add filter option, fixes sindresorhus#63

index.d.ts

@@ -32,6 +32,22 @@ declare namespace cpy {
 		```
 		*/
 		readonly rename?: string | ((basename: string) => string);
+
+		/**
+		Function to filter copied files. Return true to include, false to exclude. Can also return a Promise that resolves to true or false.
+
+		@example
+		```
+		import cpy = require('cpy');
+
+		(async () => {
+			await cpy('foo', 'destination', {
+				filter: name => !name.includes('NOCOPY')
+			});
+		})();
+		```
+		*/
+		readonly filter?: (basename: string) => (boolean | Promise<boolean>);
 	}
 
 	interface ProgressData {

index.js

@@ -4,6 +4,7 @@ const path = require('path');
 const arrify = require('arrify');
 const globby = require('globby');
 const cpFile = require('cp-file');
+const pFilter = require('p-filter');
 const CpyError = require('./cpy-error');
 
 const preprocessSourcePath = (source, options) => options.cwd ? path.resolve(options.cwd, source) : source;
@@ -50,6 +51,11 @@ module.exports = (source, destination, options = {}) => {
 			throw new CpyError(`Cannot glob \`${source}\`: ${error.message}`, error);
 		}
 
+		if (options.filter !== undefined) {
+			const filteredFiles = await pFilter(files, options.filter, {concurrency: 1024});
+			files = filteredFiles;
+		}
+
 		if (files.length === 0) {
 			progressEmitter.emit('progress', {
 				totalFiles: 0,

index.test-d.ts

@@ -23,6 +23,12 @@ expectType<Promise<string[]> & ProgressEmitter>(
 expectType<Promise<string[]> & ProgressEmitter>(
 	cpy('foo.js', 'destination', {overwrite: false})
 );
+expectType<Promise<string[]> & ProgressEmitter>(
+	cpy('foo.js', 'destination', {filter: () => true})
+);
+expectType<Promise<string[]> & ProgressEmitter>(
+	cpy('foo.js', 'destination', {filter: async () => true})
+);
 
 expectType<Promise<string[]>>(
 	cpy('foo.js', 'destination').on('progress', progress => {

package.json

@@ -45,7 +45,8 @@
 		"arrify": "^2.0.1",
 		"cp-file": "^7.0.0",
 		"globby": "^9.2.0",
-		"nested-error-stacks": "^2.1.0"
+		"nested-error-stacks": "^2.1.0",
+		"p-filter": "^2.1.0"
 	},
 	"devDependencies": {
 		"ava": "^2.1.0",

readme.md

@@ -94,7 +94,21 @@ const cpy = require('cpy');
 })();
 ```
 
+#### filter
 
+Type: `string | Function`
+
+Function to filter copied files. Return true to include, false to exclude. Can also return a Promise that resolves to true or false.
+
+```js
+const cpy = require('cpy');
+
+(async () => {
+	await cpy('foo.js', 'destination', {
+		filter: name => !name.includes('NOCOPY')
+	});
+})();
+```
 ## Progress reporting
 
 ### cpy.on('progress', handler)

test.js

@@ -49,6 +49,20 @@ test('copy array of files', async t => {
 	t.is(read('package.json'), read(t.context.tmp, 'package.json'));
 });
 
+test('copy array of files with filter', async t => {
+	await cpy(['license', 'package.json'], t.context.tmp, {filter: name => name !== 'license'});
+
+	t.false(fs.existsSync(path.join(t.context.tmp, 'license')));
+	t.is(read('package.json'), read(t.context.tmp, 'package.json'));
+});
+
+test('copy array of files with async filter', async t => {
+	await cpy(['license', 'package.json'], t.context.tmp, {filter: async name => name !== 'license'});
+
+	t.false(fs.existsSync(path.join(t.context.tmp, 'license')));
+	t.is(read('package.json'), read(t.context.tmp, 'package.json'));
+});
+
 test('cwd', async t => {
 	fs.mkdirSync(t.context.tmp);
 	fs.mkdirSync(path.join(t.context.tmp, 'cwd'));