Implement mixin-based internal libraries.

Fixes haskell#4155.

Needs a doc update.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Cabal/Distribution/Backpack/ComponentsGraph.hs

@@ -18,6 +18,7 @@ import Distribution.Types.UnqualComponentName
 import Distribution.Simple.Utils
 import Distribution.Compat.Graph (Node(..))
 import qualified Distribution.Compat.Graph as Graph
+import Distribution.Types.Mixin
 
 import Distribution.Text
     ( Text(disp) )
@@ -58,18 +59,19 @@ toComponentsGraph enabled pkg_descr =
          [ CExeName toolname
          | (ExeDependency _ toolname _)
             <- getAllInternalToolDependencies pkg_descr bi ]
+         ++ mixin_deps
+         ++ if null mixin_deps -- the implicit dependency!
+                then [ CLibName
+                     | Dependency pn _ <- targetBuildDepends bi
+                     , pn == packageName pkg_descr ]
+                else []
 
-      ++ [ if pkgname == packageName pkg_descr
-           then CLibName
-           else CSubLibName toolname
-         | Dependency pkgname _ <- targetBuildDepends bi
-         , let toolname = packageNameToUnqualComponentName pkgname
-         , toolname `elem` internalPkgDeps ]
       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/Configure.hs

@@ -82,7 +82,7 @@ configureComponentLocalBuildInfos
                         (dispComponentsGraph graph0)
 
     let conf_pkg_map = Map.fromList
-            [(pc_pkgname pkg, (pc_cid pkg, pc_pkgid pkg))
+            [((pc_pkgname pkg, CLibName), (pc_cid pkg, pc_pkgid pkg))
             | pkg <- prePkgDeps]
         graph1 = toConfiguredComponents use_external_internal_deps
                     flagAssignment

Cabal/Distribution/Backpack/ConfiguredComponent.hs

@@ -78,101 +78,105 @@ dispConfiguredComponent cc =
                | incl <- cc_includes cc
                ])
 
--- | Construct a 'ConfiguredComponent', given that the 'ComponentId'
--- and library/executable dependencies are known.  The primary
--- work this does is handling implicit @backpack-include@ fields.
-mkConfiguredComponent
-    :: PackageId
+-- | 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, 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
-    -> [(PackageName, (ComponentId, PackageId))]
-    -> [ComponentId]
+    -> ConfiguredComponentMap
     -> Component
     -> ConfiguredComponent
-mkConfiguredComponent this_pid this_cid lib_deps exe_deps component =
+toConfiguredComponent pkg_descr this_cid deps_map component =
     ConfiguredComponent {
         cc_cid = this_cid,
-        cc_pkgid = this_pid,
+        cc_pkgid = package pkg_descr,
         cc_component = component,
         cc_public = is_public,
         cc_internal_build_tools = exe_deps,
         cc_includes = explicit_includes ++ implicit_includes
     }
   where
+    pn = packageName pkg_descr
     bi = componentBuildInfo component
-    deps = map snd lib_deps
-    deps_map = Map.fromList lib_deps
 
     -- Resolve each @backpack-include@ into the actual dependency
     -- from @lib_deps@.
     explicit_includes
-        = [ let (cid, pid) =
-                    case Map.lookup name deps_map of
-                        Nothing ->
-                            error $ "Mix-in refers to non-existent package " ++ display name ++
-                                    " (did you forget to add the package to build-depends?)"
-                        Just r  -> r
+        = [ let cname = maybe CLibName CSubLibName mb_lib_name
+                (cid, pid) = case Map.lookup (name, cname) deps_map of
+                    -- TODO: give a better error message here if the
+                    -- *package* exists, but doesn't have this
+                    -- component.
+                    Nothing ->
+                        error $ "Mix-in refers to non-existent component " ++ display cname ++
+                                " in " ++ display name ++
+                                " (did you forget to add the package to build-depends?)"
+                    Just r -> r
             in ComponentInclude {
                 ci_id       = cid,
-                -- TODO: Check what breaks if you remove this edit
-                ci_pkgid    = pid { pkgName = name },
+                ci_pkgid    = pid,
                 ci_renaming = rns
                }
-          | Mixin name rns <- mixins bi ]
+          | Mixin name mb_lib_name rns <- mixins bi ]
 
     -- Any @build-depends@ which is not explicitly mentioned in
     -- @backpack-include@ is converted into an "implicit" include.
-    used_explicitly = Set.fromList (map ci_id explicit_includes)
-    implicit_includes
-        = map (\(cid, pid) -> ComponentInclude {
-                                ci_id = cid,
-                                ci_pkgid = pid,
-                                ci_renaming = defaultIncludeRenaming
-                              })
-        $ filter (flip Set.notMember used_explicitly . fst) deps
-
-    is_public = componentName component == CLibName
-
-type ConfiguredComponentMap =
-        (Map PackageName (ComponentId, PackageId), -- libraries
-         Map UnqualComponentName ComponentId)      -- executables
-
--- 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
-    -> Map PackageName (ComponentId, PackageId) -- external
-    -> ConfiguredComponentMap
-    -> Component
-    -> ConfiguredComponent
-toConfiguredComponent pkg_descr this_cid
-       external_lib_map (lib_map, exe_map) component =
-    mkConfiguredComponent
-       (package pkg_descr) this_cid
-       lib_deps exe_deps component
-  where
-    bi = componentBuildInfo component
-    find_it :: PackageName -> (ComponentId, PackageId)
-    find_it name =
-        fromMaybe (error ("toConfiguredComponent: " ++ display (packageName pkg_descr) ++
-                            " " ++ display name)) $
-            Map.lookup name lib_map <|>
-            Map.lookup name external_lib_map
+    -- NB: This INCLUDES if you depend pkg:sublib (because other way
+    -- there's no way to depend on a sublib without depending on the
+    -- main library as well).
+    used_explicitly = Set.fromList (map (packageName . ci_pkgid) explicit_includes)
     lib_deps
         | newPackageDepsBehaviour pkg_descr
-        = [ (name, find_it name)
-          | Dependency name _ <- targetBuildDepends bi ]
+        = [ case Map.lookup (name, CLibName) deps_map of
+                Nothing ->
+                    error ("toConfiguredComponent: " ++ display (packageName pkg_descr) ++
+                            " " ++ display name)
+                Just r -> r
+          | Dependency name _ <- targetBuildDepends bi
+          , Set.notMember name used_explicitly ]
         | otherwise
-        = Map.toList external_lib_map
+        -- deps_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.
+        = [ r
+          | ((dep_pn,dep_cn), r) <- Map.toList deps_map
+          , dep_pn /= pn
+          , dep_cn == CLibName
+          , Set.notMember dep_pn used_explicitly ]
+    implicit_includes
+        = map (\(cid, pid) ->
+                    ComponentInclude {
+                        ci_id       = cid,
+                        ci_pkgid    = pid,
+                        ci_renaming = defaultIncludeRenaming
+                    }) lib_deps
+
     exe_deps = [ cid
                | (ExeDependency _ toolName _)
                  <- getAllInternalToolDependencies pkg_descr bi
-               , Just cid <- [ Map.lookup toolName exe_map ] ]
+               , let cn = CExeName toolName
+               -- NB: we silently swallow non-existent build-tools,
+               -- because historically they did not have to correspond
+               -- to Haskell executables.
+               , Just (cid, _) <- [ Map.lookup (pn, cn) deps_map ] ]
+
+    is_public = componentName component == CLibName
 
 -- | Also computes the 'ComponentId', and sets cc_public if necessary.
 -- This is Cabal-only; cabal-install won't use this.
@@ -182,45 +186,30 @@ toConfiguredComponent'
     -> PackageDescription
     -> Flag String      -- configIPID (todo: remove me)
     -> Flag ComponentId -- configCID
-    -> Map PackageName (ComponentId, PackageId) -- external
     -> ConfiguredComponentMap
     -> Component
     -> ConfiguredComponent
 toConfiguredComponent' use_external_internal_deps flags
                 pkg_descr ipid_flag cid_flag
-                external_lib_map (lib_map, exe_map) component =
+                deps_map component =
     let cc = toConfiguredComponent
                 pkg_descr this_cid
-                external_lib_map (lib_map, exe_map) component
+                deps_map component
     in if use_external_internal_deps
         then cc { cc_public = True }
         else cc
   where
     this_cid = computeComponentId ipid_flag cid_flag (package pkg_descr)
                 (componentName component) (Just (deps, flags))
-    deps = [ cid | (cid, _) <- Map.elems external_lib_map ]
+    deps = [ cid | ((dep_pn, _), (cid, _)) <- Map.toList deps_map
+                 , dep_pn /= packageName pkg_descr ]
 
 extendConfiguredComponentMap
     :: ConfiguredComponent
     -> ConfiguredComponentMap
     -> ConfiguredComponentMap
-extendConfiguredComponentMap cc (lib_map, exe_map) =
-    (lib_map', exe_map')
-  where
-    lib_map'
-      = case cc_name cc of
-          CLibName ->
-            Map.insert (pkgName (cc_pkgid cc))
-                       (cc_cid cc, cc_pkgid cc) lib_map
-          CSubLibName str ->
-            Map.insert (unqualComponentNameToPackageName str)
-                       (cc_cid cc, cc_pkgid cc) lib_map
-          _ -> lib_map
-    exe_map'
-      = case cc_name cc of
-          CExeName str ->
-            Map.insert str (cc_cid cc) exe_map
-          _ -> exe_map
+extendConfiguredComponentMap cc deps_map =
+    Map.insert (pkgName (cc_pkgid cc), cc_name cc) (cc_cid cc, cc_pkgid cc) deps_map
 
 -- Compute the 'ComponentId's for a graph of 'Component's.  The
 -- list of internal components must be topologically sorted
@@ -232,18 +221,18 @@ toConfiguredComponents
     -> Flag String -- configIPID
     -> Flag ComponentId -- configCID
     -> PackageDescription
-    -> Map PackageName (ComponentId, PackageId)
+    -> ConfiguredComponentMap
     -> [Component]
     -> [ConfiguredComponent]
 toConfiguredComponents
     use_external_internal_deps flags ipid_flag cid_flag pkg_descr
-    external_lib_map comps
-    = snd (mapAccumL go (Map.empty, Map.empty) comps)
+    deps_map comps
+    = snd (mapAccumL go deps_map comps)
   where
     go m component = (extendConfiguredComponentMap cc m, cc)
       where cc = toConfiguredComponent'
                         use_external_internal_deps flags pkg_descr ipid_flag cid_flag
-                        external_lib_map m component
+                        m component
 
 
 newPackageDepsBehaviourMinVersion :: Version

Cabal/Distribution/Parsec/Class.hs

@@ -375,9 +375,12 @@ instance Parsec IncludeRenaming where
 instance Parsec Mixin where
     parsec = do
         mod_name <- parsec
+        mb_lib_name <- P.option Nothing $ do
+            _ <- P.char ':'
+            fmap Just parsec
         P.spaces
         incl <- parsec
-        return (Mixin mod_name incl)
+        return (Mixin mod_name mb_lib_name incl)
 
 -------------------------------------------------------------------------------
 -- Utilities

Cabal/Distribution/Types/Mixin.hs

@@ -8,25 +8,32 @@ module Distribution.Types.Mixin (
 import Prelude ()
 import Distribution.Compat.Prelude
 
-import Text.PrettyPrint ((<+>))
+import Text.PrettyPrint ((<+>), colon)
 import Distribution.Compat.ReadP
 import Distribution.Text
 
 import Distribution.Package
 import Distribution.Types.IncludeRenaming
+import Distribution.Types.UnqualComponentName
 
 data Mixin = Mixin { mixinPackageName :: PackageName
+                   , mixinLibraryName :: Maybe UnqualComponentName
                    , mixinIncludeRenaming :: IncludeRenaming }
     deriving (Show, Read, Eq, Ord, Typeable, Data, Generic)
 
 instance Binary Mixin
 
 instance Text Mixin where
-    disp (Mixin pkg_name incl) =
+    disp (Mixin pkg_name Nothing incl) =
         disp pkg_name <+> disp incl
+    disp (Mixin pkg_name (Just lib_name) incl) =
+        disp pkg_name <<>> colon <<>> disp lib_name <+> disp incl
 
     parse = do
         pkg_name <- parse
+        mb_lib_name <- option Nothing $ do
+            _ <- char ':'
+            fmap Just parse
         skipSpaces
         incl <- parse
-        return (Mixin pkg_name incl)
+        return (Mixin pkg_name mb_lib_name incl)

cabal-testsuite/PackageTests/InternalLibraries/Executable/foo.cabal

@@ -14,5 +14,6 @@ library foo-internal
 
 executable foo
   main-is: Main.hs
-  build-depends:       base, foo-internal
+  build-depends:       base
+  mixins: foo:foo-internal
   hs-source-dirs: exe

cabal-testsuite/PackageTests/InternalLibraries/Library/foolib/foolib.cabal

@@ -13,5 +13,6 @@ library foolib-internal
 
 library
   exposed-modules:     Foo
-  build-depends:       base, foolib-internal
+  build-depends:       base
+  mixins:              foolib:foolib-internal
   default-language:    Haskell2010

cabal-testsuite/PackageTests/InternalLibraries/p/p.cabal

@@ -13,11 +13,13 @@ library q
   default-language:    Haskell2010
 
 library
-  build-depends:       base, q
+  build-depends:       base
+  mixins:              p:q
   exposed-modules:     P
   hs-source-dirs:      p
   default-language:    Haskell2010
 
 executable foo
-  build-depends:       base, q
+  build-depends:       base, p
+  mixins:              p:q
   main-is:             Foo.hs