module: add createRequireFunction method

PR-URL: #19360 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Jan Krems <[email protected]> Reviewed-By: Bradley Farias <[email protected]> Reviewed-By: John-David Dalton <[email protected]>
nodejs · Sep 25, 2018 · 600c225 · 600c225
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diff --git a/doc/api/modules.md b/doc/api/modules.md
@@ -888,12 +888,30 @@ by the [module wrapper][]. To access it, require the `Module` module:
 const builtin = require('module').builtinModules;
 ```
 
+### module.createRequireFromPath(filename)
+<!-- YAML
+added: REPLACEME
+-->
+
+* `filename` {string} Filename to be used to construct the relative require
+  function.
+* Returns: {[`require`][]} Require function
+
+```js
+const { createRequireFromPath } = require('module');
+const requireUtil = createRequireFromPath('../src/utils');
+
+// require `../src/utils/some-tool`
+requireUtil('./some-tool');
+```
+
 [`__dirname`]: #modules_dirname
 [`__filename`]: #modules_filename
 [`Error`]: errors.html#errors_class_error
 [`module` object]: #modules_the_module_object
 [`path.dirname()`]: path.html#path_path_dirname_path
 [GLOBAL_FOLDERS]: #modules_loading_from_the_global_folders
+[`require`]: #modules_require
 [exports shortcut]: #modules_exports_shortcut
 [module resolution]: #modules_all_together
 [module wrapper]: #modules_the_module_wrapper

diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
@@ -23,6 +23,7 @@
 
 const { NativeModule } = require('internal/bootstrap/loaders');
 const util = require('util');
+const { pathToFileURL } = require('internal/url');
 const vm = require('vm');
 const assert = require('assert').ok;
 const fs = require('fs');
@@ -54,7 +55,6 @@ module.exports = Module;
 let asyncESM;
 let ModuleJob;
 let createDynamicModule;
-let pathToFileURL;
 let decorateErrorStack;
 
 function lazyLoadESM() {
@@ -63,7 +63,6 @@ function lazyLoadESM() {
   createDynamicModule = require(
     'internal/modules/esm/create_dynamic_module');
   decorateErrorStack = require('internal/util').decorateErrorStack;
-  pathToFileURL = require('internal/url').pathToFileURL;
 }
 
 const {
@@ -745,6 +744,13 @@ Module.runMain = function() {
   process._tickCallback();
 };
 
+Module.createRequireFromPath = (filename) => {
+  const m = new Module(filename);
+  m.filename = filename;
+  m.paths = Module._nodeModulePaths(path.dirname(filename));
+  return makeRequireFunction(m);
+};
+
 Module._initPaths = function() {
   const isWindows = process.platform === 'win32';
 

diff --git a/test/parallel/test-module-create-require.js b/test/parallel/test-module-create-require.js
@@ -0,0 +1,12 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const path = require('path');
+
+const { createRequireFromPath } = require('module');
+
+const p = path.resolve(__dirname, '..', 'fixtures', 'fake.js');
+
+const req = createRequireFromPath(p);
+assert.strictEqual(req('./baz'), 'perhaps I work');