Hide custom filters textbox if dev mode is off and there're no custom filters.

browser/resources/settings/default_brave_shields_page/brave_adblock_subpage.ts

@@ -90,6 +90,12 @@ class AdBlockSubpage extends AdBlockSubpageBase {
       'brave_adblock.onGetListSubscriptions', (value: SubscriptionInfo[]) => {
         this.subscriptionList_ = value
     })
+    this.browserProxy_.addWebUiListener(
+      'brave_adblock.onCustomFiltersChanged',
+      (value: string) => {
+        this.customFilters_ = value
+      }
+    )
   }
 
   private handleShowList_() {

browser/resources/settings/default_brave_shields_page/components/brave_adblock_editor.html

@@ -47,16 +47,18 @@
 </style>
 
 <div>
-  <div class="editor-box">
-    <textarea
-      disabled="[[!prefs.brave.ad_block.developer_mode.value]]"
-      type="text"
-      spellcheck="false"
-      class="textbox"
-      on-input="handleInputChange_"
-      value="{{value}}">
-    </textarea>
-  </div>
+  <template is="dom-if" if="[[shouldShowEditor]]">
+    <div class="editor-box">
+      <textarea
+        disabled="[[!prefs.brave.ad_block.developer_mode.value]]"
+        type="text"
+        spellcheck="false"
+        class="textbox"
+        on-input="handleInputChange_"
+        value="{{value}}">
+      </textarea>
+    </div>
+  </template>
   <cr-button
     on-click="handleSave_"
     disabled="[[!prefs.brave.ad_block.developer_mode.value]]">

browser/resources/settings/default_brave_shields_page/components/brave_adblock_editor.ts

@@ -28,11 +28,19 @@ class AdBlockFiltersEditor extends AdBlockFiltersEditorBase {
     return {
       value: {
         type: String
+      },
+      shouldShowEditor: {
+        type: Boolean
       }
     }
   }
 
+  static get observers() {
+    return ['updateState_(prefs.brave.ad_block.developer_mode.value, value)']
+  }
+
   private value: string
+  private shouldShowEditor: boolean
 
   override ready() {
     super.ready()
@@ -45,6 +53,10 @@ class AdBlockFiltersEditor extends AdBlockFiltersEditorBase {
   handleSave_() {
     this.fire('save', { value: this.value })
   }
+
+  private updateState_(dev_mode: boolean, value: string) {
+    this.shouldShowEditor = dev_mode || value.trim().length !== 0
+  }
 }
 
 customElements.define(AdBlockFiltersEditor.is, AdBlockFiltersEditor)

browser/ui/webui/settings/brave_adblock_handler.cc

@@ -5,7 +5,6 @@
 
 #include "brave/browser/ui/webui/settings/brave_adblock_handler.h"
 
-#include <memory>
 #include <string>
 #include <utility>
 
@@ -20,11 +19,9 @@
 #include "brave/components/brave_shields/core/browser/ad_block_component_service_manager.h"
 #include "brave/components/brave_shields/core/browser/ad_block_custom_resource_provider.h"
 #include "brave/components/brave_shields/core/common/features.h"
+#include "brave/components/brave_shields/core/common/pref_names.h"
 #include "chrome/browser/browser_process.h"
-#include "chrome/browser/content_settings/host_content_settings_map_factory.h"
-#include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser_finder.h"
-#include "chrome/browser/ui/browser_navigator_params.h"
 #include "chrome/browser/ui/singleton_tabs.h"
 #include "content/public/browser/web_ui.h"
 #include "ui/base/l10n/time_format.h"
@@ -34,7 +31,6 @@ BraveAdBlockHandler::BraveAdBlockHandler() = default;
 BraveAdBlockHandler::~BraveAdBlockHandler() = default;
 
 void BraveAdBlockHandler::RegisterMessages() {
-  profile_ = Profile::FromWebUI(web_ui());
   web_ui()->RegisterMessageCallback(
       "brave_adblock.getRegionalLists",
       base::BindRepeating(&BraveAdBlockHandler::GetRegionalLists,
@@ -109,15 +105,21 @@ void BraveAdBlockHandler::RegisterMessages() {
       "brave_adblock.removeCustomScriptlet",
       base::BindRepeating(&BraveAdBlockHandler::RemoveCustomScriptlet,
                           base::Unretained(this)));
+  pref_change_registrar_.Init(g_browser_process->local_state());
 }
 
 void BraveAdBlockHandler::OnJavascriptAllowed() {
   service_observer_.Observe(g_brave_browser_process->ad_block_service()
                                 ->subscription_service_manager());
+  pref_change_registrar_.Add(
+      brave_shields::prefs::kAdBlockCustomFilters,
+      base::BindRepeating(&BraveAdBlockHandler::RefreshCustomFilters,
+                          weak_factory_.GetWeakPtr()));
 }
 
 void BraveAdBlockHandler::OnJavascriptDisallowed() {
   service_observer_.Reset();
+  pref_change_registrar_.RemoveAll();
 }
 
 void BraveAdBlockHandler::OnServiceUpdateEvent() {
@@ -364,6 +366,15 @@ void BraveAdBlockHandler::RefreshSubscriptionsList() {
   FireWebUIListener("brave_adblock.onGetListSubscriptions", GetSubscriptions());
 }
 
+void BraveAdBlockHandler::RefreshCustomFilters() {
+  const std::string& custom_filters =
+      g_brave_browser_process->ad_block_service()
+          ->custom_filters_provider()
+          ->GetCustomFilters();
+  FireWebUIListener("brave_adblock.onCustomFiltersChanged",
+                    base::Value(custom_filters));
+}
+
 base::Value::List BraveAdBlockHandler::GetSubscriptions() {
   auto list_subscriptions = g_brave_browser_process->ad_block_service()
                                 ->subscription_service_manager()

browser/ui/webui/settings/brave_adblock_handler.h

@@ -8,13 +8,13 @@
 
 #include <string>
 
-#include "base/memory/raw_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/scoped_observation.h"
 #include "brave/components/brave_shields/content/browser/ad_block_subscription_service_manager.h"
 #include "brave/components/brave_shields/content/browser/ad_block_subscription_service_manager_observer.h"
 #include "brave/components/brave_shields/core/browser/ad_block_custom_resource_provider.h"
 #include "chrome/browser/ui/webui/settings/settings_page_ui_handler.h"
+#include "components/prefs/pref_change_registrar.h"
 
 class Profile;
 using brave_shields::AdBlockSubscriptionServiceManager;
@@ -60,17 +60,18 @@ class BraveAdBlockHandler : public settings::SettingsPageUIHandler,
       brave_shields::AdBlockCustomResourceProvider::ErrorCode error_code);
 
   void RefreshSubscriptionsList();
+  void RefreshCustomFilters();
 
   base::Value::List GetSubscriptions();
 
   void OnFilterListsUpdated(std::string callback_id, bool success);
 
-  raw_ptr<Profile> profile_ = nullptr;
-
   base::ScopedObservation<AdBlockSubscriptionServiceManager,
                           AdBlockSubscriptionServiceManagerObserver>
       service_observer_{this};
 
+  PrefChangeRegistrar pref_change_registrar_;
+
   base::WeakPtrFactory<BraveAdBlockHandler> weak_factory_{this};
 };