[spambayes-dev] OptionsClass.is_valid too picky?

[Tim Peters]

[Skip Montanaro]
> I believe OptionsClass.HEADER_VALUE refers to the value of a
> particular, not its name.  Everything you wrote is correct for
> OptionsClass.HEADER_NAME. Right now, both have the same value:
>
>     HEADER_NAME = r"[\w\.\-\*]+"
>     HEADER_VALUE = r"[\w\.\-\*]+"
>
> I am happy to leave HEADER_NAME as is, but would like to change
> HEADER_VALUE to
>
>     HEADER_VALUE = "[ -~]+"
>
> or should that be
>
>     HEADER_VALUE = "[\t -~]+"

        http://www.faqs.org/rfcs/rfc822.html

        The field-body may be composed of any ASCII characters, except
        CR or LF.  (While CR and/or LF may be present in the actual text,
        they are removed by the action of unfolding the field.)

This seems to contradict the definition of "text" given later, which allows
bare CR and bare LF too, just the CRLF combination.  "ASCII characters"
isn't clearly defined, although the lexical definition for CHAR later is
*described* as "any ASCII character" in English and *defined* as decimal 0
to decimal 127.

One reason email clients get incompatible is that these early standards can
be darned hard to make full sense of.  So "suit yourself" is what many do in
practice, although "be liberal in what you accept" is the Official Mantra
offered as equally fuzzy advice <wink>.