Per-component new-build support (no Custom support yet).

A bit of a megapatch.  Here's what's in it:

* First, a few miscellaneous utility functions and reexports
  in Cabal.  I could have split these into a separate commit
  but I was too lazy to.

* Distribution.Client.Install got refactored:
  instead of using PackageFixedDeps, it uses IsUnit
  instead.  This is because we weren't using ComponentDeps
  in a nontrivial way; we just need some graph structure
  and IsNode (with UnitId keys) fulfills that. I also removed the
  invariant checking and error reporting because it was
  being annoying (we check the invariants already in
  SolverInstallPlan).

* Look at Distribution.Client.ProjectPlanning.Types.
  This contains the primary type change: ElaboratedConfiguredPackage
  is now EITHER a monolithic ElaboratedPackage, or a per-component
  ElaboratedComponent (it should get renamed but I didn't do that
  in this patch.)  These are what we're going to store in our
  plans: if a package we're building has a Setup script which supports
  per-component builds, we'll explode it into a component.  Otherwise
  we'll keep it as a package.  We'll see codepaths for both
  throughout.

* OK, so the expansion happens in ProjectPlanning, mostly in
  'elaborateAndExpandSolverPackage'.  You should review the
  package hash computation code closely.  When we can separate
  components, we compute a hash for each INDEPENDENTLY.  This
  is good: we get more sharing.

* We need to adjust the target resolution and pruning code
  in ProjectOrchestration and ProjectPlanning.  I did a dumb
  but easy idea: if a user mentions 'packagename' in a
  target name, I spray the PackageTarget on every
  possibly relevant IPID in buildTargets', and then pare
  it down later.

* And of course there's code in ProjectBuilding to actual
  do a configure and then build.

* We change the layout of build directories so that we can
  track each component separately.  While I was doing that,
  I also added compiler and platform information.

Custom doesn't work yet because I need to give them their own
separate component, and teach Cabal how to build them specially.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Cabal/Distribution/Package.hs

@@ -27,6 +27,7 @@ module Distribution.Package (
         UnitId(..),
         mkUnitId,
         mkLegacyUnitId,
+        unitIdComponentId,
         getHSLibraryName,
         InstalledPackageId, -- backwards compat
 
@@ -176,6 +177,10 @@ mkUnitId = SimpleUnitId . ComponentId
 mkLegacyUnitId :: PackageId -> UnitId
 mkLegacyUnitId = SimpleUnitId . ComponentId . display
 
+-- | Extract 'ComponentId' from 'UnitId'.
+unitIdComponentId :: UnitId -> ComponentId
+unitIdComponentId (SimpleUnitId cid) = cid
+
 -- ------------------------------------------------------------
 -- * Package source dependencies
 -- ------------------------------------------------------------

Cabal/Distribution/Simple/Configure.hs

@@ -35,6 +35,8 @@ module Distribution.Simple.Configure (configure,
                                       tryGetPersistBuildConfig,
                                       maybeGetPersistBuildConfig,
                                       findDistPref, findDistPrefOrDefault,
+                                      mkComponentsGraph,
+                                      getInternalPackages,
                                       computeComponentId,
                                       computeCompatPackageKey,
                                       computeCompatPackageName,

Cabal/Distribution/Types/ComponentEnabledSpec.hs

@@ -54,7 +54,7 @@ data ComponentEnabledSpec
     = ComponentEnabledSpec { testsEnabled :: Bool,
                              benchmarksEnabled :: Bool }
     | OneComponentEnabledSpec ComponentName
-  deriving (Generic, Read, Show)
+  deriving (Generic, Read, Show, Eq)
 instance Binary ComponentEnabledSpec
 
 -- | The default set of enabled components.  Historically tests and

Cabal/Distribution/Types/PackageDescription.hs

@@ -43,6 +43,7 @@ module Distribution.Types.PackageDescription (
     updatePackageDescription,
     pkgComponents,
     pkgBuildableComponents,
+    enabledComponents,
     lookupComponent,
     getComponent,
   ) where
@@ -57,6 +58,7 @@ import Distribution.Types.Benchmark
 
 import Distribution.Types.Component
 import Distribution.Types.ComponentName
+import Distribution.Types.ComponentEnabledSpec
 import Distribution.Types.SetupBuildInfo
 import Distribution.Types.BuildInfo
 import Distribution.Types.BuildType
@@ -346,6 +348,13 @@ pkgComponents pkg =
 pkgBuildableComponents :: PackageDescription -> [Component]
 pkgBuildableComponents = filter componentBuildable . pkgComponents
 
+-- | A list of all components in the package that are enabled.
+--
+-- @since 2.0.0.0
+--
+enabledComponents :: PackageDescription -> ComponentEnabledSpec -> [Component]
+enabledComponents pkg enabled = filter (componentEnabled enabled) $ pkgBuildableComponents pkg
+
 lookupComponent :: PackageDescription -> ComponentName -> Maybe Component
 lookupComponent pkg CLibName = fmap CLib (library pkg)
 lookupComponent pkg (CSubLibName name) =

cabal-install/Distribution/Client/CmdBuild.hs

@@ -63,6 +63,7 @@ buildAction (configFlags, configExFlags, installFlags, haddockFlags)
     -- repl targets (as opposed to say repl or haddock targets).
     selectBuildTargets =
       selectTargets
+        verbosity
         BuildDefaultComponents
         BuildSpecificComponent
 

cabal-install/Distribution/Client/CmdFreeze.hs

@@ -7,13 +7,11 @@ module Distribution.Client.CmdFreeze (
   ) where
 
 import Distribution.Client.ProjectPlanning
-         ( ElaboratedInstallPlan, rebuildInstallPlan )
 import Distribution.Client.ProjectConfig
          ( ProjectConfig(..), ProjectConfigShared(..)
          , commandLineFlagsToProjectConfig, writeProjectLocalFreezeConfig
          , findProjectRoot )
 import Distribution.Client.ProjectPlanning.Types
-         ( ElaboratedConfiguredPackage(..) )
 import Distribution.Client.Targets
          ( UserConstraint(..) )
 import Distribution.Solver.Types.ConstraintSource
@@ -149,8 +147,9 @@ projectFreezeConstraints plan =
     flagAssignments =
       Map.fromList
         [ (pkgname, flags)
-        | InstallPlan.Configured pkg <- InstallPlan.toList plan
-        , let flags   = pkgFlagAssignment pkg
+        | InstallPlan.Configured pkg_or_comp <- InstallPlan.toList plan
+        , let pkg     = getElaboratedPackage pkg_or_comp
+              flags   = pkgFlagAssignment pkg
               pkgname = packageName pkg
         , not (null flags) ]
 
@@ -158,7 +157,8 @@ projectFreezeConstraints plan =
     localPackages =
       Map.fromList
         [ (packageName pkg, ())
-        | InstallPlan.Configured pkg <- InstallPlan.toList plan
+        | InstallPlan.Configured pkg_or_comp <- InstallPlan.toList plan
+        , let pkg = getElaboratedPackage pkg_or_comp
         , pkgLocalToProject pkg
         ]
 

cabal-install/Distribution/Client/CmdRepl.hs

@@ -67,6 +67,7 @@ replAction (configFlags, configExFlags, installFlags, haddockFlags)
     -- repl targets (as opposed to say build or haddock targets).
     selectReplTargets =
       selectTargets
+        verbosity
         ReplDefaultComponent
         ReplSpecificComponent
 

cabal-install/Distribution/Client/DistDirLayout.hs

@@ -5,17 +5,43 @@
 -- The layout of the .\/dist\/ directory where cabal keeps all of it's state
 -- and build artifacts.
 --
-module Distribution.Client.DistDirLayout where
+module Distribution.Client.DistDirLayout (
+    -- 'DistDirLayout'
+    DistDirLayout(..),
+    DistDirParams(..),
+    defaultDistDirLayout,
+
+    -- * 'CabalDirLayout'
+    CabalDirLayout(..),
+    defaultCabalDirLayout,
+) where
 
 import System.FilePath
 import Distribution.Package
-         ( PackageId )
+         ( PackageId, UnitId(..) )
 import Distribution.Compiler
 import Distribution.Simple.Compiler (PackageDB(..))
 import Distribution.Text
+import Distribution.Types.ComponentName
+import Distribution.System
 import Distribution.Client.Types
          ( InstalledPackageId )
 
+-- | Information which can be used to construct the path to
+-- the build directory of a build.  This is LESS fine-grained
+-- than what goes into the hashed 'InstalledPackageId',
+-- and for good reason: we don't want this path to change if
+-- the user, say, adds a dependency to their project.
+data DistDirParams = DistDirParams {
+    distParamUnitId         :: UnitId,
+    distParamPackageId      :: PackageId,
+    distParamComponentName  :: Maybe ComponentName,
+    distParamCompilerId     :: CompilerId,
+    distParamPlatform       :: Platform
+    -- TODO (see #3343):
+    --  Flag assignments
+    --  Optimization
+    }
 
 
 -- | The layout of the project state directory. Traditionally this has been
@@ -31,11 +57,11 @@ data DistDirLayout = DistDirLayout {
        -- | The directory under dist where we keep the build artifacts for a
        -- package we're building from a local directory.
        --
-       -- This uses a 'PackageId' not just a 'PackageName' because technically
+       -- This uses a 'UnitId' not just a 'PackageName' because technically
        -- we can have multiple instances of the same package in a solution
        -- (e.g. setup deps).
        --
-       distBuildDirectory           :: PackageId -> FilePath,
+       distBuildDirectory           :: DistDirParams -> FilePath,
        distBuildRootDirectory       :: FilePath,
 
        -- | The directory under dist where we put the unpacked sources of
@@ -55,8 +81,8 @@ data DistDirLayout = DistDirLayout {
        -- | The location for package-specific cache files (e.g. state used in
        -- incremental rebuilds).
        --
-       distPackageCacheFile         :: PackageId -> String -> FilePath,
-       distPackageCacheDirectory    :: PackageId -> FilePath,
+       distPackageCacheFile         :: DistDirParams -> String -> FilePath,
+       distPackageCacheDirectory    :: DistDirParams -> FilePath,
 
        distTempDirectory            :: FilePath,
        distBinDirectory             :: FilePath,
@@ -88,7 +114,17 @@ defaultDistDirLayout projectRootDirectory =
     --TODO: switch to just dist at some point, or some other new name
 
     distBuildRootDirectory   = distDirectory </> "build"
-    distBuildDirectory pkgid = distBuildRootDirectory </> display pkgid
+    distBuildDirectory params =
+        distBuildRootDirectory </>
+        display (distParamPlatform params) </>
+        display (distParamCompilerId params) </>
+        display (distParamPackageId params) </>
+        (case fmap componentNameString (distParamComponentName params) of
+            Nothing         -> ""
+            Just Nothing    -> ""
+            Just (Just str) -> "c" </> str) </>
+        (case distParamUnitId params of -- For Backpack
+            SimpleUnitId _ -> "")
 
     distUnpackedSrcRootDirectory   = distDirectory </> "src"
     distUnpackedSrcDirectory pkgid = distUnpackedSrcRootDirectory
@@ -97,8 +133,8 @@ defaultDistDirLayout projectRootDirectory =
     distProjectCacheDirectory = distDirectory </> "cache"
     distProjectCacheFile name = distProjectCacheDirectory </> name
 
-    distPackageCacheDirectory pkgid = distBuildDirectory pkgid </> "cache"
-    distPackageCacheFile pkgid name = distPackageCacheDirectory pkgid </> name
+    distPackageCacheDirectory params = distBuildDirectory params </> "cache"
+    distPackageCacheFile params name = distPackageCacheDirectory params </> name
 
     distTempDirectory = distDirectory </> "tmp"
 

cabal-install/Distribution/Client/Install.hs

@@ -116,7 +116,6 @@ import           Distribution.Solver.Types.ConstraintSource
 import           Distribution.Solver.Types.LabeledPackageConstraint
 import           Distribution.Solver.Types.OptionalStanza
 import qualified Distribution.Solver.Types.PackageIndex as SourcePackageIndex
-import           Distribution.Solver.Types.PackageFixedDeps
 import           Distribution.Solver.Types.PkgConfigDb
                    ( PkgConfigDb, readPkgConfigDb )
 import           Distribution.Solver.Types.SourcePackage as SourcePackage
@@ -614,12 +613,12 @@ packageStatus installedPkgIndex cpkg =
     changes :: Installed.InstalledPackageInfo
             -> ReadyPackage
             -> [MergeResult PackageIdentifier PackageIdentifier]
-    changes pkg pkg' = filter changed $
+    changes pkg (ReadyPackage pkg') = filter changed $
       mergeBy (comparing packageName)
         -- deps of installed pkg
         (resolveInstalledIds $ Installed.depends pkg)
         -- deps of configured pkg
-        (resolveInstalledIds $ CD.nonSetupDeps (depends pkg'))
+        (resolveInstalledIds $ map confInstId (CD.nonSetupDeps (confPkgDeps pkg')))
 
     -- convert to source pkg ids via index
     resolveInstalledIds :: [UnitId] -> [PackageIdentifier]

cabal-install/Distribution/Client/PackageHash.hs

@@ -43,6 +43,7 @@ import Distribution.Text
          ( display )
 import Distribution.Client.Types
          ( InstalledPackageId )
+import qualified Distribution.Solver.Types.ComponentDeps as CD
 
 import qualified Hackage.Security.Client    as Sec
 
@@ -133,6 +134,7 @@ hashedInstalledPackageIdShort pkghashinputs@PackageHashInputs{pkgHashPkgId} =
 --
 data PackageHashInputs = PackageHashInputs {
        pkgHashPkgId         :: PackageId,
+       pkgHashComponent     :: Maybe CD.Component,
        pkgHashSourceHash    :: PackageSourceHash,
        pkgHashDirectDeps    :: Set InstalledPackageId,
        pkgHashOtherConfig   :: PackageHashConfigInputs
@@ -188,6 +190,7 @@ hashPackageHashInputs = hashValue . renderPackageHashInputs
 renderPackageHashInputs :: PackageHashInputs -> LBS.ByteString
 renderPackageHashInputs PackageHashInputs{
                           pkgHashPkgId,
+                          pkgHashComponent,
                           pkgHashSourceHash,
                           pkgHashDirectDeps,
                           pkgHashOtherConfig =
@@ -209,6 +212,7 @@ renderPackageHashInputs PackageHashInputs{
     -- use the config file infrastructure so it can be read back in again.
     LBS.pack $ unlines $ catMaybes
       [ entry "pkgid"       display pkgHashPkgId
+      , mentry "component"  show pkgHashComponent
       , entry "src"         showHashValue pkgHashSourceHash
       , entry "deps"        (intercalate ", " . map display
                                               . Set.toList) pkgHashDirectDeps
@@ -239,6 +243,7 @@ renderPackageHashInputs PackageHashInputs{
       ]
   where
     entry key     format value = Just (key ++ ": " ++ format value)
+    mentry key    format value = fmap (\v -> key ++ ": " ++ format v) value
     opt   key def format value
          | value == def = Nothing
          | otherwise    = entry key format value

cabal-install/Distribution/Client/ProjectOrchestration.hs

@@ -58,6 +58,7 @@ module Distribution.Client.ProjectOrchestration (
 
 import           Distribution.Client.ProjectConfig
 import           Distribution.Client.ProjectPlanning
+import           Distribution.Client.ProjectPlanning.Types
 import           Distribution.Client.ProjectBuilding
 
 import           Distribution.Client.Types
@@ -79,7 +80,7 @@ import qualified Distribution.PackageDescription as PD
 import           Distribution.PackageDescription (FlagAssignment)
 import           Distribution.Simple.Setup (HaddockFlags)
 
-import           Distribution.Simple.Utils (die, notice)
+import           Distribution.Simple.Utils (die, notice, debug)
 import           Distribution.Verbosity
 import           Distribution.Text
 
@@ -183,7 +184,7 @@ runProjectPreBuildPhase
     -- This also gives us more accurate reasons for the --dry-run output.
     --
     (elaboratedPlan'', pkgsBuildStatus) <-
-      rebuildTargetsDryRun distDirLayout
+      rebuildTargetsDryRun verbosity distDirLayout elaboratedShared
                            elaboratedPlan'
 
     return ProjectBuildContext {
@@ -243,14 +244,34 @@ runProjectBuildPhase verbosity ProjectBuildContext {..} =
 -- | Adjust an 'ElaboratedInstallPlan' by selecting just those parts of it
 -- required to build the given user targets.
 --
--- How to get the 'PackageTarget's from the 'UserBuildTarget' is customisable.
+-- How to get the 'PackageTarget's from the 'UserBuildTarget' is customisable,
+-- so that we can change the meaning of @pkgname@ to target a build or
+-- repl depending on which command is calling it.
 --
-selectTargets :: PackageTarget
+-- Conceptually, every target identifies one or more roots in the
+-- 'ElaboratedInstallPlan', which we then use to determine the closure
+-- of what packages need to be built, dropping everything from
+-- 'ElaboratedInstallPlan' that is unnecessary.
+--
+-- There is a complication, however: In an ideal world, every
+-- possible target would be a node in the graph.  However, it is
+-- currently not possible (and possibly not even desirable) to invoke a
+-- Setup script to build *just* one file.  Similarly, it is not possible
+-- to invoke a pre Cabal-1.25 custom Setup script and build only one
+-- component.  In these cases, we want to build the entire package, BUT
+-- only actually building some of the files/components.  This is what
+-- 'pkgBuildTargets', 'pkgReplTarget' and 'pkgBuildHaddock' control.
+-- Arguably, these should an out-of-band mechanism rather than stored
+-- in 'ElaboratedInstallPlan', but it's what we have.  We have
+-- to fiddle around with the ElaboratedConfiguredPackage roots to say
+-- what it will build.
+--
+selectTargets :: Verbosity -> PackageTarget
               -> (ComponentTarget -> PackageTarget)
               -> [UserBuildTarget]
               -> ElaboratedInstallPlan
               -> IO ElaboratedInstallPlan
-selectTargets targetDefaultComponents targetSpecificComponent
+selectTargets verbosity targetDefaultComponents targetSpecificComponent
               userBuildTargets installPlan = do
 
     -- Match the user targets against the available targets. If no targets are
@@ -277,6 +298,7 @@ selectTargets targetDefaultComponents targetSpecificComponent
                        targetSpecificComponent
                        installPlan
                        buildTargets
+    debug verbosity ("buildTargets': " ++ show buildTargets')
 
     -- Finally, prune the install plan to cover just those target packages
     -- and their deps.
@@ -285,7 +307,8 @@ selectTargets targetDefaultComponents targetSpecificComponent
   where
     localPackages =
       [ (pkgDescription pkg, pkgSourceLocation pkg)
-      | InstallPlan.Configured pkg <- InstallPlan.toList installPlan ]
+      | InstallPlan.Configured pkg_or_comp <- InstallPlan.toList installPlan
+      , let pkg = getElaboratedPackage pkg_or_comp ]
       --TODO: [code cleanup] is there a better way to identify local packages?
 
 
@@ -301,7 +324,8 @@ resolveAndCheckTargets targetDefaultComponents
                        installPlan targets =
     case partitionEithers (map checkTarget targets) of
       ([], targets') -> Right $ Map.fromListWith (++)
-                                  [ (ipkgid, [t]) | (ipkgid, t) <- targets' ]
+                                  [ (ipkgid, [t]) | (ipkgids, t) <- targets'
+                                                  , ipkgid <- ipkgids ]
       (problems, _)  -> Left problems
   where
     -- TODO [required eventually] currently all build targets refer to packages
@@ -342,16 +366,20 @@ resolveAndCheckTargets targetDefaultComponents
       = Left (BuildTargetNotInProject (buildTargetPackage t))
 
 
-    projAllPkgs, projLocalPkgs :: Map PackageName InstalledPackageId
+    -- 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 =
-      Map.fromList
-        [ (packageName pkg, installedPackageId pkg)
+      Map.fromListWith (++)
+        [ (packageName pkg, [installedPackageId pkg])
         | pkg <- InstallPlan.toList installPlan ]
 
     projLocalPkgs =
-      Map.fromList
-        [ (packageName pkg, installedPackageId pkg)
-        | InstallPlan.Configured pkg <- InstallPlan.toList installPlan
+      Map.fromListWith (++)
+        [ (packageName pkg, [installedPackageId pkg_or_comp])
+        | InstallPlan.Configured pkg_or_comp <- InstallPlan.toList installPlan
+        , let pkg = getElaboratedPackage pkg_or_comp
         , case pkgSourceLocation pkg of
             LocalUnpackedPackage _ -> True; _ -> False
           --TODO: [code cleanup] is there a better way to identify local packages?
@@ -418,18 +446,25 @@ printPlan verbosity
     wouldWill | buildSettingDryRun = "would"
               | otherwise          = "will"
 
-    showPkg pkg = display (packageId pkg)
+    showPkg (ReadyPackage (ElabPackage pkg)) = display (packageId pkg)
+    showPkg (ReadyPackage (ElabComponent comp)) =
+        display (packageId (elabComponentPackage comp)) ++
+        " (" ++ maybe "custom" display (elabComponentName comp) ++ ")"
 
     showPkgAndReason :: ElaboratedReadyPackage -> String
-    showPkgAndReason (ReadyPackage pkg) =
-      display (packageId pkg) ++
-      showTargets pkg ++
+    showPkgAndReason (ReadyPackage pkg_or_comp) =
+      display (installedUnitId pkg_or_comp) ++
+      (case pkg_or_comp of
+          ElabPackage _ -> showTargets pkg ++ showStanzas pkg
+          ElabComponent comp ->
+            " (" ++ maybe "custom" display (elabComponentName comp) ++ ")") ++
       showFlagAssignment (nonDefaultFlags pkg) ++
-      showStanzas pkg ++
-      let buildStatus = pkgsBuildStatus Map.! installedPackageId pkg in
+      let buildStatus = pkgsBuildStatus Map.! installedPackageId pkg_or_comp in
       " (" ++ showBuildStatus buildStatus ++ ")"
+     where
+      pkg = getElaboratedPackage pkg_or_comp
 
-    nonDefaultFlags :: ElaboratedConfiguredPackage -> FlagAssignment
+    nonDefaultFlags :: ElaboratedPackage -> FlagAssignment
     nonDefaultFlags pkg = pkgFlagAssignment pkg \\ pkgFlagDefaults pkg
 
     showStanzas pkg = concat

cabal-install/Distribution/Client/ProjectPlanOutput.hs

@@ -9,8 +9,6 @@ module Distribution.Client.ProjectPlanOutput (
   ) where
 
 import           Distribution.Client.ProjectPlanning.Types
-                   ( ElaboratedInstallPlan, ElaboratedConfiguredPackage(..)
-                   , ElaboratedSharedConfig(..) )
 import           Distribution.Client.DistDirLayout
 
 import qualified Distribution.Client.InstallPlan as InstallPlan
@@ -66,27 +64,46 @@ encodePlanAsJson elaboratedInstallPlan _elaboratedSharedConfig =
       J.object
         [ "type"       J..= J.String "pre-existing"
         , "id"         J..= jdisplay (installedUnitId ipi)
-        , "components" J..= J.object
-          [ "lib" J..= J.object [ "depends" J..= map jdisplay (installedDepends ipi) ] ]
+        , "depends" J..= map jdisplay (installedDepends ipi)
         ]
 
-    -- ecp :: ElaboratedConfiguredPackage
-    toJ (InstallPlan.Configured ecp) =
+    -- pkg :: ElaboratedPackage
+    toJ (InstallPlan.Configured (ElabPackage pkg)) =
       J.object
         [ "type"       J..= J.String "configured"
-        , "id"         J..= (jdisplay . installedUnitId) ecp
+        , "id"         J..= (jdisplay . installedUnitId) pkg
         , "components" J..= components
+        , "depends"    J..= map (jdisplay . confInstId) flat_deps
         , "flags"      J..= J.object [ fn J..= v
-                                     | (PD.FlagName fn,v) <- pkgFlagAssignment ecp ]
+                                     | (PD.FlagName fn,v) <-
+                                            pkgFlagAssignment pkg ]
         ]
       where
+        flat_deps = ordNub (ComponentDeps.flatDeps (pkgDependencies pkg))
         components = J.object
           [ comp2str c J..= J.object
             [ "depends" J..= map (jdisplay . installedUnitId) v ]
-          | (c,v) <- ComponentDeps.toList (pkgDependencies ecp) ]
+          -- NB: does NOT contain order-only dependencies
+          | (c,v) <- ComponentDeps.toList (pkgDependencies pkg) ]
+
+    -- ecp :: ElaboratedConfiguredPackage
+    toJ (InstallPlan.Configured (ElabComponent comp)) =
+      J.object
+        [ "type"       J..= J.String "configured-component"
+        , "id"         J..= (jdisplay . installedUnitId) comp
+        , "name"       J..= J.String (comp2str (elabComponent comp))
+        , "flags"      J..= J.object [ fn J..= v
+                                     | (PD.FlagName fn,v) <-
+                                            pkgFlagAssignment pkg ]
+        -- NB: does NOT contain order-only dependencies
+        , "depends"    J..= map (jdisplay . installedUnitId) (elabComponentDependencies comp)
+        ]
+      where
+        pkg = elabComponentPackage comp
 
     -- TODO: maybe move this helper to "ComponentDeps" module?
     --       Or maybe define a 'Text' instance?
+    comp2str :: ComponentDeps.Component -> String
     comp2str c = case c of
         ComponentDeps.ComponentLib     -> "lib"
         ComponentDeps.ComponentSubLib s -> "lib:"   <> s

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

-{-# LANGUAGE DeriveGeneric, DeriveDataTypeable #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE TypeFamilies #-}
 
 -- | Types used while planning how to build everything in a project.
 --
@@ -10,6 +12,17 @@ module Distribution.Client.ProjectPlanning.Types (
     -- * Elaborated install plan types
     ElaboratedInstallPlan,
     ElaboratedConfiguredPackage(..),
+
+    getElaboratedPackage,
+    elabInstallDirs,
+    elabDistDirParams,
+    elabRequiresRegistration,
+    elabBuildTargets,
+    elabReplTarget,
+    elabBuildHaddocks,
+
+    ElaboratedComponent(..),
+    ElaboratedPackage(..),
     ElaboratedPlanPackage,
     ElaboratedSharedConfig(..),
     ElaboratedReadyPackage,
@@ -32,7 +45,9 @@ import           Distribution.Client.InstallPlan
                    ( GenericInstallPlan, GenericPlanPackage )
 import           Distribution.Client.SolverInstallPlan
                    ( SolverInstallPlan )
+import           Distribution.Client.DistDirLayout
 
+import           Distribution.Types.ComponentEnabledSpec
 import           Distribution.Package
                    hiding (InstalledPackageId, installedPackageId)
 import           Distribution.System
@@ -46,9 +61,10 @@ import qualified Distribution.Simple.InstallDirs as InstallDirs
 import           Distribution.Simple.InstallDirs (PathTemplate)
 import           Distribution.Version
 
+import qualified Distribution.Solver.Types.ComponentDeps as CD
 import           Distribution.Solver.Types.ComponentDeps (ComponentDeps)
 import           Distribution.Solver.Types.OptionalStanza
-import           Distribution.Solver.Types.PackageFixedDeps
+import           Distribution.Compat.Graph (IsNode(..))
 
 import           Data.Map (Map)
 import           Data.Set (Set)
@@ -91,16 +107,151 @@ data ElaboratedSharedConfig
 
 instance Binary ElaboratedSharedConfig
 
+-- TODO: This is a misnomer, but I didn't want to rename things
+-- willy-nilly yet
 data ElaboratedConfiguredPackage
-   = ElaboratedConfiguredPackage {
+    = ElabPackage   ElaboratedPackage
+    | ElabComponent ElaboratedComponent
+  deriving (Eq, Show, Generic)
+
+instance IsNode ElaboratedConfiguredPackage where
+    type Key ElaboratedConfiguredPackage = UnitId
+    nodeKey (ElabPackage pkg) = nodeKey pkg
+    nodeKey (ElabComponent comp) = nodeKey comp
+    nodeNeighbors (ElabPackage pkg) = nodeNeighbors pkg
+    nodeNeighbors (ElabComponent comp) = nodeNeighbors comp
+
+elabDistDirParams :: ElaboratedSharedConfig -> ElaboratedConfiguredPackage -> DistDirParams
+elabDistDirParams shared (ElabPackage pkg) = DistDirParams {
+        distParamUnitId = pkgInstalledId pkg,
+        distParamPackageId = pkgSourceId pkg,
+        distParamComponentName = Nothing,
+        distParamCompilerId = compilerId (pkgConfigCompiler shared),
+        distParamPlatform = pkgConfigPlatform shared
+    }
+elabDistDirParams shared (ElabComponent comp) = DistDirParams {
+        distParamUnitId = elabComponentId comp,
+        distParamPackageId = packageId comp, -- NB: NOT the munged ID
+        distParamComponentName = elabComponentName comp, -- TODO: Ick. Change type.
+        distParamCompilerId = compilerId (pkgConfigCompiler shared),
+        distParamPlatform = pkgConfigPlatform shared
+    }
+
+-- TODO: give each component a separate install dir prefix
+elabInstallDirs :: ElaboratedConfiguredPackage -> InstallDirs.InstallDirs FilePath
+elabInstallDirs = pkgInstallDirs . getElaboratedPackage
+
+elabRequiresRegistration :: ElaboratedConfiguredPackage -> Bool
+elabRequiresRegistration (ElabPackage pkg) = pkgRequiresRegistration pkg
+elabRequiresRegistration (ElabComponent comp)
+    = case elabComponent comp of
+        CD.ComponentLib -> True
+        CD.ComponentSubLib _ -> True
+        _ -> False
+
+elabBuildTargets :: ElaboratedConfiguredPackage -> [ComponentTarget]
+elabBuildTargets (ElabPackage pkg) = pkgBuildTargets pkg
+elabBuildTargets (ElabComponent comp)
+    | Just cname <- elabComponentName comp
+    = map (ComponentTarget cname) $ elabComponentBuildTargets comp
+    | otherwise = []