From 94f58686a91ab19ea202514b2119f840b7d42422 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Fri, 13 Dec 2024 16:06:49 +0900
Subject: [PATCH 01/15] feat: `$removeparam`

---
 packages/adblocker/src/engine/engine.ts   | 70 +++++++++++++++--------
 packages/adblocker/src/filters/network.ts | 10 ++++
 2 files changed, 56 insertions(+), 24 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index 007710642a..218aebc902 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -8,6 +8,8 @@
 
 import type { IMessageFromBackground } from '@ghostery/adblocker-content';
 
+import { URLSearchParams } from 'node:url';
+
 import Config from '../config.js';
 import { StaticDataView, sizeOfASCII, sizeOfByte, sizeOfBool } from '../data-view.js';
 import { EventEmitter } from '../events.js';
@@ -779,7 +781,7 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
           exceptions.push(filter);
         } else if (filter.isImportant()) {
           importants.push(filter);
-        } else if (filter.isRedirect()) {
+        } else if (filter.isRedirect() || filter.isRemoveParam()) {
           redirects.push(filter);
         } else {
           filters.push(filter);
@@ -1450,6 +1452,7 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
 
       let redirectNone: NetworkFilter | undefined;
       let redirectRule: NetworkFilter | undefined;
+      let redirectUrl: string | undefined;
 
       // If `result.filter` is `undefined`, it means there was no $important
       // filter found so far. We look for a $redirect filter.  There is some
@@ -1460,21 +1463,40 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
       // * Else if redirect-rule is found, only redirect if request would be blocked.
       // * Else if redirect is found, redirect.
       if (result.filter === undefined) {
-        const redirects = this.redirects
-          .matchAll(request, this.isFilterExcluded.bind(this))
-          // highest priorty wins
-          .sort((a, b) => b.getRedirectPriority() - a.getRedirectPriority());
-
-        if (redirects.length !== 0) {
-          for (const filter of redirects) {
-            if (filter.getRedirectResource() === 'none') {
-              redirectNone = filter;
-            } else if (filter.isRedirectRule()) {
-              if (redirectRule === undefined) {
-                redirectRule = filter;
+        const redirectFilters = this.redirects.matchAll(request, this.isFilterExcluded.bind(this));
+        const resourceRedirects: NetworkFilter[] = [];
+        const requestRedirects: NetworkFilter[] = [];
+        for (const filter of redirectFilters) {
+          if (filter.isRemoveParam()) {
+            requestRedirects.push(filter);
+          } else {
+            resourceRedirects.push(filter);
+          }
+        }
+
+        const searchParamsIndex = request.url.indexOf('?') + 1;
+        if (searchParamsIndex !== 0 && resourceRedirects.length !== 0) {
+          const searchParams = new URLSearchParams(request.url.slice(searchParamsIndex + 1));
+          for (const redirect of requestRedirects) {
+            searchParams.delete(redirect.optionValue!);
+          }
+          redirectUrl = `${request.url.slice(0, searchParamsIndex)}?${searchParams.toString()}`;
+        } else {
+          const redirects = resourceRedirects
+            // highest priorty wins
+            .sort((a, b) => b.getRedirectPriority() - a.getRedirectPriority());
+
+          if (redirects.length !== 0) {
+            for (const filter of redirects) {
+              if (filter.getRedirectResource() === 'none') {
+                redirectNone = filter;
+              } else if (filter.isRedirectRule()) {
+                if (redirectRule === undefined) {
+                  redirectRule = filter;
+                }
+              } else if (result.filter === undefined) {
+                result.filter = filter;
               }
-            } else if (result.filter === undefined) {
-              result.filter = filter;
             }
           }
         }
@@ -1505,15 +1527,15 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
       //
       // 1. Check if a redirect=none rule was found, which acts as exception.
       // 2. If no exception was found, prepare `result.redirect` response.
-      if (
-        result.filter !== undefined &&
-        result.exception === undefined &&
-        result.filter.isRedirect()
-      ) {
-        if (redirectNone !== undefined) {
-          result.exception = redirectNone;
-        } else {
-          result.redirect = this.resources.getResource(result.filter.getRedirectResource());
+      if (result.filter !== undefined && result.exception === undefined) {
+        if (result.filter.isRedirect()) {
+          if (redirectNone !== undefined) {
+            result.exception = redirectNone;
+          } else {
+            result.redirect = this.resources.getResource(result.filter.getRedirectResource());
+          }
+        } else if (result.filter.isRemoveParam()) {
+          result.redirect = { body: '', contentType: 'text', dataUrl: redirectUrl! };
         }
       }
     }
diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index 16e487f5b3..cec0ae7c44 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -153,6 +153,7 @@ export const enum NETWORK_FILTER_MASK {
   isHostnameAnchor = 1 << 28,
   isRedirectRule = 1 << 29,
   isRedirect = 1 << 30,
+  isRemoveParam = 1 << 31,
   // IMPORTANT: the mask is now full, no more options can be added
   // Consider creating a separate fitler type for isReplace if a new
   // network filter option is needed.
@@ -887,6 +888,11 @@ export default class NetworkFilter implements IFilter {
             mask = setBit(mask, NETWORK_FILTER_MASK.isReplace);
             optionValue = value;
 
+            break;
+          case 'removeparam':
+            mask = setBit(mask, NETWORK_FILTER_MASK.isRemoveParam);
+            optionValue = value;
+
             break;
           default: {
             // Handle content type options separatly
@@ -1608,6 +1614,10 @@ export default class NetworkFilter implements IFilter {
     return getBit(this.getMask(), NETWORK_FILTER_MASK.isReplace);
   }
 
+  public isRemoveParam(): boolean {
+    return getBit(this.getMask(), NETWORK_FILTER_MASK.isRemoveParam);
+  }
+
   // Expected to be called only with `$replace` modifiers
   public getHtmlModifier(): HTMLModifier | null {
     // Empty `$replace` modifier is to disable all replace modifiers on exception

From 29e9c39852275f8adbc4cf712540b6b29b8ea5f4 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Fri, 13 Dec 2024 16:18:32 +0900
Subject: [PATCH 02/15] fix: check `parametersRemoved` to prevent infinite loop

---
 packages/adblocker/src/engine/engine.ts | 48 ++++++++++++++-----------
 1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index 218aebc902..02c9603b27 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -1477,26 +1477,34 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
         const searchParamsIndex = request.url.indexOf('?') + 1;
         if (searchParamsIndex !== 0 && resourceRedirects.length !== 0) {
           const searchParams = new URLSearchParams(request.url.slice(searchParamsIndex + 1));
+          let parametersRemoved = 0;
           for (const redirect of requestRedirects) {
-            searchParams.delete(redirect.optionValue!);
+            if (searchParams.has(redirect.optionValue!)) {
+              parametersRemoved++;
+              searchParams.delete(redirect.optionValue!);
+            }
           }
-          redirectUrl = `${request.url.slice(0, searchParamsIndex)}?${searchParams.toString()}`;
-        } else {
-          const redirects = resourceRedirects
-            // highest priorty wins
-            .sort((a, b) => b.getRedirectPriority() - a.getRedirectPriority());
-
-          if (redirects.length !== 0) {
-            for (const filter of redirects) {
-              if (filter.getRedirectResource() === 'none') {
-                redirectNone = filter;
-              } else if (filter.isRedirectRule()) {
-                if (redirectRule === undefined) {
-                  redirectRule = filter;
-                }
-              } else if (result.filter === undefined) {
-                result.filter = filter;
+          if (parametersRemoved !== 0) {
+            redirectUrl = `${request.url.slice(0, searchParamsIndex)}?${searchParams.toString()}`;
+            // TODO: More than one filter needs to be returned
+            result.filter = requestRedirects[0];
+          }
+        }
+
+        const redirects = resourceRedirects
+          // highest priorty wins
+          .sort((a, b) => b.getRedirectPriority() - a.getRedirectPriority());
+
+        if (redirects.length !== 0) {
+          for (const filter of redirects) {
+            if (filter.getRedirectResource() === 'none') {
+              redirectNone = filter;
+            } else if (filter.isRedirectRule()) {
+              if (redirectRule === undefined) {
+                redirectRule = filter;
               }
+            } else if (result.filter === undefined) {
+              result.filter = filter;
             }
           }
         }
@@ -1528,14 +1536,14 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
       // 1. Check if a redirect=none rule was found, which acts as exception.
       // 2. If no exception was found, prepare `result.redirect` response.
       if (result.filter !== undefined && result.exception === undefined) {
-        if (result.filter.isRedirect()) {
+        if (redirectUrl !== undefined) {
+          result.redirect = { body: '', contentType: 'text', dataUrl: redirectUrl };
+        } else {
           if (redirectNone !== undefined) {
             result.exception = redirectNone;
           } else {
             result.redirect = this.resources.getResource(result.filter.getRedirectResource());
           }
-        } else if (result.filter.isRemoveParam()) {
-          result.redirect = { body: '', contentType: 'text', dataUrl: redirectUrl! };
         }
       }
     }

From 3ec118108ca1980450395f65f8ea5359768dead3 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Fri, 13 Dec 2024 16:23:45 +0900
Subject: [PATCH 03/15] fix: parsing and restoration

---
 packages/adblocker/src/filters/network.ts | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index cec0ae7c44..8297ae4595 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -890,6 +890,10 @@ export default class NetworkFilter implements IFilter {
 
             break;
           case 'removeparam':
+            if (value.length === 0) {
+              return null;
+            }
+
             mask = setBit(mask, NETWORK_FILTER_MASK.isRemoveParam);
             optionValue = value;
 
@@ -1541,6 +1545,10 @@ export default class NetworkFilter implements IFilter {
       options.push('badfilter');
     }
 
+    if (this.isRemoveParam()) {
+      options.push(`removeparam=${this.optionValue!}`);
+    }
+
     if (options.length > 0) {
       if (typeof modifierReplacer === 'function') {
         filter += `$${options.map(modifierReplacer).join(',')}`;

From fd43ad1e1012375d0da9355f3b851205fd261b35 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Fri, 13 Dec 2024 16:29:05 +0900
Subject: [PATCH 04/15] feat: removeparam without option value

---
 packages/adblocker/src/engine/engine.ts   | 15 ++++++++++++---
 packages/adblocker/src/filters/network.ts | 10 +++++-----
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index 02c9603b27..cfe0811a7f 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -1479,9 +1479,18 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
           const searchParams = new URLSearchParams(request.url.slice(searchParamsIndex + 1));
           let parametersRemoved = 0;
           for (const redirect of requestRedirects) {
-            if (searchParams.has(redirect.optionValue!)) {
-              parametersRemoved++;
-              searchParams.delete(redirect.optionValue!);
+            // When removeparam used without any option value, remove all parameter.
+            if (redirect.optionValue === undefined) {
+              redirectUrl = request.url.slice(0, searchParamsIndex);
+              result.filter = requestRedirects[0];
+              // Prevent next branch after the loop to be executed.
+              parametersRemoved = 0;
+              break;
+            } else {
+              if (searchParams.has(redirect.optionValue)) {
+                parametersRemoved++;
+                searchParams.delete(redirect.optionValue);
+              }
             }
           }
           if (parametersRemoved !== 0) {
diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index 8297ae4595..d3d84f2db1 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -890,10 +890,6 @@ export default class NetworkFilter implements IFilter {
 
             break;
           case 'removeparam':
-            if (value.length === 0) {
-              return null;
-            }
-
             mask = setBit(mask, NETWORK_FILTER_MASK.isRemoveParam);
             optionValue = value;
 
@@ -1546,7 +1542,11 @@ export default class NetworkFilter implements IFilter {
     }
 
     if (this.isRemoveParam()) {
-      options.push(`removeparam=${this.optionValue!}`);
+      if (this.optionValue !== undefined) {
+        options.push(`removeparam=${this.optionValue}`);
+      } else {
+        options.push('removeparam');
+      }
     }
 
     if (options.length > 0) {

From 9497047a6879aad4682d93c203ca954505eeac55 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Wed, 25 Dec 2024 16:33:08 +0900
Subject: [PATCH 05/15] refactor: drop use of URLSearchParams

---
 packages/adblocker/src/engine/engine.ts   | 81 +++++++++++++----------
 packages/adblocker/src/filters/network.ts |  8 +++
 2 files changed, 54 insertions(+), 35 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index cfe0811a7f..e8641db0ab 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -8,8 +8,6 @@
 
 import type { IMessageFromBackground } from '@ghostery/adblocker-content';
 
-import { URLSearchParams } from 'node:url';
-
 import Config from '../config.js';
 import { StaticDataView, sizeOfASCII, sizeOfByte, sizeOfBool } from '../data-view.js';
 import { EventEmitter } from '../events.js';
@@ -1445,7 +1443,7 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
     if (request.isSupported) {
       // Check the filters in the following order:
       // 1. $important (not subject to exceptions)
-      // 2. redirection ($redirect=resource)
+      // 2. redirection ($removeparam and $redirect=resource)
       // 3. normal filters
       // 4. exceptions
       result.filter = this.importants.match(request, this.isFilterExcluded.bind(this));
@@ -1455,13 +1453,7 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
       let redirectUrl: string | undefined;
 
       // If `result.filter` is `undefined`, it means there was no $important
-      // filter found so far. We look for a $redirect filter.  There is some
-      // extra logic to handle special cases like redirect-rule and
-      // redirect=none.
-      //
-      // * If redirect=none is found, then cancel all redirects.
-      // * Else if redirect-rule is found, only redirect if request would be blocked.
-      // * Else if redirect is found, redirect.
+      // filter found so far. We look for $removeparam and $redirect filter.
       if (result.filter === undefined) {
         const redirectFilters = this.redirects.matchAll(request, this.isFilterExcluded.bind(this));
         const resourceRedirects: NetworkFilter[] = [];
@@ -1474,37 +1466,55 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
           }
         }
 
-        const searchParamsIndex = request.url.indexOf('?') + 1;
-        if (searchParamsIndex !== 0 && resourceRedirects.length !== 0) {
-          const searchParams = new URLSearchParams(request.url.slice(searchParamsIndex + 1));
-          let parametersRemoved = 0;
-          for (const redirect of requestRedirects) {
-            // When removeparam used without any option value, remove all parameter.
-            if (redirect.optionValue === undefined) {
-              redirectUrl = request.url.slice(0, searchParamsIndex);
-              result.filter = requestRedirects[0];
-              // Prevent next branch after the loop to be executed.
-              parametersRemoved = 0;
-              break;
-            } else {
-              if (searchParams.has(redirect.optionValue)) {
-                parametersRemoved++;
-                searchParams.delete(redirect.optionValue);
+        // We don't need to match `removeparam` at all if:
+        // * `removeparam` filters not matched
+        // * URL doesn't have `?` — parameter separator
+        // * URL has `?` but ends right after the separator
+        if (resourceRedirects.length !== 0) {
+          const searchParamsSeparatorAt = request.url.indexOf('?');
+          if (
+            searchParamsSeparatorAt !== -1 &&
+            searchParamsSeparatorAt + 1 !== request.url.length
+          ) {
+            for (const redirect of requestRedirects) {
+              // If `removeparam` without a value found, we drop all params
+              if (redirect.removeparam!.length === 0) {
+                result.filter = redirect;
+                redirectUrl = request.url.slice(0, searchParamsSeparatorAt);
+                break;
+              }
+              const searchParamStartsWith = `${redirect.removeparam!}=`;
+              const searchParamStartsAt = request.url.indexOf(
+                searchParamStartsWith,
+                searchParamsSeparatorAt,
+              );
+              if (searchParamStartsAt === -1) {
+                continue;
               }
+              let searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt + 1);
+              if (searchParamEndsAt === -1) {
+                searchParamEndsAt = request.url.length;
+              }
+              result.filter = redirect;
+              redirectUrl =
+                request.url.slice(0, searchParamStartsAt) + request.url.slice(searchParamEndsAt);
+              break;
             }
           }
-          if (parametersRemoved !== 0) {
-            redirectUrl = `${request.url.slice(0, searchParamsIndex)}?${searchParams.toString()}`;
-            // TODO: More than one filter needs to be returned
-            result.filter = requestRedirects[0];
-          }
         }
 
-        const redirects = resourceRedirects
-          // highest priorty wins
-          .sort((a, b) => b.getRedirectPriority() - a.getRedirectPriority());
+        // If `result.filter` is still remains `undefined`, there
+        // is some extra logic to handle special cases like
+        // redirect-rule and redirect=none.
+        //
+        // * If redirect=none is found, then cancel all redirects.
+        // * Else if redirect-rule is found, only redirect if request would be blocked.
+        // * Else if redirect is found, redirect.
+        if (result.filter === undefined && resourceRedirects.length !== 0) {
+          const redirects = resourceRedirects
+            // highest priorty wins
+            .sort((a, b) => b.getRedirectPriority() - a.getRedirectPriority());
 
-        if (redirects.length !== 0) {
           for (const filter of redirects) {
             if (filter.getRedirectResource() === 'none') {
               redirectNone = filter;
@@ -1545,6 +1555,7 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
       // 1. Check if a redirect=none rule was found, which acts as exception.
       // 2. If no exception was found, prepare `result.redirect` response.
       if (result.filter !== undefined && result.exception === undefined) {
+        // Prioritize if `redirectUrl` is set.
         if (redirectUrl !== undefined) {
           result.redirect = { body: '', contentType: 'text', dataUrl: redirectUrl };
         } else {
diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index d3d84f2db1..bbb3d7377f 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -1271,6 +1271,14 @@ export default class NetworkFilter implements IFilter {
     return this.optionValue;
   }
 
+  public get removeparam(): string | undefined {
+    if (!this.isRemoveParam()) {
+      return undefined;
+    }
+
+    return this.optionValue || '';
+  }
+
   public isCosmeticFilter(): this is CosmeticFilter {
     return false;
   }

From 56f90cc1dfee926723066601140ccc88a32a8bb4 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Wed, 25 Dec 2024 17:55:56 +0900
Subject: [PATCH 06/15] feat: introduce
 `NetworkFilter.prototype.isRedirectable`

---
 packages/adblocker/src/engine/engine.ts       | 23 +++++++++++--------
 packages/adblocker/src/filters/network.ts     |  4 ++++
 packages/adblocker/test/engine/engine.test.ts | 10 ++++----
 3 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index e8641db0ab..cec9336c3f 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -779,7 +779,7 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
           exceptions.push(filter);
         } else if (filter.isImportant()) {
           importants.push(filter);
-        } else if (filter.isRedirect() || filter.isRemoveParam()) {
+        } else if (filter.isRedirectable()) {
           redirects.push(filter);
         } else {
           filters.push(filter);
@@ -1470,7 +1470,7 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
         // * `removeparam` filters not matched
         // * URL doesn't have `?` — parameter separator
         // * URL has `?` but ends right after the separator
-        if (resourceRedirects.length !== 0) {
+        if (requestRedirects.length !== 0) {
           const searchParamsSeparatorAt = request.url.indexOf('?');
           if (
             searchParamsSeparatorAt !== -1 &&
@@ -1491,13 +1491,12 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
               if (searchParamStartsAt === -1) {
                 continue;
               }
-              let searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt + 1);
-              if (searchParamEndsAt === -1) {
-                searchParamEndsAt = request.url.length;
-              }
+              const searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt + 1);
               result.filter = redirect;
-              redirectUrl =
-                request.url.slice(0, searchParamStartsAt) + request.url.slice(searchParamEndsAt);
+              redirectUrl = request.url.slice(0, searchParamStartsAt);
+              if (searchParamEndsAt !== -1) {
+                redirectUrl += request.url.slice(searchParamEndsAt);
+              }
               break;
             }
           }
@@ -1554,10 +1553,14 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
       //
       // 1. Check if a redirect=none rule was found, which acts as exception.
       // 2. If no exception was found, prepare `result.redirect` response.
-      if (result.filter !== undefined && result.exception === undefined) {
+      if (
+        result.filter !== undefined &&
+        result.exception === undefined &&
+        result.filter.isRedirectable()
+      ) {
         // Prioritize if `redirectUrl` is set.
         if (redirectUrl !== undefined) {
-          result.redirect = { body: '', contentType: 'text', dataUrl: redirectUrl };
+          result.redirect = { body: '', contentType: 'text/plain', dataUrl: redirectUrl };
         } else {
           if (redirectNone !== undefined) {
             result.exception = redirectNone;
diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index bbb3d7377f..b439df7848 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -1634,6 +1634,10 @@ export default class NetworkFilter implements IFilter {
     return getBit(this.getMask(), NETWORK_FILTER_MASK.isRemoveParam);
   }
 
+  public isRedirectable(): boolean {
+    return this.isRedirect() || this.isRemoveParam();
+  }
+
   // Expected to be called only with `$replace` modifiers
   public getHtmlModifier(): HTMLModifier | null {
     // Empty `$replace` modifier is to disable all replace modifiers on exception
diff --git a/packages/adblocker/test/engine/engine.test.ts b/packages/adblocker/test/engine/engine.test.ts
index a002f84234..d246731ef0 100644
--- a/packages/adblocker/test/engine/engine.test.ts
+++ b/packages/adblocker/test/engine/engine.test.ts
@@ -77,14 +77,14 @@ function test({
       expect(importants).to.include(result.filter.rawLine);
 
       // Handle case where important filter is also a redirect
-      if (filter.isRedirect()) {
+      if (filter.isRedirectable()) {
         expect(redirects).to.include(result.filter.rawLine);
       }
     }
 
     expect(result.exception).to.be.undefined;
 
-    if (!filter.isRedirect()) {
+    if (!filter.isRedirectable()) {
       expect(result.redirect).to.be.undefined;
     }
 
@@ -108,7 +108,7 @@ function test({
     expect(result.filter).not.to.be.undefined;
     expect(result.redirect).to.be.undefined;
     expect(result.match).to.be.false;
-  } else if (filter.isRedirect() && exceptions.length === 0 && importants.length === 0) {
+  } else if (filter.isRedirectable() && exceptions.length === 0 && importants.length === 0) {
     const result = engine.match(request);
     expect(result.filter).not.to.be.undefined;
     if (
@@ -661,11 +661,11 @@ $csp=baz,domain=bar.com
               importants.push(filter);
             }
 
-            if (parsed.isRedirect()) {
+            if (parsed.isRedirectable()) {
               redirects.push(filter);
             }
 
-            if (!parsed.isRedirect() && !parsed.isException() && !parsed.isImportant()) {
+            if (!parsed.isRedirectable() && !parsed.isException() && !parsed.isImportant()) {
               normalFilters.push(filter);
             }
           }

From 47b13023667f356306f23dc6acd0e4108ce5b589 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Wed, 25 Dec 2024 19:37:51 +0900
Subject: [PATCH 07/15] refactor: improve matching search param key

---
 packages/adblocker/src/engine/engine.ts   | 11 ++++++++---
 packages/adblocker/src/filters/network.ts |  1 +
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index cec9336c3f..4c8675bb2f 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -1483,11 +1483,16 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
                 redirectUrl = request.url.slice(0, searchParamsSeparatorAt);
                 break;
               }
-              const searchParamStartsWith = `${redirect.removeparam!}=`;
-              const searchParamStartsAt = request.url.indexOf(
-                searchParamStartsWith,
+              let searchParamStartsAt = request.url.indexOf(
+                `?${redirect.removeparam!}`,
                 searchParamsSeparatorAt,
               );
+              if (searchParamStartsAt === -1) {
+                searchParamStartsAt = request.url.indexOf(
+                  `&${redirect.removeparam!}`,
+                  searchParamsSeparatorAt + 3 /* '?x='.length */,
+                );
+              }
               if (searchParamStartsAt === -1) {
                 continue;
               }
diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index b439df7848..8b2fe7650f 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -890,6 +890,7 @@ export default class NetworkFilter implements IFilter {
 
             break;
           case 'removeparam':
+            // TODO: Support regex
             mask = setBit(mask, NETWORK_FILTER_MASK.isRemoveParam);
             optionValue = value;
 

From 7ea4488708df86e666c0c8d56ef9fb3fb2877c95 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Fri, 27 Dec 2024 17:57:16 +0900
Subject: [PATCH 08/15] test: removeparam

test: add `isRemoveParam` and `isRedirectable`

chore: reject on `removeparam` negation

test: parsing removeparam

test: removeparam

test: removeparam
---
 packages/adblocker/src/engine/engine.ts       | 70 +++++++++++++-----
 packages/adblocker/src/filters/network.ts     |  4 +
 packages/adblocker/test/engine/engine.test.ts | 74 +++++++++++++++++++
 packages/adblocker/test/parsing.test.ts       | 32 ++++++++
 4 files changed, 161 insertions(+), 19 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index 4c8675bb2f..f9a506611c 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -1477,32 +1477,64 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
             searchParamsSeparatorAt + 1 !== request.url.length
           ) {
             for (const redirect of requestRedirects) {
+              const target = redirect.removeparam!;
               // If `removeparam` without a value found, we drop all params
-              if (redirect.removeparam!.length === 0) {
+              if (target.length === 0) {
                 result.filter = redirect;
                 redirectUrl = request.url.slice(0, searchParamsSeparatorAt);
                 break;
               }
-              let searchParamStartsAt = request.url.indexOf(
-                `?${redirect.removeparam!}`,
-                searchParamsSeparatorAt,
-              );
-              if (searchParamStartsAt === -1) {
-                searchParamStartsAt = request.url.indexOf(
-                  `&${redirect.removeparam!}`,
-                  searchParamsSeparatorAt + 3 /* '?x='.length */,
-                );
+              // Try to find `searchParamStartsAt` recursively
+              let searchParamStartsAt: number = -1;
+              for (
+                let lookupAfter = searchParamsSeparatorAt;
+                lookupAfter < request.url.length;
+                searchParamStartsAt = -1
+              ) {
+                searchParamStartsAt = request.url.indexOf(target, lookupAfter);
+                // No match found in this string, try to fast exit in the first loop.
+                if (searchParamStartsAt === -1) {
+                  break;
+                }
+
+                // VALID only if the next character is equal sign or EOL:
+                if (
+                  searchParamStartsAt + target.length === request.url.length ||
+                  request.url.charCodeAt(searchParamStartsAt + target.length) === 61 /* '=' */
+                ) {
+                  // In case of first param:
+                  if (searchParamsSeparatorAt === searchParamStartsAt - 1) {
+                    result.filter = redirect;
+                    const searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt);
+                    if (searchParamEndsAt === -1) {
+                      redirectUrl = request.url.slice(0, searchParamStartsAt);
+                    } else {
+                      redirectUrl =
+                        request.url.slice(0, searchParamStartsAt) +
+                        request.url.slice(searchParamEndsAt + 1);
+                    }
+                    break;
+                  } else if (request.url.charCodeAt(searchParamStartsAt - 1) === 38 /* '&' */) {
+                    result.filter = redirect;
+                    const searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt);
+                    // In case of last param:
+                    if (searchParamEndsAt === -1) {
+                      redirectUrl = request.url.slice(0, searchParamStartsAt - 1);
+                    } else {
+                      // In case of param in the middle:
+                      redirectUrl =
+                        request.url.slice(0, searchParamStartsAt) +
+                        request.url.slice(searchParamEndsAt + 1);
+                    }
+                    break;
+                  }
+                }
+
+                lookupAfter = searchParamStartsAt + target.length;
               }
-              if (searchParamStartsAt === -1) {
-                continue;
-              }
-              const searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt + 1);
-              result.filter = redirect;
-              redirectUrl = request.url.slice(0, searchParamStartsAt);
-              if (searchParamEndsAt !== -1) {
-                redirectUrl += request.url.slice(searchParamEndsAt);
+              if (searchParamStartsAt !== -1) {
+                break;
               }
-              break;
             }
           }
         }
diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index 8b2fe7650f..b66c24380f 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -891,6 +891,10 @@ export default class NetworkFilter implements IFilter {
             break;
           case 'removeparam':
             // TODO: Support regex
+            if (negation || value.startsWith('/')) {
+              return null;
+            }
+
             mask = setBit(mask, NETWORK_FILTER_MASK.isRemoveParam);
             optionValue = value;
 
diff --git a/packages/adblocker/test/engine/engine.test.ts b/packages/adblocker/test/engine/engine.test.ts
index d246731ef0..c8ff8cfc44 100644
--- a/packages/adblocker/test/engine/engine.test.ts
+++ b/packages/adblocker/test/engine/engine.test.ts
@@ -600,6 +600,80 @@ $csp=baz,domain=bar.com
       expect((filter as NetworkFilter).toString()).to.equal('||foo.com$image,redirect=foo.js');
       expect(redirect).to.be.undefined;
     });
+
+    context('removeparam', () => {
+      function urlToDocumentRequest(url: string) {
+        return Request.fromRawDetails({
+          sourceUrl: 'https://foo.com',
+          url,
+          type: 'document',
+        });
+      }
+
+      const requests = [
+        'https://foo.com?utm',
+        'https://foo.com?utm=',
+        'https://foo.com?utm=a',
+        'https://foo.com?utm=a&utm_source=organic',
+        'https://foo.com?utm_source=organic&utm=a',
+      ].map(urlToDocumentRequest);
+
+      describe('removeparam removes all parameters', () => {
+        const engine = createEngine('||foo.com$removeparam');
+        for (const { match, redirect, request } of requests.map((request) => ({
+          ...engine.match(request),
+          request,
+        }))) {
+          it(`removeparam all from "${request.url}"`, () => {
+            expect(match).to.be.true;
+            expect(redirect).not.to.be.undefined;
+            expect(redirect!.body).to.be.eql('');
+            expect(redirect!.contentType).to.be.eql('text/plain');
+            expect(redirect!.dataUrl).to.be.eql('https://foo.com');
+          });
+        }
+      });
+
+      describe('removeparam removes specific parameter', () => {
+        const engine = createEngine('||foo.com$removeparam=utm');
+        for (const { match, redirect, request } of requests.map((request) => ({
+          ...engine.match(request),
+          request,
+        }))) {
+          it(`removeparam "utm" from "${request.url}"`, () => {
+            expect(match).to.be.true;
+            expect(redirect).not.to.be.undefined;
+            expect(redirect!.body).to.be.eql('');
+            expect(redirect!.contentType).to.be.eql('text/plain');
+            expect(redirect!.dataUrl).not.to.include('?utm=');
+            expect(redirect!.dataUrl).not.to.include('&utm=');
+          });
+        }
+      });
+
+      describe('removeparam removes specific parameter regardless of ordering', () => {
+        const engine = createEngine('||foo.com$removeparam=utm');
+        for (const { match, redirect, request } of [
+          // First
+          'https://foo.com?utm=a&utm_source=organic&utm_event=b',
+          // Middle
+          'https://foo.com?utm_source=organic&utm=a&utm_event=b',
+          // Last
+          'https://foo.com?utm_source=organic&utm_event=b&utm=a',
+        ]
+          .map(urlToDocumentRequest)
+          .map((request) => ({
+            ...engine.match(request),
+            request,
+          }))) {
+          it(`removeparam "utm" from "${request.url}"`, () => {
+            expect(match).to.be.true;
+            expect(redirect).not.to.be.undefined;
+            expect(redirect!.dataUrl).to.be.eql('https://foo.com?utm_source=organic&utm_event=b');
+          });
+        }
+      });
+    });
   });
 
   describe('network filters', () => {
diff --git a/packages/adblocker/test/parsing.test.ts b/packages/adblocker/test/parsing.test.ts
index 1b9da5b8b5..421c79d57b 100644
--- a/packages/adblocker/test/parsing.test.ts
+++ b/packages/adblocker/test/parsing.test.ts
@@ -34,6 +34,7 @@ function network(filter: string, expected: any) {
       denyallow: parsed.denyallow,
       domains: parsed.domains,
       redirect: parsed.getRedirect(),
+      removeparam: parsed.removeparam,
 
       // Filter type
       isBadFilter: parsed.isBadFilter(),
@@ -48,6 +49,8 @@ function network(filter: string, expected: any) {
       isPlain: parsed.isPlain(),
       isRedirect: parsed.isRedirect(),
       isRedirectRule: parsed.isRedirectRule(),
+      isRemoveParam: parsed.isRemoveParam(),
+      isRedirectable: parsed.isRedirectable(),
       isRegex: parsed.isRegex(),
       isRightAnchor: parsed.isRightAnchor(),
 
@@ -101,6 +104,8 @@ const DEFAULT_NETWORK_FILTER = {
   isPlain: false,
   isRedirect: false,
   isRedirectRule: false,
+  isRemoveParam: false,
+  isRedirectable: false,
   isRegex: false,
   isRightAnchor: false,
 
@@ -845,11 +850,13 @@ describe('Network filters', () => {
         network('||foo.com$redirect-rule=bar.js', {
           isRedirect: true,
           isRedirectRule: true,
+          isRedirectable: true,
           redirect: 'bar.js',
         });
         network('$redirect-rule=bar.js', {
           isRedirect: true,
           isRedirectRule: true,
+          isRedirectable: true,
           redirect: 'bar.js',
         });
       });
@@ -872,6 +879,31 @@ describe('Network filters', () => {
         network('||foo.com', {
           isRedirectRule: false,
           redirect: '',
+          isRedirectable: true,
+        });
+      });
+    });
+
+    describe('removeparam', () => {
+      it('parses ~removeparam', () => {
+        // ~removeparam is not a valid option
+        network('||foo.com$~removeparam=utm', null);
+        network('||fo.com$~removeparam', null);
+      });
+
+      it('parses removeparam', () => {
+        network('||foo.com$removeparam=utm', {
+          removeparam: 'utm',
+          isRemoveParam: true,
+          isRedirectable: true,
+        });
+      });
+
+      it('parses removeparam without a value', () => {
+        network('||foo.com$removeparam', {
+          removeparam: '',
+          isRemoveParam: true,
+          isRedirectable: true,
         });
       });
     });

From 29e90221cdb5e0928f814e6e3e10d7859139ee98 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Fri, 27 Dec 2024 19:55:09 +0900
Subject: [PATCH 09/15] test: removeparam removes parameter sequentially

---
 packages/adblocker/test/engine/engine.test.ts | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/packages/adblocker/test/engine/engine.test.ts b/packages/adblocker/test/engine/engine.test.ts
index c8ff8cfc44..3379635b04 100644
--- a/packages/adblocker/test/engine/engine.test.ts
+++ b/packages/adblocker/test/engine/engine.test.ts
@@ -673,6 +673,22 @@ $csp=baz,domain=bar.com
           });
         }
       });
+
+      it('removeparam removes parameter sequentially', () => {
+        const params = ['utm', 'utm_source', 'utm_event'];
+        let request = urlToDocumentRequest('https://foo.com?utm_source=organic&utm_event=b&utm=a');
+        const engine = createEngine(
+          params.map((param) => `||foo.com$removeparam=${param}`).join('\n'),
+        );
+        for (let i = 0; i < params.length; i++) {
+          const { redirect } = engine.match(request);
+          expect(redirect).not.to.be.undefined;
+          request = urlToDocumentRequest(redirect!.dataUrl);
+        }
+        for (const param of params) {
+          expect(request.url).not.to.include(param);
+        }
+      });
     });
   });
 

From 3cb0861f1031c86226572930dc8d668206a68bab Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Fri, 27 Dec 2024 19:56:51 +0900
Subject: [PATCH 10/15] fix(test): unintentional isRedirectable definition

---
 packages/adblocker/test/parsing.test.ts | 1 -
 1 file changed, 1 deletion(-)

diff --git a/packages/adblocker/test/parsing.test.ts b/packages/adblocker/test/parsing.test.ts
index 421c79d57b..7f65daa518 100644
--- a/packages/adblocker/test/parsing.test.ts
+++ b/packages/adblocker/test/parsing.test.ts
@@ -879,7 +879,6 @@ describe('Network filters', () => {
         network('||foo.com', {
           isRedirectRule: false,
           redirect: '',
-          isRedirectable: true,
         });
       });
     });

From 9c1e12b1dc1b60bc68d026427823166eff73d0a2 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Mon, 6 Jan 2025 14:58:39 +0900
Subject: [PATCH 11/15] refactor: use `URL` constructor

refs https://github.com/ghostery/adblocker/pull/4528#discussion_r1902696043
---
 packages/adblocker/src/engine/engine.ts       | 80 +++++--------------
 packages/adblocker/test/engine/engine.test.ts | 14 ++--
 2 files changed, 25 insertions(+), 69 deletions(-)

diff --git a/packages/adblocker/src/engine/engine.ts b/packages/adblocker/src/engine/engine.ts
index f9a506611c..64832010b9 100644
--- a/packages/adblocker/src/engine/engine.ts
+++ b/packages/adblocker/src/engine/engine.ts
@@ -1468,71 +1468,27 @@ export default class FilterEngine extends EventEmitter<EngineEventHandlers> {
 
         // We don't need to match `removeparam` at all if:
         // * `removeparam` filters not matched
-        // * URL doesn't have `?` — parameter separator
-        // * URL has `?` but ends right after the separator
+        // * URL doesn't have search parameter
         if (requestRedirects.length !== 0) {
-          const searchParamsSeparatorAt = request.url.indexOf('?');
-          if (
-            searchParamsSeparatorAt !== -1 &&
-            searchParamsSeparatorAt + 1 !== request.url.length
-          ) {
-            for (const redirect of requestRedirects) {
-              const target = redirect.removeparam!;
-              // If `removeparam` without a value found, we drop all params
-              if (target.length === 0) {
-                result.filter = redirect;
-                redirectUrl = request.url.slice(0, searchParamsSeparatorAt);
+          const url = new URL(request.url);
+          if (url.searchParams.size !== 0) {
+            for (const filter of requestRedirects) {
+              const key = filter.removeparam!;
+
+              // Remove all params in case of option value is empty
+              if (key === '') {
+                result.filter = filter;
+                redirectUrl = request.url.slice(0, request.url.indexOf('?'));
+
                 break;
               }
-              // Try to find `searchParamStartsAt` recursively
-              let searchParamStartsAt: number = -1;
-              for (
-                let lookupAfter = searchParamsSeparatorAt;
-                lookupAfter < request.url.length;
-                searchParamStartsAt = -1
-              ) {
-                searchParamStartsAt = request.url.indexOf(target, lookupAfter);
-                // No match found in this string, try to fast exit in the first loop.
-                if (searchParamStartsAt === -1) {
-                  break;
-                }
-
-                // VALID only if the next character is equal sign or EOL:
-                if (
-                  searchParamStartsAt + target.length === request.url.length ||
-                  request.url.charCodeAt(searchParamStartsAt + target.length) === 61 /* '=' */
-                ) {
-                  // In case of first param:
-                  if (searchParamsSeparatorAt === searchParamStartsAt - 1) {
-                    result.filter = redirect;
-                    const searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt);
-                    if (searchParamEndsAt === -1) {
-                      redirectUrl = request.url.slice(0, searchParamStartsAt);
-                    } else {
-                      redirectUrl =
-                        request.url.slice(0, searchParamStartsAt) +
-                        request.url.slice(searchParamEndsAt + 1);
-                    }
-                    break;
-                  } else if (request.url.charCodeAt(searchParamStartsAt - 1) === 38 /* '&' */) {
-                    result.filter = redirect;
-                    const searchParamEndsAt = request.url.indexOf('&', searchParamStartsAt);
-                    // In case of last param:
-                    if (searchParamEndsAt === -1) {
-                      redirectUrl = request.url.slice(0, searchParamStartsAt - 1);
-                    } else {
-                      // In case of param in the middle:
-                      redirectUrl =
-                        request.url.slice(0, searchParamStartsAt) +
-                        request.url.slice(searchParamEndsAt + 1);
-                    }
-                    break;
-                  }
-                }
-
-                lookupAfter = searchParamStartsAt + target.length;
-              }
-              if (searchParamStartsAt !== -1) {
+
+              if (url.searchParams.has(key)) {
+                url.searchParams.delete(key);
+
+                result.filter = filter;
+                redirectUrl = url.toString();
+
                 break;
               }
             }
diff --git a/packages/adblocker/test/engine/engine.test.ts b/packages/adblocker/test/engine/engine.test.ts
index 3379635b04..eeef041ef5 100644
--- a/packages/adblocker/test/engine/engine.test.ts
+++ b/packages/adblocker/test/engine/engine.test.ts
@@ -618,13 +618,13 @@ $csp=baz,domain=bar.com
         'https://foo.com?utm_source=organic&utm=a',
       ].map(urlToDocumentRequest);
 
-      describe('removeparam removes all parameters', () => {
+      describe('removes all parameters', () => {
         const engine = createEngine('||foo.com$removeparam');
         for (const { match, redirect, request } of requests.map((request) => ({
           ...engine.match(request),
           request,
         }))) {
-          it(`removeparam all from "${request.url}"`, () => {
+          it(`removes all params from "${request.url}"`, () => {
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.body).to.be.eql('');
@@ -634,13 +634,13 @@ $csp=baz,domain=bar.com
         }
       });
 
-      describe('removeparam removes specific parameter', () => {
+      describe('removes specific parameter', () => {
         const engine = createEngine('||foo.com$removeparam=utm');
         for (const { match, redirect, request } of requests.map((request) => ({
           ...engine.match(request),
           request,
         }))) {
-          it(`removeparam "utm" from "${request.url}"`, () => {
+          it(`removes "utm" from "${request.url}"`, () => {
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.body).to.be.eql('');
@@ -651,7 +651,7 @@ $csp=baz,domain=bar.com
         }
       });
 
-      describe('removeparam removes specific parameter regardless of ordering', () => {
+      describe('removes specific parameter regardless of ordering', () => {
         const engine = createEngine('||foo.com$removeparam=utm');
         for (const { match, redirect, request } of [
           // First
@@ -669,12 +669,12 @@ $csp=baz,domain=bar.com
           it(`removeparam "utm" from "${request.url}"`, () => {
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
-            expect(redirect!.dataUrl).to.be.eql('https://foo.com?utm_source=organic&utm_event=b');
+            expect(redirect!.dataUrl).to.be.eql('https://foo.com/?utm_source=organic&utm_event=b');
           });
         }
       });
 
-      it('removeparam removes parameter sequentially', () => {
+      it('removes parameter sequentially', () => {
         const params = ['utm', 'utm_source', 'utm_event'];
         let request = urlToDocumentRequest('https://foo.com?utm_source=organic&utm_event=b&utm=a');
         const engine = createEngine(

From c8da3bbec6949a4869d9f010806ab001ad0c6411 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Mon, 6 Jan 2025 15:02:29 +0900
Subject: [PATCH 12/15] refactor: clarify `removeparam` getter

---
 packages/adblocker/src/filters/network.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/adblocker/src/filters/network.ts b/packages/adblocker/src/filters/network.ts
index b66c24380f..d7999a3593 100644
--- a/packages/adblocker/src/filters/network.ts
+++ b/packages/adblocker/src/filters/network.ts
@@ -1281,7 +1281,7 @@ export default class NetworkFilter implements IFilter {
       return undefined;
     }
 
-    return this.optionValue || '';
+    return this.optionValue;
   }
 
   public isCosmeticFilter(): this is CosmeticFilter {
@@ -1555,7 +1555,7 @@ export default class NetworkFilter implements IFilter {
     }
 
     if (this.isRemoveParam()) {
-      if (this.optionValue !== undefined) {
+      if (this.removeparam!.length > 0) {
         options.push(`removeparam=${this.optionValue}`);
       } else {
         options.push('removeparam');

From 533110ecee31387ea0d6c3881886b35f6d30cd9b Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Tue, 14 Jan 2025 19:30:22 +0900
Subject: [PATCH 13/15] refactor: move heavy calls to `before`

---
 packages/adblocker/test/engine/engine.test.ts | 34 +++++++++++++------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/packages/adblocker/test/engine/engine.test.ts b/packages/adblocker/test/engine/engine.test.ts
index eeef041ef5..50f1a30904 100644
--- a/packages/adblocker/test/engine/engine.test.ts
+++ b/packages/adblocker/test/engine/engine.test.ts
@@ -610,16 +610,22 @@ $csp=baz,domain=bar.com
         });
       }
 
-      const requests = [
-        'https://foo.com?utm',
-        'https://foo.com?utm=',
-        'https://foo.com?utm=a',
-        'https://foo.com?utm=a&utm_source=organic',
-        'https://foo.com?utm_source=organic&utm=a',
-      ].map(urlToDocumentRequest);
+      let requests: Request[];
+      before(() => {
+        requests = [
+          'https://foo.com?utm',
+          'https://foo.com?utm=',
+          'https://foo.com?utm=a',
+          'https://foo.com?utm=a&utm_source=organic',
+          'https://foo.com?utm_source=organic&utm=a',
+        ].map(urlToDocumentRequest);
+      });
 
       describe('removes all parameters', () => {
-        const engine = createEngine('||foo.com$removeparam');
+        let engine: FilterEngine;
+        before(() => {
+          engine = createEngine('||foo.com$removeparam');
+        });
         for (const { match, redirect, request } of requests.map((request) => ({
           ...engine.match(request),
           request,
@@ -635,7 +641,10 @@ $csp=baz,domain=bar.com
       });
 
       describe('removes specific parameter', () => {
-        const engine = createEngine('||foo.com$removeparam=utm');
+        let engine: FilterEngine;
+        before(() => {
+          engine = createEngine('||foo.com$removeparam=utm');
+        });
         for (const { match, redirect, request } of requests.map((request) => ({
           ...engine.match(request),
           request,
@@ -652,7 +661,10 @@ $csp=baz,domain=bar.com
       });
 
       describe('removes specific parameter regardless of ordering', () => {
-        const engine = createEngine('||foo.com$removeparam=utm');
+        let engine: FilterEngine;
+        before(() => {
+          engine = createEngine('||foo.com$removeparam=utm');
+        });
         for (const { match, redirect, request } of [
           // First
           'https://foo.com?utm=a&utm_source=organic&utm_event=b',
@@ -676,10 +688,10 @@ $csp=baz,domain=bar.com
 
       it('removes parameter sequentially', () => {
         const params = ['utm', 'utm_source', 'utm_event'];
-        let request = urlToDocumentRequest('https://foo.com?utm_source=organic&utm_event=b&utm=a');
         const engine = createEngine(
           params.map((param) => `||foo.com$removeparam=${param}`).join('\n'),
         );
+        let request = urlToDocumentRequest('https://foo.com?utm_source=organic&utm_event=b&utm=a');
         for (let i = 0; i < params.length; i++) {
           const { redirect } = engine.match(request);
           expect(redirect).not.to.be.undefined;

From 1c070255fd0ac03ee89a3204a4f8e18f4203a784 Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Wed, 15 Jan 2025 16:17:07 +0900
Subject: [PATCH 14/15] fix(test): invalid scopes

---
 packages/adblocker/test/engine/engine.test.ts | 41 +++++++------------
 1 file changed, 15 insertions(+), 26 deletions(-)

diff --git a/packages/adblocker/test/engine/engine.test.ts b/packages/adblocker/test/engine/engine.test.ts
index 50f1a30904..5ae6efd57c 100644
--- a/packages/adblocker/test/engine/engine.test.ts
+++ b/packages/adblocker/test/engine/engine.test.ts
@@ -601,7 +601,7 @@ $csp=baz,domain=bar.com
       expect(redirect).to.be.undefined;
     });
 
-    context('removeparam', () => {
+    context.only('removeparam', () => {
       function urlToDocumentRequest(url: string) {
         return Request.fromRawDetails({
           sourceUrl: 'https://foo.com',
@@ -610,27 +610,22 @@ $csp=baz,domain=bar.com
         });
       }
 
-      let requests: Request[];
-      before(() => {
-        requests = [
-          'https://foo.com?utm',
-          'https://foo.com?utm=',
-          'https://foo.com?utm=a',
-          'https://foo.com?utm=a&utm_source=organic',
-          'https://foo.com?utm_source=organic&utm=a',
-        ].map(urlToDocumentRequest);
-      });
+      const requests = [
+        'https://foo.com?utm',
+        'https://foo.com?utm=',
+        'https://foo.com?utm=a',
+        'https://foo.com?utm=a&utm_source=organic',
+        'https://foo.com?utm_source=organic&utm=a',
+      ].map(urlToDocumentRequest);
 
       describe('removes all parameters', () => {
         let engine: FilterEngine;
         before(() => {
           engine = createEngine('||foo.com$removeparam');
         });
-        for (const { match, redirect, request } of requests.map((request) => ({
-          ...engine.match(request),
-          request,
-        }))) {
+        for (const request of requests) {
           it(`removes all params from "${request.url}"`, () => {
+            const { match, redirect } = engine.match(request);
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.body).to.be.eql('');
@@ -645,11 +640,9 @@ $csp=baz,domain=bar.com
         before(() => {
           engine = createEngine('||foo.com$removeparam=utm');
         });
-        for (const { match, redirect, request } of requests.map((request) => ({
-          ...engine.match(request),
-          request,
-        }))) {
+        for (const request of requests) {
           it(`removes "utm" from "${request.url}"`, () => {
+            const { match, redirect } = engine.match(request);
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.body).to.be.eql('');
@@ -665,20 +658,16 @@ $csp=baz,domain=bar.com
         before(() => {
           engine = createEngine('||foo.com$removeparam=utm');
         });
-        for (const { match, redirect, request } of [
+        for (const request of [
           // First
           'https://foo.com?utm=a&utm_source=organic&utm_event=b',
           // Middle
           'https://foo.com?utm_source=organic&utm=a&utm_event=b',
           // Last
           'https://foo.com?utm_source=organic&utm_event=b&utm=a',
-        ]
-          .map(urlToDocumentRequest)
-          .map((request) => ({
-            ...engine.match(request),
-            request,
-          }))) {
+        ].map(urlToDocumentRequest)) {
           it(`removeparam "utm" from "${request.url}"`, () => {
+            const { match, redirect } = engine.match(request);
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.dataUrl).to.be.eql('https://foo.com/?utm_source=organic&utm_event=b');

From 90d051b886b9a517777823521ef7dace9a78ee2c Mon Sep 17 00:00:00 2001
From: HoJeong Go <seia@outlook.kr>
Date: Wed, 15 Jan 2025 16:23:50 +0900
Subject: [PATCH 15/15] refactor: remove url transforms outside of before hook

---
 packages/adblocker/test/engine/engine.test.ts | 24 +++++++++----------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/packages/adblocker/test/engine/engine.test.ts b/packages/adblocker/test/engine/engine.test.ts
index 5ae6efd57c..1615c224ed 100644
--- a/packages/adblocker/test/engine/engine.test.ts
+++ b/packages/adblocker/test/engine/engine.test.ts
@@ -610,22 +610,22 @@ $csp=baz,domain=bar.com
         });
       }
 
-      const requests = [
+      const urls = [
         'https://foo.com?utm',
         'https://foo.com?utm=',
         'https://foo.com?utm=a',
         'https://foo.com?utm=a&utm_source=organic',
         'https://foo.com?utm_source=organic&utm=a',
-      ].map(urlToDocumentRequest);
+      ];
 
       describe('removes all parameters', () => {
         let engine: FilterEngine;
         before(() => {
           engine = createEngine('||foo.com$removeparam');
         });
-        for (const request of requests) {
-          it(`removes all params from "${request.url}"`, () => {
-            const { match, redirect } = engine.match(request);
+        for (const url of urls) {
+          it(`removes all params from "${url}"`, () => {
+            const { match, redirect } = engine.match(urlToDocumentRequest(url));
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.body).to.be.eql('');
@@ -640,9 +640,9 @@ $csp=baz,domain=bar.com
         before(() => {
           engine = createEngine('||foo.com$removeparam=utm');
         });
-        for (const request of requests) {
-          it(`removes "utm" from "${request.url}"`, () => {
-            const { match, redirect } = engine.match(request);
+        for (const url of urls) {
+          it(`removes "utm" from "${url}"`, () => {
+            const { match, redirect } = engine.match(urlToDocumentRequest(url));
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.body).to.be.eql('');
@@ -658,16 +658,16 @@ $csp=baz,domain=bar.com
         before(() => {
           engine = createEngine('||foo.com$removeparam=utm');
         });
-        for (const request of [
+        for (const url of [
           // First
           'https://foo.com?utm=a&utm_source=organic&utm_event=b',
           // Middle
           'https://foo.com?utm_source=organic&utm=a&utm_event=b',
           // Last
           'https://foo.com?utm_source=organic&utm_event=b&utm=a',
-        ].map(urlToDocumentRequest)) {
-          it(`removeparam "utm" from "${request.url}"`, () => {
-            const { match, redirect } = engine.match(request);
+        ]) {
+          it(`removeparam "utm" from "${url}"`, () => {
+            const { match, redirect } = engine.match(urlToDocumentRequest(url));
             expect(match).to.be.true;
             expect(redirect).not.to.be.undefined;
             expect(redirect!.dataUrl).to.be.eql('https://foo.com/?utm_source=organic&utm_event=b');