AG-50918 Fix parsing of cosmetic rules with $path modifier to correctly extract domain from pattern

Squashed commit of the following:

commit 540f0a4
Merge: 3056752 50e4b60
Author: scripthunter7 <d.tota@adguard.com>
Date:   Fri Feb 13 18:19:43 2026 +0100

    Merge branch 'master' into fix/AG-50918

commit 3056752
Author: scripthunter7 <d.tota@adguard.com>
Date:   Fri Feb 13 16:31:26 2026 +0100

    Update changelog

commit d95f353
Author: scripthunter7 <d.tota@adguard.com>
Date:   Thu Feb 12 16:17:29 2026 +0100

    AG-50640 Fix parsing of cosmetic rules with $path modifier to correctly extract domain from pattern
    
    Handle cosmetic rules with $path modifier by extracting domain from the remaining pattern after the closing bracket when no domain is found in the modifier list. Add test coverage for $path modifier rules and verify they are not disabled by $generichide.

Author: scripthunter7

packages/tsurlfilter/CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+- Parsing cosmetic rules with `$path` modifier.
+
 ## [4.0.0] - TBD
 
 ### Added

packages/tsurlfilter/src/filterlist/rule-parts.ts

@@ -508,30 +508,37 @@ function buildCosmeticRuleParts(
             i += 1;
         }
 
-        if (rule[i] === '$') {
-            // find last unescaped ] from separator
-            let j = offset - 1;
+        if (rule[i] !== '$') {
+            // invalid rule
+            return null;
+        }
 
-            while (j >= realStart) {
-                if (rule[j] === CLOSE_SQUARE && rule[j - 1] !== ESCAPE) {
-                    break;
-                }
-                j -= 1;
-            }
+        // find last unescaped ] from separator
+        let j = offset - 1;
 
-            if (j < realStart) {
-                return null;
+        while (j >= realStart) {
+            if (rule[j] === CLOSE_SQUARE && rule[j - 1] !== ESCAPE) {
+                break;
             }
+            j -= 1;
+        }
 
-            const domain = extractDomainsFromModifierList(rule, i + 1, j);
+        if (j < realStart) {
+            return null;
+        }
 
-            if (domain !== null) {
-                domainsStart = decodeDomainsStart(domain);
-                domainsEnd = decodeDomainsEnd(domain);
-            }
+        const domain = extractDomainsFromModifierList(rule, i + 1, j);
+
+        if (domain !== null) {
+            domainsStart = decodeDomainsStart(domain);
+            domainsEnd = decodeDomainsEnd(domain);
         } else {
-            // invalid rule
-            return null;
+            // take the rest of the pattern as domains, skipping whitespace after ]
+            const restStart = findNextNonWhitespace(rule, j + 1, offset);
+            if (restStart < offset) {
+                domainsStart = restStart;
+                domainsEnd = offset;
+            }
         }
     } else if (realStart < offset) {
         domainsStart = realStart;

packages/tsurlfilter/test/engine/engine.test.ts

@@ -1432,3 +1432,26 @@ describe('Async engine creation', () => {
         expect(result.getBasicResult()).not.toBeNull();
     });
 });
+
+describe('$path cosmetic modifier', () => {
+    it('$generichide should not disable path modifier rules', () => {
+        const rulesLocal = [
+            '[$path=/subpage1]example.org##.ad-banner',
+            '@@||example.org^$generichide',
+        ];
+        const engine = Engine.createSync({
+            filters: [
+                {
+                    id: 1,
+                    content: rulesLocal.join('\n'),
+                },
+            ],
+        });
+
+        const result = engine.getCosmeticResult(
+            createRequest('http://example.org/subpage1'),
+            CosmeticOption.CosmeticOptionAll,
+        );
+        expect(result.elementHiding.specific.length).toEqual(1);
+    });
+});

packages/tsurlfilter/test/filterlist/rule-parts.test.ts

@@ -56,6 +56,19 @@ describe('getRuleParts', () => {
         expect(rule.slice(parts!.domainsStart, parts!.domainsEnd)).toBe('example.com');
     });
 
+    test('parses cosmetic rule with modifiers 2', () => {
+        const rule = '[$path=/AdguardTeam]github.com##body';
+        const parts = getRuleParts(rule) as CosmeticRuleParts;
+
+        expect(parts).not.toBeNull();
+        expect(parts!.category).toBe(RuleCategory.Cosmetic);
+        expect(parts!.allowlist).toBeFalsy();
+        expect(parts!.type).toBe(CosmeticRuleType.ElementHidingRule);
+        expect(rule.slice(parts!.contentStart, parts!.contentEnd)).toBe('body');
+        expect(rule.slice(parts!.separatorStart, parts!.separatorEnd)).toBe('##');
+        expect(rule.slice(parts!.domainsStart, parts!.domainsEnd)).toBe('github.com');
+    });
+
     test('parses HTML cosmetic rule', () => {
         const rule = 'example.com$$.ad';
         const parts = getRuleParts(rule) as CosmeticRuleParts;