[wip] LinkedList cycle fix (#941)

packages/protocol/contracts/common/linkedlists/LinkedList.sol

@@ -40,6 +40,10 @@ library LinkedList {
   {
     require(key != bytes32(0), "Key must be defined");
     require(!contains(list, key), "Can't insert an existing element");
+    require(
+      previousKey != key && nextKey != key,
+      "Key cannot be the same as previousKey or nextKey"
+    );
 
     Element storage element = list.elements[key];
     element.exists = true;

packages/protocol/contracts/common/test/LinkedListTest.sol

@@ -0,0 +1,48 @@
+pragma solidity ^0.5.8;
+
+import "../linkedlists/LinkedList.sol";
+
+contract LinkedListTest {
+  using LinkedList for LinkedList.List;
+
+  LinkedList.List private list;
+
+  function insert(bytes32 key, bytes32 previousKey, bytes32 nextKey) external {
+    list.insert(key, previousKey, nextKey);
+  }
+
+  function update(bytes32 key, bytes32 previousKey, bytes32 nextKey) external {
+    list.update(key, previousKey, nextKey);
+  }
+
+  function remove(bytes32 key) external {
+    list.remove(key);
+  }
+
+  function contains(bytes32 key) external view returns (bool) {
+    return list.contains(key);
+  }
+
+  function getNumElements() external view returns (uint256) {
+    return list.numElements;
+  }
+
+  function getKeys()
+    external
+    view
+    returns (
+        bytes32[] memory
+    )
+  {
+    return list.getKeys();
+  }
+
+  function head() external view returns (bytes32) {
+    return list.head;
+  }
+
+  function tail() external view returns (bytes32) {
+    return list.tail;
+  }
+
+}

packages/protocol/migrationsConfig.js

@@ -70,7 +70,7 @@ const DefaultConfig = {
 }
 
 const linkedLibraries = {
-  LinkedList: ['AddressLinkedList', 'SortedLinkedList'],
+  LinkedList: ['AddressLinkedList', 'SortedLinkedList', 'LinkedListTest'],
   SortedLinkedList: [
     'AddressSortedLinkedList',
     'IntegerSortedLinkedList',

packages/protocol/test/common/linkedlist.ts

@@ -0,0 +1,86 @@
+import { assertRevert } from '@celo/protocol/lib/test-utils'
+// import BigNumber from 'bignumber.js'
+import { LinkedListTestContract, LinkedListTestInstance } from 'types'
+
+const LinkedListTest: LinkedListTestContract = artifacts.require('LinkedListTest')
+
+// @ts-ignore
+// TODO(mcortesi): Use BN
+LinkedListTest.numberFormat = 'BigNumber'
+
+contract('LinkedListTest', () => {
+  let linkedListTest: LinkedListTestInstance
+
+  beforeEach(async () => {
+    linkedListTest = await LinkedListTest.new()
+  })
+
+  describe('#insert()', () => {
+    const NULL_KEY = '0x00'
+    const firstKey = '0x01'
+    const keys = ['0x01', '0x02', '0x03']
+    const middleKey = '0x02'
+    const lastKey = '0x03'
+    const addedKey = '0x04'
+
+    describe('when inserting to empty list', () => {
+      it('should revert if previous is equal to key', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, addedKey, NULL_KEY))
+      })
+
+      it('should revert if next is equal to key', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, NULL_KEY, addedKey))
+      })
+    })
+
+    describe('when inserting to singleton', () => {
+      beforeEach(async () => {
+        await linkedListTest.insert(firstKey, NULL_KEY, NULL_KEY)
+      })
+
+      it('should revert if next is equal to key', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, firstKey, addedKey))
+      })
+
+      it('should revert if previous is equal to key', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, addedKey, firstKey))
+      })
+    })
+
+    describe('when inserting to a list with more items', () => {
+      beforeEach(async () => {
+        await linkedListTest.insert(firstKey, NULL_KEY, NULL_KEY)
+        for (let i = 1; i < keys.length; i++)
+          await linkedListTest.insert(keys[i], NULL_KEY, keys[i - 1])
+      })
+
+      it('should revert if next is equal to key (beginning)', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, firstKey, addedKey))
+      })
+
+      it('should revert if previous is equal to key (beginning)', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, addedKey, firstKey))
+      })
+
+      it('should revert if next is equal to key (end)', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, lastKey, addedKey))
+      })
+
+      it('should revert if previous is equal to key (end)', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, addedKey, lastKey))
+      })
+
+      it('should revert if next is equal to key (middle)', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, middleKey, addedKey))
+      })
+
+      it('should revert if previous is equal to key (middle)', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, addedKey, middleKey))
+      })
+
+      it('should revert if next and previous equal to key', async () => {
+        await assertRevert(linkedListTest.insert(addedKey, addedKey, addedKey))
+      })
+    })
+  })
+})