301 lines
		
	
	
	
		
			11 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
			
		
		
	
	
			301 lines
		
	
	
	
		
			11 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
# resolve <sup>[![Version Badge][2]][1]</sup>
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implements the [node `require.resolve()` algorithm](https://nodejs.org/api/modules.html#modules_all_together) such that you can `require.resolve()` on behalf of a file asynchronously and synchronously
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[![github actions][actions-image]][actions-url]
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[![coverage][codecov-image]][codecov-url]
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[![dependency status][5]][6]
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[![dev dependency status][7]][8]
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[![License][license-image]][license-url]
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[![Downloads][downloads-image]][downloads-url]
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[![npm badge][11]][1]
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# example
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asynchronously resolve:
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```js
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var resolve = require('resolve/async'); // or, require('resolve')
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resolve('tap', { basedir: __dirname }, function (err, res) {
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    if (err) console.error(err);
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    else console.log(res);
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});
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```
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```
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$ node example/async.js
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/home/substack/projects/node-resolve/node_modules/tap/lib/main.js
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```
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synchronously resolve:
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```js
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var resolve = require('resolve/sync'); // or, `require('resolve').sync
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var res = resolve('tap', { basedir: __dirname });
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console.log(res);
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```
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```
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$ node example/sync.js
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/home/substack/projects/node-resolve/node_modules/tap/lib/main.js
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```
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# methods
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```js
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var resolve = require('resolve');
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var async = require('resolve/async');
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var sync = require('resolve/sync');
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```
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For both the synchronous and asynchronous methods, errors may have any of the following `err.code` values:
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- `MODULE_NOT_FOUND`: the given path string (`id`) could not be resolved to a module
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- `INVALID_BASEDIR`: the specified `opts.basedir` doesn't exist, or is not a directory
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- `INVALID_PACKAGE_MAIN`: a `package.json` was encountered with an invalid `main` property (eg. not a string)
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## resolve(id, opts={}, cb)
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Asynchronously resolve the module path string `id` into `cb(err, res [, pkg])`, where `pkg` (if defined) is the data from `package.json`.
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options are:
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* opts.basedir - directory to begin resolving from
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* opts.package - `package.json` data applicable to the module being loaded
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* opts.extensions - array of file extensions to search in order
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* opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search
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* opts.readFile - how to read files asynchronously
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* opts.isFile - function to asynchronously test whether a file exists
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* opts.isDirectory - function to asynchronously test whether a file exists and is a directory
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* opts.realpath - function to asynchronously resolve a potential symlink to its real path
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* `opts.readPackage(readFile, pkgfile, cb)` - function to asynchronously read and parse a package.json file
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  * readFile - the passed `opts.readFile` or `fs.readFile` if not specified
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  * pkgfile - path to package.json
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  * cb - callback
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* `opts.packageFilter(pkg, pkgfile, dir)` - transform the parsed package.json contents before looking at the "main" field
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  * pkg - package data
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  * pkgfile - path to package.json
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  * dir - directory that contains package.json
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* `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package
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  * pkg - package data
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  * path - the path being resolved
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  * relativePath - the path relative from the package.json location
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  * returns - a relative path that will be joined from the package.json location
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* opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this)
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  For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function
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    * request - the import specifier being resolved
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    * start - lookup path
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    * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
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    * opts - the resolution options
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* `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this)
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    * request - the import specifier being resolved
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    * start - lookup path
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    * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
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    * opts - the resolution options
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* opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"`
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* opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving.
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This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag.
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**Note:** this property is currently `true` by default but it will be changed to
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`false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*.
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default `opts` values:
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```js
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{
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    paths: [],
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    basedir: __dirname,
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    extensions: ['.js'],
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    includeCoreModules: true,
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    readFile: fs.readFile,
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    isFile: function isFile(file, cb) {
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        fs.stat(file, function (err, stat) {
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            if (!err) {
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                return cb(null, stat.isFile() || stat.isFIFO());
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            }
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            if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false);
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            return cb(err);
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        });
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    },
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    isDirectory: function isDirectory(dir, cb) {
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        fs.stat(dir, function (err, stat) {
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            if (!err) {
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                return cb(null, stat.isDirectory());
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            }
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            if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false);
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            return cb(err);
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        });
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    },
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    realpath: function realpath(file, cb) {
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        var realpath = typeof fs.realpath.native === 'function' ? fs.realpath.native : fs.realpath;
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        realpath(file, function (realPathErr, realPath) {
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            if (realPathErr && realPathErr.code !== 'ENOENT') cb(realPathErr);
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            else cb(null, realPathErr ? file : realPath);
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        });
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    },
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    readPackage: function defaultReadPackage(readFile, pkgfile, cb) {
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        readFile(pkgfile, function (readFileErr, body) {
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            if (readFileErr) cb(readFileErr);
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            else {
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                try {
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                    var pkg = JSON.parse(body);
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                    cb(null, pkg);
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                } catch (jsonErr) {
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                    cb(null);
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                }
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            }
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        });
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    },
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    moduleDirectory: 'node_modules',
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    preserveSymlinks: true
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}
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```
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## resolve.sync(id, opts)
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Synchronously resolve the module path string `id`, returning the result and
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throwing an error when `id` can't be resolved.
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options are:
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* opts.basedir - directory to begin resolving from
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* opts.extensions - array of file extensions to search in order
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* opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search
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* opts.readFileSync - how to read files synchronously
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* opts.isFile - function to synchronously test whether a file exists
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* opts.isDirectory - function to synchronously test whether a file exists and is a directory
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* opts.realpathSync - function to synchronously resolve a potential symlink to its real path
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* `opts.readPackageSync(readFileSync, pkgfile)` - function to synchronously read and parse a package.json file
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  * readFileSync - the passed `opts.readFileSync` or `fs.readFileSync` if not specified
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  * pkgfile - path to package.json
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* `opts.packageFilter(pkg, dir)` - transform the parsed package.json contents before looking at the "main" field
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  * pkg - package data
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  * dir - directory that contains package.json (Note: the second argument will change to "pkgfile" in v2)
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* `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package
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  * pkg - package data
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  * path - the path being resolved
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  * relativePath - the path relative from the package.json location
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  * returns - a relative path that will be joined from the package.json location
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* opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this)
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  For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function
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    * request - the import specifier being resolved
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    * start - lookup path
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    * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
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    * opts - the resolution options
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* `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this)
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    * request - the import specifier being resolved
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    * start - lookup path
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    * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
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    * opts - the resolution options
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* opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"`
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* opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving.
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This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag.
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**Note:** this property is currently `true` by default but it will be changed to
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`false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*.
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default `opts` values:
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```js
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{
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    paths: [],
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    basedir: __dirname,
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    extensions: ['.js'],
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    includeCoreModules: true,
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    readFileSync: fs.readFileSync,
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    isFile: function isFile(file) {
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        try {
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            var stat = fs.statSync(file);
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        } catch (e) {
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            if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false;
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            throw e;
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        }
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        return stat.isFile() || stat.isFIFO();
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    },
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    isDirectory: function isDirectory(dir) {
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        try {
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            var stat = fs.statSync(dir);
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        } catch (e) {
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            if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false;
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            throw e;
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        }
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        return stat.isDirectory();
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    },
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    realpathSync: function realpathSync(file) {
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        try {
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            var realpath = typeof fs.realpathSync.native === 'function' ? fs.realpathSync.native : fs.realpathSync;
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            return realpath(file);
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        } catch (realPathErr) {
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            if (realPathErr.code !== 'ENOENT') {
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                throw realPathErr;
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            }
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        }
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        return file;
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    },
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    readPackageSync: function defaultReadPackageSync(readFileSync, pkgfile) {
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        var body = readFileSync(pkgfile);
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        try {
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            var pkg = JSON.parse(body);
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            return pkg;
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        } catch (jsonErr) {}
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    },
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    moduleDirectory: 'node_modules',
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    preserveSymlinks: true
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}
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```
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# install
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With [npm](https://npmjs.org) do:
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```sh
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npm install resolve
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```
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# license
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MIT
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[1]: https://npmjs.org/package/resolve
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[2]: https://versionbadg.es/browserify/resolve.svg
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[5]: https://david-dm.org/browserify/resolve.svg
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[6]: https://david-dm.org/browserify/resolve
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[7]: https://david-dm.org/browserify/resolve/dev-status.svg
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[8]: https://david-dm.org/browserify/resolve#info=devDependencies
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[11]: https://nodei.co/npm/resolve.png?downloads=true&stars=true
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[license-image]: https://img.shields.io/npm/l/resolve.svg
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[license-url]: LICENSE
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[downloads-image]: https://img.shields.io/npm/dm/resolve.svg
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[downloads-url]: https://npm-stat.com/charts.html?package=resolve
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[codecov-image]: https://codecov.io/gh/browserify/resolve/branch/main/graphs/badge.svg
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[codecov-url]: https://app.codecov.io/gh/browserify/resolve/
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[actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/browserify/resolve
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[actions-url]: https://github.com/browserify/resolve/actions
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