Implement RFC 6134 Sieve Extension: Externally Stored Lists

[johnlettman]

[!IMPORTANT] The change is blocked by a unique grammar element for multi-line strings missing from the Bison declarations. See: https://github.com/dburkart/check-sieve/issues/55#issuecomment-1703683448

This change implements support for RFC 6134 Sieve Extension: Externally Stored Lists, closing #55. The RFC introduces the following elements:

• :list tag (match type for supported tests)

  The new ":list" match type changes the interpretation of the "key-list" parameter (the second parameter) in supported tests. When the match type is ":list", the key-list becomes a list of names of externally stored lists. The external lists are queried, perhaps through a list-specific mechanism, and the test evaluates to "true" if any of the specified values matches any member of one or more of the lists.

• valid_ext_list test

  The "valid_ext_list" test is true if all of the external list names in the ext-list-names argument are supported, and they are valid both syntactically (including URI parameters) and semantically (including implementation-specific semantic restrictions). Otherwise, the test returns false.

  This test MUST perform exactly the same validation of an external list name as would be performed by the "header :list" test.

[johnlettman]

GitHub didn't link the issue, so adding this: Fixes #55

Edit: nevermind, still doesn't work.

[dburkart]

We should actually support these weird strings (you can see the rules in the flex file). But I wouldn't be surprised if something is broken, as I'm sure most people don't use this syntax in their sieves.

I'll look into it.

[dburkart]

@johnlettman This is actually a bug in the example you got from RFC 6134. As per RFC 5228, multi-line strings begin with "text:", not ":text" (the latter of which is a tag, which would be something else). The relevent section of RFC 5228 is:

For entering larger amounts of text, such as an email message, a multi-line form is allowed. It starts with the keyword "text:", followed by a CRLF, and ends with the sequence of a CRLF, a single period, and another CRLF. The CRLF before the final period is considered part of the value.

Changing that, and the indentation of your test makes it pass. I've pushed it up to your branch (since it was fiddly).

[johnlettman]

Ah! Good catch. I must have glanced over the colon placement when looking that up. The changes LGTM thanks!

[johnlettman]

I'll also add in the README and manpage references quick, one sec..