[mv3] Fix potentially broken custom cosmetic filters

Related issue:
uBlockOrigin/uBOL-home#670

Regression from 46852eb

Author: gorhill

platform/mv3/extension/js/background.js

@@ -57,6 +57,7 @@ import {
     broadcastMessage,
     hostnameFromMatch,
     hostnamesFromMatches,
+    intFromVersion,
 } from './utils.js';
 
 import {
@@ -664,10 +665,34 @@ async function startSession() {
     // The default rulesets may have changed, find out new ruleset to enable,
     // obsolete ruleset to remove.
     if ( isNewVersion ) {
+        const previousVersion = rulesetConfig.version;
         ubolLog(`Version change: ${rulesetConfig.version} => ${currentVersion}`);
         rulesetConfig.version = currentVersion;
         await patchDefaultRulesets();
         saveRulesetConfig();
+        // https://github.com/uBlockOrigin/uBOL-home/issues/670
+        if ( intFromVersion(previousVersion) <= intFromVersion('2026.423.0000') ) {
+            const promises = [];
+            const customFilters = await getAllCustomFilters();
+            for ( const [ hostname, selectors ] of customFilters ) {
+                let modified = false;
+                for ( let i = 0; i < selectors.length; i++ ) {
+                    const selector = selectors[i];
+                    if ( selector.startsWith('0') === false ) { continue; }
+                    selectors[i] = selector.slice(1);
+                    modified = true;
+                }
+                if ( modified === false ) { continue; }
+                promises.push(
+                    removeAllCustomFilters(hostname).then(( ) =>
+                        addCustomFilters(hostname, selectors)
+                    )
+                );
+            }
+            if ( promises.length !== 0 ) {
+                await Promise.all(promises);
+            }
+        }
     }
 
     const rulesetsUpdated = await enableRulesets(rulesetConfig.enabledRulesets);