Ignore URLs with custom protocols (#178)

Author: sindresorhus

index.d.ts

@@ -285,6 +285,8 @@ export interface Options {
 /**
 [Normalize](https://en.wikipedia.org/wiki/URL_normalization) a URL.
 
+URLs with custom protocols are not normalized and just passed through by default. Supported protocols are: `https`, `http`, `file`, and `data`.
+
 @param url - URL to normalize, including [data URL](https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URIs).
 
 @example

index.js

@@ -4,6 +4,21 @@ const DATA_URL_DEFAULT_CHARSET = 'us-ascii';
 
 const testParameter = (name, filters) => filters.some(filter => filter instanceof RegExp ? filter.test(name) : filter === name);
 
+const supportedProtocols = new Set([
+	'https:',
+	'http:',
+	'file:',
+]);
+
+const hasCustomProtocol = urlString => {
+	try {
+		const {protocol} = new URL(urlString);
+		return protocol.endsWith(':') && !supportedProtocols.has(protocol);
+	} catch {
+		return false;
+	}
+};
+
 const normalizeDataURL = (urlString, {stripHash}) => {
 	const match = /^data:(?<type>[^,]*?),(?<data>[^#]*?)(?:#(?<hash>.*))?$/.exec(urlString);
 
@@ -81,8 +96,8 @@ export default function normalizeUrl(urlString, options) {
 		return normalizeDataURL(urlString, options);
 	}
 
-	if (/^view-source:/i.test(urlString)) {
-		throw new Error('`view-source:` is not supported as it is a non-standard protocol');
+	if (hasCustomProtocol(urlString)) {
+		return urlString;
 	}
 
 	const hasRelativeProtocol = urlString.startsWith('//');

readme.md

@@ -30,6 +30,8 @@ normalizeUrl('//www.sindresorhus.com:80/../baz?b=bar&a=foo');
 
 ### normalizeUrl(url, options?)
 
+URLs with custom protocols are not normalized and just passed through by default. Supported protocols are: `https`, `http`, `file`, and `data`.
+
 #### url
 
 Type: `string`

test.js

@@ -12,7 +12,6 @@ test('main', t => {
 	t.is(normalizeUrl('http://sindresorhus.com'), 'http://sindresorhus.com');
 	t.is(normalizeUrl('http://sindresorhus.com:80'), 'http://sindresorhus.com');
 	t.is(normalizeUrl('https://sindresorhus.com:443'), 'https://sindresorhus.com');
-	t.is(normalizeUrl('ftp://sindresorhus.com:21'), 'ftp://sindresorhus.com');
 	t.is(normalizeUrl('http://www.sindresorhus.com'), 'http://sindresorhus.com');
 	t.is(normalizeUrl('www.com'), 'http://www.com');
 	t.is(normalizeUrl('http://www.www.sindresorhus.com'), 'http://www.www.sindresorhus.com');
@@ -37,27 +36,25 @@ test('main', t => {
 	t.is(normalizeUrl('http://sindresorhus.com/foo#bar:~:text=hello%20world', {stripHash: true}), 'http://sindresorhus.com/foo');
 	t.is(normalizeUrl('http://sindresorhus.com/foo/bar/../baz'), 'http://sindresorhus.com/foo/baz');
 	t.is(normalizeUrl('http://sindresorhus.com/foo/bar/./baz'), 'http://sindresorhus.com/foo/bar/baz');
-	t.is(normalizeUrl('sindre://www.sorhus.com'), 'sindre://sorhus.com');
-	t.is(normalizeUrl('sindre://www.sorhus.com/'), 'sindre://sorhus.com');
-	t.is(normalizeUrl('sindre://www.sorhus.com/foo/bar'), 'sindre://sorhus.com/foo/bar');
+	// t.is(normalizeUrl('sindre://www.sorhus.com'), 'sindre://sorhus.com');
+	// t.is(normalizeUrl('sindre://www.sorhus.com/'), 'sindre://sorhus.com');
+	// t.is(normalizeUrl('sindre://www.sorhus.com/foo/bar'), 'sindre://sorhus.com/foo/bar');
 	t.is(normalizeUrl('https://i.vimeocdn.com/filter/overlay?src0=https://i.vimeocdn.com/video/598160082_1280x720.jpg&src1=https://f.vimeocdn.com/images_v6/share/play_icon_overlay.png'), 'https://i.vimeocdn.com/filter/overlay?src0=https://i.vimeocdn.com/video/598160082_1280x720.jpg&src1=https://f.vimeocdn.com/images_v6/share/play_icon_overlay.png');
 });
 
 test('stripAuthentication option', t => {
 	t.is(normalizeUrl('http://user:[email protected]'), 'http://sindresorhus.com');
 	t.is(normalizeUrl('https://user:[email protected]'), 'https://sindresorhus.com');
 	t.is(normalizeUrl('https://user:[email protected]/@user'), 'https://sindresorhus.com/@user');
-	t.is(normalizeUrl('user:[email protected]'), 'http://sindresorhus.com');
 	t.is(normalizeUrl('http://user:password@www.êxample.com'), 'http://xn--xample-hva.com');
-	t.is(normalizeUrl('sindre://user:[email protected]'), 'sindre://sorhus.com');
+	// t.is(normalizeUrl('sindre://user:[email protected]'), 'sindre://sorhus.com');
 
 	const options = {stripAuthentication: false};
 	t.is(normalizeUrl('http://user:[email protected]', options), 'http://user:[email protected]');
 	t.is(normalizeUrl('https://user:[email protected]', options), 'https://user:[email protected]');
 	t.is(normalizeUrl('https://user:[email protected]/@user', options), 'https://user:[email protected]/@user');
-	t.is(normalizeUrl('user:[email protected]', options), 'http://user:[email protected]');
 	t.is(normalizeUrl('http://user:password@www.êxample.com', options), 'http://user:[email protected]');
-	t.is(normalizeUrl('sindre://user:[email protected]', options), 'sindre://user:[email protected]');
+	// t.is(normalizeUrl('sindre://user:[email protected]', options), 'sindre://user:[email protected]');
 });
 
 test('stripProtocol option', t => {
@@ -66,8 +63,6 @@ test('stripProtocol option', t => {
 	t.is(normalizeUrl('http://sindresorhus.com', options), 'sindresorhus.com');
 	t.is(normalizeUrl('https://www.sindresorhus.com', options), 'sindresorhus.com');
 	t.is(normalizeUrl('//www.sindresorhus.com', options), 'sindresorhus.com');
-	t.is(normalizeUrl('sindre://user:[email protected]', options), 'sindre://sorhus.com');
-	t.is(normalizeUrl('sindre://www.sorhus.com', options), 'sindre://sorhus.com');
 });
 
 test('stripTextFragment option', t => {
@@ -98,7 +93,7 @@ test('stripWWW option', t => {
 	t.is(normalizeUrl('http://www.sindresorhus.com', options), 'http://www.sindresorhus.com');
 	t.is(normalizeUrl('www.sindresorhus.com', options), 'http://www.sindresorhus.com');
 	t.is(normalizeUrl('http://www.êxample.com', options), 'http://www.xn--xample-hva.com');
-	t.is(normalizeUrl('sindre://www.sorhus.com', options), 'sindre://www.sorhus.com');
+	// t.is(normalizeUrl('sindre://www.sorhus.com', options), 'sindre://www.sorhus.com');
 
 	const options2 = {stripWWW: true};
 	t.is(normalizeUrl('http://www.vue.amsterdam', options2), 'http://vue.amsterdam');
@@ -393,14 +388,6 @@ test('prevents homograph attack', t => {
 	t.is(normalizeUrl('https://ebаy.com'), 'https://xn--eby-7cd.com');
 });
 
-test('view-source URL', t => {
-	t.throws(() => {
-		normalizeUrl('view-source:https://www.sindresorhus.com');
-	}, {
-		message: '`view-source:` is not supported as it is a non-standard protocol',
-	});
-});
-
 test('does not have exponential performance for data URLs', t => {
 	for (let index = 0; index < 1000; index += 50) {
 		const url = 'data:' + Array.from({length: index}).fill(',#').join('') + '\ra';
@@ -414,3 +401,9 @@ test('does not have exponential performance for data URLs', t => {
 		t.true(difference < 100, `Execution time: ${difference}`);
 	}
 });
+
+test('ignore custom schemes', t => {
+	t.is(normalizeUrl('tel:004346382763'), 'tel:004346382763');
+	t.is(normalizeUrl('mailto:[email protected]'), 'mailto:[email protected]');
+	t.is(normalizeUrl('sindre://www.sindresorhus.com'), 'sindre://www.sindresorhus.com');
+});