Another installment in the never ending Re: processing litany.

chrome/content/TbHelper.js

@@ -11,10 +11,8 @@ const TbHelper = {
   copyMessageToFolder(msgHdr, newSubject, content) {
     // Setting the subject here to the version where the Re: prefix was removed,
     // as returned from `updateSubject()`, seems to have a positive effect.
-    // This is the result of quite some experimentation. In reality
-    // this appears to be another workaround for
-    // https://bugzilla.mozilla.org/show_bug.cgi?id=1629555
-    // as the correct subject should have already been stored in that function.
+    // This is the result of quite some experimentation.
+    // Ideally the correct subject should have already been stored in that function.
     if (newSubject) msgHdr.subject = newSubject;
 
     // Copy copied form Header Tools Lite. There is a variation in Enigmail.

chrome/content/TbMessageView.js

@@ -23,7 +23,8 @@ const TbMessageView = {
     }
     for (let p of prefixes) {
       let regEx = new RegExp(`^(${p}: )+`, "i");
-      subject = subject.replace(regEx, "");  // Remove prefix.
+      // Remove prefix.
+      subject = subject.replace(regEx, "");
     }
     let hadRe = (subject != content);
 
@@ -33,22 +34,19 @@ const TbMessageView = {
     // The database doesn't like raw UTF apparently.
     subject = jsmime.headeremitter.emitStructuredHeader("subject", subject, {}).substring(9);
 
-    // We should store the subject without any Re: prefix, but
-    // https://bugzilla.mozilla.org/show_bug.cgi?id=1629555
-    // gets in the way. So the correct code is commented out for now.
-    // Correct would be these two lines ...
-    // if (hadRe) msgHdr.flags |= Ci.nsMsgMessageFlags.HasRe;
-    // msgHdr.subject = subject;
-    // ... and replace the if-else below.
     if (msgHdr.flags & Ci.nsMsgMessageFlags.HasRe) {
       // If the flag is already set, we can just store the subject.
       msgHdr.subject = subject;
     } else {
-      // This is WRONG. Should not prepend "Re: " but instead set the flag. See above.
+      // It would be nice to store the subject without the "Re:" prefix and set
+      // the HasRe flag instead. That works when calling
+      // tree.view.db.NotifyHdrChangeAll(msgHdr, msgHdr.flags | Ci.nsMsgMessageFlags.HasRe, msgHdr.flags, {});
+      // but sadly the solution falls apart when copying messages between
+      // IMAP folders or between local and IMAP folders.
       // eslint-disable-next-line prefer-template
       msgHdr.subject = hadRe ? "Re: " + subject : subject;
     }
-    if (tree) tree.invalidate();
+    if (tree && tree.view && tree.view.selection) tree.invalidateRow(tree.view.selection.currentIndex);
 
     return subject;
   },

chrome/content/pepmessengercompose.js

@@ -235,9 +235,9 @@ var pEpComposer = {
           };
         }
 
-        // Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1629555
-        // that doesn't allow us to correctly store the HasRe flag.
-        // So now we need to fix the side effects :-(
+        // Workaround for the fact that some messages have a "Re:" stored
+        // in the subject and don't have the HasRe flag set. In that case
+        // we receive a doubled up "Re:".
         let subjElem = document.getElementById("msgSubject");
         if (subjElem) {
           let prefixes = Services.prefs.getStringPref("mailnews.localizedRe", "");