Bug 1577835 - Fix eslint "no-useless-concat" errors in mailnews/. r=mkmelin

mailnews/base/prefs/content/AccountManager.js

@@ -1834,7 +1834,7 @@ var gAccountTree = {
       if (server) {
         treecell.setAttribute(
           "properties",
-          "folderNameCol isServer-true" + " serverType-" + server.type
+          "folderNameCol isServer-true serverType-" + server.type
         );
         // For IM accounts, we can try to fetch a protocol specific icon.
         if (server.type == "im") {

mailnews/base/test/unit/test_nsMsgDBView.js

@@ -483,9 +483,7 @@ function ensure_view_ordering(
     if (inGroup) {
       let groupValue = groupValueGetter(msgHdr);
       if (groupValue in previouslySeenGroupValues) {
-        do_throw(
-          "Group value " + groupValue + " observed in more than one " + "group!"
-        );
+        do_throw(`Group value ${groupValue} observed in more than one group!`);
       }
       if (curGroupValue == null) {
         curGroupValue = groupValue;

mailnews/base/util/mailstoreConverter.jsm

@@ -211,7 +211,7 @@ function installNewRoot(server, dir, newStoreTypeID) {
   // exists in "parentPath". If yes, remove it.
   let lastSlash = accountRootFolder.path.lastIndexOf("/");
   let parentPath = accountRootFolder.parent.path;
-  log.info("Path to parent folder of account root" + " folder: " + parentPath);
+  log.info("Path to parent folder of account root folder: " + parentPath);
 
   let parent = new FileUtils.File(parentPath);
   log.info("Path to parent folder of account root folder: " + parent.path);

mailnews/compose/test/unit/test_messageHeaders.js

@@ -630,7 +630,7 @@ async function testSentMessage() {
       {
         "Content-Type": "application/octet-stream",
         "X-Mozilla-Cloud-Part":
-          "cloudFile; url=http://localhost.invalid/; " + "name=attachment.html",
+          "cloudFile; url=http://localhost.invalid/; name=attachment.html",
       },
       "2"
     );

mailnews/db/gloda/modules/datastore.js

@@ -1318,7 +1318,7 @@ var GlodaDatastore = {
       this.asyncConnection.asyncClose();
     } catch (ex) {
       this._log.debug(
-        "Potentially expected exception during connection " + "closure: " + ex
+        "Potentially expected exception during connection closure: " + ex
       );
     }
 

mailnews/db/gloda/test/unit/resources/glodaTestHelper.js

@@ -621,7 +621,7 @@ var _indexMessageState = {
       this.expectedFailedToRecoverCount != this._workerFailedToRecoverCount
     ) {
       mark_failure([
-        "Expected worker-failed-to-recover count did not match " + "actual!",
+        "Expected worker-failed-to-recover count did not match actual!",
         "Expected",
         this.expectedFailedToRecoverCount,
         "actual",

mailnews/extensions/newsblog/content/FeedUtils.jsm

@@ -1661,7 +1661,7 @@ var FeedUtils = {
     let ds = this.rdf.GetDataSourceBlocking(url);
     if (!ds) {
       throw new Error(
-        "FeedUtils.getItemsDS: can't get feed items " + "data source - " + url
+        "FeedUtils.getItemsDS: can't get feed items data source - " + url
       );
     }
     // Note that it this point the datasource may not be loaded yet.

mailnews/extensions/newsblog/content/feed-parser.js

@@ -522,7 +522,7 @@ FeedParser.prototype = {
 
     if (!aFeed.title) {
       FeedUtils.log.error(
-        "FeedParser.parseAsAtom: missing mandatory element " + "<title>"
+        "FeedParser.parseAsAtom: missing mandatory element <title>"
       );
       aFeed.onParseError(aFeed);
       return [];
@@ -726,7 +726,7 @@ FeedParser.prototype = {
 
     if (!aFeed.title) {
       FeedUtils.log.error(
-        "FeedParser.parseAsAtomIETF: missing mandatory element " + "<title>"
+        "FeedParser.parseAsAtomIETF: missing mandatory element <title>"
       );
       aFeed.onParseError(aFeed);
       return [];

mailnews/mime/test/unit/test_mimeContentType.js

@@ -41,7 +41,7 @@ function run_test() {
       result: "",
     },
     {
-      header: "Content-Type:\r\n" + "\r\n",
+      header: "Content-Type:\r\n\r\n",
       result: "",
     },
     {