582 lines
19 KiB
Markdown
582 lines
19 KiB
Markdown
# cosmiconfig
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[](https://travis-ci.org/davidtheclark/cosmiconfig) [](https://ci.appveyor.com/project/davidtheclark/cosmiconfig/branch/main)
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[](https://codecov.io/gh/davidtheclark/cosmiconfig)
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Cosmiconfig searches for and loads configuration for your program.
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It features smart defaults based on conventional expectations in the JavaScript ecosystem.
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But it's also flexible enough to search wherever you'd like to search, and load whatever you'd like to load.
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By default, Cosmiconfig will start where you tell it to start and search up the directory tree for the following:
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- a `package.json` property
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- a JSON or YAML, extensionless "rc file"
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- an "rc file" with the extensions `.json`, `.yaml`, `.yml`, `.js`, or `.cjs`
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- any of the above two inside a `.config` subdirectory
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- a `.config.js` or `.config.cjs` CommonJS module
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For example, if your module's name is "myapp", cosmiconfig will search up the directory tree for configuration in the following places:
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- a `myapp` property in `package.json`
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- a `.myapprc` file in JSON or YAML format
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- a `.myapprc.json`, `.myapprc.yaml`, `.myapprc.yml`, `.myapprc.js`, or `.myapprc.cjs` file
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- a `myapprc`, `myapprc.json`, `myapprc.yaml`, `myapprc.yml`, `myapprc.js` or `myapprc.cjs` file inside a `.config` subdirectory`
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- a `myapp.config.js` or `myapp.config.cjs` CommonJS module exporting an object
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Cosmiconfig continues to search up the directory tree, checking each of these places in each directory, until it finds some acceptable configuration (or hits the home directory).
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## Table of contents
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- [Installation](#installation)
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- [Usage](#usage)
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- [Result](#result)
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- [Asynchronous API](#asynchronous-api)
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- [cosmiconfig()](#cosmiconfig-1)
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- [explorer.search()](#explorersearch)
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- [explorer.load()](#explorerload)
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- [explorer.clearLoadCache()](#explorerclearloadcache)
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- [explorer.clearSearchCache()](#explorerclearsearchcache)
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- [explorer.clearCaches()](#explorerclearcaches)
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- [Synchronous API](#synchronous-api)
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- [cosmiconfigSync()](#cosmiconfigsync)
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- [explorerSync.search()](#explorersyncsearch)
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- [explorerSync.load()](#explorersyncload)
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- [explorerSync.clearLoadCache()](#explorersyncclearloadcache)
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- [explorerSync.clearSearchCache()](#explorersyncclearsearchcache)
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- [explorerSync.clearCaches()](#explorersyncclearcaches)
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- [cosmiconfigOptions](#cosmiconfigoptions)
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- [searchPlaces](#searchplaces)
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- [loaders](#loaders)
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- [packageProp](#packageprop)
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- [stopDir](#stopdir)
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- [cache](#cache)
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- [transform](#transform)
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- [ignoreEmptySearchPlaces](#ignoreemptysearchplaces)
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- [Caching](#caching)
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- [Differences from rc](#differences-from-rc)
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- [Contributing & Development](#contributing--development)
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## Installation
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```
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npm install cosmiconfig
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```
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Tested in Node 10+.
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## Usage
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Create a Cosmiconfig explorer, then either `search` for or directly `load` a configuration file.
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```js
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const { cosmiconfig, cosmiconfigSync } = require('cosmiconfig');
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// ...
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const explorer = cosmiconfig(moduleName);
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// Search for a configuration by walking up directories.
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// See documentation for search, below.
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explorer.search()
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.then((result) => {
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// result.config is the parsed configuration object.
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// result.filepath is the path to the config file that was found.
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// result.isEmpty is true if there was nothing to parse in the config file.
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})
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.catch((error) => {
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// Do something constructive.
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});
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// Load a configuration directly when you know where it should be.
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// The result object is the same as for search.
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// See documentation for load, below.
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explorer.load(pathToConfig).then(..);
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// You can also search and load synchronously.
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const explorerSync = cosmiconfigSync(moduleName);
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const searchedFor = explorerSync.search();
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const loaded = explorerSync.load(pathToConfig);
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```
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## Result
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The result object you get from `search` or `load` has the following properties:
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- **config:** The parsed configuration object. `undefined` if the file is empty.
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- **filepath:** The path to the configuration file that was found.
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- **isEmpty:** `true` if the configuration file is empty. This property will not be present if the configuration file is not empty.
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## Asynchronous API
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### cosmiconfig()
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```js
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const { cosmiconfig } = require('cosmiconfig');
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const explorer = cosmiconfig(moduleName[, cosmiconfigOptions])
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```
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Creates a cosmiconfig instance ("explorer") configured according to the arguments, and initializes its caches.
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#### moduleName
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Type: `string`. **Required.**
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Your module name. This is used to create the default [`searchPlaces`] and [`packageProp`].
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If your [`searchPlaces`] value will include files, as it does by default (e.g. `${moduleName}rc`), your `moduleName` must consist of characters allowed in filenames. That means you should not copy scoped package names, such as `@my-org/my-package`, directly into `moduleName`.
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**[`cosmiconfigOptions`] are documented below.**
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You may not need them, and should first read about the functions you'll use.
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### explorer.search()
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```js
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explorer.search([searchFrom]).then(result => {..})
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```
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Searches for a configuration file. Returns a Promise that resolves with a [result] or with `null`, if no configuration file is found.
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You can do the same thing synchronously with [`explorerSync.search()`].
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Let's say your module name is `goldengrahams` so you initialized with `const explorer = cosmiconfig('goldengrahams');`.
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Here's how your default [`search()`] will work:
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- Starting from `process.cwd()` (or some other directory defined by the `searchFrom` argument to [`search()`]), look for configuration objects in the following places:
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1. A `goldengrahams` property in a `package.json` file.
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2. A `.goldengrahamsrc` file with JSON or YAML syntax.
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3. A `.goldengrahamsrc.json`, `.goldengrahamsrc.yaml`, `.goldengrahamsrc.yml`, `.goldengrahamsrc.js`, or `.goldengrahamsrc.cjs` file.
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4. A `goldengrahamsrc`, `goldengrahamsrc.json`, `goldengrahamsrc.yaml`, `goldengrahamsrc.yml`, `goldengrahamsrc.js`, or `goldengrahamsrc.cjs` file in the `.config` subdirectory.
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5. A `goldengrahams.config.js` or `goldengrahams.config.cjs` CommonJS module exporting the object.
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- If none of those searches reveal a configuration object, move up one directory level and try again.
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So the search continues in `./`, `../`, `../../`, `../../../`, etc., checking the same places in each directory.
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- Continue searching until arriving at your home directory (or some other directory defined by the cosmiconfig option [`stopDir`]).
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- If at any point a parsable configuration is found, the [`search()`] Promise resolves with its [result] \(or, with [`explorerSync.search()`], the [result] is returned).
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- If no configuration object is found, the [`search()`] Promise resolves with `null` (or, with [`explorerSync.search()`], `null` is returned).
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- If a configuration object is found *but is malformed* (causing a parsing error), the [`search()`] Promise rejects with that error (so you should `.catch()` it). (Or, with [`explorerSync.search()`], the error is thrown.)
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**If you know exactly where your configuration file should be, you can use [`load()`], instead.**
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**The search process is highly customizable.**
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Use the cosmiconfig options [`searchPlaces`] and [`loaders`] to precisely define where you want to look for configurations and how you want to load them.
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#### searchFrom
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Type: `string`.
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Default: `process.cwd()`.
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A filename.
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[`search()`] will start its search here.
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If the value is a directory, that's where the search starts.
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If it's a file, the search starts in that file's directory.
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### explorer.load()
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```js
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explorer.load(loadPath).then(result => {..})
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```
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Loads a configuration file. Returns a Promise that resolves with a [result] or rejects with an error (if the file does not exist or cannot be loaded).
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Use `load` if you already know where the configuration file is and you just need to load it.
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```js
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explorer.load('load/this/file.json'); // Tries to load load/this/file.json.
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```
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If you load a `package.json` file, the result will be derived from whatever property is specified as your [`packageProp`].
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You can do the same thing synchronously with [`explorerSync.load()`].
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### explorer.clearLoadCache()
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Clears the cache used in [`load()`].
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### explorer.clearSearchCache()
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Clears the cache used in [`search()`].
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### explorer.clearCaches()
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Performs both [`clearLoadCache()`] and [`clearSearchCache()`].
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## Synchronous API
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### cosmiconfigSync()
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```js
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const { cosmiconfigSync } = require('cosmiconfig');
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const explorerSync = cosmiconfigSync(moduleName[, cosmiconfigOptions])
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```
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Creates a *synchronous* cosmiconfig instance ("explorerSync") configured according to the arguments, and initializes its caches.
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See [`cosmiconfig()`].
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### explorerSync.search()
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```js
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const result = explorerSync.search([searchFrom]);
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```
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Synchronous version of [`explorer.search()`].
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Returns a [result] or `null`.
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### explorerSync.load()
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```js
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const result = explorerSync.load(loadPath);
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```
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Synchronous version of [`explorer.load()`].
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Returns a [result].
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### explorerSync.clearLoadCache()
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Clears the cache used in [`load()`].
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### explorerSync.clearSearchCache()
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Clears the cache used in [`search()`].
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### explorerSync.clearCaches()
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Performs both [`clearLoadCache()`] and [`clearSearchCache()`].
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## cosmiconfigOptions
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Type: `Object`.
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Possible options are documented below.
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### searchPlaces
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Type: `Array<string>`.
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Default: See below.
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An array of places that [`search()`] will check in each directory as it moves up the directory tree.
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Each place is relative to the directory being searched, and the places are checked in the specified order.
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**Default `searchPlaces`:**
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```js
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[
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'package.json',
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`.${moduleName}rc`,
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`.${moduleName}rc.json`,
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`.${moduleName}rc.yaml`,
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`.${moduleName}rc.yml`,
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`.${moduleName}rc.js`,
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`.${moduleName}rc.cjs`,
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`.config/${moduleName}rc`,
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`.config/${moduleName}rc.json`,
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`.config/${moduleName}rc.yaml`,
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`.config/${moduleName}rc.yml`,
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`.config/${moduleName}rc.js`,
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`.config/${moduleName}rc.cjs`,
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`${moduleName}.config.js`,
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`${moduleName}.config.cjs`,
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]
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```
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Create your own array to search more, fewer, or altogether different places.
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Every item in `searchPlaces` needs to have a loader in [`loaders`] that corresponds to its extension.
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(Common extensions are covered by default loaders.)
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Read more about [`loaders`] below.
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`package.json` is a special value: When it is included in `searchPlaces`, Cosmiconfig will always parse it as JSON and load a property within it, not the whole file.
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That property is defined with the [`packageProp`] option, and defaults to your module name.
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Examples, with a module named `porgy`:
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```js
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// Disallow extensions on rc files:
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[
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'package.json',
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'.porgyrc',
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'porgy.config.js'
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]
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// ESLint searches for configuration in these places:
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[
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'.eslintrc.js',
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'.eslintrc.yaml',
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'.eslintrc.yml',
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'.eslintrc.json',
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'.eslintrc',
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'package.json'
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]
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// Babel looks in fewer places:
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[
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'package.json',
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'.babelrc'
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]
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// Maybe you want to look for a wide variety of JS flavors:
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[
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'porgy.config.js',
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'porgy.config.mjs',
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'porgy.config.ts',
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'porgy.config.coffee'
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]
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// ^^ You will need to designate custom loaders to tell
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// Cosmiconfig how to handle these special JS flavors.
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// Look within a .config/ subdirectory of every searched directory:
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[
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'package.json',
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'.porgyrc',
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'.config/.porgyrc',
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'.porgyrc.json',
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'.config/.porgyrc.json'
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]
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```
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### loaders
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Type: `Object`.
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Default: See below.
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An object that maps extensions to the loader functions responsible for loading and parsing files with those extensions.
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Cosmiconfig exposes its default loaders on a named export `defaultLoaders`.
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**Default `loaders`:**
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```js
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const { defaultLoaders } = require('cosmiconfig');
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console.log(Object.entries(defaultLoaders))
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// [
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// [ '.cjs', [Function: loadJs] ],
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// [ '.js', [Function: loadJs] ],
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// [ '.json', [Function: loadJson] ],
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// [ '.yaml', [Function: loadYaml] ],
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// [ '.yml', [Function: loadYaml] ],
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// [ 'noExt', [Function: loadYaml] ]
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// ]
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```
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(YAML is a superset of JSON; which means YAML parsers can parse JSON; which is how extensionless files can be either YAML *or* JSON with only one parser.)
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**If you provide a `loaders` object, your object will be *merged* with the defaults.**
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So you can override one or two without having to override them all.
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**Keys in `loaders`** are extensions (starting with a period), or `noExt` to specify the loader for files *without* extensions, like `.myapprc`.
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**Values in `loaders`** are a loader function (described below) whose values are loader functions.
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**The most common use case for custom loaders value is to load extensionless `rc` files as strict JSON**, instead of JSON *or* YAML (the default).
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To accomplish that, provide the following `loaders` value:
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```js
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{
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noExt: defaultLoaders['.json']
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}
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```
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If you want to load files that are not handled by the loader functions Cosmiconfig exposes, you can write a custom loader function or use one from NPM if it exists.
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**Third-party loaders:**
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- [cosmiconfig-typescript-loader](https://github.com/codex-/cosmiconfig-typescript-loader)
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**Use cases for custom loader function:**
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- Allow configuration syntaxes that aren't handled by Cosmiconfig's defaults, like JSON5, INI, or XML.
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- Allow ES2015 modules from `.mjs` configuration files.
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- Parse JS files with Babel before deriving the configuration.
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**Custom loader functions** have the following signature:
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```js
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// Sync
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(filepath: string, content: string) => Object | null
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// Async
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(filepath: string, content: string) => Object | null | Promise<Object | null>
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```
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Cosmiconfig reads the file when it checks whether the file exists, so it will provide you with both the file's path and its content.
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Do whatever you need to, and return either a configuration object or `null` (or, for async-only loaders, a Promise that resolves with one of those).
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`null` indicates that no real configuration was found and the search should continue.
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A few things to note:
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- If you use a custom loader, be aware of whether it's sync or async: you cannot use async customer loaders with the sync API ([`cosmiconfigSync()`]).
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- **Special JS syntax can also be handled by using a `require` hook**, because `defaultLoaders['.js']` just uses `require`.
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Whether you use custom loaders or a `require` hook is up to you.
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Examples:
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```js
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// Allow JSON5 syntax:
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{
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'.json': json5Loader
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}
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// Allow a special configuration syntax of your own creation:
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{
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'.special': specialLoader
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}
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// Allow many flavors of JS, using custom loaders:
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{
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'.mjs': esmLoader,
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'.ts': typeScriptLoader,
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'.coffee': coffeeScriptLoader
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}
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// Allow many flavors of JS but rely on require hooks:
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{
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'.mjs': defaultLoaders['.js'],
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'.ts': defaultLoaders['.js'],
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'.coffee': defaultLoaders['.js']
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}
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```
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### packageProp
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Type: `string | Array<string>`.
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Default: `` `${moduleName}` ``.
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Name of the property in `package.json` to look for.
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Use a period-delimited string or an array of strings to describe a path to nested properties.
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For example, the value `'configs.myPackage'` or `['configs', 'myPackage']` will get you the `"myPackage"` value in a `package.json` like this:
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```json
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{
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"configs": {
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"myPackage": {..}
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}
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}
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```
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If nested property names within the path include periods, you need to use an array of strings. For example, the value `['configs', 'foo.bar', 'baz']` will get you the `"baz"` value in a `package.json` like this:
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```json
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{
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"configs": {
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"foo.bar": {
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"baz": {..}
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}
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}
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}
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```
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If a string includes period but corresponds to a top-level property name, it will not be interpreted as a period-delimited path. For example, the value `'one.two'` will get you the `"three"` value in a `package.json` like this:
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```json
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{
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"one.two": "three",
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"one": {
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"two": "four"
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}
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}
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```
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### stopDir
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||
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Type: `string`.
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Default: Absolute path to your home directory.
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Directory where the search will stop.
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||
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### cache
|
||
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Type: `boolean`.
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Default: `true`.
|
||
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If `false`, no caches will be used.
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||
Read more about ["Caching"](#caching) below.
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### transform
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||
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Type: `(Result) => Promise<Result> | Result`.
|
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A function that transforms the parsed configuration. Receives the [result].
|
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If using [`search()`] or [`load()`] \(which are async), the transform function can return the transformed result or return a Promise that resolves with the transformed result.
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If using `cosmiconfigSync`, [`search()`] or [`load()`], the function must be synchronous and return the transformed result.
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|
||
The reason you might use this option — instead of simply applying your transform function some other way — is that *the transformed result will be cached*. If your transformation involves additional filesystem I/O or other potentially slow processing, you can use this option to avoid repeating those steps every time a given configuration is searched or loaded.
|
||
|
||
### ignoreEmptySearchPlaces
|
||
|
||
Type: `boolean`.
|
||
Default: `true`.
|
||
|
||
By default, if [`search()`] encounters an empty file (containing nothing but whitespace) in one of the [`searchPlaces`], it will ignore the empty file and move on.
|
||
If you'd like to load empty configuration files, instead, set this option to `false`.
|
||
|
||
Why might you want to load empty configuration files?
|
||
If you want to throw an error, or if an empty configuration file means something to your program.
|
||
|
||
## Caching
|
||
|
||
As of v2, cosmiconfig uses caching to reduce the need for repetitious reading of the filesystem or expensive transforms. Every new cosmiconfig instance (created with `cosmiconfig()`) has its own caches.
|
||
|
||
To avoid or work around caching, you can do the following:
|
||
|
||
- Set the `cosmiconfig` option [`cache`] to `false`.
|
||
- Use the cache-clearing methods [`clearLoadCache()`], [`clearSearchCache()`], and [`clearCaches()`].
|
||
- Create separate instances of cosmiconfig (separate "explorers").
|
||
|
||
## Differences from [rc](https://github.com/dominictarr/rc)
|
||
|
||
[rc](https://github.com/dominictarr/rc) serves its focused purpose well. cosmiconfig differs in a few key ways — making it more useful for some projects, less useful for others:
|
||
|
||
- Looks for configuration in some different places: in a `package.json` property, an rc file, a `.config.js` file, and rc files with extensions.
|
||
- Built-in support for JSON, YAML, and CommonJS formats.
|
||
- Stops at the first configuration found, instead of finding all that can be found up the directory tree and merging them automatically.
|
||
- Options.
|
||
- Asynchronous by default (though can be run synchronously).
|
||
|
||
## Contributing & Development
|
||
|
||
Please note that this project is released with a [Contributor Code of Conduct](CODE_OF_CONDUCT.md). By participating in this project you agree to abide by its terms.
|
||
|
||
And please do participate!
|
||
|
||
[result]: #result
|
||
|
||
[`load()`]: #explorerload
|
||
|
||
[`search()`]: #explorersearch
|
||
|
||
[`clearloadcache()`]: #explorerclearloadcache
|
||
|
||
[`clearsearchcache()`]: #explorerclearsearchcache
|
||
|
||
[`cosmiconfig()`]: #cosmiconfig
|
||
|
||
[`cosmiconfigSync()`]: #cosmiconfigsync
|
||
|
||
[`clearcaches()`]: #explorerclearcaches
|
||
|
||
[`packageprop`]: #packageprop
|
||
|
||
[`cache`]: #cache
|
||
|
||
[`stopdir`]: #stopdir
|
||
|
||
[`searchplaces`]: #searchplaces
|
||
|
||
[`loaders`]: #loaders
|
||
|
||
[`cosmiconfigoptions`]: #cosmiconfigoptions
|
||
|
||
[`explorerSync.search()`]: #explorersyncsearch
|
||
|
||
[`explorerSync.load()`]: #explorersyncload
|
||
|
||
[`explorer.search()`]: #explorersearch
|
||
|
||
[`explorer.load()`]: #explorerload
|