From 6736994827eb295593842afe1a2b159ee84b4a4f Mon Sep 17 00:00:00 2001 From: Sebastian Luther Date: Tue, 15 Jun 2010 23:15:30 +0200 Subject: slot_collision_handler: Add more documentation --- pym/_emerge/resolver/slot_collision.py | 59 ++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) (limited to 'pym/_emerge') diff --git a/pym/_emerge/resolver/slot_collision.py b/pym/_emerge/resolver/slot_collision.py index f4d5411b1..8b499ec00 100644 --- a/pym/_emerge/resolver/slot_collision.py +++ b/pym/_emerge/resolver/slot_collision.py @@ -10,7 +10,66 @@ from portage.versions import cpv_getversion, vercmp class slot_conflict_handler(object): """This class keeps track of all slot conflicts and provides an interface to get possible solutions. + + How it works: + If two packages have been pulled into a slot, one needs to + go away. This class focuses on cases where this can be achieved + with a change in USE settings. + + 1) Find out if what causes a given slot conflict. There are + three possibilities: + + a) One parent needs foo-1:0 and another one needs foo-2:0, + nothing we can do about this. This is called a 'version + based conflict'. + + b) All parents of one of the conflict packages could use + another conflict package. This is called an 'unspecific + conflict'. This should be caught by the backtracking logic. + Ask the user to enable -uN (if not already enabled). If -uN is + enabled, this case is treated in the same way as c). + + c) Neither a 'version based conflict' nor an 'unspecific + conflict'. Ignoring use deps would result result in an + 'unspecific conflict'. This is called a 'specific conflict'. + This is the only conflict we try to find suggestions for. + + 2) Computing suggestions. + + Def.: "configuration": A list of packages, containing exactly one + package from each slot conflict. + + We try to find USE changes such that all parents of conflict packages + can work with a package in the configuration we're looking at. This + is done for all possible configurations, except if the 'all-ebuild' + configuration has a suggestion. In this case we immediately abort the + search. + For the current configuration, all use flags that are part of violated + use deps are computed. This is done for every slot conflict on its own. + + Def.: "solution (candidate)": An assignment of "enabled" / "disabled" + values for the use flags that are part of violated use deps. + + Now all involved use flags for the current configuration are known. For + now they have an undetermined value. Fix their value in the + following cases: + * The use dep in the parent atom is unconditional. + * The parent package is 'installed'. + * The conflict package is 'installed'. + + USE of 'installed' packages can't be changed. This always requires an + non-installed package. + + During this procedure, contradictions may occur. In this case the + configuration has no solution. + + Now generate all possible solution candidates with fixed values. Check + if they don't introduce new conflicts. + + We have found a valid assignment for all involved use flags. Compute + the needed USE changes and prepare the message for the user. """ + def __init__(self, slot_collision_info, all_parents, myopts): self.myopts = myopts self.debug = "--debug" in myopts -- cgit v1.2.3-1-g7c22