From 786ded3e43665746814933398d3830df1c771d3b Mon Sep 17 00:00:00 2001
From: VegOwOtenks <vegowotenks@jossco.de>
Date: Fri, 22 Aug 2025 10:54:10 +0200
Subject: [PATCH] fix[test]: quickcheck-instances panics when creating empty
 arrays

---
 hon.cabal                   |  1 +
 src/Data/Array/Arbitrary.hs | 22 ++++++++++++++++++++++
 src/Language/Json.hs        |  7 +++----
 3 files changed, 26 insertions(+), 4 deletions(-)
 create mode 100644 src/Data/Array/Arbitrary.hs

diff --git a/hon.cabal b/hon.cabal
index 2b54b4f..847184f 100644
--- a/hon.cabal
+++ b/hon.cabal
@@ -19,6 +19,7 @@ extra-source-files:
 
 library
   exposed-modules:
+      Data.Array.Arbitrary
       Language.Json
       Language.Json.Parser
       Language.Json.Path
diff --git a/src/Data/Array/Arbitrary.hs b/src/Data/Array/Arbitrary.hs
new file mode 100644
index 0000000..d1a052a
--- /dev/null
+++ b/src/Data/Array/Arbitrary.hs
@@ -0,0 +1,22 @@
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE InstanceSigs #-}
+{-# LANGUAGE FlexibleContexts #-}
+module Data.Array.Arbitrary (ArbitraryArray(..), get) where
+import Test.QuickCheck (Arbitrary (arbitrary), Gen)
+import Data.Array.IArray (listArray, IArray, Ix)
+import Data.List (genericLength)
+
+newtype ArbitraryArray a i e = ArbitraryArray { getArbitraryArray :: a i e }
+  deriving stock (Show)
+
+get :: ArbitraryArray a i e -> a i e
+get = getArbitraryArray
+
+instance (Arbitrary e, Num i, Ix i, IArray a e) => Arbitrary (ArbitraryArray a i e) where
+  arbitrary :: Gen (ArbitraryArray a i e)
+  arbitrary = do
+    xs <- arbitrary
+    pure . ArbitraryArray $ case xs of
+      [] -> listArray (1, 0) xs
+      _  -> listArray (0, genericLength xs - 1) xs
+
diff --git a/src/Language/Json.hs b/src/Language/Json.hs
index d9f7f95..70f77e1 100644
--- a/src/Language/Json.hs
+++ b/src/Language/Json.hs
@@ -28,8 +28,7 @@ import GHC.Generics ( Generic, Generically(..) )
 import Pretty.Serialize (PrettySerialize)
 import Test.QuickCheck (Arbitrary (arbitrary), Gen, UnicodeString (getUnicodeString), PrintableString (getPrintableString))
 import qualified Test.QuickCheck.Gen as Gen
-import Test.QuickCheck.Instances.Array ()
-import Test.QuickCheck.Instances.Natural ()
+import Data.Array.Arbitrary (ArbitraryArray(getArbitraryArray))
 
 
 data Value
@@ -50,7 +49,7 @@ instance Arbitrary Value where
     , String . Text.pack . getUnicodeString <$> arbitrary
     , Boolean <$> arbitrary
     , Number <$> arbitrary
-    , Array <$> Gen.scale (`div` 2) arbitrary
+    , Array . getArbitraryArray <$> Gen.scale (`div` 2) arbitrary
     , Object . Map.mapKeys (Text.pack . getUnicodeString) <$> Gen.scale (`div` 2) arbitrary
     ]
 
@@ -64,7 +63,7 @@ instance Arbitrary PrintableValue where
     , String . Text.pack . getPrintableString <$> arbitrary
     , Boolean <$> arbitrary
     , Number <$> arbitrary
-    , Array <$> Gen.scale (`div` 2) arbitrary
+    , Array . getArbitraryArray <$> Gen.scale (`div` 2) arbitrary
     , Object . Map.mapKeys (Text.pack . getPrintableString) <$> Gen.scale (`div` 2) arbitrary
     ]