[plt-scheme] feature request for PLaneT

Hans Oesterholt-Dijkema wrote:

> If I release major=1 and minor=5, I would be very glad, if
> dependent modules would download the newer 1 5 version
> automatically. 

Currently PLaneT distinguishes between three cases:

1. The program doing the requiring has been around and is already linked 
to version 1.4. In this case PLaneT does not (and I think should not) 
try to get a new version automatically ---- you have to ask.

2. The program doing the requiring is not already linked to a particular 
version, and there's no package already on the user's system that would 
satisfy the request. In this case PLaneT goes to the network.

3. The program doing the requiring is not already linked to a particular 
version, but there is a package installed on the user's system that 
would satisfy the request. In this case, PLaneT currently uses the 
installed package --- I think you're suggesting that it shouldn't do 
that, preferring instead to check the network. I've thought about 
changing this behavior too, and I might do it. But there are two things 
to consider:

   * It increases the chance that the same package will get loaded twice 
with two different versions. This is a dangerous situation to be in, and 
currently PLaneT automatically prevents packages from being loaded twice 
with two separate versions unless the packages specifically announce 
that this is okay.

   * It makes PLaneT connect to the network more often and download more 
packages. (The design tries to minimize this, though experience suggests 
that maybe nobody really cares.)

-jacob