add interface for receiveApproval and relevant test cases

contracts/ApprovalRecipient.sol

@@ -0,0 +1,6 @@
+pragma solidity ^0.4.8;
+
+contract ApprovalRecipient {
+    function receiveApproval(address _from, uint256 _value, address _tokenContract, bytes _extraData)
+        returns (bool success);
+}

contracts/HumanStandardToken.sol

@@ -12,6 +12,7 @@ Machine-based, rapid creation of many tokens would not necessarily need these ex
 .*/
 
 import "./StandardToken.sol";
+import "./ApprovalRecipient.sol";
 
 pragma solidity ^0.4.8;
 
@@ -45,13 +46,13 @@ contract HumanStandardToken is StandardToken {
 
     /* Approves and then calls the receiving contract */
     function approveAndCall(address _spender, uint256 _value, bytes _extraData) returns (bool success) {
-        allowed[msg.sender][_spender] = _value;
-        Approval(msg.sender, _spender, _value);
+        // first approve the amount for the spender
+        require(approve(_spender, _value));
 
         //call the receiveApproval function on the contract you want to be notified. This crafts the function signature manually so one doesn't have to include a contract in here just for this.
         //receiveApproval(address _from, uint256 _value, address _tokenContract, bytes _extraData)
         //it is assumed when one does this that the call *should* succeed, otherwise one would use vanilla approve instead.
-        require(_spender.call(bytes4(bytes32(sha3("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData));
+        require(ApprovalRecipient(_spender).receiveApproval(msg.sender, _value, this, _extraData));
         return true;
     }
 }

package.json

@@ -34,6 +34,7 @@
     "eslint-plugin-node": "^5.1.0",
     "eslint-plugin-react": "^7.1.0",
     "eslint-plugin-standard": "^3.0.1",
+    "left-pad": "^1.1.3",
     "standard": "^10.0.2"
   },
   "standard": {

test/humanStandardToken.js

@@ -2,6 +2,7 @@ const expectThrow = require('./utils').expectThrow
 const HumanStandardTokenAbstraction = artifacts.require('HumanStandardToken')
 const SampleRecipientSuccess = artifacts.require('SampleRecipientSuccess')
 const SampleRecipientThrow = artifacts.require('SampleRecipientThrow')
+const leftPad = require('left-pad')
 let HST
 
 contract('HumanStandardToken', function (accounts) {
@@ -89,6 +90,29 @@ contract('HumanStandardToken', function (accounts) {
     return expectThrow(HST.approveAndCall.call(SRS.address, 100, '0x42', {from: accounts[0]}))
   })
 
+  const EXTRA_DATA_TEST_CASES = [
+    '',
+    '0x',
+    '0x42',
+     // 24 bytes (<1 word)
+    `0x${leftPad('', 48, 'f')}`,
+     // 32 bytes (1 word)
+    `0x${leftPad('', 64, 'f')}`,
+     // 46 bytes (>1 word, <2 words)
+    `0x${leftPad('', 92, 'f')}`,
+     // 64 bytes (2 words)
+    `0x${leftPad('', 128, 'f')}`
+  ]
+
+  EXTRA_DATA_TEST_CASES.forEach(extraData => {
+    it(`approvals: approveAndCall correctly passes _extraData (${Math.max(0, extraData.length - 2)} bytes) to the receiving contract`, async () => {
+      const SRS = await SampleRecipientSuccess.new({from: accounts[0]})
+
+      await HST.approveAndCall(SRS.address, 100, extraData, {from: accounts[0]})
+      assert.strictEqual(await SRS.extraData(), extraData === '' ? '0x' : extraData)
+    })
+  })
+
   // bit overkill. But is for testing a bug
   it('approvals: msg.sender approves accounts[1] of 100 & withdraws 20 once.', async () => {
     const balance0 = await HST.balanceOf.call(accounts[0])