[pacman-dev] Pacman doesn't handle properly the multiple satisfiers, localdb corruption

[ngaba at petra.hos.u-szeged.hu]

Hi!

Well, you probably will ask me to send patch, but I'm waiting for your 
decision.
First, here is the problem:
===requiredby005.py==
self.description = "Remove lp1, requiredby should move from lp1 to lp2"

lp1 = pmpkg("foo")
lp1.requiredby = ["pkg3"]
self.addpkg2db("local", lp1)

lp2 = pmpkg("pkg2")
lp2.provides = ["foo"]
self.addpkg2db("local", lp2)

lp3 = pmpkg("pkg3")
lp3.depends = ["foo"]
self.addpkg2db("local", lp3)


self.args = "-R %s" % lp1.name

self.addrule("PACMAN_RETCODE=0")
self.addrule("!PKG_EXIST=foo")
self.addrule("PKG_EXIST=pkg2")
self.addrule("PKG_REQUIREDBY=pkg2|pkg3")
-------------------------
This test fails and hence the database becomes corrupt: alpm_checkdeps 
is clever enough to let pacman remove foo, however update of pkg2's 
requiredby is missing after the remove. However, this is not a pactest 
to commit: as you see, pkg2's requiredby field is missing: this can 
happen, if pkg3 was the last installed package, because 
_alpm_trans_update_depends works in a "funny" way: it fills in the 
"literal" satisfier's requiredby only or _all_ "provider" satisfiers' 
requiredby.
So, my question, how I fix this? How should we store multiple 
satisfiers in localdb?
case 1: We find all satisfier package and fill in _all_ requiredby fields.
case 2: We flag only one package as a satisfier with requiredby, and we 
handle properly these requiredby "moves".
case 3: any other idea?
We must choose one, because this is not defined in pacman now. I prefer 
case 1.
Pros:
-easy to implement (only _alpm_trans_update_depends needs patching)
-by doing this, we clean up _alpm_trans_update_depends using alpm_depcmp
-_alpm_pkg_update_requiredby prefers this way now
-this won't break prepare/commit hierarchy (because alpm_checkdeps 
should somehow inform remove_commit in case 2)
-when using -d switch, implement case 2 is difficult
Contras:
-slower!! (we need to check for providers always)
-some users may have corrupted(?) localdb as shown in the pactest file 
(this is rare)
-one satisfier is enough

Bye, ngaba


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