test: add es6 module global leakage tests

* created testing es6 module for global leakage tests
* fixed a couple basic errors (vars -> lets, ...)
* added globals leakage detection to es module tests
* reversed whitespace change
* whitespace change reversed

PR-URL: https://github.com/nodejs/node/pull/16341
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/common/index.mjs

@@ -0,0 +1,109 @@
+// Flags: --experimental-modules
+/* eslint-disable required-modules */
+
+import assert from 'assert';
+
+let knownGlobals = [
+  Buffer,
+  clearImmediate,
+  clearInterval,
+  clearTimeout,
+  console,
+  constructor, // Enumerable in V8 3.21.
+  global,
+  process,
+  setImmediate,
+  setInterval,
+  setTimeout
+];
+
+if (process.env.NODE_TEST_KNOWN_GLOBALS) {
+  const knownFromEnv = process.env.NODE_TEST_KNOWN_GLOBALS.split(',');
+  allowGlobals(...knownFromEnv);
+}
+
+export function allowGlobals(...whitelist) {
+  knownGlobals = knownGlobals.concat(whitelist);
+}
+
+export function leakedGlobals() {
+  //add possible expected globals
+  if (global.gc) {
+    knownGlobals.push(global.gc);
+  }
+
+  if (global.DTRACE_HTTP_SERVER_RESPONSE) {
+    knownGlobals.push(DTRACE_HTTP_SERVER_RESPONSE);
+    knownGlobals.push(DTRACE_HTTP_SERVER_REQUEST);
+    knownGlobals.push(DTRACE_HTTP_CLIENT_RESPONSE);
+    knownGlobals.push(DTRACE_HTTP_CLIENT_REQUEST);
+    knownGlobals.push(DTRACE_NET_STREAM_END);
+    knownGlobals.push(DTRACE_NET_SERVER_CONNECTION);
+  }
+
+  if (global.COUNTER_NET_SERVER_CONNECTION) {
+    knownGlobals.push(COUNTER_NET_SERVER_CONNECTION);
+    knownGlobals.push(COUNTER_NET_SERVER_CONNECTION_CLOSE);
+    knownGlobals.push(COUNTER_HTTP_SERVER_REQUEST);
+    knownGlobals.push(COUNTER_HTTP_SERVER_RESPONSE);
+    knownGlobals.push(COUNTER_HTTP_CLIENT_REQUEST);
+    knownGlobals.push(COUNTER_HTTP_CLIENT_RESPONSE);
+  }
+
+  if (global.LTTNG_HTTP_SERVER_RESPONSE) {
+    knownGlobals.push(LTTNG_HTTP_SERVER_RESPONSE);
+    knownGlobals.push(LTTNG_HTTP_SERVER_REQUEST);
+    knownGlobals.push(LTTNG_HTTP_CLIENT_RESPONSE);
+    knownGlobals.push(LTTNG_HTTP_CLIENT_REQUEST);
+    knownGlobals.push(LTTNG_NET_STREAM_END);
+    knownGlobals.push(LTTNG_NET_SERVER_CONNECTION);
+  }
+
+  if (global.ArrayBuffer) {
+    knownGlobals.push(ArrayBuffer);
+    knownGlobals.push(Int8Array);
+    knownGlobals.push(Uint8Array);
+    knownGlobals.push(Uint8ClampedArray);
+    knownGlobals.push(Int16Array);
+    knownGlobals.push(Uint16Array);
+    knownGlobals.push(Int32Array);
+    knownGlobals.push(Uint32Array);
+    knownGlobals.push(Float32Array);
+    knownGlobals.push(Float64Array);
+    knownGlobals.push(DataView);
+  }
+
+  // Harmony features.
+  if (global.Proxy) {
+    knownGlobals.push(Proxy);
+  }
+
+  if (global.Symbol) {
+    knownGlobals.push(Symbol);
+  }
+
+  const leaked = [];
+
+  for (const val in global) {
+    if (!knownGlobals.includes(global[val])) {
+      leaked.push(val);
+    }
+  }
+
+  if (global.__coverage__) {
+    return leaked.filter((varname) => !/^(?:cov_|__cov)/.test(varname));
+  } else {
+    return leaked;
+  }
+}
+
+// Turn this off if the test should not check for global leaks.
+export let globalCheck = true;  // eslint-disable-line
+
+process.on('exit', function() {
+  if (!globalCheck) return;
+  const leaked = leakedGlobals();
+  if (leaked.length > 0) {
+    assert.fail(`Unexpected global(s) found: ${leaked.join(', ')}`);
+  }
+});

test/es-module/test-esm-json.mjs

@@ -1,5 +1,6 @@
 // Flags: --experimental-modules
 /* eslint-disable required-modules */
+import '../common/index';
 import assert from 'assert';
 import ok from './test-esm-ok.mjs';
 import json from './json.json';

test/es-module/test-esm-named-exports.mjs

@@ -1,5 +1,6 @@
 // Flags: --experimental-modules --loader ./test/fixtures/es-module-loaders/builtin-named-exports-loader.mjs
 /* eslint-disable required-modules */
+import '../common/index';
 import { readFile } from 'fs';
 import assert from 'assert';
 import ok from './test-esm-ok.mjs';

test/es-module/test-esm-namespace.mjs

@@ -1,6 +1,7 @@
 // Flags: --experimental-modules
 /* eslint-disable required-modules */
 
+import '../common/index';
 import * as fs from 'fs';
 import assert from 'assert';
 

test/es-module/test-esm-snapshot.mjs

@@ -1,5 +1,6 @@
 // Flags: --experimental-modules
 /* eslint-disable required-modules */
+import '../common/index';
 import './esm-snapshot-mutator';
 import one from './esm-snapshot';
 import assert from 'assert';