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module: deprecate module.parent
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This feature does not work when a module is imported using ECMAScript
modules specification, therefore it is deprecated.

Fixes: nodejs/modules#469

Backport-PR-URL: #33533
PR-URL: #32217
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
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aduh95 authored and MylesBorins committed Jul 16, 2020
1 parent b2cd87e commit 8d7330b
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33 changes: 33 additions & 0 deletions doc/api/deprecations.md
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Expand Up @@ -2707,6 +2707,39 @@ Type: Runtime
`Transform._transformState` will be removed in future versions where it is
no longer required due to simplification of the implementation.

<a id="DEP0144"></a>
### DEP0144: `module.parent`
<!-- YAML
changes:
- version: REPLACEME
pr-url: https://github.com/nodejs/node/pull/32217
description: Documentation-only deprecation.
-->

Type: Documentation-only

A CommonJS module can access the first module that required it using
`module.parent`. This feature is deprecated because it does not work
consistently in the presence of ECMAScript modules and because it gives an
inaccurate representation of the CommonJS module graph.

Some modules use it to check if they are the entry point of the current process.
Instead, it is recommended to compare `require.main` and `module`:

```js
if (require.main === module) {
// Code section that will run only if current file is the entry point.
}
```

When looking for the CommonJS modules that have required the current one,
`require.cache` and `module.children` can be used:

```js
const moduleParents = Object.values(require.cache)
.filter((m) => m.children.includes(module));
```

<a id="DEP0XXX"></a>
### DEP0XXX: `socket.bufferSize`
<!-- YAML
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12 changes: 10 additions & 2 deletions doc/api/modules.md
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Expand Up @@ -905,11 +905,17 @@ loading.
### `module.parent`
<!-- YAML
added: v0.1.16
deprecated: REPLACEME
-->

* {module}
> Stability: 0 - Deprecated: Please use [`require.main`][] and
> [`module.children`][] instead.
* {module | null | undefined}

The module that first required this one.
The module that first required this one, or `null` if the current module is the
entry point of the current process, or `undefined` if the module was loaded by
something that is not a CommonJS module (E.G.: REPL or `import`).

### `module.path`
<!-- YAML
Expand Down Expand Up @@ -1133,13 +1139,15 @@ consists of the following keys:
[`createRequire()`]: #modules_module_createrequire_filename
[`module` object]: #modules_the_module_object
[`module.id`]: #modules_module_id
[`module.children`]: #modules_module_children
[`path.dirname()`]: path.html#path_path_dirname_path
[ECMAScript Modules]: esm.html
[an error]: errors.html#errors_err_require_esm
[exports shortcut]: #modules_exports_shortcut
[module resolution]: #modules_all_together
[module wrapper]: #modules_the_module_wrapper
[native addons]: addons.html
[`require.main`]: #modules_require_main
[source map include directives]: https://sourcemaps.info/spec.html#h.lmz475t4mvbx
[`--enable-source-maps`]: cli.html#cli_enable_source_maps
[`NODE_V8_COVERAGE=dir`]: cli.html#cli_node_v8_coverage_dir
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3 changes: 2 additions & 1 deletion lib/internal/modules/cjs/loader.js
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Expand Up @@ -1247,7 +1247,8 @@ Module._extensions['.js'] = function(module, filename) {
const pkg = readPackageScope(filename);
// Function require shouldn't be used in ES modules.
if (pkg && pkg.data && pkg.data.type === 'module') {
const parentPath = module.parent && module.parent.filename;
const { parent } = module;
const parentPath = parent && parent.filename;
const packageJsonPath = path.resolve(pkg.path, 'package.json');
throw new ERR_REQUIRE_ESM(filename, parentPath, packageJsonPath);
}
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4 changes: 2 additions & 2 deletions test/common/index.js
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Expand Up @@ -59,12 +59,12 @@ if (process.argv.length === 2 &&
!process.env.NODE_SKIP_FLAG_CHECK &&
isMainThread &&
hasCrypto &&
module.parent &&
require.main &&
require('cluster').isMaster) {
// The copyright notice is relatively big and the flags could come afterwards.
const bytesToRead = 1500;
const buffer = Buffer.allocUnsafe(bytesToRead);
const fd = fs.openSync(module.parent.filename, 'r');
const fd = fs.openSync(require.main.filename, 'r');
const bytesRead = fs.readSync(fd, buffer, 0, bytesToRead);
fs.closeSync(fd);
const source = buffer.toString('utf8', 0, bytesRead);
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2 changes: 1 addition & 1 deletion test/common/require-as.js
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@@ -1,7 +1,7 @@
/* eslint-disable node-core/require-common-first, node-core/required-modules */
'use strict';

if (module.parent) {
if (require.main !== module) {
const { spawnSync } = require('child_process');

function runModuleAs(filename, flags, spawnOptions, role) {
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2 changes: 1 addition & 1 deletion test/js-native-api/test_instance_data/test.js
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Expand Up @@ -4,7 +4,7 @@
const common = require('../../common');
const assert = require('assert');

if (module.parent) {
if (module !== require.main) {
// When required as a module, run the tests.
const test_instance_data =
require(`./build/${common.buildType}/test_instance_data`);
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2 changes: 1 addition & 1 deletion test/node-api/test_instance_data/test.js
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Expand Up @@ -3,7 +3,7 @@

const common = require('../../common');

if (module.parent) {
if (module !== require.main) {
// When required as a module, run the tests.
const test_instance_data =
require(`./build/${common.buildType}/test_instance_data`);
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2 changes: 1 addition & 1 deletion test/parallel/test-cli-eval.js
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Expand Up @@ -20,7 +20,7 @@
// USE OR OTHER DEALINGS IN THE SOFTWARE.

'use strict';
if (module.parent) {
if (module !== require.main) {
// Signal we've been loaded as a module.
// The following console.log() is part of the test.
console.log('Loaded as a module, exiting with status code 42.');
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