Allow the CACHE_DIR environment variable to override the cache location

index.js

@@ -5,6 +5,8 @@ const commonDir = require('commondir');
 const pkgDir = require('pkg-dir');
 const makeDir = require('make-dir');
 
+const {env} = process;
+
 const isWritable = path => {
 	try {
 		fs.accessSync(path, fs.constants.W_OK);
@@ -14,8 +16,36 @@ const isWritable = path => {
 	}
 };
 
+function useDirectory(directory, options) {
+	if (options.create) {
+		makeDir.sync(directory);
+	}
+
+	if (options.thunk) {
+		return (...arguments_) => path.join(directory, ...arguments_);
+	}
+
+	return directory;
+}
+
+function getNodeModuleDirectory(directory) {
+	const nodeModules = path.join(directory, 'node_modules');
+
+	if (
+		!isWritable(nodeModules) &&
+		(fs.existsSync(nodeModules) || !isWritable(path.join(directory)))
+	) {
+		return;
+	}
+
+	return nodeModules;
+}
+
 module.exports = (options = {}) => {
-	const {name} = options;
+	if (env.CACHE_DIR) {
+		return useDirectory(path.join(env.CACHE_DIR, 'find-cache-dir'), options);
+	}
+
 	let directory = options.cwd || process.cwd();
 
 	if (options.files) {
@@ -25,24 +55,11 @@ module.exports = (options = {}) => {
 	directory = pkgDir.sync(directory);
 
 	if (directory) {
-		const nodeModules = path.join(directory, 'node_modules');
-		if (
-			!isWritable(nodeModules) &&
-			(fs.existsSync(nodeModules) || !isWritable(path.join(directory)))
-		) {
+		const nodeModules = getNodeModuleDirectory(directory);
+		if (!nodeModules) {
 			return undefined;
 		}
 
-		directory = path.join(directory, 'node_modules', '.cache', name);
-
-		if (options.create) {
-			makeDir.sync(directory);
-		}
-
-		if (options.thunk) {
-			return (...arguments_) => path.join(directory, ...arguments_);
-		}
+		return useDirectory(path.join(directory, 'node_modules', '.cache', options.name), options);
 	}
-
-	return directory;
 };

package.json

@@ -32,6 +32,7 @@
 		"coveralls": "^3.0.9",
 		"del": "^4.0.0",
 		"nyc": "^14.1.1",
+		"tempy": "^0.4.0",
 		"xo": "^0.25.3"
 	},
 	"nyc": {

readme.md

@@ -38,11 +38,17 @@ findCacheDir({name: 'unicorns'});
 //=> '/user/path/node-modules/.cache/unicorns'
 ```
 
+
+## Tips
+
+- To test modules using `find-cache-dir`, set the `CACHE_DIR` environmental variable to temporarily override the directory that is resolved.
+
+
 ## API
 
 ### findCacheDir(options?)
 
-Finds the cache directory using the supplied options. The algorithm tries to find a `package.json` file, searching every parent directory of the `cwd` specified (or implied from other options). It returns a `string` containing the absolute path to the cache directory, or `undefined` if `package.json` was never found or if the `node_modules` directory is unwritable.
+Finds the cache directory using the supplied options. The algorithm checks for the `CACHE_DIR` environmental variable, and if one is not found, it tries to find a `package.json` file, searching every parent directory of the `cwd` specified (or implied from other options). It returns a `string` containing the absolute path to the cache directory, or `undefined` if `package.json` was never found or if the `node_modules` directory is unwritable.
 
 #### options
 

test.js

@@ -2,6 +2,7 @@ import fs from 'fs';
 import path from 'path';
 import {serial as test} from 'ava';
 import del from 'del';
+import {directory as tempDirectory} from 'tempy';
 import findCacheDir from '.';
 
 test('finds from a list of files', t => {
@@ -39,3 +40,20 @@ test('returns undefined if it can\'t find package.json', t => {
 	process.chdir(path.join(__dirname, '..'));
 	t.is(findCacheDir({name: 'foo'}), undefined);
 });
+
+test('supports CACHE_DIR environment variable', t => {
+	const newCacheDirectory = tempDirectory();
+	const finalDirectory = path.join(newCacheDirectory, 'find-cache-dir');
+	process.env.CACHE_DIR = newCacheDirectory;
+
+	t.is(findCacheDir(), finalDirectory);
+
+	findCacheDir({create: true});
+	t.true(fs.existsSync(finalDirectory));
+
+	const thunk = findCacheDir({thunk: true});
+	t.is(thunk('foo'), path.join(finalDirectory, 'foo'));
+	t.is(thunk('bar'), path.join(finalDirectory, 'bar'));
+
+	delete process.env.CACHE_DIR;
+});