Use temporary directory for tutorial example files (#503)

... as suggested by @sol

dhall.cabal

@@ -274,9 +274,11 @@ Test-Suite doctest
     Main-Is: Main.hs
     GHC-Options: -Wall
     Build-Depends:
-        base                      ,
-        Diff    >= 0.2   && < 0.4 ,
-        doctest >= 0.7.0 && < 0.17
+        base                          ,
+        directory >= 1.2.2.0 && < 1.4 ,
+        filepath                < 1.5 ,
+        mockery                 < 0.4 ,
+        doctest   >= 0.7.0   && < 0.17
     Default-Language: Haskell2010
 
 Benchmark dhall-parser

doctest/Main.hs

@@ -1,12 +1,29 @@
 module Main where
 
+import Data.Monoid ((<>))
+import System.FilePath ((</>))
+
+import qualified System.Directory
+import qualified Test.Mockery.Directory
 import qualified Test.DocTest
 
 main :: IO ()
-main =
-    Test.DocTest.doctest
-        [ "-isrc"
-        , "src/Dhall.hs"
-        , "src/Dhall/Import.hs"
-        , "src/Dhall/Tutorial.hs"
-        ]
+main = do
+    pwd    <- System.Directory.getCurrentDirectory
+    prefix <- System.Directory.makeAbsolute pwd
+
+    Test.Mockery.Directory.inTempDirectory $ do
+        writeFile "makeBools" "λ(n : Bool) → [ n && True, n && False, n || True, n || False ]"
+        writeFile "bool1" "True"
+        writeFile "bool2" "False"
+        writeFile "both" "./bool1 && ./bool2"
+        writeFile "file2" "./file1"
+        writeFile "file1" "./file2"
+
+        Test.DocTest.doctest
+            [ "--fast"
+            , "-i" <> (prefix </> "src")
+            , prefix </> "src/Dhall.hs"
+            , prefix </> "src/Dhall/Import.hs"
+            , prefix </> "src/Dhall/Tutorial.hs"
+            ]

nix/dhall.nix

@@ -2,7 +2,7 @@
 , containers, contravariant, criterion, cryptonite, deepseq, Diff
 , directory, doctest, exceptions, filepath, haskeline, http-client
 , http-client-tls, insert-ordered-containers, lens-family-core
-, megaparsec, memory, mtl, optparse-applicative, parsers
+, megaparsec, memory, mockery, mtl, optparse-applicative, parsers
 , prettyprinter, prettyprinter-ansi-terminal, repline, scientific
 , stdenv, tasty, tasty-hunit, template-haskell, text, transformers
 , unordered-containers, vector
@@ -23,8 +23,8 @@ mkDerivation {
   ];
   executableHaskellDepends = [ base ];
   testHaskellDepends = [
-    base deepseq Diff doctest insert-ordered-containers prettyprinter
-    tasty tasty-hunit text vector
+    base deepseq directory doctest filepath insert-ordered-containers
+    mockery prettyprinter tasty tasty-hunit text vector
   ];
   benchmarkHaskellDepends = [
     base containers criterion directory text

src/Dhall/Tutorial.hs

@@ -171,12 +171,6 @@ import Dhall
 -- $setup
 --
 -- >>> :set -XOverloadedStrings
--- >>> writeFile "makeBools" "λ(n : Bool) → [ n && True, n && False, n || True, n || False ]"
--- >>> writeFile "bool1" "True"
--- >>> writeFile "bool2" "False"
--- >>> writeFile "both" "./bool1 && ./bool2"
--- >>> writeFile "file2" "./file1"
--- >>> writeFile "file1" "./file2"
 
 -- $introduction
 --
@@ -2822,14 +2816,3 @@ import Dhall
 -- this guide:
 --
 -- <https://github.com/dhall-lang/dhall-lang/wiki/How-to-translate-recursive-code-to-Dhall How to translate recursive code to Dhall>
-
--- $cleanup
---
--- >>> System.Directory.removeFile "bool"
--- >>> System.Directory.removeFile "bool1"
--- >>> System.Directory.removeFile "bool2"
--- >>> System.Directory.removeFile "both"
--- >>> System.Directory.removeFile "file1"
--- >>> System.Directory.removeFile "file2"
--- >>> System.Directory.removeFile "baz"
--- >>> System.Directory.removeFile "makeBools"