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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

PR-URL: #32217
Backport-PR-URL: #34592
Reviewed-By: Gus Caplan <[email protected]>
Reviewed-By: Bradley Farias <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
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aduh95 authored and BethGriggs committed Aug 18, 2020
1 parent e5049f2 commit 729799d
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35 changes: 35 additions & 0 deletions doc/api/deprecations.md
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Expand Up @@ -2560,6 +2560,41 @@ written twice. This introduces a race condition between threads, and is a
potential security vulnerability. There is no safe, cross-platform alternative
API.

<a id="DEP0144"></a>
### DEP0144: `module.parent`
<!-- YAML
changes:
- version:
- REPLACEME
- v14.6.0
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));
```

[`--http-parser=legacy`]: cli.html#cli_http_parser_library
[`--pending-deprecation`]: cli.html#cli_pending_deprecation
[`--throw-deprecation`]: cli.html#cli_throw_deprecation
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14 changes: 12 additions & 2 deletions doc/api/modules.md
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Expand Up @@ -894,11 +894,19 @@ loading.
### `module.parent`
<!-- YAML
added: v0.1.16
deprecated:
- REPLACEME
- v14.6.0
-->

* {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 @@ -1122,13 +1130,15 @@ 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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