Make semantic integrity check insensitive to field order (#552)

... as standardized in https://github.com/dhall-lang/dhall-lang/pull/223

Fixes #548

This changes β-normalization to sort fields so that semantic integrity
checks don't change when reordering fields

* Fix test failure

The Nix build sets `HOME=/homeless-shelter`, which leads to a test failure
since the test tries to create a "${HOME}/.cache" directory without first
checking if "${HOME}" is accessible.  This changes the `assertDirectory`
function to recursively check parent directories to avoid this issue, which
in turn fixes the test (since it gracefully creates no directories if none are
accessible).

dhall.cabal

@@ -181,6 +181,7 @@ Library
         directory                   >= 1.2.7.1  && < 1.4 ,
         exceptions                  >= 0.8.3    && < 0.11,
         filepath                    >= 1.4      && < 1.5 ,
+        hashable                                   < 1.3 ,
         haskeline                   >= 0.7.3.0  && < 0.8 ,
         insert-ordered-containers   >= 0.2.1.0  && < 0.3 ,
         lens-family-core            >= 1.0.0    && < 1.3 ,
@@ -266,7 +267,7 @@ Test-Suite tasty
         containers                                     ,
         deepseq                   >= 1.2.0.1  && < 1.5 ,
         dhall                                          ,
-        hashable                                 < 1.3 ,
+        hashable                                       ,
         insert-ordered-containers == 0.2.1.0           ,
         prettyprinter                                  ,
         QuickCheck                >= 2.10     && < 2.12,

src/Dhall/Core.hs

@@ -64,6 +64,7 @@ import Crypto.Hash (SHA256)
 import Data.Bifunctor (Bifunctor(..))
 import Data.Data (Data)
 import Data.Foldable
+import Data.Hashable (Hashable)
 import Data.HashMap.Strict.InsOrd (InsOrdHashMap)
 import Data.HashSet (HashSet)
 import Data.String (IsString(..))
@@ -81,8 +82,10 @@ import Prelude hiding (succ)
 
 import qualified Control.Monad
 import qualified Crypto.Hash
+import qualified Data.List
 import qualified Data.HashMap.Strict.InsOrd
 import qualified Data.HashSet
+import qualified Data.Ord
 import qualified Data.Sequence
 import qualified Data.Set
 import qualified Data.Text
@@ -1371,6 +1374,12 @@ denote (Project a b         ) = Project (denote a) b
 denote (ImportAlt a b       ) = ImportAlt (denote a) (denote b)
 denote (Embed a             ) = Embed a
 
+sortMap :: (Ord k, Hashable k) => InsOrdHashMap k v -> InsOrdHashMap k v
+sortMap =
+      Data.HashMap.Strict.InsOrd.fromList
+    . Data.List.sortBy (Data.Ord.comparing fst)
+    . Data.HashMap.Strict.InsOrd.toList
+
 {-| Reduce an expression to its normal form, performing beta reduction and applying
     any custom definitions.
 
@@ -1646,16 +1655,16 @@ normalizeWith ctx e0 = loop (denote e0)
         es' = fmap loop es
     OptionalFold -> OptionalFold
     OptionalBuild -> OptionalBuild
-    Record kts -> Record kts'
+    Record kts -> Record (sortMap kts')
       where
         kts' = fmap loop kts
-    RecordLit kvs -> RecordLit kvs'
+    RecordLit kvs -> RecordLit (sortMap kvs')
       where
         kvs' = fmap loop kvs
-    Union kts -> Union kts'
+    Union kts -> Union (sortMap kts')
       where
         kts' = fmap loop kts
-    UnionLit k v kvs -> UnionLit k v' kvs'
+    UnionLit k v kvs -> UnionLit k v' (sortMap kvs')
       where
         v'   =      loop v
         kvs' = fmap loop kvs

src/Dhall/Import.hs

@@ -186,6 +186,7 @@ import qualified Dhall.Pretty.Internal
 import qualified Dhall.TypeCheck
 import qualified System.Environment
 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
@@ -535,6 +536,8 @@ getCacheFile hash = do
                     guard (accessible permissions)
 
                 else do
+                    assertDirectory (FilePath.takeDirectory directory)
+
                     liftIO (Directory.createDirectory directory)
 
                     liftIO (Directory.setPermissions directory private)

tests/Import.hs

@@ -47,6 +47,10 @@ importTests =
                 "works"
                 "./tests/import/data/foo/bar"
                 "./tests/import/relative.dhall"
+            , shouldNotFailRelative
+                "a semantic integrity check if fields are reordered"
+                "./tests/import/"
+                "./tests/import/fieldOrderC.dhall"
             ]
         ]
 

tests/import/fieldOrderA.dhall

@@ -0,0 +1 @@
+{ foo = 1, bar = True }

tests/import/fieldOrderB.dhall

@@ -0,0 +1 @@
+{ bar = True, foo = 1 }

tests/import/fieldOrderC.dhall

@@ -0,0 +1,3 @@
+{ example0 = ./fieldOrderA.dhall sha256:c8e5944a964f1b35da4f2a7dc16b8de0221a518997fd84b0363a955d8f4459a4 
+, example1 = ./fieldOrderB.dhall sha256:c8e5944a964f1b35da4f2a7dc16b8de0221a518997fd84b0363a955d8f4459a4 
+}