Merge pull request #1587 from 0xProject/fix/abiEncoder/DefaultTypesOnNullInput

Handle ABI decoding NULL for all data types

16 files changed, 470 insertions, 78 deletions

diff --git a/packages/utils/CHANGELOG.json b/packages/utils/CHANGELOG.json
index 8671729d3..8e8a125ef 100644
--- a/packages/utils/CHANGELOG.json
+++ b/packages/utils/CHANGELOG.json
@@ -1,5 +1,14 @@
 [
     {
+        "version": "4.0.2",
+        "changes": [
+            {
+                "note": "ABI Decode NULL for all data types",
+                "pr": 1587
+            }
+        ]
+    },
+    {
         "version": "4.0.1",
         "changes": [
             {
diff --git a/packages/utils/src/abi_encoder/abstract_data_types/data_type.ts b/packages/utils/src/abi_encoder/abstract_data_types/data_type.ts
index f23324721..db4f02b89 100644
--- a/packages/utils/src/abi_encoder/abstract_data_types/data_type.ts
+++ b/packages/utils/src/abi_encoder/abstract_data_types/data_type.ts
@@ -47,7 +47,8 @@ export abstract class DataType {
         const hasSelector = !_.isUndefined(selector);
         const rawCalldata = new RawCalldata(calldata, hasSelector);
         const rules_ = _.isUndefined(rules) ? constants.DEFAULT_DECODING_RULES : rules;
-        const value = this.generateValue(rawCalldata, rules_);
+        const value =
+            rawCalldata.getSizeInBytes() > 0 ? this.generateValue(rawCalldata, rules_) : this.getDefaultValue(rules_);
         return value;
     }
 
@@ -71,6 +72,7 @@ export abstract class DataType {
 
     public abstract generateCalldataBlock(value: any, parentBlock?: CalldataBlock): CalldataBlock;
     public abstract generateValue(calldata: RawCalldata, rules: DecodingRules): any;
+    public abstract getDefaultValue(rules?: DecodingRules): any;
     public abstract getSignatureType(): string;
     public abstract isStatic(): boolean;
 }
diff --git a/packages/utils/src/abi_encoder/abstract_data_types/types/set.ts b/packages/utils/src/abi_encoder/abstract_data_types/types/set.ts
index 2c6c4b0f6..d45088482 100644
--- a/packages/utils/src/abi_encoder/abstract_data_types/types/set.ts
+++ b/packages/utils/src/abi_encoder/abstract_data_types/types/set.ts
@@ -97,6 +97,27 @@ export abstract class AbstractSetDataType extends DataType {
         return isStatic;
     }
 
+    public getDefaultValue(rules?: DecodingRules): any[] | object {
+        let defaultValue: any[] | object;
+        if (this._isArray && _.isUndefined(this._arrayLength)) {
+            defaultValue = [];
+        } else if (!_.isUndefined(rules) && rules.shouldConvertStructsToObjects && !this._isArray) {
+            defaultValue = {};
+            _.each(this._memberIndexByName, (idx: number, key: string) => {
+                const member = this._members[idx];
+                const memberValue = member.getDefaultValue();
+                (defaultValue as { [key: string]: any })[key] = memberValue;
+            });
+        } else {
+            defaultValue = [];
+            _.each(this._members, (member: DataType, idx: number) => {
+                const memberValue = member.getDefaultValue();
+                (defaultValue as any[]).push(memberValue);
+            });
+        }
+        return defaultValue;
+    }
+
     protected _generateCalldataBlockFromArray(value: any[], parentBlock?: CalldataBlock): SetCalldataBlock {
         // Sanity check: if the set has a defined length then `value` must have the same length.
         if (!_.isUndefined(this._arrayLength) && value.length !== this._arrayLength) {
diff --git a/packages/utils/src/abi_encoder/calldata/raw_calldata.ts b/packages/utils/src/abi_encoder/calldata/raw_calldata.ts
index 189841989..dbc9d4942 100644
--- a/packages/utils/src/abi_encoder/calldata/raw_calldata.ts
+++ b/packages/utils/src/abi_encoder/calldata/raw_calldata.ts
@@ -79,4 +79,9 @@ export class RawCalldata {
     public getSelector(): string {
         return this._selector;
     }
+
+    public getSizeInBytes(): number {
+        const sizeInBytes = this._value.byteLength;
+        return sizeInBytes;
+    }
 }
diff --git a/packages/utils/src/abi_encoder/evm_data_types/address.ts b/packages/utils/src/abi_encoder/evm_data_types/address.ts
index 2278830eb..7e92d3888 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/address.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/address.ts
@@ -12,6 +12,7 @@ export class AddressDataType extends AbstractBlobDataType {
     private static readonly _ADDRESS_SIZE_IN_BYTES = 20;
     private static readonly _DECODED_ADDRESS_OFFSET_IN_BYTES =
         constants.EVM_WORD_WIDTH_IN_BYTES - AddressDataType._ADDRESS_SIZE_IN_BYTES;
+    private static readonly _DEFAULT_VALUE = '0x0000000000000000000000000000000000000000';
 
     public static matchType(type: string): boolean {
         return type === SolidityTypes.Address;
@@ -43,6 +44,10 @@ export class AddressDataType extends AbstractBlobDataType {
         return valueLowercase;
     }
 
+    public getDefaultValue(): string {
+        return AddressDataType._DEFAULT_VALUE;
+    }
+
     public getSignatureType(): string {
         return SolidityTypes.Address;
     }
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 ffccd6e53..24887c509 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/bool.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/bool.ts
@@ -10,6 +10,7 @@ import { constants } from '../utils/constants';
 
 export class BoolDataType extends AbstractBlobDataType {
     private static readonly _SIZE_KNOWN_AT_COMPILE_TIME: boolean = true;
+    private static readonly _DEFAULT_VALUE: boolean = false;
 
     public static matchType(type: string): boolean {
         return type === SolidityTypes.Bool;
@@ -47,6 +48,10 @@ export class BoolDataType extends AbstractBlobDataType {
         return value;
     }
 
+    public getDefaultValue(): boolean {
+        return BoolDataType._DEFAULT_VALUE;
+    }
+
     public getSignatureType(): string {
         return SolidityTypes.Bool;
     }
diff --git a/packages/utils/src/abi_encoder/evm_data_types/dynamic_bytes.ts b/packages/utils/src/abi_encoder/evm_data_types/dynamic_bytes.ts
index fa38b63c0..7a49a84b4 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/dynamic_bytes.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/dynamic_bytes.ts
@@ -9,6 +9,7 @@ import { constants } from '../utils/constants';
 
 export class DynamicBytesDataType extends AbstractBlobDataType {
     private static readonly _SIZE_KNOWN_AT_COMPILE_TIME: boolean = false;
+    private static readonly _DEFAULT_VALUE = '0x';
 
     public static matchType(type: string): boolean {
         return type === SolidityTypes.Bytes;
@@ -65,6 +66,10 @@ export class DynamicBytesDataType extends AbstractBlobDataType {
         return value;
     }
 
+    public getDefaultValue(): string {
+        return DynamicBytesDataType._DEFAULT_VALUE;
+    }
+
     public getSignatureType(): string {
         return SolidityTypes.Bytes;
     }
diff --git a/packages/utils/src/abi_encoder/evm_data_types/int.ts b/packages/utils/src/abi_encoder/evm_data_types/int.ts
index f8be1f778..02278f666 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/int.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/int.ts
@@ -15,6 +15,7 @@ export class IntDataType extends AbstractBlobDataType {
     private static readonly _SIZE_KNOWN_AT_COMPILE_TIME: boolean = true;
     private static readonly _MAX_WIDTH: number = 256;
     private static readonly _DEFAULT_WIDTH: number = IntDataType._MAX_WIDTH;
+    private static readonly _DEFAULT_VALUE = new BigNumber(0);
     private readonly _width: number;
     private readonly _minValue: BigNumber;
     private readonly _maxValue: BigNumber;
@@ -50,13 +51,20 @@ export class IntDataType extends AbstractBlobDataType {
     public decodeValue(calldata: RawCalldata): BigNumber | number {
         const valueBuf = calldata.popWord();
         const value = EncoderMath.safeDecodeNumericValue(valueBuf, this._minValue, this._maxValue);
-        const numberOfBytesInUint8 = 8;
-        if (this._width === numberOfBytesInUint8) {
+        if (this._width === constants.NUMBER_OF_BYTES_IN_INT8) {
             return value.toNumber();
         }
         return value;
     }
 
+    public getDefaultValue(): BigNumber | number {
+        const defaultValue = IntDataType._DEFAULT_VALUE;
+        if (this._width === constants.NUMBER_OF_BYTES_IN_INT8) {
+            return defaultValue.toNumber();
+        }
+        return defaultValue;
+    }
+
     public getSignatureType(): string {
         return `${SolidityTypes.Int}${this._width}`;
     }
diff --git a/packages/utils/src/abi_encoder/evm_data_types/pointer.ts b/packages/utils/src/abi_encoder/evm_data_types/pointer.ts
index 250db7c64..50f68f5ea 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/pointer.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/pointer.ts
@@ -18,4 +18,9 @@ export class PointerDataType extends AbstractPointerDataType {
     public getSignature(isDetailed?: boolean): string {
         return this._destination.getSignature(isDetailed);
     }
+
+    public getDefaultValue(): any {
+        const defaultValue = this._destination.getDefaultValue();
+        return defaultValue;
+    }
 }
diff --git a/packages/utils/src/abi_encoder/evm_data_types/static_bytes.ts b/packages/utils/src/abi_encoder/evm_data_types/static_bytes.ts
index cbf1957d7..a965f6796 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/static_bytes.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/static_bytes.ts
@@ -58,6 +58,13 @@ export class StaticBytesDataType extends AbstractBlobDataType {
         return value;
     }
 
+    public getDefaultValue(): string {
+        const valueBufPadded = constants.EMPTY_EVM_WORD_BUFFER;
+        const valueBuf = valueBufPadded.slice(0, this._width);
+        const value = ethUtil.bufferToHex(valueBuf);
+        return value;
+    }
+
     private _sanityCheckValue(value: string | Buffer): void {
         if (typeof value === 'string') {
             if (!_.startsWith(value, '0x')) {
diff --git a/packages/utils/src/abi_encoder/evm_data_types/string.ts b/packages/utils/src/abi_encoder/evm_data_types/string.ts
index 97ac46442..f54d739b4 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/string.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/string.ts
@@ -9,6 +9,7 @@ import { constants } from '../utils/constants';
 
 export class StringDataType extends AbstractBlobDataType {
     private static readonly _SIZE_KNOWN_AT_COMPILE_TIME: boolean = false;
+    private static readonly _DEFAULT_VALUE = '';
 
     public static matchType(type: string): boolean {
         return type === SolidityTypes.String;
@@ -52,6 +53,10 @@ export class StringDataType extends AbstractBlobDataType {
         return value;
     }
 
+    public getDefaultValue(): string {
+        return StringDataType._DEFAULT_VALUE;
+    }
+
     public getSignatureType(): string {
         return SolidityTypes.String;
     }
diff --git a/packages/utils/src/abi_encoder/evm_data_types/uint.ts b/packages/utils/src/abi_encoder/evm_data_types/uint.ts
index a82aa789e..d530606b9 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/uint.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/uint.ts
@@ -16,6 +16,7 @@ export class UIntDataType extends AbstractBlobDataType {
     private static readonly _MAX_WIDTH: number = 256;
     private static readonly _DEFAULT_WIDTH: number = UIntDataType._MAX_WIDTH;
     private static readonly _MIN_VALUE = new BigNumber(0);
+    private static readonly _DEFAULT_VALUE = new BigNumber(0);
     private readonly _width: number;
     private readonly _maxValue: BigNumber;
 
@@ -49,13 +50,20 @@ export class UIntDataType extends AbstractBlobDataType {
     public decodeValue(calldata: RawCalldata): BigNumber | number {
         const valueBuf = calldata.popWord();
         const value = EncoderMath.safeDecodeNumericValue(valueBuf, UIntDataType._MIN_VALUE, this._maxValue);
-        const numberOfBytesInUint8 = 8;
-        if (this._width === numberOfBytesInUint8) {
+        if (this._width === constants.NUMBER_OF_BYTES_IN_UINT8) {
             return value.toNumber();
         }
         return value;
     }
 
+    public getDefaultValue(): BigNumber | number {
+        const defaultValue = UIntDataType._DEFAULT_VALUE;
+        if (this._width === constants.NUMBER_OF_BYTES_IN_UINT8) {
+            return defaultValue.toNumber();
+        }
+        return defaultValue;
+    }
+
     public getSignatureType(): string {
         return `${SolidityTypes.Uint}${this._width}`;
     }
diff --git a/packages/utils/src/abi_encoder/utils/constants.ts b/packages/utils/src/abi_encoder/utils/constants.ts
index fc586f295..b45b5b8e8 100644
--- a/packages/utils/src/abi_encoder/utils/constants.ts
+++ b/packages/utils/src/abi_encoder/utils/constants.ts
@@ -1,3 +1,5 @@
+import * as ethUtil from 'ethereumjs-util';
+
 import { DecodingRules, EncodingRules } from './rules';
 
 export const constants = {
@@ -14,4 +16,8 @@ export const constants = {
     DEFAULT_DECODING_RULES: { shouldConvertStructsToObjects: true } as DecodingRules,
     DEFAULT_ENCODING_RULES: { shouldOptimize: true, shouldAnnotate: false } as EncodingRules,
     /* tslint:enable no-object-literal-type-assertion */
+    EMPTY_EVM_WORD_STRING: '0x0000000000000000000000000000000000000000000000000000000000000000',
+    EMPTY_EVM_WORD_BUFFER: ethUtil.toBuffer('0x0000000000000000000000000000000000000000000000000000000000000000'),
+    NUMBER_OF_BYTES_IN_UINT8: 8,
+    NUMBER_OF_BYTES_IN_INT8: 8,
 };
diff --git a/packages/utils/test/abi_encoder/abi_samples/return_value_abis.ts b/packages/utils/test/abi_encoder/abi_samples/return_value_abis.ts
index ac2124011..ad07b3d24 100644
--- a/packages/utils/test/abi_encoder/abi_samples/return_value_abis.ts
+++ b/packages/utils/test/abi_encoder/abi_samples/return_value_abis.ts
@@ -97,3 +97,28 @@ export const mixedStaticAndDynamicReturnValues: MethodAbi = {
     stateMutability: 'nonpayable',
     type: 'function',
 };
+
+export const structuredReturnValue: MethodAbi = {
+    constant: false,
+    inputs: [],
+    name: 'fillOrder',
+    outputs: [
+        {
+            components: [
+                {
+                    name: 'makerAssetFilledAmount',
+                    type: 'uint256',
+                },
+                {
+                    name: 'takerAssetFilledAmount',
+                    type: 'uint256',
+                },
+            ],
+            name: 'fillResults',
+            type: 'tuple',
+        },
+    ],
+    payable: false,
+    stateMutability: 'nonpayable',
+    type: 'function',
+};
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 c146890e0..c09c0d929 100644
--- a/packages/utils/test/abi_encoder/evm_data_types_test.ts
+++ b/packages/utils/test/abi_encoder/evm_data_types_test.ts
@@ -11,6 +11,7 @@ const expect = chai.expect;
 
 describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
     const encodingRules: AbiEncoder.EncodingRules = { shouldOptimize: false }; // optimizer is tested separately.
+    const nullEncodedArgs = '0x';
     describe('Array', () => {
         it('Fixed size; Static elements', async () => {
             // Create DataType object
@@ -207,6 +208,51 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
                 dataType.encode(args, encodingRules);
             }).to.throw('Tried to assign NaN value');
         });
+        it('Should decode NULL to default values (Fixed size; Static elements)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'testArray', type: 'int[2]' };
+            const dataType = new AbiEncoder.Array(testDataItem);
+            const args = [new BigNumber(0), new BigNumber(0)];
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
+        it('Should decode NULL to default values (Dynamic size; Static elements)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'testArray', type: 'int[]' };
+            const dataType = new AbiEncoder.Array(testDataItem);
+            const args: BigNumber[] = [];
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
+        it('Should decode NULL to default values (Fixed size; Dynamic elements)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'testArray', type: 'string[2]' };
+            const dataType = new AbiEncoder.Array(testDataItem);
+            const args = ['', ''];
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
+        it('Should decode NULL to default values (Dynamic size; Dynamic elements)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'testArray', type: 'string[]' };
+            const dataType = new AbiEncoder.Array(testDataItem);
+            const args: string[] = [];
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
+        it('Should decode NULL to default values (Dynamic Size; Multidimensional; Dynamic Elements)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'testArray', type: 'bytes[][]' };
+            const dataType = new AbiEncoder.Array(testDataItem);
+            const args: string[][] = [];
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 
     describe('Tuple', () => {
@@ -407,6 +453,46 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
                 dataType.encode(args, encodingRules);
             }).to.throw('Could not assign tuple to object: missing key \'field_2\' in object {"field_1":"-5"}');
         });
+        it('Should decode NULL to default values (static elements only)', async () => {
+            // Create DataType object
+            const testDataItem = {
+                name: 'Tuple',
+                type: 'tuple',
+                components: [{ name: 'field_1', type: 'int32' }, { name: 'field_2', type: 'bool' }],
+            };
+            const dataType = new AbiEncoder.Tuple(testDataItem);
+            // Construct args to be encoded
+            const args = { field_1: new BigNumber(0), field_2: false };
+            // Decode Encoded Args and validate result
+            const decodingRules: AbiEncoder.DecodingRules = { shouldConvertStructsToObjects: true };
+            const decodedArgs = dataType.decode(nullEncodedArgs, decodingRules);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
+        it('Should decode NULL to default values (static and dynamic elements)', async () => {
+            // Create DataType object
+            const testDataItem = {
+                name: 'Tuple',
+                type: 'tuple',
+                components: [
+                    { name: 'field_1', type: 'int32' },
+                    { name: 'field_2', type: 'string' },
+                    { name: 'field_3', type: 'bool' },
+                    { name: 'field_4', type: 'bytes' },
+                ],
+            };
+            const dataType = new AbiEncoder.Tuple(testDataItem);
+            // Construct args to be encoded
+            const args = {
+                field_1: new BigNumber(0),
+                field_2: '',
+                field_3: false,
+                field_4: '0x',
+            };
+            // Decode Encoded Args and validate result
+            const decodingRules: AbiEncoder.DecodingRules = { shouldConvertStructsToObjects: true };
+            const decodedArgs = dataType.decode(nullEncodedArgs, decodingRules);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 
     describe('Address', () => {
@@ -450,6 +536,15 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
                 dataType.encode(args, encodingRules);
             }).to.throw(`Invalid address: '${args}'`);
         });
+        it('Should decode NULL to default value of address zero', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'Address', type: 'address' };
+            const dataType = new AbiEncoder.Address(testDataItem);
+            const args = '0x0000000000000000000000000000000000000000';
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 
     describe('Bool', () => {
@@ -489,23 +584,14 @@ 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.
+        it('Should decode NULL to default value of False', async () => {
             // 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);
+            const decodedArgs = dataType.decode(nullEncodedArgs);
             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);
         });
     });
 
@@ -705,6 +791,15 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
                 dataType.encode(args, encodingRules);
             }).to.throw();
         });
+        it('Should decode NULL to default value of 0', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'Integer (256)', type: 'int' };
+            const dataType = new AbiEncoder.Int(testDataItem);
+            const args = new BigNumber(0);
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 
     describe('Unsigned Integer', () => {
@@ -867,6 +962,15 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
                 dataType.encode(args, encodingRules);
             }).to.throw();
         });
+        it('Should decode NULL to default value of 0', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'Unsigned Integer (256)', type: 'uint' };
+            const dataType = new AbiEncoder.UInt(testDataItem);
+            const args = new BigNumber(0);
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 
     describe('Static Bytes', () => {
@@ -1030,6 +1134,33 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
                 dataType.encode(args, encodingRules);
             }).to.throw('Tried to assign 0x010, which is contains a half-byte. Use full bytes only.');
         });
+        it('Should decode NULL to default value - Single Byte (byte)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'Static Byte', type: 'byte' };
+            const dataType = new AbiEncoder.StaticBytes(testDataItem);
+            const args = '0x00';
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
+        it('Should decode NULL to default value - 4 Bytes (bytes4)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'Static Bytes4', type: 'bytes4' };
+            const dataType = new AbiEncoder.StaticBytes(testDataItem);
+            const args = '0x00000000';
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
+        it('Should decode NULL to default value - 32 Bytes (bytes32)', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'Static Bytes32', type: 'bytes32' };
+            const dataType = new AbiEncoder.StaticBytes(testDataItem);
+            const args = '0x0000000000000000000000000000000000000000000000000000000000000000';
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 
     describe('Dynamic Bytes', () => {
@@ -1117,6 +1248,15 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
                 dataType.encode(args, encodingRules);
             }).to.throw('Tried to assign 0x010, which is contains a half-byte. Use full bytes only.');
         });
+        it('Should decode NULL to empty byte array', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'Dynamic Bytes', type: 'bytes' };
+            const dataType = new AbiEncoder.DynamicBytes(testDataItem);
+            const args = '0x';
+            // Decode Encoded Args and validate result
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 
     describe('String', () => {
@@ -1182,5 +1322,14 @@ describe('ABI Encoder: EVM Data Type Encoding/Decoding', () => {
             const argsEncodedFromSignature = dataTypeFromSignature.encode(args);
             expect(argsEncodedFromSignature).to.be.deep.equal(expectedEncodedArgs);
         });
+        it('Should decode NULL to empty string', async () => {
+            // Create DataType object
+            const testDataItem = { name: 'String', type: 'string' };
+            const dataType = new AbiEncoder.String(testDataItem);
+            // Decode Encoded Args and validate result
+            const args = '';
+            const decodedArgs = dataType.decode(nullEncodedArgs);
+            expect(decodedArgs).to.be.deep.equal(args);
+        });
     });
 });
diff --git a/packages/utils/test/abi_encoder/return_values_test.ts b/packages/utils/test/abi_encoder/return_values_test.ts
index 308d11ee5..ccdac510d 100644
--- a/packages/utils/test/abi_encoder/return_values_test.ts
+++ b/packages/utils/test/abi_encoder/return_values_test.ts
@@ -1,7 +1,7 @@
 import * as chai from 'chai';
 import 'mocha';
 
-import { AbiEncoder } from '../../src/';
+import { AbiEncoder, BigNumber } from '../../src/';
 import { chaiSetup } from '../utils/chai_setup';
 
 import * as ReturnValueAbis from './abi_samples/return_value_abis';
@@ -11,67 +11,194 @@ const expect = chai.expect;
 
 describe('ABI Encoder: Return Value Encoding/Decoding', () => {
     const encodingRules: AbiEncoder.EncodingRules = { shouldOptimize: false }; // optimizer is tested separately.
-    it('No Return Value', async () => {
-        // Decode return value
-        const method = new AbiEncoder.Method(ReturnValueAbis.noReturnValues);
-        const returnValue = '0x';
-        const decodedReturnValue = method.decodeReturnValues(returnValue, { shouldConvertStructsToObjects: false });
-        const expectedDecodedReturnValue: any[] = [];
-        expect(decodedReturnValue).to.be.deep.equal(expectedDecodedReturnValue);
-    });
-    it('Single static return value', async () => {
-        // Generate Return Value
-        const method = new AbiEncoder.Method(ReturnValueAbis.singleStaticReturnValue);
-        const returnValue = ['0x01020304'];
-        const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
-        const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
-            shouldConvertStructsToObjects: false,
-        });
-        // Validate decoded return value
-        expect(decodedReturnValue).to.be.deep.equal(returnValue);
-    });
-    it('Multiple static return values', async () => {
-        // Generate Return Value
-        const method = new AbiEncoder.Method(ReturnValueAbis.multipleStaticReturnValues);
-        const returnValue = ['0x01020304', '0x05060708'];
-        const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
-        const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
-            shouldConvertStructsToObjects: false,
-        });
-        // Validate decoded return value
-        expect(decodedReturnValue).to.be.deep.equal(returnValue);
-    });
-    it('Single dynamic return value', async () => {
-        // Generate Return Value
-        const method = new AbiEncoder.Method(ReturnValueAbis.singleDynamicReturnValue);
-        const returnValue = ['0x01020304'];
-        const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
-        const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
-            shouldConvertStructsToObjects: false,
-        });
-        // Validate decoded return value
-        expect(decodedReturnValue).to.be.deep.equal(returnValue);
-    });
-    it('Multiple dynamic return values', async () => {
-        // Generate Return Value
-        const method = new AbiEncoder.Method(ReturnValueAbis.multipleDynamicReturnValues);
-        const returnValue = ['0x01020304', '0x05060708'];
-        const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
-        const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
-            shouldConvertStructsToObjects: false,
-        });
-        // Validate decoded return value
-        expect(decodedReturnValue).to.be.deep.equal(returnValue);
+    const nullEncodedReturnValue = '0x';
+    describe('Standard encoding/decoding', () => {
+        it('No Return Value', async () => {
+            // Decode return value
+            const method = new AbiEncoder.Method(ReturnValueAbis.noReturnValues);
+            const returnValue = '0x';
+            const decodedReturnValue = method.decodeReturnValues(returnValue, { shouldConvertStructsToObjects: false });
+            const expectedDecodedReturnValue: any[] = [];
+            expect(decodedReturnValue).to.be.deep.equal(expectedDecodedReturnValue);
+        });
+        it('Single static return value', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleStaticReturnValue);
+            const returnValue = ['0x01020304'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Multiple static return values', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.multipleStaticReturnValues);
+            const returnValue = ['0x01020304', '0x05060708'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Single dynamic return value', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleDynamicReturnValue);
+            const returnValue = ['0x01020304'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Multiple dynamic return values', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.multipleDynamicReturnValues);
+            const returnValue = ['0x01020304', '0x05060708'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Mixed static/dynamic return values', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.mixedStaticAndDynamicReturnValues);
+            const returnValue = ['0x01020304', '0x05060708'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Should decode NULL as default value (single; static)', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleStaticReturnValue);
+            const returnValue = ['0x00000000'];
+
+            const decodedReturnValue = method.decodeReturnValues(nullEncodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Should decode NULL as default value (multiple; static)', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.multipleStaticReturnValues);
+            const returnValue = ['0x00000000', '0x00000000'];
+            const decodedReturnValue = method.decodeReturnValues(nullEncodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Should decode NULL as default value (single; dynamic)', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleDynamicReturnValue);
+            const returnValue = ['0x'];
+            const decodedReturnValue = method.decodeReturnValues(nullEncodedReturnValue, {
+                shouldConvertStructsToObjects: false,
+            });
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
     });
-    it('Mixed static/dynamic return values', async () => {
-        // Generate Return Value
-        const method = new AbiEncoder.Method(ReturnValueAbis.mixedStaticAndDynamicReturnValues);
-        const returnValue = ['0x01020304', '0x05060708'];
-        const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
-        const decodedReturnValue = method.decodeReturnValues(encodedReturnValue, {
-            shouldConvertStructsToObjects: false,
-        });
-        // Validate decoded return value
-        expect(decodedReturnValue).to.be.deep.equal(returnValue);
+
+    describe('Strict encoding/decoding', () => {
+        it('No Return Value', async () => {
+            // Decode return value
+            const method = new AbiEncoder.Method(ReturnValueAbis.noReturnValues);
+            const returnValue = '0x';
+            const decodedReturnValue = method.strictDecodeReturnValue<void>(returnValue);
+            const expectedDecodedReturnValue = undefined;
+            expect(decodedReturnValue).to.be.deep.equal(expectedDecodedReturnValue);
+        });
+        it('Single static return value', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleStaticReturnValue);
+            const returnValue = ['0x01020304'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.strictDecodeReturnValue<string>(encodedReturnValue);
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue[0]);
+        });
+        it('Multiple static return values', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.multipleStaticReturnValues);
+            const returnValue = ['0x01020304', '0x05060708'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.strictDecodeReturnValue<[string, string]>(encodedReturnValue);
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Single dynamic return value', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleDynamicReturnValue);
+            const returnValue = ['0x01020304'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.strictDecodeReturnValue<string>(encodedReturnValue);
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue[0]);
+        });
+        it('Multiple dynamic return values', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.multipleDynamicReturnValues);
+            const returnValue = ['0x01020304', '0x05060708'];
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.strictDecodeReturnValue<[string, string]>(encodedReturnValue);
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Struct should include fields', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.structuredReturnValue);
+            const returnValue = {
+                fillResults: {
+                    makerAssetFilledAmount: new BigNumber(50),
+                    takerAssetFilledAmount: new BigNumber(40),
+                },
+            };
+            const encodedReturnValue = method.encodeReturnValues(returnValue, encodingRules);
+            const decodedReturnValue = method.strictDecodeReturnValue<{
+                makerAssetFilledAmount: BigNumber;
+                takerAssetFilledAmount: BigNumber;
+            }>(encodedReturnValue);
+            // Validate decoded return value
+            // Note that only the contents of `fillResults`, not the key itself, is decoded.
+            // This is by design, as only a struct's contents are encoded and returned by a funciton call.
+            expect(decodedReturnValue).to.be.deep.equal(returnValue.fillResults);
+        });
+        it('Should decode NULL as default value (single; static)', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleStaticReturnValue);
+            const returnValue = '0x00000000';
+            const encodedReturnValue = '0x';
+            const decodedReturnValue = method.strictDecodeReturnValue<string>(encodedReturnValue);
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Should decode NULL as default value (multiple; static)', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.multipleStaticReturnValues);
+            const returnValue = ['0x00000000', '0x00000000'];
+            const encodedReturnValue = '0x';
+            const decodedReturnValue = method.strictDecodeReturnValue<[string, string]>(encodedReturnValue);
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
+        it('Should decode NULL as default value (single; dynamic)', async () => {
+            // Generate Return Value
+            const method = new AbiEncoder.Method(ReturnValueAbis.singleDynamicReturnValue);
+            const returnValue = '0x';
+            const encodedReturnValue = '0x';
+            const decodedReturnValue = method.strictDecodeReturnValue<string>(encodedReturnValue);
+            // Validate decoded return value
+            expect(decodedReturnValue).to.be.deep.equal(returnValue);
+        });
     });
 });