/parallel/test-builtins-exports-submodules.js

@@ -0,0 +1,14 @@
+// Flags: --no-warnings
+'use strict';
+
+require('../common');
+const { strictEqual } = require('assert');
+const { builtinModules } = require('module');
+
+for (const module of builtinModules) {
+  if (!module.includes('/')) continue;
+  const subIdx = module.lastIndexOf('/');
+  const parent = module.slice(0, subIdx);
+  const child = module.slice(subIdx + 1);
+  strictEqual(require(parent)[child], require(module));
+}