Commit 72d0a3c8 authored by Duncan Coutts's avatar Duncan Coutts
Browse files

Detailed comments on the InstallPlan processing invariant

What they mean informally, to augment the formal definitions.
parent 48db1c08
......@@ -593,21 +593,41 @@ processingInvariant :: (IsUnit ipkg, IsUnit srcpkg)
=> GenericInstallPlan ipkg srcpkg
-> Processing -> Bool
processingInvariant plan (Processing processingSet completedSet failedSet) =
-- All the packages in the three sets are actually in the graph
all (isJust . flip Graph.lookup (planIndex plan)) (Set.toList processingSet)
&& all (isJust . flip Graph.lookup (planIndex plan)) (Set.toList completedSet)
&& all (isJust . flip Graph.lookup (planIndex plan)) (Set.toList failedSet)
-- The processing, completed and failed sets are disjoint from each other
&& noIntersection processingSet completedSet
&& noIntersection processingSet failedSet
-- intersection processingClosure failedSet is quite possible however
&& noIntersection failedSet completedSet
-- Packages that depend on a package that's still processing cannot be
-- completed
&& noIntersection (reverseClosure processingSet) completedSet
-- On the other hand, packages that depend on a package that's still
-- processing /can/ have failed (since they may have depended on multiple
-- packages that were processing, but it only takes one to fail to cause
-- knock-on failures) so it is quite possible to have an
-- intersection (reverseClosure processingSet) failedSet
-- The failed set is upwards closed, i.e. equal to its own rev dep closure
&& failedSet == reverseClosure failedSet
-- All immediate reverse deps of packges that are currently processing
-- are not currently being processed (ie not in the processing set).
&& and [ rdeppkgid `Set.notMember` processingSet
| pkgid <- Set.toList processingSet
, rdeppkgid <- maybe (internalError "processingInvariant")
(map nodeKey)
(Graph.revNeighbors (planIndex plan) pkgid)
-- Packages from the processing or failed sets are only ever in the
-- configured state.
&& and [ case Graph.lookup pkgid (planIndex plan) of
Just (Configured _) -> True
Just (PreExisting _) -> False
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