From f25a437fd1050e554ed9ab24c5e36b093a29a406 Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Fri, 11 Apr 2025 18:20:51 -0400
Subject: [PATCH] Code review re. scriptlets lookup

Possibly fixes a race condition at browser launch causing empty
scriptlets to be injected (and cached).
---
 src/js/redirect-engine.js          |  1 +
 src/js/scriptlet-filtering-core.js | 22 ++++++++++++----------
 src/js/scriptlet-filtering.js      |  1 +
 src/js/static-ext-filtering-db.js  | 10 +++++-----
 4 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/js/redirect-engine.js b/src/js/redirect-engine.js
index 5e7a55884..14df52200 100644
--- a/src/js/redirect-engine.js
+++ b/src/js/redirect-engine.js
@@ -460,6 +460,7 @@ class RedirectEngine {
         for ( const [ token, entry ] of this.resources ) {
             this.resources.set(token, RedirectEntry.fromDetails(entry));
         }
+        this.modifyTime = Date.now();
         return true;
     }
 
diff --git a/src/js/scriptlet-filtering-core.js b/src/js/scriptlet-filtering-core.js
index eda887634..5c56423c2 100644
--- a/src/js/scriptlet-filtering-core.js
+++ b/src/js/scriptlet-filtering-core.js
@@ -25,11 +25,6 @@ import { redirectEngine as reng } from './redirect-engine.js';
 
 /******************************************************************************/
 
-const $mainWorldMap = new Map();
-const $isolatedWorldMap = new Map();
-
-/******************************************************************************/
-
 // For debugging convenience: all the top function calls will appear
 // at the bottom of a generated content script
 const codeSorter = (a, b) => {
@@ -243,18 +238,27 @@ export class ScriptletFilteringEngine {
             }
         }
 
+        const mainWorldMap = new Map();
+        const isolatedWorldMap = new Map();
+
         for ( const token of scriptlets ) {
-            lookupScriptlet(token, $mainWorldMap, $isolatedWorldMap, options.debug);
+            lookupScriptlet(token, mainWorldMap, isolatedWorldMap, options.debug);
+        }
+
+        if ( scriptlets.size !== 0 ) {
+            if ( mainWorldMap.size === 0 ) {
+                if ( isolatedWorldMap.size === 0 ) { return; }
+            }
         }
 
         const mainWorldCode = [];
-        for ( const js of $mainWorldMap.values() ) {
+        for ( const js of mainWorldMap.values() ) {
             mainWorldCode.push(js);
         }
         mainWorldCode.sort(codeSorter);
 
         const isolatedWorldCode = [];
-        for ( const js of $isolatedWorldMap.values() ) {
+        for ( const js of isolatedWorldMap.values() ) {
             isolatedWorldCode.push(js);
         }
         isolatedWorldCode.sort(codeSorter);
@@ -267,8 +271,6 @@ export class ScriptletFilteringEngine {
                 ...Array.from(exceptions).map(a => decompile(a, true)),
             ],
         };
-        $mainWorldMap.clear();
-        $isolatedWorldMap.clear();
 
         const scriptletGlobals = options.scriptletGlobals || {};
 
diff --git a/src/js/scriptlet-filtering.js b/src/js/scriptlet-filtering.js
index f71b07c2f..c61444bb6 100644
--- a/src/js/scriptlet-filtering.js
+++ b/src/js/scriptlet-filtering.js
@@ -328,6 +328,7 @@ export class ScriptletFilteringEngineEx extends ScriptletFilteringEngine {
         if ( typeof details.frameId !== 'number' ) { return; }
 
         const hostname = hostnameFromURI(details.url);
+        if ( hostname === '' ) { return; }
         const domain = domainFromHostname(hostname);
 
         const scriptletDetails = this.retrieve({
diff --git a/src/js/static-ext-filtering-db.js b/src/js/static-ext-filtering-db.js
index 2e2347491..6d69fd634 100644
--- a/src/js/static-ext-filtering-db.js
+++ b/src/js/static-ext-filtering-db.js
@@ -92,9 +92,9 @@ export class StaticExtFilteringHostnameDB {
         if ( target.includes('/') ) {
             return this.#storeMatcher(target, iStr);
         }
-        const iList = this.#hostnameToStringListMap.get(target);
+        const iList = this.#hostnameToStringListMap.get(target) ?? 0;
         this.#hostnameToStringListMap.set(target, this.#linkedLists.length);
-        this.#linkedLists.push(iStr, iList !== undefined ? iList : 0);
+        this.#linkedLists.push(iStr, iList);
     }
 
     #storeMatcher(target, iStr) {
@@ -105,11 +105,11 @@ export class StaticExtFilteringHostnameDB {
             this.#matcherSlots.push({ isRegex, hn, pn, iList: 0 });
             this.#matcherMap.set(target, iMatcher);
             if ( isRegex === false ) {
-                const iMatcherList = this.#hostnameToMatcherListMap.get(hn) || 0;
+                const iMatcherList = this.#hostnameToMatcherListMap.get(hn) ?? 0;
                 this.#hostnameToMatcherListMap.set(hn, this.#linkedLists.length);
                 this.#linkedLists.push(iMatcher, iMatcherList);
             } else {
-                const iMatcherList = this.#hostnameToMatcherListMap.get('') || 0;
+                const iMatcherList = this.#hostnameToMatcherListMap.get('') ?? 0;
                 this.#hostnameToMatcherListMap.set('', this.#linkedLists.length);
                 this.#linkedLists.push(iMatcher, iMatcherList);
             }
@@ -176,7 +176,7 @@ export class StaticExtFilteringHostnameDB {
     }
 
     #retrieveSpecificsByRegex(hn, out, hostname, pathname) {
-        let iMatchList = this.#hostnameToMatcherListMap.get(hn) || 0;
+        let iMatchList = this.#hostnameToMatcherListMap.get(hn) ?? 0;
         while ( iMatchList !== 0 ) {
             const iMatchSlot = this.#linkedLists[iMatchList+0];
             const matcher = this.#matcherSlots[iMatchSlot];