Bootstrap: make global.process, global.Buffer getters

lib/internal/bootstrap/pre_execution.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const { getOptionValue } = require('internal/options');
+const { Buffer } = require('buffer');
 
 function prepareMainThreadExecution() {
   // Patch the process object with legacy properties and normalizations
@@ -221,6 +222,33 @@ function initializeDeprecations() {
                                 'process.binding() is deprecated. ' +
                                 'Please use public APIs instead.', 'DEP0111');
   }
+
+  // Create global.process and global.Buffer as getters so that we have a
+  // deprecation path for these in ES Modules.
+  // See https://github.com/nodejs/node/pull/26334.
+  let _process = process;
+  Object.defineProperty(global, 'process', {
+    get() {
+      return _process;
+    },
+    set(value) {
+      _process = value;
+    },
+    enumerable: false,
+    configurable: true
+  });
+
+  let _Buffer = Buffer;
+  Object.defineProperty(global, 'Buffer', {
+    get() {
+      return _Buffer;
+    },
+    set(value) {
+      _Buffer = value;
+    },
+    enumerable: false,
+    configurable: true
+  });
 }
 
 function setupChildProcessIpcChannel() {

test/parallel/test-global-setters.js

@@ -0,0 +1,27 @@
+/* eslint-disable strict */
+require('../common');
+const assert = require('assert');
+const _process = require('process');
+const { Buffer: _Buffer } = require('buffer');
+
+assert.strictEqual(process, _process);
+// eslint-disable-next-line no-global-assign
+process = 'asdf';
+assert.strictEqual(process, 'asdf');
+assert.strictEqual(global.process, 'asdf');
+global.process = _process;
+assert.strictEqual(process, _process);
+assert.strictEqual(
+  typeof Object.getOwnPropertyDescriptor(global, 'process').get,
+  'function');
+
+assert.strictEqual(Buffer, _Buffer);
+// eslint-disable-next-line no-global-assign
+Buffer = 'asdf';
+assert.strictEqual(Buffer, 'asdf');
+assert.strictEqual(global.Buffer, 'asdf');
+global.Buffer = _Buffer;
+assert.strictEqual(Buffer, _Buffer);
+assert.strictEqual(
+  typeof Object.getOwnPropertyDescriptor(global, 'Buffer').get,
+  'function');