Add excludeDuplicatePatterns (#12)

Author: fregante

index.ts

@@ -95,3 +95,17 @@ export function globToRegex(...globs: readonly string[]): RegExp {
 
 	return new RegExp(globs.map(x => getRawGlobRegex(x)).join('|'));
 }
+
+export function excludeDuplicatePatterns(matchPatterns: readonly string[]): string[] {
+	if (matchPatterns.includes('<all_urls>')) {
+		return ['<all_urls>'];
+	}
+
+	if (matchPatterns.includes('*://*/*')) {
+		return ['*://*/*'];
+	}
+
+	return matchPatterns.filter(possibleSubset => !matchPatterns.some(possibleSuperset =>
+		possibleSubset !== possibleSuperset && patternToRegex(possibleSuperset).test(possibleSubset),
+	));
+}

readme.md

@@ -24,17 +24,20 @@ import {patternToRegex} from 'webext-patterns';
 
 ## Usage
 
-> **Note**
-> Firefox and Chrome handle globs very slighly differently. `webext-patterns` defaults to Chrome’s logic, but if it detects a Firefox userAgent it will produce a Firefox-compatible regex.
-
 ```js
 patternToRegex('http://*/*');
 // Returns /^http:[/][/][^/]+[/].+$/
 
 globToRegex('*.example.com');
 // Returns /\.example\.com$/
+
+excludeDuplicatePatterns(['https://*.google.com/*', 'https://google.com/*']);
+// Returns ['https://*.google.com/*']
 ```
 
+> **Note**
+> Firefox and Chrome handle patterns very slighly differently. `webext-patterns` defaults to Chrome’s logic, but if it detects a Firefox userAgent it will produce a Firefox-compatible regex.
+
 ## API
 
 #### patternToRegex(pattern1, pattern2, etc)
@@ -84,6 +87,19 @@ googleRegex.test('https://google.it/search'); // -> true
 googleRegex.test('https://google.de/search'); // -> false
 ```
 
+#### excludeDuplicatePatterns([pattern1, pattern2, etc])
+
+Accepts an array of patterns and returns a filtered array without the patterns that are already covered by others. For example `"https://*/*"` already covers all "https" URLs, so having `"https://google.com/*"` in the array won't make any difference and therefore it's dropped.
+
+```js
+excludeDuplicatePatterns([
+	"https://*/*",
+	"https://google.com/*",
+	"https://*.example.com/*",
+]);
+// Returns ["https://*/*"]
+```
+
 ## Related
 
 ### Permissions

test/duplicate-patterns.js

@@ -0,0 +1,57 @@
+import test from 'ava';
+import {excludeDuplicatePatterns} from '../index.js';
+
+test('excludeDuplicatePatterns', t => {
+	t.deepEqual(
+		excludeDuplicatePatterns([
+			'http://neverssl.com/*',
+			'https://*.example.com/*',
+			'<all_urls>',
+			'https://fregante.com/*',
+			'*://*/*',
+		]),
+		['<all_urls>'],
+		'<all_urls> should catch all',
+	);
+
+	t.deepEqual(
+		excludeDuplicatePatterns([
+			'http://neverssl.com/*',
+			'https://*.example.com/*',
+			'*://*/*',
+			'https://fregante.com/*',
+		]),
+		['*://*/*'],
+		'*://*/* should catch all',
+	);
+
+	t.deepEqual(
+		excludeDuplicatePatterns([
+			'http://*.example.com/*',
+			'https://*/*',
+			'https://fregante.com/*',
+		]),
+		['http://*.example.com/*', 'https://*/*'],
+		'https://*/* should drop all other https origins',
+	);
+
+	t.deepEqual(
+		excludeDuplicatePatterns([
+			'https://git.example.com/*',
+			'https://*.example.com/*',
+			'https://example.com/*',
+			'https://fregante.com/*',
+		]),
+		['https://*.example.com/*', 'https://fregante.com/*'],
+		'A subdomain star should drop all other same-domain origins',
+	);
+
+	t.deepEqual(
+		excludeDuplicatePatterns([
+			'https://git.example.com/*',
+			'https://git.example.com/fregante/*',
+		]),
+		['https://git.example.com/*'],
+		'A pathname star should drop all other same-origin origins',
+	);
+});