support multiple libraries in one package

cabal2nix/src/Distribution/Nixpkgs/Haskell/Derivation.hs

@@ -9,6 +9,7 @@ module Distribution.Nixpkgs.Haskell.Derivation
   , cabalFlags, runHaddock, jailbreak, doCheck, doBenchmark, testFlags, testTargets, hyperlinkSource
   , enableLibraryProfiling, enableExecutableProfiling, phaseOverrides, editedCabalFile, metaSection
   , dependencies, setupDepends, benchmarkDepends, enableSeparateDataOutput, extraAttributes
+  , subLibraryDepends, subLibraryDependencies
   )
   where
 
@@ -50,6 +51,8 @@ data Derivation = MkDerivation
   , _executableDepends          :: BuildInfo
   , _testDepends                :: BuildInfo
   , _benchmarkDepends           :: BuildInfo
+  , _subLibraryDepends          :: Map String BuildInfo
+  , _subLibraryDependencies     :: Map String [String]
   , _configureFlags             :: Set String
   , _cabalFlags                 :: FlagAssignment
   , _runHaddock                 :: Bool
@@ -83,6 +86,8 @@ nullDerivation = MkDerivation
   , _executableDepends = error "undefined Derivation.executableDepends"
   , _testDepends = error "undefined Derivation.testDepends"
   , _benchmarkDepends = error "undefined Derivation.benchmarkDepends"
+  , _subLibraryDepends = mempty
+  , _subLibraryDependencies = mempty
   , _configureFlags = error "undefined Derivation.configureFlags"
   , _cabalFlags = error "undefined Derivation.cabalFlags"
   , _runHaddock = error "undefined Derivation.runHaddock"
@@ -102,15 +107,26 @@ nullDerivation = MkDerivation
 
 makeLenses ''Derivation
 
-makeLensesFor [("_setupDepends", "dependencies"), ("_libraryDepends", "dependencies"), ("_executableDepends", "dependencies"), ("_testDepends", "dependencies"), ("_benchmarkDepends", "dependencies")] ''Derivation
+-- | Traversal over all 'BuildInfo' values in a 'Derivation', including
+-- the setup, library, executable, test, benchmark, and sub-library depends.
+dependencies :: Traversal' Derivation BuildInfo
+dependencies f drv =
+  (\s l e t b sl -> drv { _setupDepends = s, _libraryDepends = l, _executableDepends = e
+                        , _testDepends = t, _benchmarkDepends = b, _subLibraryDepends = sl })
+    <$> f (_setupDepends drv)
+    <*> f (_libraryDepends drv)
+    <*> f (_executableDepends drv)
+    <*> f (_testDepends drv)
+    <*> f (_benchmarkDepends drv)
+    <*> traverse f (_subLibraryDepends drv)
 
 instance Package Derivation where
   packageId = view pkgid
 
 instance NFData Derivation
 
 instance Pretty Derivation where
-  pPrint drv@MkDerivation {..} = funargs (map text ("mkDerivation" : toAscList inputs)) $$ vcat
+  pPrint drv@MkDerivation {_subLibraryDepends = subLibDeps, _subLibraryDependencies = subLibConsumerDeps, ..} = funargs (map text ("mkDerivation" : toAscList inputs)) $$ vcat
     [ text "mkDerivation" <+> lbrace
     , nest 2 $ vcat
       [ attr "pname"   $ doubleQuotes $ pPrint (packageName _pkgid)
@@ -124,10 +140,12 @@ instance Pretty Derivation where
       , boolattr "isExecutable" (not _isLibrary || _isExecutable) _isExecutable
       , boolattr "enableSeparateDataOutput" _enableSeparateDataOutput _enableSeparateDataOutput
       , onlyIf (_setupDepends /= mempty) $ pPrintBuildInfo "setup" _setupDepends
-      , onlyIf (_libraryDepends /= mempty) $ pPrintBuildInfo "library" _libraryDepends
+      , onlyIf (mergedLibraryDepends /= mempty) $ pPrintBuildInfo "library" mergedLibraryDepends
+      , onlyIf (not (Map.null subLibDeps)) $ pPrintSubLibraryDepends subLibDeps
       , onlyIf (_executableDepends /= mempty) $ pPrintBuildInfo "executable" _executableDepends
       , onlyIf (_testDepends /= mempty) $ pPrintBuildInfo "test" _testDepends
       , onlyIf (_benchmarkDepends /= mempty) $ pPrintBuildInfo "benchmark" _benchmarkDepends
+      , onlyIf (not (Map.null subLibConsumerDeps)) $ pPrintSubLibraryDependencies subLibConsumerDeps
       , boolattr "enableLibraryProfiling" _enableLibraryProfiling _enableLibraryProfiling
       , boolattr "enableExecutableProfiling" _enableExecutableProfiling _enableExecutableProfiling
       , boolattr "doHaddock" (not _runHaddock) _runHaddock
@@ -152,8 +170,39 @@ instance Pretty Derivation where
                               Just derivKind' -> Set.fromList [derivKindFunction derivKind' | not isHackagePackage]
                           ]
 
+      -- For backwards compatibility, libraryHaskellDepends is emitted as the
+      -- union of the main library deps and all sub-library deps. New consumers
+      -- should prefer the separate subLibraryDepends attrset.
+      mergedLibraryDepends = _libraryDepends `mappend` foldMap id (Map.elems subLibDeps)
+
       renderedFlags = [ text "-f" <> (if enable then empty else char '-') <> text (unFlagName f) | (f, enable) <- unFlagAssignment _cabalFlags ]
                       ++ map text (toAscList _configureFlags)
       isHackagePackage = "mirror://hackage/" `isPrefixOf` derivUrl _src
 
       postUnpack = string $ "sourceRoot+=/" ++ _subpath ++ "; echo source root reset to $sourceRoot"
+
+pPrintSubLibraryDepends :: Map String BuildInfo -> Doc
+pPrintSubLibraryDepends libs = vcat
+  [ text "subLibraryDepends" <+> equals <+> lbrace
+  , nest 2 $ vcat entries
+  , rbrace <> semi
+  ]
+  where
+    entries = [ vcat [ text (show name) <+> equals <+> lbrace
+                     , nest 2 $ pPrintBuildInfo "" bi
+                     , rbrace <> semi
+                     ]
+              | (name, bi) <- Map.toAscList libs
+              , bi /= mempty
+              ]
+
+pPrintSubLibraryDependencies :: Map String [String] -> Doc
+pPrintSubLibraryDependencies deps = vcat
+  [ text "subLibraryDependencies" <+> equals <+> lbrace
+  , nest 2 $ vcat entries
+  , rbrace <> semi
+  ]
+  where
+    entries = [ listattrDoc (show pkgName) empty (map (doubleQuotes . text) subLibs)
+              | (pkgName, subLibs) <- Map.toAscList deps
+              ]

cabal2nix/src/Distribution/Nixpkgs/Haskell/FromCabal.hs

@@ -9,8 +9,10 @@ module Distribution.Nixpkgs.Haskell.FromCabal
 
 import Control.Lens
 import Data.Maybe
+import qualified Data.Map as Map
 import Data.Set ( Set )
 import qualified Data.Set as Set
+import qualified Distribution.Compat.NonEmptySet as NES
 import Distribution.Compiler
 import Distribution.Nixpkgs.Haskell
 import qualified Distribution.Nixpkgs.Haskell as Nix
@@ -29,6 +31,7 @@ import Distribution.System
 import Distribution.Types.PackageVersionConstraint
 import Distribution.Text ( display )
 import Distribution.Types.ComponentRequestedSpec as Cabal
+import Distribution.Types.LibraryVisibility
 #if !MIN_VERSION_Cabal(3,8,1)
 import Distribution.Types.ExeDependency as Cabal
 import Distribution.Types.LegacyExeDependency as Cabal
@@ -124,10 +127,22 @@ fromPackageDescription haskellResolver nixpkgsResolver missingDeps flags Package
     & isExecutable .~ not (null executables)
     & extraFunctionArgs .~ mempty
     & extraAttributes .~ mempty
-    & libraryDepends .~ foldMap (convertBuildInfo . libBuildInfo) (maybeToList library ++ subLibraries)
+    & libraryDepends .~ foldMap (convertBuildInfo . libBuildInfo) (maybeToList library)
+    & subLibraryDepends .~ Map.fromList
+        [ (unUnqualComponentName n, convertBuildInfo (libBuildInfo l))
+        | l <- subLibraries
+        , LSubLibName n <- [libName l]
+        ]
     & executableDepends .~ mconcat (map (convertBuildInfo . buildInfo) executables)
     & testDepends .~ mconcat (map (convertBuildInfo . testBuildInfo) testSuites)
     & benchmarkDepends .~ mconcat (map (convertBuildInfo . benchmarkBuildInfo) benchmarks)
+    & subLibraryDependencies .~ collectSubLibDeps
+        (  concatMap (targetBuildDepends . libBuildInfo) (maybeToList library)
+        ++ concatMap (targetBuildDepends . libBuildInfo) subLibraries
+        ++ concatMap (targetBuildDepends . buildInfo) executables
+        ++ concatMap (targetBuildDepends . testBuildInfo) testSuites
+        ++ concatMap (targetBuildDepends . benchmarkBuildInfo) benchmarks
+        )
     & Nix.setupDepends .~ maybe mempty convertSetupBuildInfo setupBuildInfo
     & configureFlags .~ mempty
     & cabalFlags .~ flags
@@ -201,13 +216,31 @@ fromPackageDescription haskellResolver nixpkgsResolver missingDeps flags Package
                                   | otherwise = resolveInNixpkgs i
 
     internalLibNames :: [PackageName]
-    internalLibNames = [ unqualComponentNameToPackageName n | LSubLibName n <- libName <$> subLibraries ]
+    internalLibNames = [ unqualComponentNameToPackageName n
+                       | l <- subLibraries
+                       , LSubLibName n <- [libName l]
+                       , libVisibility l /= LibraryVisibilityPublic
+                       ]
 
     doHaddockPhase :: Bool
     doHaddockPhase | not (null internalLibNames) = False
                    | Just l <- library           = not (null (exposedModules l))
                    | otherwise                   = True
 
+    -- | Collect sub-library qualifiers from dependencies on external packages.
+    -- For each external dependency that specifies sub-library names (not just
+    -- LMainLibName), record which sub-libraries are being depended upon.
+    collectSubLibDeps :: [Dependency] -> Map.Map String [String]
+    collectSubLibDeps deps = Map.fromListWith (\a b -> Set.toAscList (Set.fromList (a ++ b)))
+      [ (unPackageName x, subLibNames)
+      | Dependency x _ libs <- deps
+      , x `notElem` internalLibNames
+      , x /= pkgName package  -- exclude self-referential sub-library deps
+      , let subLibNames = [ unUnqualComponentName n | LSubLibName n <- NES.toList libs ]
+      , not (null subLibNames)
+      ]
+    pkgName (PackageIdentifier n _) = n
+
     convertBuildInfo :: Cabal.BuildInfo -> Nix.BuildInfo
     convertBuildInfo Cabal.BuildInfo {..} | not buildable = mempty
     convertBuildInfo Cabal.BuildInfo {..} = mempty

cabal2nix/src/Distribution/Nixpkgs/Haskell/FromCabal/Normalize.hs

@@ -3,6 +3,7 @@
 module Distribution.Nixpkgs.Haskell.FromCabal.Normalize ( normalize ) where
 
 import Control.Lens
+import qualified Data.Map as Map
 import qualified Data.Set as Set
 import Data.String
 import Distribution.Nixpkgs.Haskell
@@ -17,6 +18,7 @@ normalize drv = drv
   & over executableDepends (normalizeBuildInfo (packageName drv))
   & over testDepends (normalizeBuildInfo (packageName drv))
   & over benchmarkDepends (normalizeBuildInfo (packageName drv))
+  & over subLibraryDepends (Map.map (normalizeBuildInfo (packageName drv)))
   & over metaSection normalizeMeta
   & jailbreak %~ (&& (packageName drv /= "jailbreak-cabal"))
 

cabal2nix/test/golden-test-cases/haddock-library.nix.golden

@@ -6,6 +6,11 @@ mkDerivation {
   version = "1.4.5";
   sha256 = "deadbeef";
   libraryHaskellDepends = [ base bytestring deepseq transformers ];
+  subLibraryDepends = {
+    "attoparsec" = {
+      HaskellDepends = [ base bytestring deepseq ];
+    };
+  };
   testHaskellDepends = [
     base base-compat bytestring deepseq hspec QuickCheck transformers
   ];

cabal2nix/test/golden-test-cases/sub-libraries.cabal

@@ -0,0 +1,28 @@
+cabal-version:       3.0
+name:                sub-libraries
+version:             0.1.0.0
+synopsis:            Test case for sub-library support
+license:             BSD-3-Clause
+build-type:          Simple
+
+library
+  exposed-modules:     MyLib
+  build-depends:       base >=4.14
+  default-language:    Haskell2010
+
+library public-sub
+  visibility:          public
+  exposed-modules:     PublicSub
+  build-depends:       base, deepseq
+  default-language:    Haskell2010
+
+library private-sub
+  visibility:          private
+  exposed-modules:     PrivateSub
+  build-depends:       base, containers
+  default-language:    Haskell2010
+
+executable demo
+  main-is:             Main.hs
+  build-depends:       base, sub-libraries, sub-libraries:public-sub
+  default-language:    Haskell2010

cabal2nix/test/golden-test-cases/sub-libraries.nix.golden

@@ -0,0 +1,22 @@
+{ mkDerivation, base, containers, deepseq, lib }:
+mkDerivation {
+  pname = "sub-libraries";
+  version = "0.1.0.0";
+  sha256 = "deadbeef";
+  isLibrary = true;
+  isExecutable = true;
+  libraryHaskellDepends = [ base containers deepseq ];
+  subLibraryDepends = {
+    "private-sub" = {
+      HaskellDepends = [ base containers ];
+    };
+    "public-sub" = {
+      HaskellDepends = [ base deepseq ];
+    };
+  };
+  executableHaskellDepends = [ base ];
+  doHaddock = false;
+  description = "Test case for sub-library support";
+  license = lib.meta.getLicenseFromSpdxId "BSD-3-Clause";
+  mainProgram = "demo";
+}