On Mon, 2008-04-14 at 16:08 +0700, Peter Gammie wrote:
Can you expand on your squeamishness?
We should not delete files we don't know that we own. We only know we own files we're installing. So we cannot delete anything.
As I said before, I disagree. Directories like ~/lib/package/ghc-6.6.1 are clearly Cabal-directories. (Please insert some $'s to make that suitably relative). All sorts of gunk piles up in there while developing. When hacking libs, one really wants "install" to mirror what one has just built.
It may look that way but what if someone configures to use ~/lib directly? The directory structure we use is just a default, it's all completely configurable. We cannot rely on 'owning' anything.
Consider this sequence:
Step 1:
configure -p build install
Step 2:
<change implementation but not API> clean configure build install
Now the profiling libs are out of date, Cabal "owned" them before but not now...
Sure I see the problem.
Also consider:
<delete some modules from blah.cabal> configure build install and now we may have some .hi files orphaned by Cabal.
Ditto for documentation.
Yep.
Only a package manager can do that because it knows what files belong to the package we're replacing. Of course cabal-install is a package manager of sorts so if it tracked what files belonged to packages it installed then it'd know what files to remove when it replaced packages.
This is a non-solution: I've *changed* what is owned by the package.
Exactly! That's just why we need a package manager. It remembers what files belonged to the Foo package before and now that we're installing Foo again it knows that we're *replacing* Foo, so it's safe to delete all the old files that belonged to the Foo package and install all the new Foo files (and remember them for later).
I claim this is all so arbitrary that it is better for Cabal to simply throw everything out... the alternative is endless prompts: "do you really want me to clobber this file you don't care about?" or dodgy behaviour in corner cases.
This behaviour is completely consistent with all other build systems I know of. We really need package managers to solve the problem.
BTW can I really ask Cabal to install a lib into:
~/
and have all files end up there? (i.e. no ghc-6.6.1 etc. subdirs?)
Yes you can do that.
If not, we are arguing past each other.
Would be nice. You need debian-style "remove using old .cabal" "install using new .cabal" persistence though, in case the .cabal has changed.
Well, as I said, the package manager just needs to remember the set of files that belong to each installed package. A related problem is that we need to solve this problem at least within the ./dist/ directory. One of your examples was changing a .cabal file to add/remove a module. Currently we would not delete any existing .hi or .o files within ./dist/. As it happens for .o and .hi we copy out exactly the ones we need, but that's not the case for the documentation for example so we might end up copying stale .html files. To do that properly we'd need to track generated files much more closely. Duncan