From 987d6f40282862fbf9af22269e70b820240a7e08 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Wed, 1 Dec 2021 17:26:35 +0100
Subject: [PATCH] Fail gracefully when decoding enum fails

---
 contractabi/decoding.nim           | 6 +++++-
 tests/contractabi/testDecoding.nim | 7 ++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/contractabi/decoding.nim b/contractabi/decoding.nim
index bc1a234..e4a6651 100644
--- a/contractabi/decoding.nim
+++ b/contractabi/decoding.nim
@@ -94,7 +94,11 @@ func decode(decoder: var AbiDecoder, T: type bool): ?!T =
     else: failure "invalid boolean value"
 
 func decode(decoder: var AbiDecoder, T: type enum): ?!T =
-  success T(?decoder.read(uint64))
+  let value = ?decoder.read(uint64)
+  if value in T.low.uint64..T.high.uint64:
+    success T(value)
+  else:
+    failure "invalid enum value"
 
 func decode[I](decoder: var AbiDecoder, T: type array[I, byte]): ?!T =
   var arr: T
diff --git a/tests/contractabi/testDecoding.nim b/tests/contractabi/testDecoding.nim
index 1ba9dbd..916479f 100644
--- a/tests/contractabi/testDecoding.nim
+++ b/tests/contractabi/testDecoding.nim
@@ -65,7 +65,12 @@ suite "ABI decoding":
     checkDecode(one)
     checkDecode(two)
 
-  # TODO: failure to decode when invalid enum value
+  test "fails to decode enum when encountering invalid value":
+    type SomeEnum = enum
+      one = 1
+      two = 2
+    let encoded = AbiEncoder.encode(3'u8)
+    check AbiDecoder.decode(encoded, SomeEnum).error.msg == "invalid enum value"
 
   test "decodes stints":
     checkDecode(UInt128)