Fix empty sync exclude regexp behavior

https://github.com/mozilla/multi-account-containers/pull/2383

src/js/background/sync.js

@@ -128,13 +128,12 @@ const sync = {
       await sync.checkForListenersMaybeAdd();
 
       async function updateSyncIdentities() {
-        const { syncExcludeRegExp } = await browser.storage.local.get("syncExcludeRegExp");
+        const excludeRegExp = await getExcludeRegExp();
-        const excludeRegExp = new RegExp(syncExcludeRegExp, "i");
         const identities = await browser.contextualIdentities.query({});
 
         for (const identity of identities) {
           // skip excluded identities
-          if (identity.name.match(excludeRegExp)) {
+          if (excludeRegExpMatchesIdentity(excludeRegExp, identity)) {
             continue;
           }
 
@@ -334,6 +333,7 @@ async function restore() {
  */
 async function reconcileIdentities(){
   if (SYNC_DEBUG) console.log("reconcileIdentities");
+  const excludeRegExp = await getExcludeRegExp();
 
   // first delete any from the deleted list
   const deletedIdentityList =
@@ -343,6 +343,14 @@ async function reconcileIdentities(){
     const deletedCookieStoreId = 
       await identityState.lookupCookieStoreId(deletedUUID);
     if (deletedCookieStoreId){
+      if (excludeRegExp) {
+        const deletedIdentity = await identityState.get(deletedCookieStoreId);
+        // skip excluded identities
+        if (excludeRegExpMatchesIdentity(excludeRegExp, deletedIdentity)) {
+          continue;
+        }      
+      }
+
       try{
         await browser.contextualIdentities.remove(deletedCookieStoreId);
       } catch (error) {
@@ -357,6 +365,11 @@ async function reconcileIdentities(){
     await sync.storageArea.getIdentities();
   // find any local dupes created on sync storage and delete from sync storage
   for (const localIdentity of localIdentities) {
+    // skip excluded identities
+    if (excludeRegExpMatchesIdentity(excludeRegExp, localIdentity)) {
+      continue;
+    }
+
     const syncIdentitiesOfName = syncIdentitiesRemoveDupes
       .filter(identity => identity.name === localIdentity.name);
     if (syncIdentitiesOfName.length > 1) {
@@ -370,6 +383,11 @@ async function reconcileIdentities(){
     await sync.storageArea.getIdentities();
   // now compare all containers for matching names.
   for (const syncIdentity of syncIdentities) {
+    // skip excluded identities
+    if (excludeRegExpMatchesIdentity(excludeRegExp, syncIdentity)) {
+      continue;
+    }
+
     if (syncIdentity.macAddonUUID){
       const localMatch = localIdentities.find(
         localIdentity => localIdentity.name === syncIdentity.name
@@ -585,3 +603,24 @@ async function setAssignmentWithUUID(assignedSite, urlKey) {
   }
   throw new Error (`No cookieStoreId found for: ${uuid}, ${urlKey}`);
 }
+
+// Retrieve the sync exclude regexp from local storage.
+async function getExcludeRegExp() {
+  const { syncExcludeRegExp } = await browser.storage.local.get("syncExcludeRegExp");
+  if (syncExcludeRegExp) {
+    return new RegExp(syncExcludeRegExp, "i");
+  } else {
+    return false;
+  }
+}
+
+// Matching the provided exclude regexp against the provided identity and return
+// true if they match.
+function excludeRegExpMatchesIdentity(excludeRegExp, identity) {
+  if (excludeRegExp && identity.name.match(excludeRegExp)) {
+    if (SYNC_DEBUG) console.log(`Exclude regexp matches identity '${identity.name}'`);
+    return true;
+  } else {
+    return false;
+  }
+}