Write cache files atomically

Fixes #1540.

Author: sjakobi

dhall/dhall.cabal

@@ -405,6 +405,7 @@ Library
         aeson                       >= 1.0.0.0  && < 1.5 ,
         aeson-pretty                               < 0.9 ,
         ansi-terminal               >= 0.6.3.1  && < 0.11,
+        atomic-write                >= 0.2.0.7  && < 0.3 ,
         bytestring                                 < 0.11,
         case-insensitive                           < 1.3 ,
         cborg                       >= 0.2.0.0  && < 0.3 ,

dhall/src/Dhall/Import.hs

@@ -179,18 +179,18 @@ import Dhall.Import.Types
 import Dhall.Parser (Parser(..), ParseError(..), Src(..), SourcedException(..))
 import Lens.Family.State.Strict (zoom)
 
-import qualified Codec.CBOR.Encoding              as Encoding
-import qualified Codec.CBOR.Write                 as Write
+import qualified Codec.CBOR.Encoding                         as Encoding
+import qualified Codec.CBOR.Write                            as Write
 import qualified Codec.Serialise
-import qualified Control.Monad.Trans.Maybe        as Maybe
-import qualified Control.Monad.Trans.State.Strict as State
+import qualified Control.Monad.Trans.Maybe                   as Maybe
+import qualified Control.Monad.Trans.State.Strict            as State
 import qualified Data.ByteString
 import qualified Data.ByteString.Lazy
 import qualified Data.CaseInsensitive
 import qualified Data.Foldable
-import qualified Data.List.NonEmpty               as NonEmpty
+import qualified Data.List.NonEmpty                          as NonEmpty
 import qualified Data.Text.Encoding
-import qualified Data.Text                        as Text
+import qualified Data.Text                                   as Text
 import qualified Data.Text.IO
 import qualified Dhall.Binary
 import qualified Dhall.Core
@@ -199,11 +199,12 @@ import qualified Dhall.Map
 import qualified Dhall.Parser
 import qualified Dhall.Pretty.Internal
 import qualified Dhall.TypeCheck
+import qualified System.AtomicWrite.Writer.ByteString.Binary as AtomicWrite.Binary
 import qualified System.Environment
 import qualified System.Info
 import qualified System.IO
-import qualified System.Directory                 as Directory
-import qualified System.FilePath                  as FilePath
+import qualified System.Directory                            as Directory
+import qualified System.FilePath                             as FilePath
 import qualified Text.Megaparsec
 import qualified Text.Parser.Combinators
 import qualified Text.Parser.Token
@@ -554,7 +555,7 @@ writeToSemanticCache :: Dhall.Crypto.SHA256Digest -> Data.ByteString.ByteString
 writeToSemanticCache hash bytes = do
     _ <- Maybe.runMaybeT $ do
         cacheFile <- getCacheFile "dhall" hash
-        liftIO (Data.ByteString.writeFile cacheFile bytes)
+        liftIO (AtomicWrite.Binary.atomicWriteFile cacheFile bytes)
     return ()
 
 -- Check the "semi-semantic" disk cache, otherwise typecheck and normalise from
@@ -669,7 +670,7 @@ writeToSemisemanticCache :: Dhall.Crypto.SHA256Digest -> Data.ByteString.ByteStr
 writeToSemisemanticCache semisemanticHash bytes = do
     _ <- Maybe.runMaybeT $ do
         cacheFile <- getCacheFile "dhall-haskell" semisemanticHash
-        liftIO (Data.ByteString.writeFile cacheFile bytes)
+        liftIO (AtomicWrite.Binary.atomicWriteFile cacheFile bytes)
     return ()
 
 -- Fetch source code directly from disk/network

nix/atomic-write.nix

@@ -0,0 +1,17 @@
+{ mkDerivation, base, bytestring, directory, filepath, hspec
+, stdenv, temporary, text, unix-compat
+}:
+mkDerivation {
+  pname = "atomic-write";
+  version = "0.2.0.7";
+  sha256 = "b5f5c77884bc0332306fab89acf1c8a8582d76eabaa303c91b1c4072621c960d";
+  libraryHaskellDepends = [
+    base bytestring directory filepath temporary text unix-compat
+  ];
+  testHaskellDepends = [
+    base bytestring filepath hspec temporary text unix-compat
+  ];
+  homepage = "https://github.com/stackbuilders/atomic-write";
+  description = "Atomically write to a file";
+  license = stdenv.lib.licenses.mit;
+}

stack-lts-6.yaml

@@ -12,6 +12,7 @@ extra-deps:
 - aeson-pretty-0.8.7
 - ansi-terminal-0.9.1
 - ansi-wl-pprint-0.6.8.2
+- atomic-write-0.2.0.7@sha256:3b626dfbc288cd070f1ac31b1c15ddd49822a923778ffe21f92b2116ffc72dc3,4584
 - attoparsec-0.13.2.2
 - base-compat-0.10.5
 - base-orphans-0.8.1

stack.yaml

@@ -24,6 +24,7 @@ extra-deps:
   - lsp-test-0.6.1.0@sha256:df0fc403c03b6d036be13de3ff23d9951ae2506080135cd6862eded2c969a6da,3483
   - aeson-yaml-1.0.4.0@sha256:72d91a4a2ade87b8a4bdf73937d2c62bd2c60053df1841f8bf1e6204387959b8,1975
   - prettyprinter-1.5.1@sha256:fca87c3e2611d3499a0341a59857e9b424a23f31646e4737d535a18582284f96,5375
+  - atomic-write-0.2.0.7@sha256:3b626dfbc288cd070f1ac31b1c15ddd49822a923778ffe21f92b2116ffc72dc3,4584
 nix:
   packages:
     - ncurses