Distinguish between internal and external libraries in build-depends

Fixes haskell#4155.

We create a new `LibDependency` just used for parsing `build-depends`
entries for now, but I hope it has a bright future in the brave new
per-component world.

Already in 'Cabal', this type will be used instead of 'Dependency' in
most cases, implemented in the following commits of this PR. Used in:

 - Condition Trees
 - Querying the PackageIndex

-----

Not sure about which type should have the (not)ThisPackageVersion function
Also need to update some comments. Everything builds, however.

Cabal/Cabal.cabal

@@ -216,8 +216,10 @@ library
     Distribution.Types.Dependency
     Distribution.Types.ExeDependency
     Distribution.Types.LegacyExeDependency
+    Distribution.Types.LibDependency
     Distribution.Types.PkgconfigDependency
     Distribution.Types.DependencyMap
+    Distribution.Types.LibDependencyMap
     Distribution.Types.ComponentId
     Distribution.Types.MungedPackageId
     Distribution.Types.PackageId

Cabal/Distribution/Backpack/ComponentsGraph.hs

@@ -14,10 +14,10 @@ import Distribution.PackageDescription as PD hiding (Flag)
 import Distribution.Simple.BuildToolDepends
 import Distribution.Simple.LocalBuildInfo
 import Distribution.Types.ComponentRequestedSpec
-import Distribution.Types.Dependency
-import Distribution.Types.UnqualComponentName
+import Distribution.Types.LibDependency
 import Distribution.Compat.Graph (Node(..))
 import qualified Distribution.Compat.Graph as Graph
+import Distribution.Types.Mixin
 
 import Distribution.Text
     ( Text(disp) )
@@ -57,18 +57,16 @@ toComponentsGraph enabled pkg_descr =
     -- The dependencies for the given component
     componentDeps component =
       (CExeName <$> getAllInternalToolDependencies pkg_descr bi)
-
-      ++ [ if pkgname == packageName pkg_descr
-           then CLibName
-           else CSubLibName toolname
-         | Dependency pkgname _ <- targetBuildDepends bi
-         , let toolname = packageNameToUnqualComponentName pkgname
-         , toolname `elem` internalPkgDeps ]
+      ++ mixin_deps
+      ++ [ maybe CLibName CSubLibName (libDepLibraryName ld)
+         | ld  <- targetBuildDepends bi
+         , libDepPackageName ld == packageName pkg_descr ]
       where
         bi = componentBuildInfo component
-        internalPkgDeps = map (conv . libName) (allLibraries pkg_descr)
-        conv Nothing = packageNameToUnqualComponentName $ packageName pkg_descr
-        conv (Just s) = s
+        mixin_deps =
+         [ maybe CLibName CSubLibName (mixinLibraryName mix)
+         | mix <- mixins bi
+         , mixinPackageName mix == packageName pkg_descr ]
 
 -- | Error message when there is a cycle; takes the SCC of components.
 componentCycleMsg :: [ComponentName] -> Doc

Cabal/Distribution/Backpack/ConfiguredComponent.hs

@@ -19,15 +19,14 @@ import Distribution.Compat.Prelude hiding ((<>))
 
 import Distribution.Backpack.Id
 
-import Distribution.Types.Dependency
 import Distribution.Types.ExeDependency
 import Distribution.Types.IncludeRenaming
 import Distribution.Types.ComponentId
 import Distribution.Types.PackageId
 import Distribution.Types.PackageName
+import Distribution.Types.LibDependency
 import Distribution.Types.Mixin
 import Distribution.Types.ComponentName
-import Distribution.Types.UnqualComponentName
 import Distribution.Types.ComponentInclude
 import Distribution.Package
 import Distribution.PackageDescription as PD hiding (Flag)
@@ -39,7 +38,6 @@ import Distribution.Utils.LogProgress
 import Distribution.Utils.MapAccum
 
 import Control.Monad
-import qualified Data.Set as Set
 import qualified Data.Map as Map
 import Distribution.Text
 import Text.PrettyPrint
@@ -85,85 +83,84 @@ dispConfiguredComponent cc =
                | incl <- cc_includes cc
                ])
 
+-- | This is a mapping that keeps track of package-internal libraries
+-- and executables.  Although a component of the key is a general
+-- 'ComponentName', actually only 'CLib', 'CSubLib' and 'CExe' will ever
+-- be here.
 type ConfiguredComponentMap =
         Map PackageName (Map ComponentName (ComponentId, PackageId))
 
+-- Executable map must be different because an executable can
+-- have the same name as a library. Ew.
+
+-- | Given some ambient environment of package names that
+-- are "in scope", looks at the 'BuildInfo' to decide
+-- what the packages actually resolve to, and then builds
+-- a 'ConfiguredComponent'.
 toConfiguredComponent
     :: PackageDescription
     -> ComponentId
     -> ConfiguredComponentMap
     -> Component
     -> LogProgress ConfiguredComponent
 toConfiguredComponent pkg_descr this_cid dep_map component = do
-    lib_deps <-
-        if newPackageDepsBehaviour pkg_descr
-            then forM (targetBuildDepends bi) $ \(Dependency name _) -> do
-                    let keys@(pn, cn) = fixFakePkgName pkg_descr name
-                    value <- case Map.lookup cn =<< Map.lookup pn dep_map of
-                        Nothing ->
-                            dieProgress $
-                                text "Dependency on unbuildable" <+>
-                                text (showComponentName cn) <+>
-                                text "from" <+> disp pn
-                        Just v -> return v
-                    return (keys, value)
-            else return old_style_lib_deps
-
-    -- Resolve each @mixins@ into the actual dependency
-    -- from @lib_deps@.
-    explicit_includes <- forM (mixins bi) $ \(Mixin name rns) -> do
-        let (pkg, cname) = fixFakePkgName pkg_descr name
-        (cid, pid) <-
-            case Map.lookup cname =<< Map.lookup pkg dep_map of
-                Nothing ->
-                    dieProgress $
-                        text "Mix-in refers to non-existent package" <+>
-                        quotes (disp name) $$
-                        text "(did you forget to add the package to build-depends?)"
-                Just r  -> return r
+    let reg_lib_deps =
+            if newPackageDepsBehaviour pkg_descr
+            then
+                [ (pn, cn)
+                | LibDependency pn mb_ln _ <- targetBuildDepends bi
+                , let cn = libraryComponentName mb_ln ]
+            else
+                -- dep_map contains a mix of internal and external deps.
+                -- We want all the public libraries (dep_cn == CLibName)
+                -- of all external deps (dep /= pn).  Note that this
+                -- excludes the public library of the current package:
+                -- this is not supported by old-style deps behavior
+                -- because it would imply a cyclic dependency for the
+                -- library itself.
+                [ (pn, cn)
+                | (pn, comp_map) <- Map.toList dep_map
+                , pn /= packageName pkg_descr
+                , (cn, _) <- Map.toList comp_map
+                , cn == CLibName ]
+
+        reg_lib_map, mixin_map :: Map (PackageName, ComponentName) (IncludeRenaming, Bool)
+
+        reg_lib_map = Map.fromList $
+            reg_lib_deps `zip` repeat (defaultIncludeRenaming, True)
+
+        mixin_map = Map.fromList
+            [ ((pn, cn), (rns, False))
+            | Mixin pn mb_ln rns <- mixins bi
+            , let cn = libraryComponentName mb_ln ]
+
+        lib_deps = Map.toList $ reg_lib_map `Map.union` mixin_map
+
+    mixin_includes <- forM lib_deps $ \((pname, cname), (rns, implicit)) -> do
+        (cid, pid) <- case Map.lookup cname =<< Map.lookup pname dep_map of
+            Nothing -> dieProgress $
+                text "Dependency on unbuildable" <+>
+                text (showComponentName cname) <+>
+                text "from" <+> disp pname
+            Just r  -> return r
         return ComponentInclude {
                 ci_id       = cid,
                 ci_pkgid    = pid,
                 ci_compname = cname,
                 ci_renaming = rns,
-                ci_implicit = False
+                ci_implicit = implicit
             }
 
-        -- Any @build-depends@ which is not explicitly mentioned in
-        -- @backpack-include@ is converted into an "implicit" include.
-    let used_explicitly = Set.fromList (map ci_id explicit_includes)
-        implicit_includes
-            = map (\((_, cn), (cid, pid)) -> ComponentInclude {
-                                    ci_id = cid,
-                                    ci_pkgid = pid,
-                                    ci_compname = cn,
-                                    ci_renaming = defaultIncludeRenaming,
-                                    ci_implicit = True
-                                  })
-            $ filter (flip Set.notMember used_explicitly . fst . snd) lib_deps
-
     return ConfiguredComponent {
             cc_cid = this_cid,
             cc_pkgid = package pkg_descr,
             cc_component = component,
             cc_public = componentName component == CLibName,
             cc_exe_deps = exe_deps,
-            cc_includes = explicit_includes ++ implicit_includes
+            cc_includes = mixin_includes
         }
   where
     bi = componentBuildInfo component
-    -- dep_map contains a mix of internal and external deps.
-    -- We want all the public libraries (dep_cn == CLibName)
-    -- of all external deps (dep /= pn).  Note that this
-    -- excludes the public library of the current package:
-    -- this is not supported by old-style deps behavior
-    -- because it would imply a cyclic dependency for the
-    -- library itself.
-    old_style_lib_deps = [ ((pn, cn), e)
-                         | (pn, comp_map) <- Map.toList dep_map
-                         , pn /= packageName pkg_descr
-                         , (cn, e) <- Map.toList comp_map
-                         , cn == CLibName ]
     exe_deps =
         [ exe
         | ExeDependency pn cn _ <- getAllToolDependencies pkg_descr bi
@@ -249,16 +246,3 @@ newPackageDepsBehaviourMinVersion = mkVersion [1,7,1]
 newPackageDepsBehaviour :: PackageDescription -> Bool
 newPackageDepsBehaviour pkg =
    specVersion pkg >= newPackageDepsBehaviourMinVersion
-
--- | 'build-depends:' stanzas are currently ambiguous as the external packages
--- and internal libraries are specified the same. For now, we assume internal
--- libraries shadow, and this function disambiguates accordingly, but soon the
--- underlying ambiguity will be addressed.
-fixFakePkgName :: PackageDescription -> PackageName -> (PackageName, ComponentName)
-fixFakePkgName pkg_descr pn =
-  if subLibName `elem` internalLibraries
-  then (packageName pkg_descr, CSubLibName subLibName)
-  else (pn,                    CLibName)
-  where
-    subLibName = packageNameToUnqualComponentName pn
-    internalLibraries = mapMaybe libName (allLibraries pkg_descr)

Cabal/Distribution/Backpack/ReadyComponent.hs

@@ -138,6 +138,9 @@ instance HasMungedPackageId ReadyComponent where
     mungedId ReadyComponent { rc_pkgid = pkgid, rc_component = component }
       = computeCompatPackageId pkgid (componentName component)
 
+instance HasComponentName ReadyComponent where
+    sourceCompName = componentName . rc_component
+
 instance HasUnitId ReadyComponent where
     installedUnitId = rc_uid
 

Cabal/Distribution/InstalledPackageInfo.hs

@@ -60,6 +60,7 @@ import Distribution.Version
 import Distribution.Text
 import qualified Distribution.Compat.ReadP as Parse
 import Distribution.Compat.Graph
+import Distribution.Types.ComponentName
 import Distribution.Types.MungedPackageId
 import Distribution.Types.MungedPackageName
 import Distribution.Types.UnqualComponentName
@@ -202,6 +203,9 @@ instance Package.Package InstalledPackageInfo where
    packageId ipi = PackageIdentifier (sourcePackageName' ipi) ver
      where MungedPackageId _ ver = sourceMungedPackageId ipi
 
+instance Package.HasComponentName InstalledPackageInfo where
+   sourceCompName = libraryComponentName . sourceLibName
+
 instance Package.HasUnitId InstalledPackageInfo where
    installedUnitId = installedUnitId
 

Cabal/Distribution/Package.hs

@@ -26,7 +26,7 @@ module Distribution.Package
   , module Distribution.Types.PkgconfigName
   , Package(..), packageName, packageVersion
   , HasMungedPackageId(..), mungedName', mungedVersion'
-  , HasUnitId(..)
+  , HasComponentName(..), HasUnitId(..)
   , installedPackageId
   , PackageInstalled(..)
   ) where
@@ -43,6 +43,7 @@ import Distribution.Types.MungedPackageId
 import Distribution.Types.PackageId
 import Distribution.Types.UnitId
 import Distribution.Types.Module
+import Distribution.Types.ComponentName
 import Distribution.Types.MungedPackageName
 import Distribution.Types.PackageName
 import Distribution.Types.PkgconfigName
@@ -66,12 +67,12 @@ mungedName'     = mungedName    . mungedId
 mungedVersion' :: HasMungedPackageId munged => munged -> Version
 mungedVersion'  = mungedVersion . mungedId
 
-class HasMungedPackageId pkg where
-  mungedId :: pkg -> MungedPackageId
-
 instance Package PackageIdentifier where
   packageId = id
 
+class HasMungedPackageId pkg where
+  mungedId :: pkg -> MungedPackageId
+
 packageName    :: Package pkg => pkg -> PackageName
 packageName     = pkgName    . packageId
 
@@ -81,6 +82,9 @@ packageVersion  = pkgVersion . packageId
 instance HasMungedPackageId MungedPackageId where
   mungedId = id
 
+class Package pkg => HasComponentName pkg where
+  sourceCompName :: pkg -> ComponentName
+
 -- | Packages that have an installed unit ID
 class Package pkg => HasUnitId pkg where
   installedUnitId :: pkg -> UnitId
@@ -96,5 +100,5 @@ installedPackageId = installedUnitId
 -- 'InstalledPackageInfo', but when we are doing install plans in Cabal install
 -- we may have other, installed package-like things which contain more metadata.
 -- Installed packages have exact dependencies 'installedDepends'.
-class (HasUnitId pkg) => PackageInstalled pkg where
+class (HasComponentName pkg, HasUnitId pkg) => PackageInstalled pkg where
   installedDepends :: pkg -> [UnitId]