SnappyMail's Sieve editor does not support "index" extension, error "this.index is undefined"

[lje]

Describe the bug
SnappyMail's Sieve editor cannot handle an :index directive in rules.

To Reproduce
I've created the following valid Sieve script as example:

require ["index", "regex"];
if header :index 3 :regex "Received" "envelope-from <([^>]+)>" { keep; }

When trying to edit this script in SnappyMail, I get an "this.index is undefined" message

Screenshots

Please complete the following information:

• Browser: Firefox 129.0.1
• IMAP daemon: dovecot
• PHP version: 8.1
• SnappyMail Version: v2.37.1
• Mode: standalone

[the-djmaze]

it seems a part of RFC 5260 isn't implemented yet.
https://www.rfc-editor.org/rfc/rfc5260.html#section-6

[lje]

The server in quesion does support the "index" extension. The script above was not freshly created in SnappyMail but fetched from the server. I created it before using Sieve Editor and stored in to the server using the ManageSieve protocol.

Does the editor used in SnappyMail perform some kind of client side checking? All checking should be done by the server using the CHECKSCRIPT command of ManageSieve. I assume this is some kind of bug in the editor.

Extension support of the server in question:

[the-djmaze]

Keep in mind that index is a shot in the dark.
You must be 100% certain that every email you receive has the required header on the exact index.

[lje]

Thanks, I'm aware of that. The header in question is a "Received" generated by my own email provider for every incoming mail I want to catch with that filter. The :index makes sure, I don't accidentially catch a "Received" header of any previous mail server along the chain.