Decode NULL as false

3 files changed, 29 insertions, 1 deletions

diff --git a/packages/utils/CHANGELOG.json b/packages/utils/CHANGELOG.json
index 0fb199e58..d8c1bb9ce 100644
--- a/packages/utils/CHANGELOG.json
+++ b/packages/utils/CHANGELOG.json
@@ -1,5 +1,14 @@
 [
     {
+        "version": "4.0.1",
+        "changes": [
+            {
+                "note": "ABI Decode NULL as False"
+                "pr": 1582
+            }
+        ]
+    },
+    {
         "version": "4.0.0",
         "changes": [
             {
diff --git a/packages/utils/src/abi_encoder/evm_data_types/bool.ts b/packages/utils/src/abi_encoder/evm_data_types/bool.ts
index 23298bc88..ffccd6e53 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/bool.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/bool.ts
@@ -36,7 +36,8 @@ export class BoolDataType extends AbstractBlobDataType {
     public decodeValue(calldata: RawCalldata): boolean {
         const valueBuf = calldata.popWord();
         const valueHex = ethUtil.bufferToHex(valueBuf);
-        const valueNumber = new BigNumber(valueHex, constants.HEX_BASE);
+        // Hack @hysz: there are some cases where `false` is encoded as 0x instead of 0x0.
+        const valueNumber = valueHex === '0x' ? new BigNumber(0) : new BigNumber(valueHex, constants.HEX_BASE);
         if (!(valueNumber.isEqualTo(0) || valueNumber.isEqualTo(1))) {
             throw new Error(`Failed to decode boolean. Expected 0x0 or 0x1, got ${valueHex}`);
         }
diff --git a/packages/utils/test/abi_encoder/evm_data_types_test.ts b/packages/utils/test/abi_encoder/evm_data_types_test.ts
index 4814ce28b..c146890e0 100644
--- a/packages/utils/test/abi_encoder/evm_data_types_test.ts
+++ b/packages/utils/test/abi_encoder/evm_data_types_test.ts
@@ -489,6 +489,24 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
             const argsEncodedFromSignature = dataTypeFromSignature.encode(args);
             expect(argsEncodedFromSignature).to.be.deep.equal(expectedEncodedArgs);
         });
+        it('Null should decode as False', async () => {
+            // Hack @hysz: there are some cases where `false` is encoded as 0x instead of 0x0.
+            // Create DataType object
+            const testDataItem = { name: 'Boolean', type: 'bool' };
+            const dataType = new AbiEncoder.Bool(testDataItem);
+            // Construct args to be encoded
+            const args = false;
+            // Encode Args and validate result
+            const encodedArgs = '0x';
+            const expectedEncodedArgs = '0x0000000000000000000000000000000000000000000000000000000000000000';
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(encodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+            // Validate signature
+            const dataTypeFromSignature = AbiEncoder.create(dataType.getSignature(true));
+            const argsEncodedFromSignature = dataTypeFromSignature.encode(args);
+            expect(argsEncodedFromSignature).to.be.deep.equal(expectedEncodedArgs);
+        });
     });
 
     describe('Integer', () => {