Setup.hs

-- Copyright 2016 Google Inc. All Rights Reserved.
--
-- Use of this source code is governed by a BSD-style
-- license that can be found in the LICENSE file or at
-- https://developers.google.com/open-source/licenses/bsd

-- | Helper functions to generate proto files as part of a @Setup.hs@ script.
--
-- These functions assume that the @proto-lens-protoc@ executable is on the
-- PATH, and throw an exception otherwise.  That executable will be installed
-- automatically as part of installing this package; in particular, it should
-- be enough to just list `proto-lens-protoc` in a user package's
-- `build-dependencies`.
--
-- See @README.md@ for instructions on how to use proto-lens with Cabal.
{-# LANGUAGE CPP #-}
module Data.ProtoLens.Setup
    ( defaultMainGeneratingProtos
    , generatingProtos
    , generateProtos
    ) where

#if __GLASGOW_HASKELL__ < 709
import Data.Functor ((<$>))
#endif

import Distribution.PackageDescription
    ( PackageDescription(..)
    , benchmarkBuildInfo
    , buildInfo
    , extraSrcFiles
    , hsSourceDirs
    , libBuildInfo
    , testBuildInfo
    )
import Distribution.Simple.BuildPaths (autogenModulesDir)
import Distribution.Simple.LocalBuildInfo (LocalBuildInfo)
import Distribution.Simple.Utils (matchFileGlob)
import Distribution.Simple
    ( defaultMainWithHooks
    , simpleUserHooks
    , UserHooks(..)
    )
import System.FilePath
    ( (</>)
    , equalFilePath
    , isRelative
    , makeRelative
    , takeExtension
    )
import System.Directory (createDirectoryIfMissing, findExecutable)
import System.Process (callProcess)

-- | This behaves the same as 'Distribution.Simple.defaultMain', but
-- auto-generates Haskell files from the .proto files listed in
-- the @.cabal@ file under @extra-source-files@ which are located under the
-- given root directory.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
defaultMainGeneratingProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> IO ()
defaultMainGeneratingProtos root
    = defaultMainWithHooks $ generatingProtos root simpleUserHooks

-- | Augment the given 'UserHooks' to auto-generate Haskell files from the
-- .proto files listed in the @.cabal@ file under @extra-source-files@ which
-- are located under the given root directory.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
generatingProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> UserHooks -> UserHooks
generatingProtos root hooks = hooks
    { buildHook = \p l h f -> generateSources p l >> buildHook hooks p l h f
    , haddockHook = \p l h f -> generateSources p l >> haddockHook hooks p l h f
    , replHook = \p l h f args -> generateSources p l
                                        >> replHook hooks p l h f args
    , sDistHook = \p maybe_l h f -> case maybe_l of
            Nothing -> error "Can't run protoc; run 'cabal configure' first."
            Just l -> do
                        generateSources p l
                        sDistHook hooks (fudgePackageDesc l p) maybe_l h f
    }
  where
    generateSources p l = do
        -- Replicate Cabal's own logic for parsing file globs.
        files <- concat <$> mapM matchFileGlob (extraSrcFiles p)
        generateProtos root (autogenModulesDir l)
            $ filter (isSubdirectoryOf root)
            $ filter (\f -> takeExtension f == ".proto")
                files

-- | Add the autogen directory to the hs-source-dirs of all the targets in the
-- .cabal file.  Used to fool 'sdist' by pointing it to the generated source
-- files.
fudgePackageDesc :: LocalBuildInfo -> PackageDescription -> PackageDescription
fudgePackageDesc lbi p = p
    { library =
        (\lib -> lib { libBuildInfo = fudgeBuildInfo (libBuildInfo lib) })
            <$> library p
    , executables =
        (\exe -> exe { buildInfo = fudgeBuildInfo (buildInfo exe) })
            <$> executables p
    , testSuites =
        (\test -> test { testBuildInfo = fudgeBuildInfo (testBuildInfo test) })
            <$> testSuites p
    , benchmarks =
        (\bench -> bench { benchmarkBuildInfo =
                              fudgeBuildInfo (benchmarkBuildInfo bench) })
            <$> benchmarks p
    }
  where
    fudgeBuildInfo bi =
        bi { hsSourceDirs = autogenModulesDir lbi : hsSourceDirs bi }

-- | Returns whether the @root@ is a parent folder of @f@.
isSubdirectoryOf :: FilePath -> FilePath -> Bool
isSubdirectoryOf root f
    = isRelative f
      -- Note: `makeRelative root f` returns `f` when f doesn't live under the
      -- root.
      && equalFilePath f (root </> makeRelative root f)

-- | Run the proto compiler to generate Haskell files from the given .proto files.
--
-- Writes the generated files to the autogen directory (@dist\/build\/autogen@
-- for Cabal, and @.stack-work\/dist\/...\/build\/autogen@ for stack).
--
-- Throws an exception if the @proto-lens-protoc@ executable is not on the PATH.
generateProtos
    :: FilePath -- ^ The root directory under which .proto files can be found.
    -> FilePath -- ^ The output directory for the generated Haskell files.
    -> [FilePath] -- ^ The .proto files to process.
    -> IO ()
generateProtos root output files = do
    maybeProtoLensProtoc <- findExecutable "proto-lens-protoc"
    case maybeProtoLensProtoc of
        Nothing -> error "Couldn't find executable proto-lens-protoc."
        Just protoLensProtoc -> do
            createDirectoryIfMissing True output
            callProcess "protoc" $
                [ "--plugin=protoc-gen-haskell=" ++ protoLensProtoc
                , "--haskell_out=" ++ output
                , "--proto_path=" ++ root
                ]
                ++ files