Solver: Pair conflict set variables with more information about conflicts (issue #4805).

Cabal/doc/nix-local-build.rst

@@ -2115,6 +2115,23 @@ Most users generally won't need these.
     The command line variant of this field is
     ``--(no-)count-conflicts``.
 
+.. cfg-field:: fine-grained-conflicts: boolean
+               --fine-grained-conflicts
+               --no-fine-grained-conflicts
+    :synopsis: Skip a version of a package if it does not resolve any conflicts
+	       encountered in the last version (solver optimization).
+
+    :default: True
+
+    When enabled, the solver will skip a version of a package if it does not
+    resolve any of the conflicts encountered in the last version of that
+    package. For example, if ``foo-1.2`` depended on ``bar``, and the solver
+    couldn't find consistent versions for ``bar``'s dependencies, then the
+    solver would skip ``foo-1.1`` if it also depended on ``bar``.
+
+    The command line variant of this field is
+    ``--(no-)fine-grained-conflicts``.
+
 .. cfg-field:: minimize-conflict-set: boolean
                --minimize-conflict-set
                --no-minimize-conflict-set

cabal-install/Distribution/Client/Config.hs

@@ -312,6 +312,7 @@ instance Semigroup SavedConfig where
         installMaxBackjumps          = combine installMaxBackjumps,
         installReorderGoals          = combine installReorderGoals,
         installCountConflicts        = combine installCountConflicts,
+        installFineGrainedConflicts  = combine installFineGrainedConflicts,
         installMinimizeConflictSet   = combine installMinimizeConflictSet,
         installIndependentGoals      = combine installIndependentGoals,
         installShadowPkgs            = combine installShadowPkgs,

cabal-install/Distribution/Client/Dependency.hs

@@ -47,6 +47,7 @@ module Distribution.Client.Dependency (
     setPreferenceDefault,
     setReorderGoals,
     setCountConflicts,
+    setFineGrainedConflicts,
     setMinimizeConflictSet,
     setIndependentGoals,
     setAvoidReinstalls,
@@ -159,6 +160,7 @@ data DepResolverParams = DepResolverParams {
        depResolverSourcePkgIndex    :: PackageIndex.PackageIndex UnresolvedSourcePackage,
        depResolverReorderGoals      :: ReorderGoals,
        depResolverCountConflicts    :: CountConflicts,
+       depResolverFineGrainedConflicts :: FineGrainedConflicts,
        depResolverMinimizeConflictSet :: MinimizeConflictSet,
        depResolverIndependentGoals  :: IndependentGoals,
        depResolverAvoidReinstalls   :: AvoidReinstalls,
@@ -197,6 +199,7 @@ showDepResolverParams p =
   ++ "\nstrategy: "          ++ show (depResolverPreferenceDefault        p)
   ++ "\nreorder goals: "     ++ show (asBool (depResolverReorderGoals     p))
   ++ "\ncount conflicts: "   ++ show (asBool (depResolverCountConflicts   p))
+  ++ "\nfine grained conflicts: " ++ show (asBool (depResolverFineGrainedConflicts p))
   ++ "\nminimize conflict set: " ++ show (asBool (depResolverMinimizeConflictSet p))
   ++ "\nindependent goals: " ++ show (asBool (depResolverIndependentGoals p))
   ++ "\navoid reinstalls: "  ++ show (asBool (depResolverAvoidReinstalls  p))
@@ -254,6 +257,7 @@ basicDepResolverParams installedPkgIndex sourcePkgIndex =
        depResolverSourcePkgIndex    = sourcePkgIndex,
        depResolverReorderGoals      = ReorderGoals False,
        depResolverCountConflicts    = CountConflicts True,
+       depResolverFineGrainedConflicts = FineGrainedConflicts True,
        depResolverMinimizeConflictSet = MinimizeConflictSet False,
        depResolverIndependentGoals  = IndependentGoals False,
        depResolverAvoidReinstalls   = AvoidReinstalls False,
@@ -310,6 +314,12 @@ setCountConflicts count params =
       depResolverCountConflicts = count
     }
 
+setFineGrainedConflicts :: FineGrainedConflicts -> DepResolverParams -> DepResolverParams
+setFineGrainedConflicts fineGrained params =
+    params {
+      depResolverFineGrainedConflicts = fineGrained
+    }
+
 setMinimizeConflictSet :: MinimizeConflictSet -> DepResolverParams -> DepResolverParams
 setMinimizeConflictSet minimize params =
     params {
@@ -755,7 +765,8 @@ resolveDependencies platform comp pkgConfigDB solver params =
 
     Step (showDepResolverParams finalparams)
   $ fmap (validateSolverResult platform comp indGoals)
-  $ runSolver solver (SolverConfig reordGoals cntConflicts minimize indGoals noReinstalls
+  $ runSolver solver (SolverConfig reordGoals cntConflicts fineGrained minimize
+                      indGoals noReinstalls
                       shadowing strFlags allowBootLibs onlyConstrained_ maxBkjumps enableBj
                       solveExes order verbosity (PruneAfterFirstSuccess False))
                      platform comp installedPkgIndex sourcePkgIndex
@@ -769,6 +780,7 @@ resolveDependencies platform comp pkgConfigDB solver params =
       sourcePkgIndex
       reordGoals
       cntConflicts
+      fineGrained
       minimize
       indGoals
       noReinstalls
@@ -1015,9 +1027,9 @@ resolveWithoutDependencies :: DepResolverParams
                            -> Either [ResolveNoDepsError] [UnresolvedSourcePackage]
 resolveWithoutDependencies (DepResolverParams targets constraints
                               prefs defpref installedPkgIndex sourcePkgIndex
-                              _reorderGoals _countConflicts _minimizeConflictSet
-                              _indGoals _avoidReinstalls _shadowing _strFlags
-                              _maxBjumps _enableBj _solveExes
+                              _reorderGoals _countConflicts _fineGrained
+                              _minimizeConflictSet _indGoals _avoidReinstalls
+                              _shadowing _strFlags _maxBjumps _enableBj _solveExes
                               _allowBootLibInstalls _onlyConstrained _order _verbosity) =
     collectEithers $ map selectPackage (Set.toList targets)
   where

cabal-install/Distribution/Client/Fetch.hs

@@ -162,6 +162,8 @@ planPackages verbosity comp platform fetchFlags
 
       . setCountConflicts countConflicts
 
+      . setFineGrainedConflicts fineGrainedConflicts
+
       . setMinimizeConflictSet minimizeConflictSet
 
       . setShadowPkgs shadowPkgs
@@ -199,6 +201,7 @@ planPackages verbosity comp platform fetchFlags
 
     reorderGoals     = fromFlag (fetchReorderGoals     fetchFlags)
     countConflicts   = fromFlag (fetchCountConflicts   fetchFlags)
+    fineGrainedConflicts = fromFlag (fetchFineGrainedConflicts fetchFlags)
     minimizeConflictSet = fromFlag (fetchMinimizeConflictSet fetchFlags)
     independentGoals = fromFlag (fetchIndependentGoals fetchFlags)
     shadowPkgs       = fromFlag (fetchShadowPkgs       fetchFlags)

cabal-install/Distribution/Client/Freeze.hs

@@ -175,6 +175,8 @@ planPackages verbosity comp platform mSandboxPkgInfo freezeFlags
 
       . setCountConflicts countConflicts
 
+      . setFineGrainedConflicts fineGrainedConflicts
+
       . setMinimizeConflictSet minimizeConflictSet
 
       . setShadowPkgs shadowPkgs
@@ -207,6 +209,7 @@ planPackages verbosity comp platform mSandboxPkgInfo freezeFlags
 
     reorderGoals     = fromFlag (freezeReorderGoals     freezeFlags)
     countConflicts   = fromFlag (freezeCountConflicts   freezeFlags)
+    fineGrainedConflicts = fromFlag (freezeFineGrainedConflicts freezeFlags)
     minimizeConflictSet = fromFlag (freezeMinimizeConflictSet freezeFlags)
     independentGoals = fromFlag (freezeIndependentGoals freezeFlags)
     shadowPkgs       = fromFlag (freezeShadowPkgs       freezeFlags)

cabal-install/Distribution/Client/Install.hs

@@ -395,6 +395,8 @@ planPackages verbosity comp platform mSandboxPkgInfo solver
 
       . setCountConflicts countConflicts
 
+      . setFineGrainedConflicts fineGrainedConflicts
+
       . setMinimizeConflictSet minimizeConflictSet
 
       . setAvoidReinstalls avoidReinstalls
@@ -463,6 +465,7 @@ planPackages verbosity comp platform mSandboxPkgInfo solver
                        fromFlag (installReinstall         installFlags)
     reorderGoals     = fromFlag (installReorderGoals      installFlags)
     countConflicts   = fromFlag (installCountConflicts    installFlags)
+    fineGrainedConflicts = fromFlag (installFineGrainedConflicts installFlags)
     minimizeConflictSet = fromFlag (installMinimizeConflictSet installFlags)
     independentGoals = fromFlag (installIndependentGoals  installFlags)
     avoidReinstalls  = fromFlag (installAvoidReinstalls   installFlags)

cabal-install/Distribution/Client/ProjectConfig.hs

@@ -250,6 +250,7 @@ resolveSolverSettings ProjectConfig{
                                          | otherwise -> Just n
     solverSettingReorderGoals      = fromFlag projectConfigReorderGoals
     solverSettingCountConflicts    = fromFlag projectConfigCountConflicts
+    solverSettingFineGrainedConflicts = fromFlag projectConfigFineGrainedConflicts
     solverSettingMinimizeConflictSet = fromFlag projectConfigMinimizeConflictSet
     solverSettingStrongFlags       = fromFlag projectConfigStrongFlags
     solverSettingAllowBootLibInstalls = fromFlag projectConfigAllowBootLibInstalls
@@ -271,6 +272,7 @@ resolveSolverSettings ProjectConfig{
        projectConfigMaxBackjumps      = Flag defaultMaxBackjumps,
        projectConfigReorderGoals      = Flag (ReorderGoals False),
        projectConfigCountConflicts    = Flag (CountConflicts True),
+       projectConfigFineGrainedConflicts = Flag (FineGrainedConflicts True),
        projectConfigMinimizeConflictSet = Flag (MinimizeConflictSet False),
        projectConfigStrongFlags       = Flag (StrongFlags False),
        projectConfigAllowBootLibInstalls = Flag (AllowBootLibInstalls False),

cabal-install/Distribution/Client/ProjectConfig/Legacy.hs

@@ -374,6 +374,7 @@ convertLegacyAllPackageFlags globalFlags configFlags
     --installUpgradeDeps        = projectConfigUpgradeDeps,
       installReorderGoals       = projectConfigReorderGoals,
       installCountConflicts     = projectConfigCountConflicts,
+      installFineGrainedConflicts = projectConfigFineGrainedConflicts,
       installMinimizeConflictSet = projectConfigMinimizeConflictSet,
       installPerComponent       = projectConfigPerComponent,
       installIndependentGoals   = projectConfigIndependentGoals,
@@ -611,6 +612,7 @@ convertToLegacySharedConfig
       installUpgradeDeps       = mempty, --projectConfigUpgradeDeps,
       installReorderGoals      = projectConfigReorderGoals,
       installCountConflicts    = projectConfigCountConflicts,
+      installFineGrainedConflicts = projectConfigFineGrainedConflicts,
       installMinimizeConflictSet = projectConfigMinimizeConflictSet,
       installIndependentGoals  = projectConfigIndependentGoals,
       installShadowPkgs        = mempty, --projectConfigShadowPkgs,
@@ -1004,8 +1006,9 @@ legacySharedConfigFieldDescrs =
       , "one-shot", "jobs", "keep-going", "offline", "per-component"
         -- solver flags:
       , "max-backjumps", "reorder-goals", "count-conflicts"
-      , "minimize-conflict-set", "independent-goals"
-      , "strong-flags" , "allow-boot-library-installs", "reject-unconstrained-dependencies", "index-state"
+      , "fine-grained-conflicts" , "minimize-conflict-set", "independent-goals"
+      , "strong-flags" , "allow-boot-library-installs"
+      , "reject-unconstrained-dependencies", "index-state"
       ]
   . commandOptionsToFields
   ) (installOptions ParseArgs)

cabal-install/Distribution/Client/ProjectConfig/Types.hs

@@ -195,6 +195,7 @@ data ProjectConfigShared
        projectConfigMaxBackjumps      :: Flag Int,
        projectConfigReorderGoals      :: Flag ReorderGoals,
        projectConfigCountConflicts    :: Flag CountConflicts,
+       projectConfigFineGrainedConflicts :: Flag FineGrainedConflicts,
        projectConfigMinimizeConflictSet :: Flag MinimizeConflictSet,
        projectConfigStrongFlags       :: Flag StrongFlags,
        projectConfigAllowBootLibInstalls :: Flag AllowBootLibInstalls,
@@ -400,6 +401,7 @@ data SolverSettings
        solverSettingMaxBackjumps      :: Maybe Int,
        solverSettingReorderGoals      :: ReorderGoals,
        solverSettingCountConflicts    :: CountConflicts,
+       solverSettingFineGrainedConflicts :: FineGrainedConflicts,
        solverSettingMinimizeConflictSet :: MinimizeConflictSet,
        solverSettingStrongFlags       :: StrongFlags,
        solverSettingAllowBootLibInstalls :: AllowBootLibInstalls,

cabal-install/Distribution/Client/ProjectPlanning.hs

@@ -958,6 +958,8 @@ planPackages verbosity comp platform solver SolverSettings{..}
 
       . setCountConflicts solverSettingCountConflicts
 
+      . setFineGrainedConflicts solverSettingFineGrainedConflicts
+
       . setMinimizeConflictSet solverSettingMinimizeConflictSet
 
         --TODO: [required eventually] should only be configurable for

cabal-install/Distribution/Client/Setup.hs

@@ -1003,6 +1003,7 @@ data FetchFlags = FetchFlags {
       fetchMaxBackjumps     :: Flag Int,
       fetchReorderGoals     :: Flag ReorderGoals,
       fetchCountConflicts   :: Flag CountConflicts,
+      fetchFineGrainedConflicts :: Flag FineGrainedConflicts,
       fetchMinimizeConflictSet :: Flag MinimizeConflictSet,
       fetchIndependentGoals :: Flag IndependentGoals,
       fetchShadowPkgs       :: Flag ShadowPkgs,
@@ -1023,6 +1024,7 @@ defaultFetchFlags = FetchFlags {
     fetchMaxBackjumps     = Flag defaultMaxBackjumps,
     fetchReorderGoals     = Flag (ReorderGoals False),
     fetchCountConflicts   = Flag (CountConflicts True),
+    fetchFineGrainedConflicts = Flag (FineGrainedConflicts True),
     fetchMinimizeConflictSet = Flag (MinimizeConflictSet False),
     fetchIndependentGoals = Flag (IndependentGoals False),
     fetchShadowPkgs       = Flag (ShadowPkgs False),
@@ -1085,6 +1087,7 @@ fetchCommand = CommandUI {
                          fetchMaxBackjumps     (\v flags -> flags { fetchMaxBackjumps     = v })
                          fetchReorderGoals     (\v flags -> flags { fetchReorderGoals     = v })
                          fetchCountConflicts   (\v flags -> flags { fetchCountConflicts   = v })
+                         fetchFineGrainedConflicts (\v flags -> flags { fetchFineGrainedConflicts = v })
                          fetchMinimizeConflictSet (\v flags -> flags { fetchMinimizeConflictSet = v })
                          fetchIndependentGoals (\v flags -> flags { fetchIndependentGoals = v })
                          fetchShadowPkgs       (\v flags -> flags { fetchShadowPkgs       = v })
@@ -1106,6 +1109,7 @@ data FreezeFlags = FreezeFlags {
       freezeMaxBackjumps     :: Flag Int,
       freezeReorderGoals     :: Flag ReorderGoals,
       freezeCountConflicts   :: Flag CountConflicts,
+      freezeFineGrainedConflicts :: Flag FineGrainedConflicts,
       freezeMinimizeConflictSet :: Flag MinimizeConflictSet,
       freezeIndependentGoals :: Flag IndependentGoals,
       freezeShadowPkgs       :: Flag ShadowPkgs,
@@ -1124,6 +1128,7 @@ defaultFreezeFlags = FreezeFlags {
     freezeMaxBackjumps     = Flag defaultMaxBackjumps,
     freezeReorderGoals     = Flag (ReorderGoals False),
     freezeCountConflicts   = Flag (CountConflicts True),
+    freezeFineGrainedConflicts = Flag (FineGrainedConflicts True),
     freezeMinimizeConflictSet = Flag (MinimizeConflictSet False),
     freezeIndependentGoals = Flag (IndependentGoals False),
     freezeShadowPkgs       = Flag (ShadowPkgs False),
@@ -1177,6 +1182,7 @@ freezeCommand = CommandUI {
                          freezeMaxBackjumps     (\v flags -> flags { freezeMaxBackjumps     = v })
                          freezeReorderGoals     (\v flags -> flags { freezeReorderGoals     = v })
                          freezeCountConflicts   (\v flags -> flags { freezeCountConflicts   = v })
+                         freezeFineGrainedConflicts (\v flags -> flags { freezeFineGrainedConflicts = v })
                          freezeMinimizeConflictSet (\v flags -> flags { freezeMinimizeConflictSet = v })
                          freezeIndependentGoals (\v flags -> flags { freezeIndependentGoals = v })
                          freezeShadowPkgs       (\v flags -> flags { freezeShadowPkgs       = v })
@@ -1749,6 +1755,7 @@ data InstallFlags = InstallFlags {
     installMaxBackjumps     :: Flag Int,
     installReorderGoals     :: Flag ReorderGoals,
     installCountConflicts   :: Flag CountConflicts,
+    installFineGrainedConflicts :: Flag FineGrainedConflicts,
     installMinimizeConflictSet :: Flag MinimizeConflictSet,
     installIndependentGoals :: Flag IndependentGoals,
     installShadowPkgs       :: Flag ShadowPkgs,
@@ -1798,6 +1805,7 @@ defaultInstallFlags = InstallFlags {
     installMaxBackjumps    = Flag defaultMaxBackjumps,
     installReorderGoals    = Flag (ReorderGoals False),
     installCountConflicts  = Flag (CountConflicts True),
+    installFineGrainedConflicts = Flag (FineGrainedConflicts True),
     installMinimizeConflictSet = Flag (MinimizeConflictSet False),
     installIndependentGoals= Flag (IndependentGoals False),
     installShadowPkgs      = Flag (ShadowPkgs False),
@@ -2028,6 +2036,7 @@ installOptions showOrParseArgs =
                         installMaxBackjumps     (\v flags -> flags { installMaxBackjumps     = v })
                         installReorderGoals     (\v flags -> flags { installReorderGoals     = v })
                         installCountConflicts   (\v flags -> flags { installCountConflicts   = v })
+                        installFineGrainedConflicts (\v flags -> flags { installFineGrainedConflicts = v })
                         installMinimizeConflictSet (\v flags -> flags { installMinimizeConflictSet = v })
                         installIndependentGoals (\v flags -> flags { installIndependentGoals = v })
                         installShadowPkgs       (\v flags -> flags { installShadowPkgs       = v })
@@ -2860,6 +2869,7 @@ optionSolverFlags :: ShowOrParseArgs
                   -> (flags -> Flag Int   ) -> (Flag Int    -> flags -> flags)
                   -> (flags -> Flag ReorderGoals)     -> (Flag ReorderGoals     -> flags -> flags)
                   -> (flags -> Flag CountConflicts)   -> (Flag CountConflicts   -> flags -> flags)
+                  -> (flags -> Flag FineGrainedConflicts) -> (Flag FineGrainedConflicts -> flags -> flags)
                   -> (flags -> Flag MinimizeConflictSet) -> (Flag MinimizeConflictSet -> flags -> flags)
                   -> (flags -> Flag IndependentGoals) -> (Flag IndependentGoals -> flags -> flags)
                   -> (flags -> Flag ShadowPkgs)       -> (Flag ShadowPkgs       -> flags -> flags)
@@ -2868,8 +2878,8 @@ optionSolverFlags :: ShowOrParseArgs
                   -> (flags -> Flag OnlyConstrained)  -> (Flag OnlyConstrained  -> flags -> flags)
                   -> [OptionField flags]
 optionSolverFlags showOrParseArgs getmbj setmbj getrg setrg getcc setcc
-                  getmc setmc getig setig getsip setsip getstrfl setstrfl
-                  getib setib getoc setoc =
+                  getfgc setfgc getmc setmc getig setig getsip setsip
+                  getstrfl setstrfl getib setib getoc setoc =
   [ option [] ["max-backjumps"]
       ("Maximum number of backjumps allowed while solving (default: " ++ show defaultMaxBackjumps ++ "). Use a negative number to enable unlimited backtracking. Use 0 to disable backtracking completely.")
       getmbj setmbj
@@ -2885,6 +2895,11 @@ optionSolverFlags showOrParseArgs getmbj setmbj getrg setrg getcc setcc
       (fmap asBool . getcc)
       (setcc . fmap CountConflicts)
       (yesNoOpt showOrParseArgs)
+  , option [] ["fine-grained-conflicts"]
+      "Skip a version of a package if it does not resolve the conflicts encountered in the last version, as a solver optimization (default)."
+      (fmap asBool . getfgc)
+      (setfgc . fmap FineGrainedConflicts)
+      (yesNoOpt showOrParseArgs)
   , option [] ["minimize-conflict-set"]
       ("When there is no solution, try to improve the error message by finding "
         ++ "a minimal conflict set (default: false). May increase run time "

cabal-install/Distribution/Solver/Modular/Builder.hs

@@ -145,7 +145,9 @@ addChildren bs@(BS { rdeps = rdm, open = gs, next = Goals })
 -- and then handle each instance in turn.
 addChildren bs@(BS { rdeps = rdm, index = idx, next = OneGoal (PkgGoal qpn@(Q _ pn) gr) }) =
   case M.lookup pn idx of
-    Nothing  -> FailF (varToConflictSet (P qpn) `CS.union` goalReasonToCS gr) UnknownPackage
+    Nothing  -> FailF
+                (varToConflictSet (P qpn) `CS.union` goalReasonToConflictSetWithConflict qpn gr)
+                UnknownPackage
     Just pis -> PChoiceF qpn rdm gr (W.fromList (L.map (\ (i, info) ->
                                                        ([], POption i Nothing, bs { next = Instance qpn info }))
                                                      (M.toList pis)))