path: root/haddock-api/src/Haddock/Interface/Create.hs

{-# LANGUAGE CPP, TupleSections, BangPatterns, LambdaCase #-}
{-# OPTIONS_GHC -Wwarn #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Haddock.Interface.Create
-- Copyright   :  (c) Simon Marlow      2003-2006,
--                    David Waern       2006-2009,
--                    Mateusz Kowalczyk 2013
-- License     :  BSD-like
--
-- Maintainer  :  haddock@projects.haskell.org
-- Stability   :  experimental
-- Portability :  portable
-----------------------------------------------------------------------------
module Haddock.Interface.Create (createInterface) where

import Documentation.Haddock.Doc (metaDocAppend)
import Haddock.Types
import Haddock.Options
import Haddock.GhcUtils
import Haddock.Utils
import Haddock.Convert
import Haddock.Interface.LexParseRn
import Haddock.Backends.Hyperlinker.Types
import Haddock.Backends.Hyperlinker.Ast as Hyperlinker
import Haddock.Backends.Hyperlinker.Parser as Hyperlinker

import qualified Data.Map as M
import Data.Map (Map)
import Data.List
import Data.Maybe
import Data.Monoid
import Data.Ord
import Control.Applicative
import Control.Arrow (second)
import Control.DeepSeq
import Control.Monad
import Data.Function (on)
import qualified Data.Foldable as F

import qualified Packages
import qualified Module
import qualified SrcLoc
import GHC
import HscTypes
import Name
import Bag
import RdrName
import TcRnTypes
import FastString (concatFS)
import qualified Outputable as O

-- | Use a 'TypecheckedModule' to produce an 'Interface'.
-- To do this, we need access to already processed modules in the topological
-- sort. That's what's in the 'IfaceMap'.
createInterface :: TypecheckedModule -> [Flag] -> IfaceMap -> InstIfaceMap -> ErrMsgGhc Interface
createInterface tm flags modMap instIfaceMap = do

  let ms             = pm_mod_summary . tm_parsed_module $ tm
      mi             = moduleInfo tm
      L _ hsm        = parsedSource tm
      !safety        = modInfoSafe mi
      mdl            = ms_mod ms
      dflags         = ms_hspp_opts ms
      !instances     = modInfoInstances mi
      !fam_instances = md_fam_insts md
      !exportedNames = modInfoExports mi

      (TcGblEnv {tcg_rdr_env = gre, tcg_warns = warnings}, md) = tm_internals_ tm

  -- The renamed source should always be available to us, but it's best
  -- to be on the safe side.
  (group_, mayExports, mayDocHeader) <-
    case renamedSource tm of
      Nothing -> do
        liftErrMsg $ tell [ "Warning: Renamed source is not available." ]
        return (emptyRnGroup, Nothing, Nothing)
      Just (x, _, y, z) -> return (x, y, z)

  opts0 <- liftErrMsg $ mkDocOpts (haddockOptions dflags) flags mdl
  let opts
        | Flag_IgnoreAllExports `elem` flags = OptIgnoreExports : opts0
        | otherwise = opts0

  (!info, mbDoc) <- liftErrMsg $ processModuleHeader dflags gre safety mayDocHeader

  let declsWithDocs = topDecls group_
      fixMap = mkFixMap group_
      (decls, _) = unzip declsWithDocs
      localInsts = filter (nameIsLocalOrFrom mdl) $  map getName instances
                                                  ++ map getName fam_instances
      -- Locations of all TH splices
      splices = [ l | L l (SpliceD _) <- hsmodDecls hsm ]

      maps@(!docMap, !argMap, !subMap, !declMap, _) =
        mkMaps dflags gre localInsts declsWithDocs

  let exports0 = fmap (reverse . map unLoc) mayExports
      exports
        | OptIgnoreExports `elem` opts = Nothing
        | otherwise = exports0
      warningMap = mkWarningMap dflags warnings gre exportedNames

  let allWarnings = M.unions (warningMap : map ifaceWarningMap (M.elems modMap))

  exportItems <- mkExportItems modMap mdl allWarnings gre exportedNames decls
                   maps fixMap splices exports instIfaceMap dflags

  let !visibleNames = mkVisibleNames maps exportItems opts

  -- Measure haddock documentation coverage.
  let prunedExportItems0 = pruneExportItems exportItems
      !haddockable = 1 + length exportItems -- module + exports
      !haddocked = (if isJust mbDoc then 1 else 0) + length prunedExportItems0
      !coverage = (haddockable, haddocked)

  -- Prune the export list to just those declarations that have
  -- documentation, if the 'prune' option is on.
  let prunedExportItems'
        | OptPrune `elem` opts = prunedExportItems0
        | otherwise = exportItems
      !prunedExportItems = seqList prunedExportItems' `seq` prunedExportItems'

  let !aliases =
        mkAliasMap dflags $ tm_renamed_source tm
      modWarn = moduleWarning dflags gre warnings

  tokenizedSrc <- mkMaybeTokenizedSrc flags tm

  return $! Interface {
    ifaceMod             = mdl
  , ifaceOrigFilename    = msHsFilePath ms
  , ifaceInfo            = info
  , ifaceDoc             = Documentation mbDoc modWarn
  , ifaceRnDoc           = Documentation Nothing Nothing
  , ifaceOptions         = opts
  , ifaceDocMap          = docMap
  , ifaceArgMap          = argMap
  , ifaceRnDocMap        = M.empty
  , ifaceRnArgMap        = M.empty
  , ifaceExportItems     = prunedExportItems
  , ifaceRnExportItems   = []
  , ifaceExports         = exportedNames
  , ifaceVisibleExports  = visibleNames
  , ifaceDeclMap         = declMap
  , ifaceSubMap          = subMap
  , ifaceFixMap          = fixMap
  , ifaceModuleAliases   = aliases
  , ifaceInstances       = instances
  , ifaceFamInstances    = fam_instances
  , ifaceOrphanInstances   = [] -- Filled in `attachInstances`
  , ifaceRnOrphanInstances = [] -- Filled in `renameInterface`
  , ifaceHaddockCoverage = coverage
  , ifaceWarningMap      = warningMap
  , ifaceTokenizedSrc    = tokenizedSrc
  }

mkAliasMap :: DynFlags -> Maybe RenamedSource -> M.Map Module ModuleName
mkAliasMap dflags mRenamedSource =
  case mRenamedSource of
    Nothing -> M.empty
    Just (_,impDecls,_,_) ->
      M.fromList $
      mapMaybe (\(SrcLoc.L _ impDecl) -> do
        alias <- ideclAs impDecl
        return $
          (lookupModuleDyn dflags
             (fmap Module.fsToPackageKey $
              ideclPkgQual impDecl)
             (case ideclName impDecl of SrcLoc.L _ name -> name),
           alias))
        impDecls

-- similar to GHC.lookupModule
lookupModuleDyn ::
  DynFlags -> Maybe PackageKey -> ModuleName -> Module
lookupModuleDyn _ (Just pkgId) mdlName =
  Module.mkModule pkgId mdlName
lookupModuleDyn dflags Nothing mdlName =
  case Packages.lookupModuleInAllPackages dflags mdlName of
    (m,_):_ -> m
    [] -> Module.mkModule Module.mainPackageKey mdlName


-------------------------------------------------------------------------------
-- Warnings
-------------------------------------------------------------------------------

mkWarningMap :: DynFlags -> Warnings -> GlobalRdrEnv -> [Name] -> WarningMap
mkWarningMap dflags warnings gre exps = case warnings of
  NoWarnings  -> M.empty
  WarnAll _   -> M.empty
  WarnSome ws ->
    let ws' = [ (n, w) | (occ, w) <- ws, elt <- lookupGlobalRdrEnv gre occ
              , let n = gre_name elt, n `elem` exps ]
    in M.fromList $ map (second $ parseWarning dflags gre) ws'

moduleWarning :: DynFlags -> GlobalRdrEnv -> Warnings -> Maybe (Doc Name)
moduleWarning _ _ NoWarnings = Nothing
moduleWarning _ _ (WarnSome _) = Nothing
moduleWarning dflags gre (WarnAll w) = Just $ parseWarning dflags gre w

parseWarning :: DynFlags -> GlobalRdrEnv -> WarningTxt -> Doc Name
parseWarning dflags gre w = force $ case w of
  DeprecatedTxt _ msg -> format "Deprecated: " (concatFS $ map unLoc msg)
  WarningTxt    _ msg -> format "Warning: "    (concatFS $ map unLoc msg)
  where
    format x xs = DocWarning . DocParagraph . DocAppend (DocString x)
                  . processDocString dflags gre $ HsDocString xs


-------------------------------------------------------------------------------
-- Doc options
--
-- Haddock options that are embedded in the source file
-------------------------------------------------------------------------------


mkDocOpts :: Maybe String -> [Flag] -> Module -> ErrMsgM [DocOption]
mkDocOpts mbOpts flags mdl = do
  opts <- case mbOpts of
    Just opts -> case words $ replace ',' ' ' opts of
      [] -> tell ["No option supplied to DOC_OPTION/doc_option"] >> return []
      xs -> liftM catMaybes (mapM parseOption xs)
    Nothing -> return []
  hm <- if Flag_HideModule (moduleString mdl) `elem` flags
        then return $ OptHide : opts
        else return opts
  if Flag_ShowExtensions (moduleString mdl) `elem` flags
    then return $ OptShowExtensions : hm
    else return hm


parseOption :: String -> ErrMsgM (Maybe DocOption)
parseOption "hide"            = return (Just OptHide)
parseOption "prune"           = return (Just OptPrune)
parseOption "ignore-exports"  = return (Just OptIgnoreExports)
parseOption "not-home"        = return (Just OptNotHome)
parseOption "show-extensions" = return (Just OptShowExtensions)
parseOption other = tell ["Unrecognised option: " ++ other] >> return Nothing


--------------------------------------------------------------------------------
-- Maps
--------------------------------------------------------------------------------


type Maps = (DocMap Name, ArgMap Name, SubMap, DeclMap, InstMap)

-- | Create 'Maps' by looping through the declarations. For each declaration,
-- find its names, its subordinates, and its doc strings. Process doc strings
-- into 'Doc's.
mkMaps :: DynFlags
       -> GlobalRdrEnv
       -> [Name]
       -> [(LHsDecl Name, [HsDocString])]
       -> Maps
mkMaps dflags gre instances decls =
  let (a, b, c, d) = unzip4 $ map mappings decls
  in (f' $ map (nubBy ((==) `on` fst)) a , f b, f c, f d, instanceMap)
  where
    f :: (Ord a, Monoid b) => [[(a, b)]] -> Map a b
    f = M.fromListWith (<>) . concat

    f' :: [[(Name, MDoc Name)]] -> Map Name (MDoc Name)
    f' = M.fromListWith metaDocAppend . concat

    mappings :: (LHsDecl Name, [HsDocString])
             -> ( [(Name, MDoc Name)]
                , [(Name, Map Int (MDoc Name))]
                , [(Name, [Name])]
                , [(Name,  [LHsDecl Name])]
                )
    mappings (ldecl, docStrs) =
      let L l decl = ldecl
          declDoc :: [HsDocString] -> Map Int HsDocString
                  -> (Maybe (MDoc Name), Map Int (MDoc Name))
          declDoc strs m =
            let doc' = processDocStrings dflags gre strs
                m' = M.map (processDocStringParas dflags gre) m
            in (doc', m')
          (doc, args) = declDoc docStrs (typeDocs decl)
          subs :: [(Name, [HsDocString], Map Int HsDocString)]
          subs = subordinates instanceMap decl
          (subDocs, subArgs) = unzip $ map (\(_, strs, m) -> declDoc strs m) subs
          ns = names l decl
          subNs = [ n | (n, _, _) <- subs ]
          dm = [ (n, d) | (n, Just d) <- zip ns (repeat doc) ++ zip subNs subDocs ]
          am = [ (n, args) | n <- ns ] ++ zip subNs subArgs
          sm = [ (n, subNs) | n <- ns ]
          cm = [ (n, [ldecl]) | n <- ns ++ subNs ]
      in seqList ns `seq`
          seqList subNs `seq`
          doc `seq`
          seqList subDocs `seq`
          seqList subArgs `seq`
          (dm, am, sm, cm)

    instanceMap :: Map SrcSpan Name
    instanceMap = M.fromList [ (getSrcSpan n, n) | n <- instances ]

    names :: SrcSpan -> HsDecl Name -> [Name]
    names l (InstD d) = maybeToList (M.lookup loc instanceMap) -- See note [2].
      where loc = case d of
              TyFamInstD _ -> l -- The CoAx's loc is the whole line, but only for TFs
              _ -> getInstLoc d
    names _ decl = getMainDeclBinder decl

-- Note [2]:
------------
-- We relate ClsInsts to InstDecls using the SrcSpans buried inside them.
-- That should work for normal user-written instances (from looking at GHC
-- sources). We can assume that commented instances are user-written.
-- This lets us relate Names (from ClsInsts) to comments (associated
-- with InstDecls).


--------------------------------------------------------------------------------
-- Declarations
--------------------------------------------------------------------------------


-- | Get all subordinate declarations inside a declaration, and their docs.
subordinates :: InstMap -> HsDecl Name -> [(Name, [HsDocString], Map Int HsDocString)]
subordinates instMap decl = case decl of
  InstD (ClsInstD d) -> do
    DataFamInstDecl { dfid_tycon = L l _
                    , dfid_defn = def    } <- unLoc <$> cid_datafam_insts d
    [ (n, [], M.empty) | Just n <- [M.lookup l instMap] ] ++ dataSubs def

  InstD (DataFamInstD d)  -> dataSubs (dfid_defn d)
  TyClD d | isClassDecl d -> classSubs d
          | isDataDecl  d -> dataSubs (tcdDataDefn d)
  _ -> []
  where
    classSubs dd = [ (name, doc, typeDocs d) | (L _ d, doc) <- classDecls dd
                   , name <- getMainDeclBinder d, not (isValD d)
                   ]
    dataSubs dd = constrs ++ fields
      where
        cons = map unL $ (dd_cons dd)
        constrs = [ (unL cname, maybeToList $ fmap unL $ con_doc c, M.empty)
                  | c <- cons, cname <- con_names c ]
        fields  = [ (unL n, maybeToList $ fmap unL doc, M.empty)
                  | RecCon flds <- map con_details cons
                  , L _ (ConDeclField ns _ doc) <- (unLoc flds)
                  , n <- ns ]

-- | Extract function argument docs from inside types.
typeDocs :: HsDecl Name -> Map Int HsDocString
typeDocs d =
  let docs = go 0 in
  case d of
    SigD (TypeSig _ ty _) -> docs (unLoc ty)
    SigD (PatSynSig _ _ req prov ty) ->
        let allTys = ty : concat [ unLoc req, unLoc prov ]
        in F.foldMap (docs . unLoc) allTys
    ForD (ForeignImport _ ty _ _) -> docs (unLoc ty)
    TyClD (SynDecl { tcdRhs = ty }) -> docs (unLoc ty)
    _ -> M.empty
  where
    go n (HsForAllTy _ _ _ _ ty) = go n (unLoc ty)
    go n (HsFunTy (L _ (HsDocTy _ (L _ x))) (L _ ty)) = M.insert n x $ go (n+1) ty
    go n (HsFunTy _ ty) = go (n+1) (unLoc ty)
    go n (HsDocTy _ (L _ doc)) = M.singleton n doc
    go _ _ = M.empty


-- | All the sub declarations of a class (that we handle), ordered by
-- source location, with documentation attached if it exists.
classDecls :: TyClDecl Name -> [(LHsDecl Name, [HsDocString])]
classDecls class_ = filterDecls . collectDocs . sortByLoc $ decls
  where
    decls = docs ++ defs ++ sigs ++ ats
    docs  = mkDecls tcdDocs DocD class_
    defs  = mkDecls (bagToList . tcdMeths) ValD class_
    sigs  = mkDecls tcdSigs SigD class_
    ats   = mkDecls tcdATs (TyClD . FamDecl) class_


-- | The top-level declarations of a module that we care about,
-- ordered by source location, with documentation attached if it exists.
topDecls :: HsGroup Name -> [(LHsDecl Name, [HsDocString])]
topDecls = filterClasses . filterDecls . collectDocs . sortByLoc . ungroup

-- | Extract a map of fixity declarations only
mkFixMap :: HsGroup Name -> FixMap
mkFixMap group_ = M.fromList [ (n,f)
                             | L _ (FixitySig ns f) <- hs_fixds group_,
                               L _ n <- ns ]


-- | Take all declarations except pragmas, infix decls, rules from an 'HsGroup'.
ungroup :: HsGroup Name -> [LHsDecl Name]
ungroup group_ =
  mkDecls (tyClGroupConcat . hs_tyclds) TyClD  group_ ++
  mkDecls hs_derivds             DerivD group_ ++
  mkDecls hs_defds               DefD   group_ ++
  mkDecls hs_fords               ForD   group_ ++
  mkDecls hs_docs                DocD   group_ ++
  mkDecls hs_instds              InstD  group_ ++
  mkDecls (typesigs . hs_valds)  SigD   group_ ++
  mkDecls (valbinds . hs_valds)  ValD   group_
  where
    typesigs (ValBindsOut _ sigs) = filter isVanillaLSig sigs
    typesigs _ = error "expected ValBindsOut"

    valbinds (ValBindsOut binds _) = concatMap bagToList . snd . unzip $ binds
    valbinds _ = error "expected ValBindsOut"


-- | Take a field of declarations from a data structure and create HsDecls
-- using the given constructor
mkDecls :: (a -> [Located b]) -> (b -> c) -> a -> [Located c]
mkDecls field con struct = [ L loc (con decl) | L loc decl <- field struct ]


-- | Sort by source location
sortByLoc :: [Located a] -> [Located a]
sortByLoc = sortBy (comparing getLoc)


--------------------------------------------------------------------------------
-- Filtering of declarations
--
-- We filter out declarations that we don't intend to handle later.
--------------------------------------------------------------------------------


-- | Filter out declarations that we don't handle in Haddock
filterDecls :: [(LHsDecl a, doc)] -> [(LHsDecl a, doc)]
filterDecls = filter (isHandled . unL . fst)
  where
    isHandled (ForD (ForeignImport {})) = True
    isHandled (TyClD {}) = True
    isHandled (InstD {}) = True
    isHandled (SigD d) = isVanillaLSig (reL d)
    isHandled (ValD _) = True
    -- we keep doc declarations to be able to get at named docs
    isHandled (DocD _) = True
    isHandled _ = False


-- | Go through all class declarations and filter their sub-declarations
filterClasses :: [(LHsDecl a, doc)] -> [(LHsDecl a, doc)]
filterClasses decls = [ if isClassD d then (L loc (filterClass d), doc) else x
                      | x@(L loc d, doc) <- decls ]
  where
    filterClass (TyClD c) =
      TyClD $ c { tcdSigs = filter (liftA2 (||) isVanillaLSig isMinimalLSig) $ tcdSigs c }
    filterClass _ = error "expected TyClD"


--------------------------------------------------------------------------------
-- Collect docs
--
-- To be able to attach the right Haddock comment to the right declaration,
-- we sort the declarations by their SrcLoc and "collect" the docs for each
-- declaration.
--------------------------------------------------------------------------------


-- | Collect docs and attach them to the right declarations.
collectDocs :: [LHsDecl a] -> [(LHsDecl a, [HsDocString])]
collectDocs = go Nothing []
  where
    go Nothing _ [] = []
    go (Just prev) docs [] = finished prev docs []
    go prev docs (L _ (DocD (DocCommentNext str)) : ds)
      | Nothing <- prev = go Nothing (str:docs) ds
      | Just decl <- prev = finished decl docs (go Nothing [str] ds)
    go prev docs (L _ (DocD (DocCommentPrev str)) : ds) = go prev (str:docs) ds
    go Nothing docs (d:ds) = go (Just d) docs ds
    go (Just prev) docs (d:ds) = finished prev docs (go (Just d) [] ds)

    finished decl docs rest = (decl, reverse docs) : rest


-- | Build the list of items that will become the documentation, from the
-- export list.  At this point, the list of ExportItems is in terms of
-- original names.
--
-- We create the export items even if the module is hidden, since they
-- might be useful when creating the export items for other modules.
mkExportItems
  :: IfaceMap
  -> Module             -- this module
  -> WarningMap
  -> GlobalRdrEnv
  -> [Name]             -- exported names (orig)
  -> [LHsDecl Name]
  -> Maps
  -> FixMap
  -> [SrcSpan]          -- splice locations
  -> Maybe [IE Name]
  -> InstIfaceMap
  -> DynFlags
  -> ErrMsgGhc [ExportItem Name]
mkExportItems
  modMap thisMod warnings gre exportedNames decls
  maps@(docMap, argMap, subMap, declMap, instMap) fixMap splices optExports instIfaceMap dflags =
  case optExports of
    Nothing -> fullModuleContents dflags warnings gre maps fixMap splices decls
    Just exports -> liftM concat $ mapM lookupExport exports
  where
    lookupExport (IEVar (L _ x))         = declWith x
    lookupExport (IEThingAbs (L _ t))    = declWith t
    lookupExport (IEThingAll (L _ t))    = declWith t
    lookupExport (IEThingWith (L _ t) _) = declWith t
    lookupExport (IEModuleContents (L _ m)) =
      moduleExports thisMod m dflags warnings gre exportedNames decls modMap instIfaceMap maps fixMap splices
    lookupExport (IEGroup lev docStr)  = return $
      return . ExportGroup lev "" $ processDocString dflags gre docStr

    lookupExport (IEDoc docStr)        = return $
      return . ExportDoc $ processDocStringParas dflags gre docStr

    lookupExport (IEDocNamed str)      = liftErrMsg $
      findNamedDoc str [ unL d | d <- decls ] >>= return . \case
        Nothing -> []
        Just doc -> return . ExportDoc $ processDocStringParas dflags gre doc

    declWith :: Name -> ErrMsgGhc [ ExportItem Name ]
    declWith t =
      case findDecl t of
        ([L l (ValD _)], (doc, _)) -> do
          -- Top-level binding without type signature
          export <- hiValExportItem dflags t l doc (l `elem` splices) $ M.lookup t fixMap
          return [export]
        (ds, docs_) | decl : _ <- filter (not . isValD . unLoc) ds ->
          let declNames = getMainDeclBinder (unL decl)
          in case () of
            _
              -- temp hack: we filter out separately exported ATs, since we haven't decided how
              -- to handle them yet. We should really give an warning message also, and filter the
              -- name out in mkVisibleNames...
              | t `elem` declATs (unL decl)        -> return []

              -- We should not show a subordinate by itself if any of its
              -- parents is also exported. See note [1].
              | t `notElem` declNames,
                Just p <- find isExported (parents t $ unL decl) ->
                do liftErrMsg $ tell [
                     "Warning: " ++ moduleString thisMod ++ ": " ++
                     pretty dflags (nameOccName t) ++ " is exported separately but " ++
                     "will be documented under " ++ pretty dflags (nameOccName p) ++
                     ". Consider exporting it together with its parent(s)" ++
                     " for code clarity." ]
                   return []

              -- normal case
              | otherwise -> case decl of
                  -- A single signature might refer to many names, but we
                  -- create an export item for a single name only.  So we
                  -- modify the signature to contain only that single name.
                  L loc (SigD sig) ->
                    -- fromJust is safe since we already checked in guards
                    -- that 't' is a name declared in this declaration.
                    let newDecl = L loc . SigD . fromJust $ filterSigNames (== t) sig
                    in return [ mkExportDecl t newDecl docs_ ]

                  L loc (TyClD cl@ClassDecl{}) -> do
                    mdef <- liftGhcToErrMsgGhc $ minimalDef t
                    let sig = maybeToList $ fmap (noLoc . MinimalSig mempty . fmap noLoc) mdef
                    return [ mkExportDecl t
                      (L loc $ TyClD cl { tcdSigs = sig ++ tcdSigs cl }) docs_ ]

                  _ -> return [ mkExportDecl t decl docs_ ]

        -- Declaration from another package
        ([], _) -> do
          mayDecl <- hiDecl dflags t
          case mayDecl of
            Nothing -> return [ ExportNoDecl t [] ]
            Just decl ->
              -- We try to get the subs and docs
              -- from the installed .haddock file for that package.
              case M.lookup (nameModule t) instIfaceMap of
                Nothing -> do
                   liftErrMsg $ tell
                      ["Warning: Couldn't find .haddock for export " ++ pretty dflags t]
                   let subs_ = [ (n, noDocForDecl) | (n, _, _) <- subordinates instMap (unLoc decl) ]
                   return [ mkExportDecl t decl (noDocForDecl, subs_) ]
                Just iface ->
                   return [ mkExportDecl t decl (lookupDocs t warnings (instDocMap iface) (instArgMap iface) (instSubMap iface)) ]

        _ -> return []


    mkExportDecl :: Name -> LHsDecl Name -> (DocForDecl Name, [(Name, DocForDecl Name)]) -> ExportItem Name
    mkExportDecl name decl (doc, subs) = decl'
      where
        decl' = ExportDecl (restrictTo sub_names (extractDecl name mdl decl)) doc subs' [] fixities False
        mdl = nameModule name
        subs' = filter (isExported . fst) subs
        sub_names = map fst subs'
        fixities = [ (n, f) | n <- name:sub_names, Just f <- [M.lookup n fixMap] ]


    isExported = (`elem` exportedNames)


    findDecl :: Name -> ([LHsDecl Name], (DocForDecl Name, [(Name, DocForDecl Name)]))
    findDecl n
      | m == thisMod, Just ds <- M.lookup n declMap =
          (ds, lookupDocs n warnings docMap argMap subMap)
      | Just iface <- M.lookup m modMap, Just ds <- M.lookup n (ifaceDeclMap iface) =
          (ds, lookupDocs n warnings (ifaceDocMap iface) (ifaceArgMap iface) (ifaceSubMap iface))
      | otherwise = ([], (noDocForDecl, []))
      where
        m = nameModule n


hiDecl :: DynFlags -> Name -> ErrMsgGhc (Maybe (LHsDecl Name))
hiDecl dflags t = do
  mayTyThing <- liftGhcToErrMsgGhc $ lookupName t
  case mayTyThing of
    Nothing -> do
      liftErrMsg $ tell ["Warning: Not found in environment: " ++ pretty dflags t]
      return Nothing
    Just x -> case tyThingToLHsDecl x of
      Left m -> liftErrMsg (tell [bugWarn m]) >> return Nothing
      Right (m, t') -> liftErrMsg (tell $ map bugWarn m)
                      >> return (Just $ noLoc t')
    where
      warnLine x = O.text "haddock-bug:" O.<+> O.text x O.<>
                   O.comma O.<+> O.quotes (O.ppr t) O.<+>
                   O.text "-- Please report this on Haddock issue tracker!"
      bugWarn = O.showSDoc dflags . warnLine

-- | This function is called for top-level bindings without type signatures.
-- It gets the type signature from GHC and that means it's not going to
-- have a meaningful 'SrcSpan'. So we pass down 'SrcSpan' for the
-- declaration and use it instead - 'nLoc' here.
hiValExportItem :: DynFlags -> Name -> SrcSpan -> DocForDecl Name -> Bool
                -> Maybe Fixity -> ErrMsgGhc (ExportItem Name)
hiValExportItem dflags name nLoc doc splice fixity = do
  mayDecl <- hiDecl dflags name
  case mayDecl of
    Nothing -> return (ExportNoDecl name [])
    Just decl -> return (ExportDecl (fixSpan decl) doc [] [] fixities splice)
  where
    fixSpan (L l t) = L (SrcLoc.combineSrcSpans l nLoc) t
    fixities = case fixity of
      Just f  -> [(name, f)]
      Nothing -> []


-- | Lookup docs for a declaration from maps.
lookupDocs :: Name -> WarningMap -> DocMap Name -> ArgMap Name -> SubMap
           -> (DocForDecl Name, [(Name, DocForDecl Name)])
lookupDocs n warnings docMap argMap subMap =
  let lookupArgDoc x = M.findWithDefault M.empty x argMap in
  let doc = (lookupDoc n, lookupArgDoc n) in
  let subs = M.findWithDefault [] n subMap in
  let subDocs = [ (s, (lookupDoc s, lookupArgDoc s)) | s <- subs ] in
  (doc, subDocs)
  where
    lookupDoc name = Documentation (M.lookup name docMap) (M.lookup name warnings)


-- | Return all export items produced by an exported module. That is, we're
-- interested in the exports produced by \"module B\" in such a scenario:
--
-- > module A (module B) where
-- > import B (...) hiding (...)
--
-- There are three different cases to consider:
--
-- 1) B is hidden, in which case we return all its exports that are in scope in A.
-- 2) B is visible, but not all its exports are in scope in A, in which case we
--    only return those that are.
-- 3) B is visible and all its exports are in scope, in which case we return
--    a single 'ExportModule' item.
moduleExports :: Module           -- ^ Module A
              -> ModuleName       -- ^ The real name of B, the exported module
              -> DynFlags         -- ^ The flags used when typechecking A
              -> WarningMap
              -> GlobalRdrEnv     -- ^ The renaming environment used for A
              -> [Name]           -- ^ All the exports of A
              -> [LHsDecl Name]   -- ^ All the declarations in A
              -> IfaceMap         -- ^ Already created interfaces
              -> InstIfaceMap     -- ^ Interfaces in other packages
              -> Maps
              -> FixMap
              -> [SrcSpan]        -- ^ Locations of all TH splices
              -> ErrMsgGhc [ExportItem Name] -- ^ Resulting export items
moduleExports thisMod expMod dflags warnings gre _exports decls ifaceMap instIfaceMap maps fixMap splices
  | m == thisMod = fullModuleContents dflags warnings gre maps fixMap splices decls
  | otherwise =
    case M.lookup m ifaceMap of
      Just iface
        | OptHide `elem` ifaceOptions iface -> return (ifaceExportItems iface)
        | otherwise -> return [ ExportModule m ]

      Nothing -> -- We have to try to find it in the installed interfaces
                 -- (external packages).
        case M.lookup expMod (M.mapKeys moduleName instIfaceMap) of
          Just iface -> return [ ExportModule (instMod iface) ]
          Nothing -> do
            liftErrMsg $
              tell ["Warning: " ++ pretty dflags thisMod ++ ": Could not find " ++
                    "documentation for exported module: " ++ pretty dflags expMod]
            return []
  where
    m = mkModule packageKey expMod
    packageKey = modulePackageKey thisMod


-- Note [1]:
------------
-- It is unnecessary to document a subordinate by itself at the top level if
-- any of its parents is also documented. Furthermore, if the subordinate is a
-- record field or a class method, documenting it under its parent
-- indicates its special status.
--
-- A user might expect that it should show up separately, so we issue a
-- warning. It's a fine opportunity to also tell the user she might want to
-- export the subordinate through the parent export item for clarity.
--
-- The code removes top-level subordinates also when the parent is exported
-- through a 'module' export. I think that is fine.
--
-- (For more information, see Trac #69)


fullModuleContents :: DynFlags -> WarningMap -> GlobalRdrEnv -> Maps -> FixMap -> [SrcSpan]
                   -> [LHsDecl Name] -> ErrMsgGhc [ExportItem Name]
fullModuleContents dflags warnings gre (docMap, argMap, subMap, declMap, instMap) fixMap splices decls =
  liftM catMaybes $ mapM mkExportItem (expandSig decls)
  where
    -- A type signature can have multiple names, like:
    --   foo, bar :: Types..
    --
    -- We go through the list of declarations and expand type signatures, so
    -- that every type signature has exactly one name!
    expandSig :: [LHsDecl name] -> [LHsDecl name]
    expandSig = foldr f []
      where
        f :: LHsDecl name -> [LHsDecl name] -> [LHsDecl name]
        f (L l (SigD (TypeSig    names t nwcs)))     xs = foldr (\n acc -> L l (SigD (TypeSig    [n] t nwcs))     : acc) xs names
        f (L l (SigD (GenericSig names t)))          xs = foldr (\n acc -> L l (SigD (GenericSig [n] t))          : acc) xs names
        f x xs = x : xs

    mkExportItem :: LHsDecl Name -> ErrMsgGhc (Maybe (ExportItem Name))
    mkExportItem (L _ (DocD (DocGroup lev docStr))) = do
      return . Just . ExportGroup lev "" $ processDocString dflags gre docStr
    mkExportItem (L _ (DocD (DocCommentNamed _ docStr))) = do
      return . Just . ExportDoc $ processDocStringParas dflags gre docStr
    mkExportItem (L l (ValD d))
      | name:_ <- collectHsBindBinders d, Just [L _ (ValD _)] <- M.lookup name declMap =
          -- Top-level binding without type signature.
          let (doc, _) = lookupDocs name warnings docMap argMap subMap in
          fmap Just (hiValExportItem dflags name l doc (l `elem` splices) $ M.lookup name fixMap)
      | otherwise = return Nothing
    mkExportItem decl@(L l (InstD d))
      | Just name <- M.lookup (getInstLoc d) instMap =
        let (doc, subs) = lookupDocs name warnings docMap argMap subMap in
        return $ Just (ExportDecl decl doc subs [] (fixities name subs) (l `elem` splices))
    mkExportItem (L l (TyClD cl@ClassDecl{ tcdLName = L _ name, tcdSigs = sigs })) = do
      mdef <- liftGhcToErrMsgGhc $ minimalDef name
      let sig = maybeToList $ fmap (noLoc . MinimalSig mempty . fmap noLoc) mdef
      expDecl (L l (TyClD cl { tcdSigs = sig ++ sigs })) l name
    mkExportItem decl@(L l d)
      | name:_ <- getMainDeclBinder d = expDecl decl l name
      | otherwise = return Nothing

    fixities name subs = [ (n,f) | n <- name : map fst subs
                                 , Just f <- [M.lookup n fixMap] ]

    expDecl decl l name = return $ Just (ExportDecl decl doc subs [] (fixities name subs) (l `elem` splices))
      where (doc, subs) = lookupDocs name warnings docMap argMap subMap


-- | Sometimes the declaration we want to export is not the "main" declaration:
-- it might be an individual record selector or a class method.  In these
-- cases we have to extract the required declaration (and somehow cobble
-- together a type signature for it...).
extractDecl :: Name -> Module -> LHsDecl Name -> LHsDecl Name
extractDecl name mdl decl
  | name `elem` getMainDeclBinder (unLoc decl) = decl
  | otherwise  =
    case unLoc decl of
      TyClD d@ClassDecl {} ->
        let matches = [ sig | sig <- tcdSigs d, name `elem` sigName sig,
                        isVanillaLSig sig ] -- TODO: document fixity
        in case matches of
          [s0] -> let (n, tyvar_names) = (tcdName d, getTyVars d)
                      L pos sig = extractClassDecl n tyvar_names s0
                  in L pos (SigD sig)
          _ -> error "internal: extractDecl (ClassDecl)"
      TyClD d@DataDecl {} ->
        let (n, tyvar_names) = (tcdName d, map toTypeNoLoc $ getTyVars d)
        in SigD <$> extractRecSel name mdl n tyvar_names (dd_cons (tcdDataDefn d))
      InstD (DataFamInstD DataFamInstDecl { dfid_tycon = L _ n
                                          , dfid_pats = HsWB { hswb_cts = tys }
                                          , dfid_defn = defn }) ->
        SigD <$> extractRecSel name mdl n tys (dd_cons defn)
      InstD (ClsInstD ClsInstDecl { cid_datafam_insts = insts }) ->
        let matches = [ d | L _ d <- insts
                          , L _ ConDecl { con_details = RecCon rec } <- dd_cons (dfid_defn d)
                          , ConDeclField { cd_fld_names = ns } <- map unLoc (unLoc rec)
                          , L _ n <- ns
                          , n == name
                      ]
        in case matches of
          [d0] -> extractDecl name mdl (noLoc . InstD $ DataFamInstD d0)
          _ -> error "internal: extractDecl (ClsInstD)"
      _ -> error "internal: extractDecl"
  where
    getTyVars = hsLTyVarLocNames . tyClDeclTyVars


toTypeNoLoc :: Located Name -> LHsType Name
toTypeNoLoc = noLoc . HsTyVar . unLoc


extractClassDecl :: Name -> [Located Name] -> LSig Name -> LSig Name
extractClassDecl c tvs0 (L pos (TypeSig lname ltype _)) = case ltype of
  L _ (HsForAllTy expl _ tvs (L _ preds) ty) ->
    L pos (TypeSig lname (noLoc (HsForAllTy expl Nothing tvs (lctxt preds) ty)) [])
  _ -> L pos (TypeSig lname (noLoc (HsForAllTy Implicit Nothing emptyHsQTvs (lctxt []) ltype)) [])
  where
    lctxt = noLoc . ctxt
    ctxt preds = nlHsTyConApp c (map toTypeNoLoc tvs0) : preds
extractClassDecl _ _ _ = error "extractClassDecl: unexpected decl"


extractRecSel :: Name -> Module -> Name -> [LHsType Name] -> [LConDecl Name]
              -> LSig Name
extractRecSel _ _ _ _ [] = error "extractRecSel: selector not found"

extractRecSel nm mdl t tvs (L _ con : rest) =
  case con_details con of
    RecCon (L _ fields) | ((n,L _ (ConDeclField _nn ty _)) : _) <- matching_fields fields ->
      L (getLoc n) (TypeSig [noLoc nm] (noLoc (HsFunTy data_ty (getBangType ty))) [])
    _ -> extractRecSel nm mdl t tvs rest
 where
  matching_fields flds = [ (n,f) | f@(L _ (ConDeclField ns _ _)) <- flds, n <- ns, unLoc n == nm ]
  data_ty
    | ResTyGADT _ ty <- con_res con = ty
    | otherwise = foldl' (\x y -> noLoc (HsAppTy x y)) (noLoc (HsTyVar t)) tvs


-- | Keep export items with docs.
pruneExportItems :: [ExportItem Name] -> [ExportItem Name]
pruneExportItems = filter hasDoc
  where
    hasDoc (ExportDecl{expItemMbDoc = (Documentation d _, _)}) = isJust d
    hasDoc _ = True


mkVisibleNames :: Maps -> [ExportItem Name] -> [DocOption] -> [Name]
mkVisibleNames (_, _, _, _, instMap) exports opts
  | OptHide `elem` opts = []
  | otherwise = let ns = concatMap exportName exports
                in seqList ns `seq` ns
  where
    exportName e@ExportDecl {} = name ++ subs
      where subs = map fst (expItemSubDocs e)
            name = case unLoc $ expItemDecl e of
              InstD d -> maybeToList $ M.lookup (getInstLoc d) instMap
              decl    -> getMainDeclBinder decl
    exportName ExportNoDecl {} = [] -- we don't count these as visible, since
                                    -- we don't want links to go to them.
    exportName _ = []

seqList :: [a] -> ()
seqList [] = ()
seqList (x : xs) = x `seq` seqList xs

mkMaybeTokenizedSrc :: [Flag] -> TypecheckedModule
                    -> ErrMsgGhc (Maybe [RichToken])
mkMaybeTokenizedSrc flags tm
    | Flag_HyperlinkedSource `elem` flags = case renamedSource tm of
        Just src -> do
            tokens <- liftGhcToErrMsgGhc . liftIO $ mkTokenizedSrc summary src
            return $ Just tokens
        Nothing -> do
            liftErrMsg . tell . pure $ concat
                [ "Warning: Cannot hyperlink module \""
                , moduleNameString . ms_mod_name $ summary
                , "\" because renamed source is not available"
                ]
            return Nothing
    | otherwise = return Nothing
  where
    summary = pm_mod_summary . tm_parsed_module $ tm

mkTokenizedSrc :: ModSummary -> RenamedSource -> IO [RichToken]
mkTokenizedSrc ms src =
    Hyperlinker.enrich src . Hyperlinker.parse <$> rawSrc
  where
    rawSrc = readFile $ msHsFilePath ms

-- | Find a stand-alone documentation comment by its name.
findNamedDoc :: String -> [HsDecl Name] -> ErrMsgM (Maybe HsDocString)
findNamedDoc name = search
  where
    search [] = do
      tell ["Cannot find documentation for: $" ++ name]
      return Nothing
    search (DocD (DocCommentNamed name' doc) : rest)
      | name == name' = return (Just doc)
      | otherwise = search rest
    search (_other_decl : rest) = search rest