GHC/Unit/Finder.hs

    {-
    (c) The University of Glasgow, 2000-2006

    -}

    {-# LANGUAGE CPP #-}
    {-# LANGUAGE FlexibleContexts #-}

    -- | Module finder
    module GHC.Unit.Finder (
        FindResult(..),
        InstalledFindResult(..),
        FinderCache,
        flushFinderCaches,
        findImportedModule,
        findPluginModule,
        findExactModule,
        findHomeModule,
        findExposedPackageModule,
        mkHomeModLocation,
        mkHomeModLocation2,
        mkHiOnlyModLocation,
        mkHiPath,
        mkObjPath,
        addHomeModuleToFinder,
        uncacheModule,
        mkStubPaths,

        findObjectLinkableMaybe,
        findObjectLinkable,

      ) where

    #include "HsVersions.h"

    import GHC.Prelude

    import GHC.Driver.Env
    import GHC.Driver.Session

    import GHC.Platform.Ways

    import GHC.Builtin.Names ( gHC_PRIM )

    import GHC.Unit.Types
    import GHC.Unit.Module
    import GHC.Unit.Home
    import GHC.Unit.State
    import GHC.Unit.Finder.Types

    import GHC.Data.FastString
    import GHC.Data.Maybe    ( expectJust )
    import qualified GHC.Data.ShortText as ST

    import GHC.Utils.Misc
    import GHC.Utils.Outputable as Outputable
    import GHC.Utils.Panic

    import GHC.Linker.Types

    import Data.IORef       ( IORef, readIORef, atomicModifyIORef' )
    import System.Directory
    import System.FilePath
    import Control.Monad
    import Data.Time

    type FileExt = String   -- Filename extension
    type BaseName = String  -- Basename of file

    -- -----------------------------------------------------------------------------
    -- The Finder

    -- The Finder provides a thin filesystem abstraction to the rest of
    -- the compiler.  For a given module, it can tell you where the
    -- source, interface, and object files for that module live.

    -- It does *not* know which particular package a module lives in.  Use
    -- Packages.lookupModuleInAllUnits for that.

    -- -----------------------------------------------------------------------------
    -- The finder's cache

    -- remove all the home modules from the cache; package modules are
    -- assumed to not move around during a session.
    flushFinderCaches :: HscEnv -> IO ()
    flushFinderCaches hsc_env =
      atomicModifyIORef' fc_ref $ \fm -> (filterInstalledModuleEnv is_ext fm, ())
     where
            fc_ref       = hsc_FC hsc_env
            home_unit    = hsc_home_unit hsc_env
            is_ext mod _ = not (isHomeInstalledModule home_unit mod)

    addToFinderCache :: IORef FinderCache -> InstalledModule -> InstalledFindResult -> IO ()
    addToFinderCache ref key val =
      atomicModifyIORef' ref $ \c -> (extendInstalledModuleEnv c key val, ())

    removeFromFinderCache :: IORef FinderCache -> InstalledModule -> IO ()
    removeFromFinderCache ref key =
      atomicModifyIORef' ref $ \c -> (delInstalledModuleEnv c key, ())

    lookupFinderCache :: IORef FinderCache -> InstalledModule -> IO (Maybe InstalledFindResult)
    lookupFinderCache ref key = do
       c <- readIORef ref
       return $! lookupInstalledModuleEnv c key

    -- -----------------------------------------------------------------------------
    -- The three external entry points

    -- | Locate a module that was imported by the user.  We have the
    -- module's name, and possibly a package name.  Without a package
    -- name, this function will use the search path and the known exposed
    -- packages to find the module, if a package is specified then only
    -- that package is searched for the module.

    findImportedModule :: HscEnv -> ModuleName -> Maybe FastString -> IO FindResult
    findImportedModule hsc_env mod_name mb_pkg =
      case mb_pkg of
            Nothing                        -> unqual_import
            Just pkg | pkg == fsLit "this" -> home_import -- "this" is special
                     | otherwise           -> pkg_import
      where
        home_import   = findHomeModule hsc_env mod_name

        pkg_import    = findExposedPackageModule hsc_env mod_name mb_pkg

        unqual_import = home_import
                        `orIfNotFound`
                        findExposedPackageModule hsc_env mod_name Nothing

    -- | Locate a plugin module requested by the user, for a compiler
    -- plugin.  This consults the same set of exposed packages as
    -- 'findImportedModule', unless @-hide-all-plugin-packages@ or
    -- @-plugin-package@ are specified.
    findPluginModule :: HscEnv -> ModuleName -> IO FindResult
    findPluginModule hsc_env mod_name =
      findHomeModule hsc_env mod_name
      `orIfNotFound`
      findExposedPluginPackageModule hsc_env mod_name

    -- | Locate a specific 'Module'.  The purpose of this function is to
    -- create a 'ModLocation' for a given 'Module', that is to find out
    -- where the files associated with this module live.  It is used when
    -- reading the interface for a module mentioned by another interface,
    -- for example (a "system import").

    findExactModule :: HscEnv -> InstalledModule -> IO InstalledFindResult
    findExactModule hsc_env mod =
        let home_unit = hsc_home_unit hsc_env
        in if isHomeInstalledModule home_unit mod
           then findInstalledHomeModule hsc_env (moduleName mod)
           else findPackageModule hsc_env mod

    -- -----------------------------------------------------------------------------
    -- Helpers

    -- | Given a monadic actions @this@ and @or_this@, first execute
    -- @this@.  If the returned 'FindResult' is successful, return
    -- it; otherwise, execute @or_this@.  If both failed, this function
    -- also combines their failure messages in a reasonable way.
    orIfNotFound :: Monad m => m FindResult -> m FindResult -> m FindResult
    orIfNotFound this or_this = do
      res <- this
      case res of
        NotFound { fr_paths = paths1, fr_mods_hidden = mh1
                 , fr_pkgs_hidden = ph1, fr_unusables = u1, fr_suggestions = s1 }
         -> do res2 <- or_this
               case res2 of
                 NotFound { fr_paths = paths2, fr_pkg = mb_pkg2, fr_mods_hidden = mh2
                          , fr_pkgs_hidden = ph2, fr_unusables = u2
                          , fr_suggestions = s2 }
                  -> return (NotFound { fr_paths = paths1 ++ paths2
                                      , fr_pkg = mb_pkg2 -- snd arg is the package search
                                      , fr_mods_hidden = mh1 ++ mh2
                                      , fr_pkgs_hidden = ph1 ++ ph2
                                      , fr_unusables = u1 ++ u2
                                      , fr_suggestions = s1  ++ s2 })
                 _other -> return res2
        _other -> return res

    -- | Helper function for 'findHomeModule': this function wraps an IO action
    -- which would look up @mod_name@ in the file system (the home package),
    -- and first consults the 'hsc_FC' cache to see if the lookup has already
    -- been done.  Otherwise, do the lookup (with the IO action) and save
    -- the result in the finder cache and the module location cache (if it
    -- was successful.)
    homeSearchCache :: HscEnv -> ModuleName -> IO InstalledFindResult -> IO InstalledFindResult
    homeSearchCache hsc_env mod_name do_this = do
      let home_unit = hsc_home_unit hsc_env
          mod = mkHomeInstalledModule home_unit mod_name
      modLocationCache hsc_env mod do_this

    findExposedPackageModule :: HscEnv -> ModuleName -> Maybe FastString
                             -> IO FindResult
    findExposedPackageModule hsc_env mod_name mb_pkg
      = findLookupResult hsc_env
      $ lookupModuleWithSuggestions
            (hsc_units hsc_env) mod_name mb_pkg

    findExposedPluginPackageModule :: HscEnv -> ModuleName
                                   -> IO FindResult
    findExposedPluginPackageModule hsc_env mod_name
      = findLookupResult hsc_env
      $ lookupPluginModuleWithSuggestions
            (hsc_units hsc_env) mod_name Nothing

    findLookupResult :: HscEnv -> LookupResult -> IO FindResult
    findLookupResult hsc_env r = case r of
         LookupFound m pkg_conf -> do
           let im = fst (getModuleInstantiation m)
           r' <- findPackageModule_ hsc_env im (fst pkg_conf)
           case r' of
            -- TODO: ghc -M is unlikely to do the right thing
            -- with just the location of the thing that was
            -- instantiated; you probably also need all of the
            -- implicit locations from the instances
            InstalledFound loc   _ -> return (Found loc m)
            InstalledNoPackage   _ -> return (NoPackage (moduleUnit m))
            InstalledNotFound fp _ -> return (NotFound{ fr_paths = fp, fr_pkg = Just (moduleUnit m)
                                             , fr_pkgs_hidden = []
                                             , fr_mods_hidden = []
                                             , fr_unusables = []
                                             , fr_suggestions = []})
         LookupMultiple rs ->
           return (FoundMultiple rs)
         LookupHidden pkg_hiddens mod_hiddens ->
           return (NotFound{ fr_paths = [], fr_pkg = Nothing
                           , fr_pkgs_hidden = map (moduleUnit.fst) pkg_hiddens
                           , fr_mods_hidden = map (moduleUnit.fst) mod_hiddens
                           , fr_unusables = []
                           , fr_suggestions = [] })
         LookupUnusable unusable ->
           let unusables' = map get_unusable unusable
               get_unusable (m, ModUnusable r) = (moduleUnit m, r)
               get_unusable (_, r)             =
                 pprPanic "findLookupResult: unexpected origin" (ppr r)
           in return (NotFound{ fr_paths = [], fr_pkg = Nothing
                              , fr_pkgs_hidden = []
                              , fr_mods_hidden = []
                              , fr_unusables = unusables'
                              , fr_suggestions = [] })
         LookupNotFound suggest -> do
           let suggest'
                 | gopt Opt_HelpfulErrors (hsc_dflags hsc_env) = suggest
                 | otherwise = []
           return (NotFound{ fr_paths = [], fr_pkg = Nothing
                           , fr_pkgs_hidden = []
                           , fr_mods_hidden = []
                           , fr_unusables = []
                           , fr_suggestions = suggest' })

    modLocationCache :: HscEnv -> InstalledModule -> IO InstalledFindResult -> IO InstalledFindResult
    modLocationCache hsc_env mod do_this = do
      m <- lookupFinderCache (hsc_FC hsc_env) mod
      case m of
        Just result -> return result
        Nothing     -> do
            result <- do_this
            addToFinderCache (hsc_FC hsc_env) mod result
            return result

    -- This returns a module because it's more convenient for users
    addHomeModuleToFinder :: HscEnv -> ModuleName -> ModLocation -> IO Module
    addHomeModuleToFinder hsc_env mod_name loc = do
      let home_unit = hsc_home_unit hsc_env
          mod = mkHomeInstalledModule home_unit mod_name
      addToFinderCache (hsc_FC hsc_env) mod (InstalledFound loc mod)
      return (mkHomeModule home_unit mod_name)

    uncacheModule :: HscEnv -> ModuleName -> IO ()
    uncacheModule hsc_env mod_name = do
      let home_unit = hsc_home_unit hsc_env
          mod = mkHomeInstalledModule home_unit mod_name
      removeFromFinderCache (hsc_FC hsc_env) mod

    -- -----------------------------------------------------------------------------
    --      The internal workers

    findHomeModule :: HscEnv -> ModuleName -> IO FindResult
    findHomeModule hsc_env mod_name = do
      r <- findInstalledHomeModule hsc_env mod_name
      return $ case r of
        InstalledFound loc _ -> Found loc (mkHomeModule home_unit mod_name)
        InstalledNoPackage _ -> NoPackage uid -- impossible
        InstalledNotFound fps _ -> NotFound {
            fr_paths = fps,
            fr_pkg = Just uid,
            fr_mods_hidden = [],
            fr_pkgs_hidden = [],
            fr_unusables = [],
            fr_suggestions = []
          }
     where
      home_unit = hsc_home_unit hsc_env
      uid       = homeUnitAsUnit home_unit

    -- | Implements the search for a module name in the home package only.  Calling
    -- this function directly is usually *not* what you want; currently, it's used
    -- as a building block for the following operations:
    --
    --  1. When you do a normal package lookup, we first check if the module
    --  is available in the home module, before looking it up in the package
    --  database.
    --
    --  2. When you have a package qualified import with package name "this",
    --  we shortcut to the home module.
    --
    --  3. When we look up an exact 'Module', if the unit id associated with
    --  the module is the current home module do a look up in the home module.
    --
    --  4. Some special-case code in GHCi (ToDo: Figure out why that needs to
    --  call this.)
    findInstalledHomeModule :: HscEnv -> ModuleName -> IO InstalledFindResult
    findInstalledHomeModule hsc_env mod_name =
       homeSearchCache hsc_env mod_name $
       let
         dflags = hsc_dflags hsc_env
         home_unit = hsc_home_unit hsc_env
         home_path = importPaths dflags
         hisuf = hiSuf dflags
         mod = mkHomeInstalledModule home_unit mod_name

         source_exts =
          [ ("hs",   mkHomeModLocationSearched dflags mod_name "hs")
          , ("lhs",  mkHomeModLocationSearched dflags mod_name "lhs")
          , ("hsig",  mkHomeModLocationSearched dflags mod_name "hsig")
          , ("lhsig",  mkHomeModLocationSearched dflags mod_name "lhsig")
          ]

         -- we use mkHomeModHiOnlyLocation instead of mkHiOnlyModLocation so that
         -- when hiDir field is set in dflags, we know to look there (see #16500)
         hi_exts = [ (hisuf,                mkHomeModHiOnlyLocation dflags mod_name)
                   , (addBootSuffix hisuf,  mkHomeModHiOnlyLocation dflags mod_name)
                   ]

            -- In compilation manager modes, we look for source files in the home
            -- package because we can compile these automatically.  In one-shot
            -- compilation mode we look for .hi and .hi-boot files only.
         exts | isOneShot (ghcMode dflags) = hi_exts
              | otherwise                  = source_exts
       in

      -- special case for GHC.Prim; we won't find it in the filesystem.
      -- This is important only when compiling the base package (where GHC.Prim
      -- is a home module).
      if mod `installedModuleEq` gHC_PRIM
            then return (InstalledFound (error "GHC.Prim ModLocation") mod)
            else searchPathExts home_path mod exts

    -- | Search for a module in external packages only.
    findPackageModule :: HscEnv -> InstalledModule -> IO InstalledFindResult
    findPackageModule hsc_env mod = do
      let pkg_id = moduleUnit mod
      case lookupUnitId (hsc_units hsc_env) pkg_id of
         Nothing -> return (InstalledNoPackage pkg_id)
         Just u  -> findPackageModule_ hsc_env mod u

    -- | Look up the interface file associated with module @mod@.  This function
    -- requires a few invariants to be upheld: (1) the 'Module' in question must
    -- be the module identifier of the *original* implementation of a module,
    -- not a reexport (this invariant is upheld by "GHC.Unit.State") and (2)
    -- the 'UnitInfo' must be consistent with the unit id in the 'Module'.
    -- The redundancy is to avoid an extra lookup in the package state
    -- for the appropriate config.
    findPackageModule_ :: HscEnv -> InstalledModule -> UnitInfo -> IO InstalledFindResult
    findPackageModule_ hsc_env mod pkg_conf =
      ASSERT2( moduleUnit mod == unitId pkg_conf, ppr (moduleUnit mod) <+> ppr (unitId pkg_conf) )
      modLocationCache hsc_env mod $

      -- special case for GHC.Prim; we won't find it in the filesystem.
      if mod `installedModuleEq` gHC_PRIM
            then return (InstalledFound (error "GHC.Prim ModLocation") mod)
            else

      let
         dflags = hsc_dflags hsc_env
         tag = waysBuildTag (ways dflags)

               -- hi-suffix for packages depends on the build tag.
         package_hisuf | null tag  = "hi"
                       | otherwise = tag ++ "_hi"

         mk_hi_loc = mkHiOnlyModLocation dflags package_hisuf

         import_dirs = map ST.unpack $ unitImportDirs pkg_conf
          -- we never look for a .hi-boot file in an external package;
          -- .hi-boot files only make sense for the home package.
      in
      case import_dirs of
        [one] | MkDepend <- ghcMode dflags -> do
              -- there's only one place that this .hi file can be, so
              -- don't bother looking for it.
              let basename = moduleNameSlashes (moduleName mod)
              loc <- mk_hi_loc one basename
              return (InstalledFound loc mod)
        _otherwise ->
              searchPathExts import_dirs mod [(package_hisuf, mk_hi_loc)]

    -- -----------------------------------------------------------------------------
    -- General path searching

    searchPathExts :: [FilePath]      -- paths to search
                   -> InstalledModule -- module name
                   -> [ (
                         FileExt,                                -- suffix
                         FilePath -> BaseName -> IO ModLocation  -- action
                        )
                      ]
                   -> IO InstalledFindResult

    searchPathExts paths mod exts = search to_search
      where
        basename = moduleNameSlashes (moduleName mod)

        to_search :: [(FilePath, IO ModLocation)]
        to_search = [ (file, fn path basename)
                    | path <- paths,
                      (ext,fn) <- exts,
                      let base | path == "." = basename
                               | otherwise   = path </> basename
                          file = base <.> ext
                    ]

        search [] = return (InstalledNotFound (map fst to_search) (Just (moduleUnit mod)))

        search ((file, mk_result) : rest) = do
          b <- doesFileExist file
          if b
            then do { loc <- mk_result; return (InstalledFound loc mod) }
            else search rest

    mkHomeModLocationSearched :: DynFlags -> ModuleName -> FileExt
                              -> FilePath -> BaseName -> IO ModLocation
    mkHomeModLocationSearched dflags mod suff path basename =
      mkHomeModLocation2 dflags mod (path </> basename) suff

    -- -----------------------------------------------------------------------------
    -- Constructing a home module location

    -- This is where we construct the ModLocation for a module in the home
    -- package, for which we have a source file.  It is called from three
    -- places:
    --
    --  (a) Here in the finder, when we are searching for a module to import,
    --      using the search path (-i option).
    --
    --  (b) The compilation manager, when constructing the ModLocation for
    --      a "root" module (a source file named explicitly on the command line
    --      or in a :load command in GHCi).
    --
    --  (c) The driver in one-shot mode, when we need to construct a
    --      ModLocation for a source file named on the command-line.
    --
    -- Parameters are:
    --
    -- mod
    --      The name of the module
    --
    -- path
    --      (a): The search path component where the source file was found.
    --      (b) and (c): "."
    --
    -- src_basename
    --      (a): (moduleNameSlashes mod)
    --      (b) and (c): The filename of the source file, minus its extension
    --
    -- ext
    --      The filename extension of the source file (usually "hs" or "lhs").

    mkHomeModLocation :: DynFlags -> ModuleName -> FilePath -> IO ModLocation
    mkHomeModLocation dflags mod src_filename = do
       let (basename,extension) = splitExtension src_filename
       mkHomeModLocation2 dflags mod basename extension

    mkHomeModLocation2 :: DynFlags
                       -> ModuleName
                       -> FilePath  -- Of source module, without suffix
                       -> String    -- Suffix
                       -> IO ModLocation
    mkHomeModLocation2 dflags mod src_basename ext = do
       let mod_basename = moduleNameSlashes mod

           obj_fn = mkObjPath  dflags src_basename mod_basename
           hi_fn  = mkHiPath   dflags src_basename mod_basename
           hie_fn = mkHiePath  dflags src_basename mod_basename

       return (ModLocation{ ml_hs_file   = Just (src_basename <.> ext),
                            ml_hi_file   = hi_fn,
                            ml_obj_file  = obj_fn,
                            ml_hie_file  = hie_fn })

    mkHomeModHiOnlyLocation :: DynFlags
                            -> ModuleName
                            -> FilePath
                            -> BaseName
                            -> IO ModLocation
    mkHomeModHiOnlyLocation dflags mod path basename = do
       loc <- mkHomeModLocation2 dflags mod (path </> basename) ""
       return loc { ml_hs_file = Nothing }

    mkHiOnlyModLocation :: DynFlags -> Suffix -> FilePath -> String
                        -> IO ModLocation
    mkHiOnlyModLocation dflags hisuf path basename
     = do let full_basename = path </> basename
              obj_fn = mkObjPath  dflags full_basename basename
              hie_fn = mkHiePath  dflags full_basename basename
          return ModLocation{    ml_hs_file   = Nothing,
                                 ml_hi_file   = full_basename <.> hisuf,
                                    -- Remove the .hi-boot suffix from
                                    -- hi_file, if it had one.  We always
                                    -- want the name of the real .hi file
                                    -- in the ml_hi_file field.
                                 ml_obj_file  = obj_fn,
                                 ml_hie_file  = hie_fn
                      }

    -- | Constructs the filename of a .o file for a given source file.
    -- Does /not/ check whether the .o file exists
    mkObjPath
      :: DynFlags
      -> FilePath           -- the filename of the source file, minus the extension
      -> String             -- the module name with dots replaced by slashes
      -> FilePath
    mkObjPath dflags basename mod_basename = obj_basename <.> osuf
      where
                    odir = objectDir dflags
                    osuf = objectSuf dflags

                    obj_basename | Just dir <- odir = dir </> mod_basename
                                 | otherwise        = basename

    -- | Constructs the filename of a .hi file for a given source file.
    -- Does /not/ check whether the .hi file exists
    mkHiPath
      :: DynFlags
      -> FilePath           -- the filename of the source file, minus the extension
      -> String             -- the module name with dots replaced by slashes
      -> FilePath
    mkHiPath dflags basename mod_basename = hi_basename <.> hisuf
     where
                    hidir = hiDir dflags
                    hisuf = hiSuf dflags

                    hi_basename | Just dir <- hidir = dir </> mod_basename
                                | otherwise         = basename

    -- | Constructs the filename of a .hie file for a given source file.
    -- Does /not/ check whether the .hie file exists
    mkHiePath
      :: DynFlags
      -> FilePath           -- the filename of the source file, minus the extension
      -> String             -- the module name with dots replaced by slashes
      -> FilePath
    mkHiePath dflags basename mod_basename = hie_basename <.> hiesuf
     where
                    hiedir = hieDir dflags
                    hiesuf = hieSuf dflags

                    hie_basename | Just dir <- hiedir = dir </> mod_basename
                                 | otherwise          = basename

    -- -----------------------------------------------------------------------------
    -- Filenames of the stub files

    -- We don't have to store these in ModLocations, because they can be derived
    -- from other available information, and they're only rarely needed.

    mkStubPaths
      :: DynFlags
      -> ModuleName
      -> ModLocation
      -> FilePath

    mkStubPaths dflags mod location
      = let
            stubdir = stubDir dflags

            mod_basename = moduleNameSlashes mod
            src_basename = dropExtension $ expectJust "mkStubPaths"
                                                      (ml_hs_file location)

            stub_basename0
                | Just dir <- stubdir = dir </> mod_basename
                | otherwise           = src_basename

            stub_basename = stub_basename0 ++ "_stub"
         in
            stub_basename <.> "h"

    -- -----------------------------------------------------------------------------
    -- findLinkable isn't related to the other stuff in here,
    -- but there's no other obvious place for it

    findObjectLinkableMaybe :: Module -> ModLocation -> IO (Maybe Linkable)
    findObjectLinkableMaybe mod locn
       = do let obj_fn = ml_obj_file locn
            maybe_obj_time <- modificationTimeIfExists obj_fn
            case maybe_obj_time of
              Nothing -> return Nothing
              Just obj_time -> liftM Just (findObjectLinkable mod obj_fn obj_time)

    -- Make an object linkable when we know the object file exists, and we know
    -- its modification time.
    findObjectLinkable :: Module -> FilePath -> UTCTime -> IO Linkable
    findObjectLinkable mod obj_fn obj_time = return (LM obj_time mod [DotO obj_fn])
      -- We used to look for _stub.o files here, but that was a bug (#706)
      -- Now GHC merges the stub.o into the main .o (#3687)