Be more careful about ComponentId versus UnitId.

Two big ideas:

    * @--dependency@ takes a ComponentId, not UnitId.
      I used to think it should be a UnitId but it is
      now clear that you want to finger the indefinite
      unit id, which can be uniquely identified with
      a ComponentId

    * When hashing for an InstalledPackageId in
      new-build, we should produce a ComponentId,
      not a UnitId.

While cleaning up the results, for any codepaths which we don't plan on
implementing Backpack (Distribution.Client.Install, I'm looking at you),
just coerce ComponentId into UnitIds as necessary.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Cabal/Distribution/InstalledPackageInfo.hs

@@ -108,6 +108,9 @@ installedComponentId ipi = case installedUnitId ipi of
 
 {-# DEPRECATED installedPackageId "Use installedUnitId instead" #-}
 -- | Backwards compatibility with Cabal pre-1.24.
+-- This type synonym is slightly awful because in cabal-install
+-- we define an 'InstalledPackageId' but it's a ComponentId,
+-- not a UnitId!
 installedPackageId :: InstalledPackageInfo -> UnitId
 installedPackageId = installedUnitId
 

Cabal/Distribution/Package.hs

@@ -239,7 +239,7 @@ packageVersion  = pkgVersion . packageId
 instance Package PackageIdentifier where
   packageId = id
 
--- | Packages that have an installed package ID
+-- | Packages that have an installed unit ID
 class Package pkg => HasUnitId pkg where
   installedUnitId :: pkg -> UnitId
 

Cabal/Distribution/Simple/Configure.hs

@@ -1332,15 +1332,15 @@ newPackageDepsBehaviour pkg =
 -- deps in the end. So we still need to remember which installed packages to
 -- pick.
 combinedConstraints :: [Dependency] ->
-                       [(PackageName, UnitId)] ->
+                       [(PackageName, ComponentId)] ->
                        InstalledPackageIndex ->
                        Either String ([Dependency],
                                       Map PackageName InstalledPackageInfo)
 combinedConstraints constraints dependencies installedPackages = do
 
-    when (not (null badUnitIds)) $
+    when (not (null badComponentIds)) $
       Left $ render $ text "The following package dependencies were requested"
-         $+$ nest 4 (dispDependencies badUnitIds)
+         $+$ nest 4 (dispDependencies badComponentIds)
          $+$ text "however the given installed package instance does not exist."
 
     --TODO: we don't check that all dependencies are used!
@@ -1359,26 +1359,26 @@ combinedConstraints constraints dependencies installedPackages = do
                         | (_, _, Just pkg) <- dependenciesPkgInfo ]
 
     -- The dependencies along with the installed package info, if it exists
-    dependenciesPkgInfo :: [(PackageName, UnitId,
+    dependenciesPkgInfo :: [(PackageName, ComponentId,
                              Maybe InstalledPackageInfo)]
     dependenciesPkgInfo =
-      [ (pkgname, ipkgid, mpkg)
-      | (pkgname, ipkgid) <- dependencies
-      , let mpkg = PackageIndex.lookupUnitId
-                     installedPackages ipkgid
+      [ (pkgname, cid, mpkg)
+      | (pkgname, cid) <- dependencies
+      , let mpkg = PackageIndex.lookupComponentId
+                     installedPackages cid
       ]
 
     -- If we looked up a package specified by an installed package id
     -- (i.e. someone has written a hash) and didn't find it then it's
     -- an error.
-    badUnitIds =
-      [ (pkgname, ipkgid)
-      | (pkgname, ipkgid, Nothing) <- dependenciesPkgInfo ]
+    badComponentIds =
+      [ (pkgname, cid)
+      | (pkgname, cid, Nothing) <- dependenciesPkgInfo ]
 
     dispDependencies deps =
       hsep [    text "--dependency="
-             <<>> quotes (disp pkgname <<>> char '=' <<>> disp ipkgid)
-           | (pkgname, ipkgid) <- deps ]
+             <<>> quotes (disp pkgname <<>> char '=' <<>> disp cid)
+           | (pkgname, cid) <- deps ]
 
 -- -----------------------------------------------------------------------------
 -- Configuring program dependencies

Cabal/Distribution/Simple/PackageIndex.hs

@@ -77,6 +77,7 @@ module Distribution.Simple.PackageIndex (
 
   -- ** Precise lookups
   lookupUnitId,
+  lookupComponentId,
   lookupSourcePackageId,
   lookupPackageId,
   lookupPackageName,
@@ -379,14 +380,21 @@ allPackagesBySourcePackageId (PackageIndex _ pnames) =
 -- * Lookups
 --
 
--- | Does a lookup by source package id (name & version).
+-- | Does a lookup by unit identifier.
 --
 -- Since multiple package DBs mask each other by 'UnitId',
 -- then we get back at most one package.
 --
 lookupUnitId :: PackageIndex a -> UnitId
              -> Maybe a
-lookupUnitId (PackageIndex pids _) pid = Map.lookup pid pids
+lookupUnitId (PackageIndex m _) uid = Map.lookup uid m
+
+-- | Does a lookup by component identifier.  In the absence
+-- of Backpack, this is just a 'lookupUnitId'.
+--
+lookupComponentId :: PackageIndex a -> ComponentId
+                  -> Maybe a
+lookupComponentId (PackageIndex m _) uid = Map.lookup (SimpleUnitId uid) m
 
 -- | Backwards compatibility for Cabal pre-1.24.
 {-# DEPRECATED lookupInstalledPackageId "Use lookupUnitId instead" #-}

Cabal/Distribution/Simple/Setup.hs

@@ -404,7 +404,7 @@ data ConfigFlags = ConfigFlags {
     configStripLibs :: Flag Bool,      -- ^Enable library stripping
     configConstraints :: [Dependency], -- ^Additional constraints for
                                        -- dependencies.
-    configDependencies :: [(PackageName, UnitId)],
+    configDependencies :: [(PackageName, ComponentId)],
       -- ^The packages depended on.
     configConfigurationsFlags :: FlagAssignment,
     configTests               :: Flag Bool, -- ^Enable test suite compilation
@@ -709,7 +709,7 @@ configureOptions showOrParseArgs =
       ,option "" ["dependency"]
          "A list of exact dependencies. E.g., --dependency=\"void=void-0.5.8-177d5cdf20962d0581fe2e4932a6c309\""
          configDependencies (\v flags -> flags { configDependencies = v})
-         (reqArg "NAME=ID"
+         (reqArg "NAME=CID"
                  (readP_to_E (const "dependency expected") ((\x -> [x]) `fmap` parseDependency))
                  (map (\x -> display (fst x) ++ "=" ++ display (snd x))))
 
@@ -795,7 +795,7 @@ showProfDetailLevelFlag :: Flag ProfDetailLevel -> [String]
 showProfDetailLevelFlag NoFlag    = []
 showProfDetailLevelFlag (Flag dl) = [showProfDetailLevel dl]
 
-parseDependency :: Parse.ReadP r (PackageName, UnitId)
+parseDependency :: Parse.ReadP r (PackageName, ComponentId)
 parseDependency = do
   x <- parse
   _ <- Parse.char '='

cabal-install/Distribution/Client/Configure.hs

@@ -55,7 +55,7 @@ import Distribution.Simple.PackageIndex
 import Distribution.Simple.Utils
          ( defaultPackageDesc )
 import Distribution.Package
-         ( Package(..), UnitId, packageName
+         ( Package(..), packageName
          , Dependency(..), thisPackageVersion
          )
 import qualified Distribution.PackageDescription as PkgDesc
@@ -244,14 +244,14 @@ configureSetupScript packageDBs
     defaultSetupDeps = maybe False PkgDesc.defaultSetupDepends
                        maybeSetupBuildInfo
 
-    explicitSetupDeps :: Maybe [(UnitId, PackageId)]
+    explicitSetupDeps :: Maybe [(InstalledPackageId, PackageId)]
     explicitSetupDeps = do
       -- Check if there is an explicit setup stanza.
       _buildInfo <- maybeSetupBuildInfo
       -- Return the setup dependencies computed by the solver
       ReadyPackage cpkg <- mpkg
-      return [ ( uid, srcid )
-             | ConfiguredId srcid uid <- CD.setupDeps (confPkgDeps cpkg)
+      return [ ( cid, srcid )
+             | ConfiguredId srcid cid <- CD.setupDeps (confPkgDeps cpkg)
              ]
 
 -- | Warn if any constraints or preferences name packages that are not in the

cabal-install/Distribution/Client/Install.hs

@@ -77,6 +77,7 @@ import Distribution.Client.Dependency.Types
 import Distribution.Client.FetchUtils
 import Distribution.Client.HttpUtils
          ( HttpTransport (..) )
+import Distribution.Solver.Types.PackageFixedDeps
 import qualified Distribution.Client.Haddock as Haddock (regenerateHaddockIndex)
 import Distribution.Client.IndexUtils as IndexUtils
          ( getSourcePackages, getInstalledPackages )
@@ -149,10 +150,9 @@ import Distribution.Simple.Register (registerPackage)
 import Distribution.Simple.Program.HcPkg (MultiInstance(..))
 import Distribution.Package
          ( PackageIdentifier(..), PackageId, packageName, packageVersion
-         , Package(..)
+         , Package(..), HasUnitId(..)
          , Dependency(..), thisPackageVersion
-         , UnitId(..)
-         , HasUnitId(..) )
+         , UnitId(..) )
 import qualified Distribution.PackageDescription as PackageDescription
 import Distribution.PackageDescription
          ( PackageDescription, GenericPackageDescription(..), Flag(..)
@@ -618,7 +618,7 @@ packageStatus installedPkgIndex cpkg =
         -- deps of installed pkg
         (resolveInstalledIds $ Installed.depends pkg)
         -- deps of configured pkg
-        (resolveInstalledIds $ map confInstId (CD.nonSetupDeps (confPkgDeps pkg')))
+        (resolveInstalledIds $ CD.nonSetupDeps (depends pkg'))
 
     -- convert to source pkg ids via index
     resolveInstalledIds :: [UnitId] -> [PackageIdentifier]
@@ -1156,12 +1156,11 @@ performInstallations verbosity
           | otherwise                         = False
 
     substLogFileName :: PathTemplate -> PackageIdentifier -> UnitId -> FilePath
-    substLogFileName template pkg ipid = fromPathTemplate
+    substLogFileName template pkg uid = fromPathTemplate
                                   . substPathTemplate env
                                   $ template
-      where env = initialPathTemplateEnv (packageId pkg)
-                  ipid
-                  (compilerInfo comp) platform
+      where env = initialPathTemplateEnv (packageId pkg) uid
+                    (compilerInfo comp) platform
 
     miscOptions  = InstallMisc {
       libVersion = flagToMaybe (configCabalVersion configExFlags)
@@ -1179,7 +1178,7 @@ executeInstallPlan verbosity jobCtl keepGoing useLogFile plan0 installPkg =
     InstallPlan.execute
       jobCtl keepGoing depsFailure plan0 $ \pkg -> do
         buildOutcome <- installPkg pkg
-        printBuildResult (packageId pkg) (installedPackageId pkg) buildOutcome
+        printBuildResult (packageId pkg) (installedUnitId pkg) buildOutcome
         return buildOutcome
 
   where
@@ -1188,7 +1187,7 @@ executeInstallPlan verbosity jobCtl keepGoing useLogFile plan0 installPkg =
     -- Print build log if something went wrong, and 'Installed $PKGID'
     -- otherwise.
     printBuildResult :: PackageId -> UnitId -> BuildOutcome -> IO ()
-    printBuildResult pkgid ipid buildOutcome = case buildOutcome of
+    printBuildResult pkgid uid buildOutcome = case buildOutcome of
         (Right _) -> notice verbosity $ "Installed " ++ display pkgid
         (Left _)  -> do
           notice verbosity $ "Failed to install " ++ display pkgid
@@ -1196,7 +1195,7 @@ executeInstallPlan verbosity jobCtl keepGoing useLogFile plan0 installPkg =
             case useLogFile of
               Nothing                 -> return ()
               Just (mkLogFileName, _) -> do
-                let logName = mkLogFileName pkgid ipid
+                let logName = mkLogFileName pkgid uid
                 putStr $ "Build log ( " ++ logName ++ " ):\n"
                 printFile logName
 
@@ -1231,9 +1230,9 @@ installReadyPackage platform cinfo configFlags
     -- In the end only one set gets passed to Setup.hs configure, depending on
     -- the Cabal version we are talking to.
     configConstraints  = [ thisPackageVersion srcid
-                         | ConfiguredId srcid _uid <- CD.nonSetupDeps deps ],
-    configDependencies = [ (packageName srcid, uid)
-                         | ConfiguredId srcid uid <- CD.nonSetupDeps deps ],
+                         | ConfiguredId srcid _ipid <- CD.nonSetupDeps deps ],
+    configDependencies = [ (packageName srcid, dep_ipid)
+                         | ConfiguredId srcid dep_ipid <- CD.nonSetupDeps deps ],
     -- Use '--exact-configuration' if supported.
     configExactConfiguration = toFlag True,
     configBenchmarks         = toFlag False,
@@ -1415,7 +1414,7 @@ installUnpackedPackage verbosity installLock numJobs
         -- Install phase
           onFailure InstallFailed $ criticalSection installLock $ do
             -- Actual installation
-            withWin32SelfUpgrade verbosity ipid configFlags
+            withWin32SelfUpgrade verbosity uid configFlags
                                  cinfo platform pkg $ do
               setup Cabal.copyCommand copyFlags mLogPath
 
@@ -1423,8 +1422,8 @@ installUnpackedPackage verbosity installLock numJobs
             -- it can be incorporated into the final InstallPlan
             ipkgs <- genPkgConfs mLogPath
             let ipkgs' = case ipkgs of
-                            [ipkg] -> [ipkg { Installed.installedUnitId = ipid }]
-                            _ -> assert (any ((== ipid)
+                            [ipkg] -> [ipkg { Installed.installedUnitId = uid }]
+                            _ -> assert (any ((== uid)
                                               . Installed.installedUnitId)
                                              ipkgs) ipkgs
             let packageDBs = interpretPackageDbFlags
@@ -1439,7 +1438,7 @@ installUnpackedPackage verbosity installLock numJobs
 
   where
     pkgid            = packageId pkg
-    ipid             = installedUnitId rpkg
+    uid              = installedUnitId rpkg
     cinfo            = compilerInfo comp
     buildCommand'    = buildCommand conf
     buildFlags   _   = emptyBuildFlags {
@@ -1480,7 +1479,7 @@ installUnpackedPackage verbosity installLock numJobs
           }
         where
           CompilerId flavor _ = compilerInfoId cinfo
-          env         = initialPathTemplateEnv pkgid ipid cinfo platform
+          env         = initialPathTemplateEnv pkgid uid cinfo platform
           userInstall = fromFlagOrDefault defaultUserInstall
                         (configUserInstall configFlags')
 
@@ -1527,7 +1526,7 @@ installUnpackedPackage verbosity installLock numJobs
       case useLogFile of
          Nothing                 -> return Nothing
          Just (mkLogFileName, _) -> do
-           let logFileName = mkLogFileName (packageId pkg) ipid
+           let logFileName = mkLogFileName (packageId pkg) uid
                logDir      = takeDirectory logFileName
            unless (null logDir) $ createDirectoryIfMissing True logDir
            logFileExists <- doesFileExist logFileName
@@ -1570,7 +1569,7 @@ withWin32SelfUpgrade :: Verbosity
                      -> PackageDescription
                      -> IO a -> IO a
 withWin32SelfUpgrade _ _ _ _ _ _ action | buildOS /= Windows = action
-withWin32SelfUpgrade verbosity ipid configFlags cinfo platform pkg action = do
+withWin32SelfUpgrade verbosity uid configFlags cinfo platform pkg action = do
 
   defaultDirs <- InstallDirs.defaultInstallDirs
                    compFlavor
@@ -1598,10 +1597,10 @@ withWin32SelfUpgrade verbosity ipid configFlags cinfo platform pkg action = do
         templateDirs   = InstallDirs.combineInstallDirs fromFlagOrDefault
                            defaultDirs (configInstallDirs configFlags)
         absoluteDirs   = InstallDirs.absoluteInstallDirs
-                           pkgid ipid
+                           pkgid uid
                            cinfo InstallDirs.NoCopyDest
                            platform templateDirs
         substTemplate  = InstallDirs.fromPathTemplate
                        . InstallDirs.substPathTemplate env
-          where env = InstallDirs.initialPathTemplateEnv pkgid ipid
+          where env = InstallDirs.initialPathTemplateEnv pkgid uid
                       cinfo platform

cabal-install/Distribution/Client/InstallPlan.hs

@@ -423,15 +423,12 @@ configureInstallPlan solverPlan =
                            -> ConfiguredPackage UnresolvedPkgLoc
     configureSolverPackage mapDep spkg =
       ConfiguredPackage {
-        confPkgId = SimpleUnitId
-                  $ Configure.computeComponentId
+        confPkgId = Configure.computeComponentId
                         Cabal.NoFlag
                         Cabal.NoFlag
                         (packageId spkg)
                         PD.CLibName
-                        -- TODO: this is a hack that won't work for Backpack.
-                        (map ((\(SimpleUnitId cid0) -> cid0) . confInstId)
-                             (CD.libraryDeps deps))
+                        (map confInstId (CD.libraryDeps deps))
                         (solverPkgFlags spkg),
         confPkgSource = solverPkgSource spkg,
         confPkgFlags  = solverPkgFlags spkg,

cabal-install/Distribution/Client/PackageHash.hs

@@ -29,7 +29,7 @@ module Distribution.Client.PackageHash (
   ) where
 
 import Distribution.Package
-         ( PackageId, PackageIdentifier(..), mkUnitId )
+         ( PackageId, PackageIdentifier(..), ComponentId(..) )
 import Distribution.System
          ( Platform, OS(Windows), buildOS )
 import Distribution.PackageDescription
@@ -86,7 +86,7 @@ hashedInstalledPackageId
 --
 hashedInstalledPackageIdLong :: PackageHashInputs -> InstalledPackageId
 hashedInstalledPackageIdLong pkghashinputs@PackageHashInputs{pkgHashPkgId} =
-    mkUnitId $
+    ComponentId $
          display pkgHashPkgId   -- to be a bit user friendly
       ++ "-"
       ++ showHashValue (hashPackageHashInputs pkghashinputs)
@@ -111,7 +111,7 @@ hashedInstalledPackageIdLong pkghashinputs@PackageHashInputs{pkgHashPkgId} =
 --
 hashedInstalledPackageIdShort :: PackageHashInputs -> InstalledPackageId
 hashedInstalledPackageIdShort pkghashinputs@PackageHashInputs{pkgHashPkgId} =
-    mkUnitId $
+    ComponentId $
       intercalate "-"
         -- max length now 64
         [ truncateStr 14 (display name)

cabal-install/Distribution/Client/ProjectBuilding.hs

@@ -124,7 +124,7 @@ import           System.Directory
 --
 -- This is used as the result of the dry-run of building an install plan.
 --
-type BuildStatusMap = Map InstalledPackageId BuildStatus
+type BuildStatusMap = Map UnitId BuildStatus
 
 -- | The build status for an individual package is the state that the
 -- package is in /prior/ to initiating a (re)build.
@@ -336,13 +336,13 @@ foldMInstallPlanDepOrder
   => GenericInstallPlan ipkg srcpkg
   -> (GenericPlanPackage ipkg srcpkg ->
       [b] -> m b)
-  -> m (Map InstalledPackageId b)
+  -> m (Map UnitId b)
 foldMInstallPlanDepOrder plan0 visit =
     go Map.empty (InstallPlan.reverseTopologicalOrder plan0)
   where
-    go :: Map InstalledPackageId b
+    go :: Map UnitId b
        -> [GenericPlanPackage ipkg srcpkg]
-       -> m (Map InstalledPackageId b)
+       -> m (Map UnitId b)
     go !results [] = return results
 
     go !results (pkg : pkgs) = do
@@ -361,24 +361,24 @@ improveInstallPlanWithUpToDatePackages :: ElaboratedInstallPlan
                                        -> ElaboratedInstallPlan
 improveInstallPlanWithUpToDatePackages installPlan pkgsBuildStatus =
     replaceWithPrePreExisting installPlan
-      [ (installedPackageId pkg, mipkg)
+      [ (installedUnitId pkg, mipkg)
       | InstallPlan.Configured pkg
           <- InstallPlan.reverseTopologicalOrder installPlan
-      , let ipkgid = installedPackageId pkg
-            Just pkgBuildStatus = Map.lookup ipkgid pkgsBuildStatus
+      , let uid = installedUnitId pkg
+            Just pkgBuildStatus = Map.lookup uid pkgsBuildStatus
       , BuildStatusUpToDate (BuildResult { buildResultLibInfo = mipkg })
           <- [pkgBuildStatus]
       ]
   where
     replaceWithPrePreExisting =
-      foldl' (\plan (ipkgid, mipkg) ->
+      foldl' (\plan (uid, mipkg) ->
                 -- TODO: A grievous hack.  Better to have a special type
                 -- of entry representing pre-existing executables.
                 let stub_ipkg = Installed.emptyInstalledPackageInfo {
-                                    Installed.installedUnitId = ipkgid
+                                    Installed.installedUnitId = uid
                                 }
                     ipkg = fromMaybe stub_ipkg mipkg
-                in InstallPlan.preexisting ipkgid ipkg plan)
+                in InstallPlan.preexisting uid ipkg plan)
 
 
 -----------------------------
@@ -699,8 +699,8 @@ rebuildTargets verbosity
                           installPlan $ \pkg ->
         handle (return . Left) $ fmap Right $ --TODO: review exception handling
 
-        let ipkgid = installedPackageId pkg
-            Just pkgBuildStatus = Map.lookup ipkgid pkgsBuildStatus in
+        let uid = installedUnitId pkg
+            Just pkgBuildStatus = Map.lookup uid pkgsBuildStatus in
 
         rebuildTarget
           verbosity
@@ -838,8 +838,8 @@ asyncDownloadPackages verbosity withRepoCtx installPlan pkgsBuildStatus body
       [ pkgSourceLocation (getElaboratedPackage pkg_or_comp)
       | InstallPlan.Configured pkg_or_comp
          <- InstallPlan.reverseTopologicalOrder installPlan
-      , let ipkgid = installedPackageId pkg_or_comp
-            Just pkgBuildStatus = Map.lookup ipkgid pkgsBuildStatus
+      , let uid = installedUnitId pkg_or_comp
+            Just pkgBuildStatus = Map.lookup uid pkgsBuildStatus
       , BuildStatusDownload <- [pkgBuildStatus]
       ]
 
@@ -1059,7 +1059,7 @@ buildAndInstallUnpackedPackage verbosity
           -- grab and modify the InstalledPackageInfo. We decide what
           -- the installed package id is, not the build system.
           ipkg0 <- generateInstalledPackageInfo
-          let ipkg = ipkg0 { Installed.installedUnitId = ipkgid }
+          let ipkg = ipkg0 { Installed.installedUnitId = uid }
 
           criticalSection registerLock $
               Cabal.registerPackage verbosity compiler progdb
@@ -1081,7 +1081,7 @@ buildAndInstallUnpackedPackage verbosity
 
   where
     pkgid  = packageId rpkg
-    ipkgid = installedPackageId rpkg
+    uid = installedUnitId rpkg
 
     isParallelBuild = buildSettingNumJobs >= 2
 
@@ -1125,7 +1125,7 @@ buildAndInstallUnpackedPackage verbosity
     mlogFile =
       case buildSettingLogFile of
         Nothing        -> Nothing
-        Just mkLogFile -> Just (mkLogFile compiler platform pkgid ipkgid)
+        Just mkLogFile -> Just (mkLogFile compiler platform pkgid uid)
 
     initLogFile =
       case mlogFile of

cabal-install/Distribution/Client/ProjectOrchestration.hs

@@ -62,8 +62,7 @@ import           Distribution.Client.ProjectPlanning.Types
 import           Distribution.Client.ProjectBuilding
 
 import           Distribution.Client.Types
-                   ( InstalledPackageId, installedPackageId
-                   , GenericReadyPackage(..), PackageLocation(..) )
+                   ( GenericReadyPackage(..), PackageLocation(..) )
 import qualified Distribution.Client.InstallPlan as InstallPlan
 import           Distribution.Client.BuildTarget
                    ( UserBuildTarget, resolveUserBuildTargets
@@ -318,14 +317,14 @@ resolveAndCheckTargets :: PackageTarget
                        -> ElaboratedInstallPlan
                        -> [BuildTarget PackageName]
                        -> Either [BuildTargetProblem]
-                                 (Map InstalledPackageId [PackageTarget])
+                                 (Map UnitId [PackageTarget])
 resolveAndCheckTargets targetDefaultComponents
                        targetSpecificComponent
                        installPlan targets =
     case partitionEithers (map checkTarget targets) of
       ([], targets') -> Right $ Map.fromListWith (++)
-                                  [ (ipkgid, [t]) | (ipkgids, t) <- targets'
-                                                  , ipkgid <- ipkgids ]
+                                  [ (uid, [t]) | (uids, t) <- targets'
+                                               , uid <- uids ]
       (problems, _)  -> Left problems
   where
     -- TODO [required eventually] currently all build targets refer to packages
@@ -369,15 +368,15 @@ resolveAndCheckTargets targetDefaultComponents
     -- NB: It's a list of 'InstalledPackageId', because each component
     -- in the install plan from a single package needs to be associated with
     -- the same 'PackageName'.
-    projAllPkgs, projLocalPkgs :: Map PackageName [InstalledPackageId]
+    projAllPkgs, projLocalPkgs :: Map PackageName [UnitId]
     projAllPkgs =
       Map.fromListWith (++)
-        [ (packageName pkg, [installedPackageId pkg])
+        [ (packageName pkg, [installedUnitId pkg])
         | pkg <- InstallPlan.toList installPlan ]
 
     projLocalPkgs =
       Map.fromListWith (++)
-        [ (packageName pkg, [installedPackageId pkg_or_comp])
+        [ (packageName pkg, [installedUnitId pkg_or_comp])
         | InstallPlan.Configured pkg_or_comp <- InstallPlan.toList installPlan
         , let pkg = getElaboratedPackage pkg_or_comp
         , case pkgSourceLocation pkg of
@@ -459,7 +458,7 @@ printPlan verbosity
           ElabComponent comp ->
             " (" ++ maybe "custom" display (elabComponentName comp) ++ ")") ++
       showFlagAssignment (nonDefaultFlags pkg) ++
-      let buildStatus = pkgsBuildStatus Map.! installedPackageId pkg_or_comp in
+      let buildStatus = pkgsBuildStatus Map.! installedUnitId pkg_or_comp in
       " (" ++ showBuildStatus buildStatus ++ ")"
      where
       pkg = getElaboratedPackage pkg_or_comp

cabal-install/Distribution/Client/ProjectPlanOutput.hs

@@ -10,6 +10,7 @@ module Distribution.Client.ProjectPlanOutput (
 
 import           Distribution.Client.ProjectPlanning.Types
 import           Distribution.Client.DistDirLayout
+import           Distribution.Client.Types
 
 import qualified Distribution.Client.InstallPlan as InstallPlan
 import qualified Distribution.Client.Utils.Json as J
@@ -82,7 +83,7 @@ encodePlanAsJson elaboratedInstallPlan _elaboratedSharedConfig =
         flat_deps = ordNub (ComponentDeps.flatDeps (pkgDependencies pkg))
         components = J.object
           [ comp2str c J..= J.object
-            [ "depends" J..= map (jdisplay . installedUnitId) v ]
+            [ "depends" J..= map (jdisplay . confInstId) v ]
           -- NB: does NOT contain order-only dependencies
           | (c,v) <- ComponentDeps.toList (pkgDependencies pkg) ]
 
@@ -96,7 +97,7 @@ encodePlanAsJson elaboratedInstallPlan _elaboratedSharedConfig =
                                      | (PD.FlagName fn,v) <-
                                             pkgFlagAssignment pkg ]
         -- NB: does NOT contain order-only dependencies
-        , "depends"    J..= map (jdisplay . installedUnitId) (elabComponentDependencies comp)
+        , "depends"    J..= map (jdisplay . confInstId) (elabComponentDependencies comp)
         ]
       where
         pkg = elabComponentPackage comp

cabal-install/Distribution/Client/ProjectPlanning.hs

@@ -211,7 +211,7 @@ sanityCheckElaboratedPackage sharedConfig
     -- the 'hashedInstalledPackageId' we would compute from
     -- the elaborated configured package
   . assert (pkgBuildStyle == BuildInplaceOnly ||
-     installedPackageId pkg == hashedInstalledPackageId
+     pkgInstalledId == hashedInstalledPackageId
                                  (packageHashInputs sharedConfig (ElabPackage pkg)))
 
     -- either a package is built inplace, or we are not attempting to
@@ -1071,7 +1071,7 @@ elaborateInstallPlan platform compiler compilerprogdb
             ecomp = ElaboratedComponent {
                     elabComponent = cname',
                     elabComponentName = Just cname,
-                    elabComponentId = cid,
+                    elabComponentId = SimpleUnitId cid, -- Backpack later!
                     elabComponentPackage = pkg,
                     elabComponentDependencies = deps,
                     -- TODO: track dependencies on executables
@@ -1081,9 +1081,10 @@ elaborateInstallPlan platform compiler compilerprogdb
                     elabComponentReplTarget = Nothing,
                     elabComponentBuildHaddocks = False
                   }
+            cid :: ComponentId
             cid = case pkgBuildStyle pkg of
                     BuildInplaceOnly ->
-                      mkUnitId $
+                      ComponentId $
                         display pkgid ++ "-inplace" ++
                           (case Cabal.componentNameString cname of
                               Nothing -> ""
@@ -1129,7 +1130,7 @@ elaborateInstallPlan platform compiler compilerprogdb
 
         pkgInstalledId
           | shouldBuildInplaceOnly pkg
-          = mkUnitId (display pkgid ++ "-inplace")
+          = ComponentId (display pkgid ++ "-inplace")
 
           | otherwise
           = assert (isJust pkgSourceHash) $
@@ -1253,12 +1254,13 @@ elaborateInstallPlan platform compiler compilerprogdb
         pkgProgPrefix          = perPkgOptionMaybe pkgid packageConfigProgPrefix
         pkgProgSuffix          = perPkgOptionMaybe pkgid packageConfigProgSuffix
 
+        -- TODO: This needs to be overridden in per-component mode
         pkgInstallDirs
           | shouldBuildInplaceOnly pkg
           -- use the ordinary default install dirs
           = (InstallDirs.absoluteInstallDirs
                pkgid
-               pkgInstalledId
+               (SimpleUnitId pkgInstalledId)
                (compilerInfo compiler)
                InstallDirs.NoCopyDest
                platform
@@ -1513,7 +1515,7 @@ pkgBuildTargetWholeComponents (ElabComponent comp) =
 -- targets. Also, update the package config to specify which optional stanzas
 -- to enable, and which targets within each package to build.
 --