Bug 1705765 - Fix regression to allow creation and rename of imap folders containing ascii ampersand. r=benc

mailnews/base/src/nsMsgI18N.cpp

@@ -141,11 +141,20 @@ nsresult CopyUTF16toMUTF7(const nsAString& aSrc, nsACString& aDest) {
 // MUTF-7 or UTF-8.
 nsresult CopyFolderNameToUTF16(const nsACString& aSrc, nsAString& aDest) {
   if (NS_IsAscii(aSrc.BeginReading(), aSrc.Length())) {
-    return CopyMUTF7toUTF16(aSrc, aDest);
-  } else {
-    CopyUTF8toUTF16(aSrc, aDest);
-    return NS_OK;
+    // An ASCII string may not be valid MUTF-7. For example, it may contain an
+    // ampersand not immediately followed by a dash which is invalid MUTF-7.
+    // Check for validity by converting to UTF-16 and then back to MUTF-7 and
+    // the result should be unchanged. If the MUTF-7 is invalid, treat it as
+    // UTF-8.
+    if (NS_SUCCEEDED(CopyMUTF7toUTF16(aSrc, aDest))) {
+      nsAutoCString tmp;
+      CopyUTF16toMUTF7(aDest, tmp);
+      if (aSrc.Equals(tmp)) return NS_OK;
+    }
   }
+  // Do if aSrc non-ASCII or if ASCII but invalid MUTF-7.
+  CopyUTF8toUTF16(aSrc, aDest);
+  return NS_OK;
 }
 
 nsresult CopyMUTF7toUTF16(const nsACString& aSrc, nsAString& aDest) {

mailnews/imap/src/nsImapService.cpp

@@ -2166,15 +2166,15 @@ NS_IMETHODIMP nsImapService::RenameLeaf(nsIMsgFolder* srcFolder,
         urlSpec.Append(cStrFolderName);
       }
 
-      NS_ConvertUTF16toUTF8 utfNewName(newLeafName);
-      if (!NS_IsAscii(utfNewName.get())) {
-        // Convert to MUTF-7 if UTF8=ACCEPT not enabled by server.
-        bool utf8AcceptEnabled;
-        nsCOMPtr<nsIMsgImapMailFolder> imapFolder =
-            do_QueryInterface(srcFolder);
-        rv = imapFolder->GetShouldUseUtf8FolderName(&utf8AcceptEnabled);
-        NS_ENSURE_SUCCESS(rv, rv);
-        if (!utf8AcceptEnabled) CopyUTF16toMUTF7(newLeafName, utfNewName);
+      nsAutoCString utfNewName;
+      bool utf8AcceptEnabled;
+      nsCOMPtr<nsIMsgImapMailFolder> imapFolder = do_QueryInterface(srcFolder);
+      rv = imapFolder->GetShouldUseUtf8FolderName(&utf8AcceptEnabled);
+      NS_ENSURE_SUCCESS(rv, rv);
+      if (utf8AcceptEnabled) {
+        CopyUTF16toUTF8(newLeafName, utfNewName);
+      } else {
+        CopyUTF16toMUTF7(newLeafName, utfNewName);
       }
       nsCString escapedNewName;
       MsgEscapeString(utfNewName, nsINetUtil::ESCAPE_URL_PATH, escapedNewName);
@@ -2222,14 +2222,15 @@ NS_IMETHODIMP nsImapService::CreateFolder(nsIMsgFolder* parent,
         urlSpec.Append(hierarchyDelimiter);
       }
 
-      NS_ConvertUTF16toUTF8 utfNewName(newFolderName);
-      if (!NS_IsAscii(utfNewName.get())) {
-        // Convert to MUTF-7 if UTF8=ACCEPT not enabled by server.
-        bool utf8AcceptEnabled;
-        nsCOMPtr<nsIMsgImapMailFolder> imapFolder = do_QueryInterface(parent);
-        rv = imapFolder->GetShouldUseUtf8FolderName(&utf8AcceptEnabled);
-        NS_ENSURE_SUCCESS(rv, rv);
-        if (!utf8AcceptEnabled) CopyUTF16toMUTF7(newFolderName, utfNewName);
+      nsAutoCString utfNewName;
+      bool utf8AcceptEnabled;
+      nsCOMPtr<nsIMsgImapMailFolder> imapFolder = do_QueryInterface(parent);
+      rv = imapFolder->GetShouldUseUtf8FolderName(&utf8AcceptEnabled);
+      NS_ENSURE_SUCCESS(rv, rv);
+      if (utf8AcceptEnabled) {
+        CopyUTF16toUTF8(newFolderName, utfNewName);
+      } else {
+        CopyUTF16toMUTF7(newFolderName, utfNewName);
       }
       nsCString escapedFolderName;
       MsgEscapeString(utfNewName, nsINetUtil::ESCAPE_URL_PATH,