At 22:38 -0400 04/09/2009, Barry Warsaw wrote: ...
So, what I'm really asking is this. Let's say you agree that there are use cases for accessing a header value as either the raw encoded bytes or the decoded unicode. What should this return:
The raw bytes or the decoded unicode?
That's an easy one: Subject: is an unstructured header, so it must be text, thus Unicode. We're looking at a high-level representation of an email message, with parsed header fields and a MIME message tree.
Okay, so you've picked one. Now how do you spell the other way?
Oh, I see that's what you picked.
The Message class probably has these explicit methods:
(or better names... it's late and I'm tired ;). One of those maps to message['Subject'] but which is the more obvious choice?
Structured header fields are more of a problem. Any header with addresses should return a list of addresses. I think the default return type should depend on the data type. To get an explicit bytes or string or list of addresses, be explicit; otherwise, for convenience, return the appropriate type for the particular header field name.
Now, setting headers. Sometimes you have some unicode thing and sometimes you have some bytes. You need to end up with bytes in the ASCII range and you'd like to leave the header value unencoded if so. But in both cases, you might have bytes or characters outside that range, so you need an explicit encoding, defaulting to utf-8 probably.
Never for header fields. The default is always RFC 2047, unless it isn't, say for params.
The Message class should create an object of the appropriate subclass of Header based on the name (or use the existing object, see other discussion), and that should inspect its argument and DTRT or complain.
Message.set_header('Subject', 'Some text', encoding='utf-8') Message.set_header('Subject', b'Some bytes')
One of those maps to
message['Subject'] = ???
The expected data type should depend on the header field. For Subject:, it should be bytes to be parsed or verbatim text. For To:, it should be a list of addresses or bytes or text to be parsed.
The email package should be pythonic, and not require deep understanding of dozens of RFCs to use properly. Users don't need to know about the raw bytes; that's the whole point of MIME and any email package. It should be easy to set header fields with their natural data types, and doing it with bad data should produce an error. This may require a bit more care in the