Question/discussion how to resolve 8196371, 4271239, 4935610, and 6910466 about missing manifest version in Attributes#writeMain

[Philipp Kunz]

Hi,

Bugs 8196371, 4271239, 4935610, and 6910466 all are about manifests with 
no version.

Which approach would be preferable?

0) leave the impl as is - close with resolution won't fix
1) assume a version automatically if not explicitly set (suggested in 
6910466 and 4271239)
2) throw an exception in JarOutputStream (suggested in 6910466)
3) throw an exception in Manifest#write (suggested in 4935610 and 4271239)
4) issue warning (suggested in 4935610)
5) output manifest without version (suggested in 4271239 and voted 
against in 6294255)

desirable would be
a) that existing code continues to work flawlessly,
b) that no invalid manifests can be produced, and
c) notifying missing version at the earliest time possible

Spontaneously, I'd go for a default value for the version (option 1). 
Additionally, a warning could also be issued when assuming the default 
version (option 4). I figure that very few manifests have been in use 
that have no version because that would have been detected due to 
missing main attributes. Therefore, I guess it can be assumed that a 
default version would not lead to expect breaking a lot of existing 
applications though strictly possible. The default version would be the 
Manifest-Version and not the Signature-Version header but what would be 
an appropriate default manifest version value? "1.0", or maybe just "0"?

I merely collected the available information so far and would not be 
surprised if I'd missed another approach, option, or objective. Any 
suggestion or other idea?

I'm still a new contributor to the open jdk and would be glad also to 
get suggestions about how to appropriately inquire such topics or if I'm 
just going too far and asking for too much or if it's just not important 
or urgent enough or how to proceed or anything else whatever. As I 
understand someone will have to sponsor the change if there will be any. 
Is there any chance to find one or is that too early?

Regards,
Philipp