Fix Windows compatibility

Fixes #98

.gitignore

@@ -1,2 +1,3 @@
 node_modules
 yarn.lock
+dest

gulpfile.js

@@ -0,0 +1,8 @@
+import gulp from 'gulp';
+import filter from './index.js';
+
+export default function main() {
+	return gulp.src('fixtures/**/*')
+		.pipe(filter('**/*.css'))
+		.pipe(gulp.dest('dest'));
+}

index.js

@@ -1,8 +1,10 @@
+import process from 'node:process';
 import path from 'node:path';
 import PluginError from 'plugin-error';
 import multimatch from 'multimatch';
 import streamfilter from 'streamfilter';
 import toAbsoluteGlob from 'to-absolute-glob';
+import slash from 'slash';
 
 export default function plugin(pattern, options = {}) {
 	pattern = typeof pattern === 'string' ? [pattern] : pattern;
@@ -19,7 +21,8 @@ export default function plugin(pattern, options = {}) {
 			match = pattern(file);
 		} else {
 			const base = path.dirname(file.path);
-			const patterns = pattern.map(pattern => {
+
+			let patterns = pattern.map(pattern => {
 				// Filename only matching glob, prepend full path.
 				if (!pattern.includes('/')) {
 					if (pattern[0] === '!') {
@@ -40,6 +43,10 @@ export default function plugin(pattern, options = {}) {
 				return path.resolve(pattern);
 			});
 
+			if (process.platform === 'win32') {
+				patterns = patterns.map(pattern => slash(pattern));
+			}
+
 			match = multimatch(path.resolve(file.cwd, file.path), patterns, options).length > 0;
 		}
 

package.json

@@ -12,6 +12,7 @@
 	},
 	"type": "module",
 	"exports": "./index.js",
+	"sideEffects": false,
 	"engines": {
 		"node": ">=18"
 	},
@@ -36,11 +37,13 @@
 	"dependencies": {
 		"multimatch": "^7.0.0",
 		"plugin-error": "^2.0.1",
+		"slash": "^5.1.0",
 		"streamfilter": "^3.0.0",
 		"to-absolute-glob": "^3.0.0"
 	},
 	"devDependencies": {
 		"ava": "^5.3.1",
+		"gulp": "^4.0.2",
 		"p-event": "^6.0.0",
 		"vinyl": "^3.0.0",
 		"xo": "^0.56.0"