Resolve #67. Sort HashSet and HashMap Exprs

Author: phadej

ChangeLog.md

@@ -1,3 +1,14 @@
+## 0.3
+
+- Breaking change:
+  Make HashSet and HashMap ToExpr instances sort the resulting
+  lists of expressions.
+  This makes the results deterministic.
+  ... but your golden files will need adjustment.
+  https://github.com/haskellari/tree-diff/issues/67
+
+- Add `Ord Expr` and `Ord OMap` instances
+
 ## 0.2.2
 
 - Add instances for base and primitive's `ByteArray`s.

fixtures/HashSet.expr

@@ -1,14 +1,14 @@
 HS.fromList
   [
-    "az",
-    "dz",
     "ax",
+    "ay",
+    "az",
+    "bx",
+    "by",
     "bz",
     "cx",
-    "cz",
-    "dy",
-    "bx",
     "cy",
-    "by",
+    "cz",
     "dx",
-    "ay"]
+    "dy",
+    "dz"]

src/Data/TreeDiff/Class.hs

@@ -21,6 +21,7 @@ module Data.TreeDiff.Class (
     ) where
 
 import Data.Foldable    (toList)
+import Data.List        (sort)
 import Data.List.Compat (uncons)
 import Data.Proxy       (Proxy (..))
 import GHC.Generics
@@ -550,9 +551,9 @@ instance ToExpr a => ToExpr (Hashed a) where
 -------------------------------------------------------------------------------
 
 instance (ToExpr k, ToExpr v) => ToExpr (HM.HashMap k v) where
-    toExpr x = App "HM.fromList" [ toExpr $ HM.toList x ]
+    toExpr x = App "HM.fromList" [ Lst $ sort $ map toExpr $ HM.toList x ]
 instance (ToExpr k) => ToExpr (HS.HashSet k) where
-    toExpr x = App "HS.fromList" [ toExpr $ HS.toList x ]
+    toExpr x = App "HS.fromList" [ Lst $ sort $ map toExpr $ HS.toList x ]
 
 -------------------------------------------------------------------------------
 -- aeson

src/Data/TreeDiff/Expr.hs

@@ -35,7 +35,7 @@ data Expr
     = App ConstructorName [Expr]                 -- ^ application
     | Rec ConstructorName (OMap FieldName Expr)  -- ^ record constructor
     | Lst [Expr]                                 -- ^ list constructor
-  deriving (Eq, Show)
+  deriving (Eq, Ord, Show)
 
 instance NFData Expr where
     rnf (App n es) = rnf n `seq` rnf es

src/Data/TreeDiff/OMap.hs

@@ -61,12 +61,10 @@ instance (Show k, Show v) => Show (OMap k v) where
 -- False
 --
 instance (Eq k, Eq v) => Eq (OMap k v) where
-    xs == ys = go (toAscList xs) (toAscList ys) where
-        go [] [] = True
-        go _  [] = False
-        go [] _  = False
-        go ((k1, v1) : kvs1) ((k2, v2) : kvs2) =
-            k1 == k2 && v1 == v2 && go kvs1 kvs2
+    xs == ys = toAscList xs == toAscList ys
+
+instance (Ord k, Ord v) => Ord (OMap k v) where
+    compare xs ys = compare (toAscList xs) (toAscList ys)
 
 -------------------------------------------------------------------------------
 -- deepseq

tree-diff.cabal

@@ -1,6 +1,6 @@
 cabal-version:      2.2
 name:               tree-diff
-version:            0.2.2
+version:            0.3
 synopsis:           Diffing of (expression) trees.
 category:           Data, Testing
 description: