diff --git a/doc/api/cli.md b/doc/api/cli.md index 3152f9409d5721..14f53fa70a429e 100644 --- a/doc/api/cli.md +++ b/doc/api/cli.md @@ -1034,6 +1034,10 @@ following permissions are restricted: added: - v22.0.0 - v20.17.0 +changes: + - version: REPLACEME + pr-url: https://github.com/nodejs/node/pull/55085 + description: This is now true by default. --> > Stability: 1.1 - Active Development @@ -1659,6 +1663,24 @@ added: v16.6.0 Use this flag to disable top-level await in REPL. +### `--no-experimental-require-module` + + + +> Stability: 1.1 - Active Development + +Disable support for loading a synchronous ES module graph in `require()`. + +See [Loading ECMAScript modules using `require()`][]. + ### `--no-experimental-websocket` -This flag is only useful when `--experimental-require-module` is enabled. - -If the ES module being `require()`'d contains top-level await, this flag +If the ES module being `require()`'d contains top-level `await`, this flag allows Node.js to evaluate the module, try to locate the top-level awaits, and print their location to help users find them. diff --git a/doc/api/errors.md b/doc/api/errors.md index 71671c33be47f0..10b0aea8754da1 100644 --- a/doc/api/errors.md +++ b/doc/api/errors.md @@ -2426,8 +2426,8 @@ object. > Stability: 1 - Experimental -When trying to `require()` a [ES Module][] under `--experimental-require-module`, -a CommonJS to ESM or ESM to CommonJS edge participates in an immediate cycle. +When trying to `require()` a [ES Module][], a CommonJS to ESM or ESM to CommonJS edge +participates in an immediate cycle. This is not allowed because ES Modules cannot be evaluated while they are already being evaluated. @@ -2441,8 +2441,8 @@ module, and should be done lazily in an inner function. > Stability: 1 - Experimental -When trying to `require()` a [ES Module][] under `--experimental-require-module`, -the module turns out to be asynchronous. That is, it contains top-level await. +When trying to `require()` a [ES Module][], the module turns out to be asynchronous. +That is, it contains top-level await. To see where the top-level await is, use `--experimental-print-required-tla` (this would execute the modules @@ -2452,12 +2452,20 @@ before looking for the top-level awaits). ### `ERR_REQUIRE_ESM` -> Stability: 1 - Experimental + + +> Stability: 0 - Deprecated An attempt was made to `require()` an [ES Module][]. -To enable `require()` for synchronous module graphs (without -top-level `await`), use `--experimental-require-module`. +This error has been deprecated since `require()` now supports loading synchronous +ES modules. When `require()` encounters an ES module that contains top-level +`await`, it will throw [`ERR_REQUIRE_ASYNC_MODULE`][] instead. @@ -4061,6 +4069,7 @@ Type stripping is not supported for files descendent of a `node_modules` directo [`ERR_INVALID_ARG_TYPE`]: #err_invalid_arg_type [`ERR_MISSING_MESSAGE_PORT_IN_TRANSFER_LIST`]: #err_missing_message_port_in_transfer_list [`ERR_MISSING_TRANSFERABLE_IN_TRANSFER_LIST`]: #err_missing_transferable_in_transfer_list +[`ERR_REQUIRE_ASYNC_MODULE`]: #err_require_async_module [`EventEmitter`]: events.md#class-eventemitter [`MessagePort`]: worker_threads.md#class-messageport [`Object.getPrototypeOf`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getPrototypeOf diff --git a/doc/api/esm.md b/doc/api/esm.md index d1215b3caf5be5..9f7f2b094e1ab2 100644 --- a/doc/api/esm.md +++ b/doc/api/esm.md @@ -468,7 +468,7 @@ compatibility. ### `require` The CommonJS module `require` currently only supports loading synchronous ES -modules when `--experimental-require-module` is enabled. +modules (that is, ES modules that do not use top-level `await`). See [Loading ECMAScript modules using `require()`][] for details. diff --git a/doc/api/modules.md b/doc/api/modules.md index c60a334a52143d..2d2198830e4b98 100644 --- a/doc/api/modules.md +++ b/doc/api/modules.md @@ -170,15 +170,18 @@ relative, and based on the real path of the files making the calls to ## Loading ECMAScript modules using `require()` + + The `.mjs` extension is reserved for [ECMAScript Modules][]. -Currently, if the flag `--experimental-require-module` is not used, loading -an ECMAScript module using `require()` will throw a [`ERR_REQUIRE_ESM`][] -error, and users need to use [`import()`][] instead. See -[Determining module system][] section for more info +See [Determining module system][] section for more info regarding which files are parsed as ECMAScript modules. -If `--experimental-require-module` is enabled, and the ECMAScript module being -loaded by `require()` meets the following requirements: +`require()` only supports loading ECMAScript modules that meet the following requirements: * The module is fully synchronous (contains no top-level `await`); and * One of these conditions are met: @@ -187,8 +190,8 @@ loaded by `require()` meets the following requirements: 3. The file has a `.js` extension, the closest `package.json` does not contain `"type": "commonjs"`, and the module contains ES module syntax. -`require()` will load the requested module as an ES Module, and return -the module namespace object. In this case it is similar to dynamic +If the ES Module being loaded meet the requirements, `require()` can load it and +return the module namespace object. In this case it is similar to dynamic `import()` but is run synchronously and returns the name space object directly. @@ -207,7 +210,7 @@ class Point { export default Point; ``` -A CommonJS module can load them with `require()` under `--experimental-detect-module`: +A CommonJS module can load them with `require()`: ```cjs const distance = require('./distance.mjs'); @@ -236,13 +239,19 @@ conventions. Code authored directly in CommonJS should avoid depending on it. If the module being `require()`'d contains top-level `await`, or the module graph it `import`s contains top-level `await`, [`ERR_REQUIRE_ASYNC_MODULE`][] will be thrown. In this case, users should -load the asynchronous module using `import()`. +load the asynchronous module using [`import()`][]. If `--experimental-print-required-tla` is enabled, instead of throwing `ERR_REQUIRE_ASYNC_MODULE` before evaluation, Node.js will evaluate the module, try to locate the top-level awaits, and print their location to help users fix them. +Support for loading ES modules using `require()` is currently +experimental and can be disabled using `--no-experimental-require-module`. +When `require()` actually encounters an ES module for the +first time in the process, it will emit an experimental warning. The +warning is expected to be removed when this feature stablizes. + ## All together @@ -272,8 +281,7 @@ require(X) from module at path Y MAYBE_DETECT_AND_LOAD(X) 1. If X parses as a CommonJS module, load X as a CommonJS module. STOP. -2. Else, if `--experimental-require-module` is - enabled, and the source code of X can be parsed as ECMAScript module using +2. Else, if the source code of X can be parsed as ECMAScript module using DETECT_MODULE_SYNTAX defined in the ESM resolver, a. Load X as an ECMAScript module. STOP. @@ -1190,7 +1198,6 @@ This section was moved to [`"main"`]: packages.md#main [`"type"`]: packages.md#type [`ERR_REQUIRE_ASYNC_MODULE`]: errors.md#err_require_async_module -[`ERR_REQUIRE_ESM`]: errors.md#err_require_esm [`ERR_UNSUPPORTED_DIR_IMPORT`]: errors.md#err_unsupported_dir_import [`MODULE_NOT_FOUND`]: errors.md#module_not_found [`__dirname`]: #__dirname diff --git a/doc/api/packages.md b/doc/api/packages.md index 5648f56df68996..13100dd65a33e7 100644 --- a/doc/api/packages.md +++ b/doc/api/packages.md @@ -172,8 +172,7 @@ There is the CommonJS module loader: * It treats all files that lack `.json` or `.node` extensions as JavaScript text files. * It can only be used to [load ECMASCript modules from CommonJS modules][] if - the module graph is synchronous (that contains no top-level `await`) when - `--experimental-require-module` is enabled. + the module graph is synchronous (that contains no top-level `await`). When used to load a JavaScript text file that is not an ECMAScript module, the file will be loaded as a CommonJS module. @@ -662,8 +661,7 @@ specific to least specific as conditions should be defined: * `"require"` - matches when the package is loaded via `require()`. The referenced file should be loadable with `require()` although the condition matches regardless of the module format of the target file. Expected - formats include CommonJS, JSON, native addons, and ES modules - if `--experimental-require-module` is enabled. _Always mutually + formats include CommonJS, JSON, native addons, and ES modules. _Always mutually exclusive with `"import"`._ * `"module-sync"` - matches no matter the package is loaded via `import`, `import()` or `require()`. The format is expected to be ES modules that does diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js index 674aaca5b4a508..32fe45ead67f97 100644 --- a/lib/internal/modules/cjs/loader.js +++ b/lib/internal/modules/cjs/loader.js @@ -438,7 +438,6 @@ function initializeCJS() { Module._extensions['.ts'] = loadTS; } if (getOptionValue('--experimental-require-module')) { - emitExperimentalWarning('Support for loading ES Module in require()'); Module._extensions['.mjs'] = loadESMFromCJS; if (tsEnabled) { Module._extensions['.mts'] = loadESMFromCJS; @@ -1386,6 +1385,7 @@ function loadESMFromCJS(mod, filename) { // ESM won't be accessible via process.mainModule. setOwnProperty(process, 'mainModule', undefined); } else { + emitExperimentalWarning('Support for loading ES Module in require()'); const { wrap, namespace, diff --git a/lib/internal/modules/esm/load.js b/lib/internal/modules/esm/load.js index 8b157f0f461c7b..1932dd3c9ca369 100644 --- a/lib/internal/modules/esm/load.js +++ b/lib/internal/modules/esm/load.js @@ -131,11 +131,6 @@ async function defaultLoad(url, context = kEmptyObject) { validateAttributes(url, format, importAttributes); - // Use the synchronous commonjs translator which can deal with cycles. - if (format === 'commonjs' && getOptionValue('--experimental-require-module')) { - format = 'commonjs-sync'; - } - if (getOptionValue('--experimental-strip-types') && (format === 'module-typescript' || format === 'commonjs-typescript') && isUnderNodeModules(url)) { @@ -191,11 +186,6 @@ function defaultLoadSync(url, context = kEmptyObject) { validateAttributes(url, format, importAttributes); - // Use the synchronous commonjs translator which can deal with cycles. - if (format === 'commonjs' && getOptionValue('--experimental-require-module')) { - format = 'commonjs-sync'; - } - return { __proto__: null, format, diff --git a/lib/internal/modules/esm/loader.js b/lib/internal/modules/esm/loader.js index 26aec37d6e084a..787793c527698d 100644 --- a/lib/internal/modules/esm/loader.js +++ b/lib/internal/modules/esm/loader.js @@ -373,15 +373,15 @@ class ModuleLoader { defaultLoadSync ??= require('internal/modules/esm/load').defaultLoadSync; const loadResult = defaultLoadSync(url, { format, importAttributes }); - const { - format: finalFormat, - source, - } = loadResult; + + // Use the synchronous commonjs translator which can deal with cycles. + const finalFormat = loadResult.format === 'commonjs' ? 'commonjs-sync' : loadResult.format; if (finalFormat === 'wasm') { assert.fail('WASM is currently unsupported by require(esm)'); } + const { source } = loadResult; const isMain = (parentURL === undefined); const wrap = this.#translate(url, finalFormat, source, isMain); assert(wrap instanceof ModuleWrap, `Translator used for require(${url}) should not be async`); diff --git a/lib/internal/modules/esm/module_job.js b/lib/internal/modules/esm/module_job.js index 62206fcc44c2d1..413fcd27703e3e 100644 --- a/lib/internal/modules/esm/module_job.js +++ b/lib/internal/modules/esm/module_job.js @@ -361,6 +361,7 @@ class ModuleJobSync extends ModuleJobBase { } runSync() { + // TODO(joyeecheung): add the error decoration logic from the async instantiate. this.module.instantiateSync(); setHasStartedUserESMExecution(); const namespace = this.module.evaluateSync(); diff --git a/lib/internal/modules/esm/utils.js b/lib/internal/modules/esm/utils.js index 2799af0f8dd492..99061e62976e7c 100644 --- a/lib/internal/modules/esm/utils.js +++ b/lib/internal/modules/esm/utils.js @@ -75,17 +75,15 @@ function initializeDefaultConditions() { const userConditions = getOptionValue('--conditions'); const noAddons = getOptionValue('--no-addons'); const addonConditions = noAddons ? [] : ['node-addons']; - + const moduleConditions = getOptionValue('--experimental-require-module') ? ['module-sync'] : []; defaultConditions = ObjectFreeze([ 'node', 'import', + ...moduleConditions, ...addonConditions, ...userConditions, ]); defaultConditionsSet = new SafeSet(defaultConditions); - if (getOptionValue('--experimental-require-module')) { - defaultConditionsSet.add('module-sync'); - } } /** diff --git a/src/node_options.cc b/src/node_options.cc index 77e68f5104c0b1..234684eb7cee85 100644 --- a/src/node_options.cc +++ b/src/node_options.cc @@ -374,9 +374,10 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() { &EnvironmentOptions::print_required_tla, kAllowedInEnvvar); AddOption("--experimental-require-module", - "Allow loading explicit ES Modules in require().", + "Allow loading synchronous ES Modules in require().", &EnvironmentOptions::require_module, - kAllowedInEnvvar); + kAllowedInEnvvar, + true); AddOption("--diagnostic-dir", "set dir for all output files" " (default: current working directory)", diff --git a/src/node_options.h b/src/node_options.h index b521ca76185512..443ac5a7a47bc0 100644 --- a/src/node_options.h +++ b/src/node_options.h @@ -117,7 +117,7 @@ class EnvironmentOptions : public Options { std::vector conditions; bool detect_module = true; bool print_required_tla = false; - bool require_module = false; + bool require_module = true; std::string dns_result_order; bool enable_source_maps = false; bool experimental_eventsource = false; diff --git a/test/es-module/test-cjs-esm-warn.js b/test/es-module/test-cjs-esm-warn.js index ccd4d276fdd535..0945a737fb72c4 100644 --- a/test/es-module/test-cjs-esm-warn.js +++ b/test/es-module/test-cjs-esm-warn.js @@ -1,3 +1,6 @@ +// Previously, this tested that require(esm) throws ERR_REQUIRE_ESM, which is no longer applicable +// since require(esm) is now supported. The test has been repurposed to ensure that the old behavior +// is preserved when the --no-experimental-require-module flag is used. 'use strict'; const { spawnPromisified } = require('../common'); @@ -22,7 +25,9 @@ describe('CJS ↔︎ ESM interop warnings', { concurrency: !process.env.TEST_PAR fixtures.path('/es-modules/package-type-module/cjs.js') ); const basename = 'cjs.js'; - const { code, signal, stderr } = await spawnPromisified(execPath, [requiringCjsAsEsm]); + const { code, signal, stderr } = await spawnPromisified(execPath, [ + '--no-experimental-require-module', requiringCjsAsEsm, + ]); assert.ok( stderr.replaceAll('\r', '').includes( @@ -48,7 +53,9 @@ describe('CJS ↔︎ ESM interop warnings', { concurrency: !process.env.TEST_PAR fixtures.path('/es-modules/package-type-module/esm.js') ); const basename = 'esm.js'; - const { code, signal, stderr } = await spawnPromisified(execPath, [requiringEsm]); + const { code, signal, stderr } = await spawnPromisified(execPath, [ + '--no-experimental-require-module', requiringEsm, + ]); assert.ok( stderr.replace(/\r/g, '').includes( diff --git a/test/es-module/test-esm-detect-ambiguous.mjs b/test/es-module/test-esm-detect-ambiguous.mjs index 5d5a2744afcd14..8da2fea8022a63 100644 --- a/test/es-module/test-esm-detect-ambiguous.mjs +++ b/test/es-module/test-esm-detect-ambiguous.mjs @@ -402,15 +402,16 @@ describe('Module syntax detection', { concurrency: !process.env.TEST_PARALLEL }, }); }); -// Validate temporarily disabling `--abort-on-uncaught-exception` -// while running `containsModuleSyntax`. +// Checks the error caught during module detection does not trigger abort when +// `--abort-on-uncaught-exception` is passed in (as that's a caught internal error). // Ref: https://github.com/nodejs/node/issues/50878 describe('Wrapping a `require` of an ES module while using `--abort-on-uncaught-exception`', () => { it('should work', async () => { const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [ '--abort-on-uncaught-exception', + '--no-warnings', '--eval', - 'assert.throws(() => require("./package-type-module/esm.js"), { code: "ERR_REQUIRE_ESM" })', + 'require("./package-type-module/esm.js")', ], { cwd: fixtures.path('es-modules'), }); diff --git a/test/es-module/test-esm-loader-hooks.mjs b/test/es-module/test-esm-loader-hooks.mjs index a36e726810431e..50e9ccdb38c398 100644 --- a/test/es-module/test-esm-loader-hooks.mjs +++ b/test/es-module/test-esm-loader-hooks.mjs @@ -774,6 +774,7 @@ describe('Loader hooks', { concurrency: !process.env.TEST_PARALLEL }, () => { describe('should use hooks', async () => { const { code, signal, stdout, stderr } = await spawnPromisified(process.execPath, [ + '--no-experimental-require-module', '--import', fixtures.fileURL('es-module-loaders/builtin-named-exports.mjs'), fixtures.path('es-modules/require-esm-throws-with-loaders.js'), diff --git a/test/es-module/test-esm-type-field-errors-2.js b/test/es-module/test-esm-type-field-errors-2.js new file mode 100644 index 00000000000000..3ea259446c7fb2 --- /dev/null +++ b/test/es-module/test-esm-type-field-errors-2.js @@ -0,0 +1,17 @@ +// Flags: --no-experimental-require-module +// Previously, this tested that require(esm) throws ERR_REQUIRE_ESM, which is no longer applicable +// since require(esm) is now supported. The test has been repurposed to ensure that the old behavior +// is preserved when the --no-experimental-require-module flag is used. + +'use strict'; +require('../common'); +const assert = require('assert'); +const { describe, it } = require('node:test'); + +describe('Errors related to ESM type field', () => { + it('Should throw an error when loading CJS from a `type: "module"` package.', () => { + assert.throws(() => require('../fixtures/es-modules/package-type-module/index.js'), { + code: 'ERR_REQUIRE_ESM' + }); + }); +}); diff --git a/test/es-module/test-esm-type-field-errors.js b/test/es-module/test-esm-type-field-errors.js index 9ec9aa64e18c07..4bf52f3ad6e7d3 100644 --- a/test/es-module/test-esm-type-field-errors.js +++ b/test/es-module/test-esm-type-field-errors.js @@ -50,12 +50,6 @@ describe('ESM type field errors', { concurrency: true }, () => { true, ); }); - - it('--input-type=module disallowed for directories', () => { - assert.throws(() => require('../fixtures/es-modules/package-type-module/index.js'), { - code: 'ERR_REQUIRE_ESM' - }); - }); }); function expect(opt = '', inputFile, want, wantsError = false) { diff --git a/test/es-module/test-require-module-preload.js b/test/es-module/test-require-module-preload.js index f2e572969a050c..65ec1a93bc9d4b 100644 --- a/test/es-module/test-require-module-preload.js +++ b/test/es-module/test-require-module-preload.js @@ -3,9 +3,12 @@ require('../common'); const { spawnSyncAndAssert } = require('../common/child_process'); const { fixturesDir } = require('../common/fixtures'); -const stderr = /ExperimentalWarning: Support for loading ES Module in require/; +const warningRE = /ExperimentalWarning: Support for loading ES Module in require/; function testPreload(preloadFlag) { + // The warning is only emitted when ESM is loaded by --require. + const stderr = preloadFlag !== '--import' ? warningRE : undefined; + // Test named exports. { spawnSyncAndAssert( @@ -112,7 +115,7 @@ testPreload('--import'); }, { stdout: /^package-type-module\s+A$/, - stderr, + stderr: warningRE, trim: true, } ); diff --git a/test/es-module/test-typescript-commonjs.mjs b/test/es-module/test-typescript-commonjs.mjs index 0ee687e0dcdbe6..c24576c4a0c392 100644 --- a/test/es-module/test-typescript-commonjs.mjs +++ b/test/es-module/test-typescript-commonjs.mjs @@ -100,6 +100,7 @@ test('execute a .cts file importing a .ts file export', async () => { test('execute a .cts file importing a .mts file export', async () => { const result = await spawnPromisified(process.execPath, [ '--experimental-strip-types', + '--no-experimental-require-module', fixtures.path('typescript/cts/test-require-mts-module.cts'), ]); @@ -158,6 +159,7 @@ test('expect failure of a .ts file in node_modules', async () => { test('expect failure of a .cts requiring esm without default type module', async () => { const result = await spawnPromisified(process.execPath, [ '--experimental-strip-types', + '--no-experimental-require-module', fixtures.path('typescript/cts/test-mts-node_modules.cts'), ]); diff --git a/test/es-module/test-typescript-module.mjs b/test/es-module/test-typescript-module.mjs index 7b75466e02ce9b..6b6b0e68f251f6 100644 --- a/test/es-module/test-typescript-module.mjs +++ b/test/es-module/test-typescript-module.mjs @@ -67,6 +67,7 @@ test('execute an .mts file importing a .cts file', async () => { test('execute an .mts file with wrong default module', async () => { const result = await spawnPromisified(process.execPath, [ '--experimental-strip-types', + '--no-experimental-require-module', '--experimental-default-type=commonjs', fixtures.path('typescript/mts/test-import-module.mts'), ]); @@ -76,6 +77,18 @@ test('execute an .mts file with wrong default module', async () => { strictEqual(result.code, 1); }); +test('execute an .mts file with wrong default module', async () => { + const result = await spawnPromisified(process.execPath, [ + '--experimental-strip-types', + '--experimental-require-module', + '--experimental-default-type=commonjs', + fixtures.path('typescript/mts/test-import-module.mts'), + ]); + + match(result.stdout, /Hello, TypeScript!/); + strictEqual(result.code, 0); +}); + test('execute an .mts file from node_modules', async () => { const result = await spawnPromisified(process.execPath, [ '--experimental-strip-types', diff --git a/test/es-module/test-typescript.mjs b/test/es-module/test-typescript.mjs index 496e42178f4a3e..9732a51c4122d7 100644 --- a/test/es-module/test-typescript.mjs +++ b/test/es-module/test-typescript.mjs @@ -32,11 +32,11 @@ test('execute a TypeScript file with imports', async () => { const result = await spawnPromisified(process.execPath, [ '--no-warnings', '--eval', - `assert.throws(() => require(${JSON.stringify(fixtures.path('typescript/ts/test-import-fs.ts'))}), {code: 'ERR_REQUIRE_ESM'})`, + `require(${JSON.stringify(fixtures.path('typescript/ts/test-import-fs.ts'))})`, ]); strictEqual(result.stderr, ''); - strictEqual(result.stdout, ''); + match(result.stdout, /Hello, TypeScript!/); strictEqual(result.code, 0); }); @@ -283,9 +283,8 @@ test('execute a TypeScript file with CommonJS syntax requiring .mts', async () = fixtures.path('typescript/ts/test-require-mts.ts'), ]); - strictEqual(result.stdout, ''); - match(result.stderr, /Error \[ERR_REQUIRE_ESM\]: require\(\) of ES Module/); - strictEqual(result.code, 1); + match(result.stdout, /Hello, TypeScript!/); + strictEqual(result.code, 0); }); test('execute a TypeScript file with CommonJS syntax requiring .mts with require-module', async () => { diff --git a/test/fixtures/es-module-loaders/loader-with-custom-condition.mjs b/test/fixtures/es-module-loaders/loader-with-custom-condition.mjs index 3aefed51d57d3e..90c55fa576bb3c 100644 --- a/test/fixtures/es-module-loaders/loader-with-custom-condition.mjs +++ b/test/fixtures/es-module-loaders/loader-with-custom-condition.mjs @@ -5,6 +5,7 @@ export async function resolve(specifier, context, defaultResolve) { deepStrictEqual([...context.conditions].sort(), [ 'import', + 'module-sync', 'node', 'node-addons', ]); diff --git a/test/parallel/test-require-mjs.js b/test/parallel/test-require-mjs.js index 112f08879d4290..c169ec07ab6bd8 100644 --- a/test/parallel/test-require-mjs.js +++ b/test/parallel/test-require-mjs.js @@ -1,3 +1,8 @@ +// Flags: --no-experimental-require-module +// Previously, this tested that require(esm) throws ERR_REQUIRE_ESM, which is no longer applicable +// since require(esm) is now supported. The test has been repurposed to ensure that the old behavior +// is preserved when the --no-experimental-require-module flag is used. + 'use strict'; require('../common'); const assert = require('assert');