Improve an error message when an inorrect number of constructor params is passed

2 files changed, 15 insertions, 2 deletions

diff --git a/packages/deployer/CHANGELOG.md b/packages/deployer/CHANGELOG.md
index a63d9cf3b..d8bbbbf89 100644
--- a/packages/deployer/CHANGELOG.md
+++ b/packages/deployer/CHANGELOG.md
@@ -2,7 +2,8 @@
 
 ## v0.2.0 - _TBD, 2018_
 
-    * Check dependencies when determining if contracts should be recompiled (#408).
+    * Check dependencies when determining if contracts should be recompiled (#408)
+    * Improve an error message for when deployer is supplied with an incorrect number of constructor arguments (#TBD)
 
 ## v0.1.0 - _February 16, 2018_
 
diff --git a/packages/deployer/src/deployer.ts b/packages/deployer/src/deployer.ts
index 6710bcc85..e87d2ab0e 100644
--- a/packages/deployer/src/deployer.ts
+++ b/packages/deployer/src/deployer.ts
@@ -1,4 +1,4 @@
-import { TxData } from '@0xproject/types';
+import { AbiType, TxData } from '@0xproject/types';
 import { Web3Wrapper } from '@0xproject/web3-wrapper';
 import * as _ from 'lodash';
 import * as Web3 from 'web3';
@@ -49,6 +49,18 @@ export class Deployer {
             gas,
         };
         const abi = contractNetworkDataIfExists.abi;
+        const constructorAbi = _.find(abi, { type: AbiType.Constructor }) as Web3.ConstructorAbi;
+        const constructorArgs = _.isUndefined(constructorAbi) ? [] : constructorAbi.inputs;
+        if (constructorArgs.length !== args.length) {
+            const constructorSignature = `constructor(${_.map(constructorArgs, arg => `${arg.type} ${arg.name}`).join(
+                ', ',
+            )})`;
+            throw new Error(
+                `${contractName} expects ${constructorArgs.length} constructor params: ${constructorSignature}. Got ${
+                    args.length
+                }`,
+            );
+        }
         const web3ContractInstance = await this._deployFromAbiAsync(abi, args, txData);
         utils.consoleLog(`${contractName}.sol successfully deployed at ${web3ContractInstance.address}`);
         const contractInstance = new Contract(web3ContractInstance, this._defaults);