Make the Tx.&& and Tx.|| short-circuit also in Haskell

Author: bezirg

plutus-tx/changelog.d/20251119_101254_bezirg_short_circuit_haskell.md

@@ -0,0 +1,4 @@
+### Changed
+
+- Made the (&&) and (||) operators short-circuit also in the Haskell side.
+uplc code is unaffected and is already short-circuiting.

plutus-tx/plutus-tx.cabal

@@ -208,6 +208,7 @@ test-suite plutus-tx-test
     Blueprint.Definition.Spec
     Blueprint.Spec
     List.Spec
+    Bool.Spec
     Rational.Laws
     Rational.Laws.Additive
     Rational.Laws.Construction

plutus-tx/src/PlutusTx/Bool.hs

@@ -10,27 +10,35 @@ import Prelude (Bool (..), otherwise)
 
 -- `(&&)` and `(||)` are handled specially in the plugin to make sure they can short-circuit.
 -- See Note [Lazy boolean operators] in the plugin.
+-- In the Haskell-side, we are using `default-extensions: Strict` throughout PlutusTx,
+-- which means that we have to sure that the second argument is lazy to short-circuit the `(&&)` and `(||)`.
 
 {-| Logical AND. Short-circuits if the first argument evaluates to `False`.
 
   >>> True && False
   False
+
+  >>> False && error ()
+  False
 -}
 infixr 3 &&
 
 (&&) :: Bool -> Bool -> Bool
-(&&) l r = if l then r else False
+(&&) l ~r = if l then r else False
 {-# OPAQUE (&&) #-}
 
 {-| Logical OR. Short-circuits if the first argument evaluates to `True`.
 
   >>> True || False
   True
+
+  >>> True || error ()
+  True
 -}
 infixr 2 ||
 
 (||) :: Bool -> Bool -> Bool
-(||) l r = if l then True else r
+(||) l ~r = if l then True else r
 {-# OPAQUE (||) #-}
 
 {-| Logical negation

plutus-tx/test/Bool/Spec.hs

@@ -0,0 +1,18 @@
+module Bool.Spec (boolTests) where
+
+import PlutusTx.Builtins as Tx
+import PlutusTx.Bool qualified as Tx
+
+import Prelude (($))
+import Test.Tasty
+import Test.Tasty.HUnit
+
+boolTests :: TestTree
+boolTests =
+  testGroup
+    "PlutusTx.Bool tests"
+    -- in uplc the &&,|| are treated specially to short-circuit
+    -- this makes sures that the Haskell counterparts also short-circuit
+    [ testCase "shortcircuit_&&" $ Tx.False Tx.&& Tx.error () @?= Tx.False
+    , testCase "shortcircuit_||" $ Tx.True Tx.&& Tx.error () @?= Tx.True
+    ]

plutus-tx/test/Spec.hs

@@ -19,6 +19,7 @@ import Hedgehog (MonadGen, Property, PropertyT, annotateShow, assert, forAll, pr
 import Hedgehog.Gen qualified as Gen
 import Hedgehog.Range qualified as Range
 import List.Spec (listTests)
+import Bool.Spec (boolTests)
 import PlutusCore.Data (Data (B, Constr, I, List, Map))
 import PlutusTx.Enum (Enum (..))
 import PlutusTx.Numeric (negate)
@@ -45,6 +46,7 @@ tests =
     , bytestringTests
     , enumTests
     , listTests
+    , boolTests
     , lawsTests
     , Show.Spec.propertyTests
     , Show.Spec.goldenTests