Re: More liberal MIME decoding (unencoded question marks in encoded words)

[Reiner Steib <reinersteib+gmane@imap.cc>]

On Mon, Nov 26 2007, Katsumi Yamaoka wrote:

>>>>>> Reiner Steib wrote:
>> The mistake on Google's side is not to encode the (trailing) question
>> mark.  How can we make Gnus' decoder more liberal?
>
> Maybe the patch below does it

Thanks.

> but we must check it thoroughly.

Agreed.

> Would we be able to make complete test cases?
>
> (rfc2047-decode-string "=?ISO-8859-1?Q??foo?=")
> "?foo"
> (rfc2047-decode-string "=?ISO-8859-1?Q?=foo?=")
> "=foo"
> (rfc2047-decode-string "=?ISO-8859-1?Q?foo??=")
> "foo?"
> (rfc2047-decode-string "=?ISO-8859-1?Q?foo?=?=")
> "foo?="
> (rfc2047-decode-string "=?ISO-8859-1?Q?foo?==?ISO-8859-1?Q?bar?=")
> "foobar"

Do you see the other examples often in the wild?  If not, I'd rather
not make the decode too liberal.  And we probably should have an
option to toggle strict/loose decoding.

BTW, another problem is that we "double encode"
(`rfc2047-encode-encoded-words') such subjects:

ELISP> (rfc2047-decode-string "=?ISO-8859-1?Q?foo??=")
"=?ISO-8859-1?Q?foo??="
ELISP> (rfc2047-encode-string "=?ISO-8859-1?Q?foo??=")
"=?us-ascii?Q?=3D=3FISO-8859-1=3FQ=3Ffoo=3F=3F=3D?="

AFAICS, Gnus (`rfc2047-encodable-p'?) simply looks for "=?".  When
found, the string is (double) encoded.  I'm not sure if this behavior
is wrong, but RFC2047 says the an encoded word is...


,----[ RFC2047 ]
|    Generally, an "encoded-word" is a sequence of printable ASCII
|    characters that begins with "=?", ends with "?=", and has two "?"s in
|    between.  It specifies a character set and an encoding method, and
|    also includes the original text encoded as graphic ASCII characters,
|    according to the rules for that encoding method.
`----

..., i.e. shouldn't we use "=\\?.+\\?[qb]\\?.+\\?=" (or similar)
instead of "=?"?

Bye, Reiner.
-- 
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