Add ERC20 token with snapshoting mechanism (#1209) #1331

jbogacz · 2018-09-18T19:20:40Z

🚀 Description

This pull request is based on changes introduced with frangio:feature-snapshot-token. It adds snapshoting mechanism to regular ERC20 token.

Fixes #1209

[+ ] 📘 I've reviewed the OpenZeppelin Contributor Guidelines
[ +] ✅ I've added tests where applicable to test my new functionality.
[ +] 📖 I've made sure that my contracts are well-documented.
[ +] 🎨 I've run the JS/Solidity linters and fixed any issues (npm run lint:fix).

frangio

Awesome @jbogacz! Here's some initial comments. I'll get back to you on the tests tomorrow.

contracts/token/ERC20/ERC20Snapshot.sol

contracts/utils/Arrays.sol

jbogacz · 2018-09-21T18:16:51Z

@frangio thanks for nice code review. I will apply your comments.

Require reason message removed Inline documentation in NatSpec added Snapshot added to _mint and _burn method

jbogacz · 2018-09-23T10:19:45Z

Hey, @frangio I have followed your comments and hope this time it looks better.

…lin#1329) * release candidate v2.0.0-rc.1 * fix linter error (cherry picked from commit c12a1c6) * Roles now emit events in construction and when renouncing.

* Add the missing test for ERC721Holder * fix lint * Move the holder test to a separate file

* Removed mintingFinished from ERC20Mintable. * Removed MintingFinished from ERC721Mintable. * Removed MintingFinished event.

* Improved bounty tests. * Fixed linter errors. * Addressed review comments.

…Zeppelin#1338) * Add BigNumber support to expectEvent/inLogs (OpenZeppelin#1026) * switched direct logs array check to expectEvent method in AllowanceCrowdsale.test.js * Refactor expectEvent.inLogs function to use simple value number check * Introduced should.be.bignumber method to compare BigNumber values * Destructure transaction object to extract logs field

@nventuro

* fix: refactor sign.js and related tests * fix: remove unused dep * fix: update package.json correctly * Add missing tests to ECRecovery * fix lint * Reorganize the tests * Reuse signature * fix static errors * Apply suggestions by @frangion and @nventuro * Remove only * More suggestions * Remove unnecessary max-len * remove only

…penZeppelin#1343) * Add BigNumber support to expectEvent/inLogs (OpenZeppelin#1026) * switched direct logs array check to expectEvent method in AllowanceCrowdsale.test.js * Refactor expectEvent.inLogs function to use simple value number check * Introduced should.be.bignumber method to compare BigNumber values * Use expectEvent to test logs (OpenZeppelin#1232) * Removed trailing space

…n#1360) * add test for msg.data too short * fix test to hit that branch * Update SignatureBouncer.test.js

nventuro

Hey there @jbogacz! This is in quite a good place, except that we're missing tests for the Arrays library. How would you feel about opening a new PR with just that library (and its tests), and then continuing this one on top? That way feedback can be more focused, and we don't have to be thinking about multiple things at once :)

jbogacz · 2018-09-28T10:01:50Z

Yeah, @nventuro you are absolutely right! I will go for Arrays unit test first.

nventuro · 2018-09-28T10:05:56Z

Great! I'll put this PR on hold then until that one is merged.

* signing prefix added * Minor improvement * Tests changed * Successfully tested * Minor improvements * Minor improvements * Revert "Dangling commas are now required. (OpenZeppelin#1359)" This reverts commit a688977. * fixes OpenZeppelin#1358 * linting done * suggested changes

…ppelin#1368) * signing prefix added * Minor improvement * Tests changed * Successfully tested * Minor improvements * Minor improvements * Revert "Dangling commas are now required. (OpenZeppelin#1359)" This reverts commit a688977. * fixex OpenZeppelin#1355 * linting * suggested changes * Update BreakInvariantBounty.test.js

frangio · 2018-10-01T21:47:59Z

Definitely agree with @nventuro! Let's work on Arrays first and get back to this later.

The fixes to my previous review look good!

…nZeppelin#1364)

mswezey23 · 2018-10-09T03:39:49Z

contracts/mocks/ERC20SnapshotMock.sol

+  function burn(address account, uint256 amount) public {
+    _burn(account, amount);
+  }
+}


Does not include _burnFrom from the current v2 RC2 OZ

It's a mock for unit test purpose so I don't know if this even need mint and burn functions.

burn and mint functions (and burnFrom) impact the total supply. Which is important to keep history of for specific purposes.

Examples include:
Voting Power
Dividend Share

Which both are dependent on the ratio of held tokens at a specified time. In which knowing the total supply is necessary.

mswezey23 · 2018-10-09T03:40:27Z

contracts/token/ERC20/ERC20Snapshot.sol

+   * @return An uint256 representing current snapshot id.
+   */
+  function snapshot() external returns (uint256) {
+    currentSnapshotId += 1;


Does not utilize SafeMath

Thanks, you are right!

mswezey23 · 2018-10-09T03:42:44Z

contracts/token/ERC20/ERC20Snapshot.sol

+  function transfer(address to, uint256 value) public returns (bool) {
+    updateSnapshot(msg.sender);
+    updateSnapshot(to);
+    return super.transfer(to, value);


super.transfer() should be called first to follow OZ's standard of failing early.
Also the balanceOf() function call made below after calling updateSnapshot() will not be correct as the state change has not occurred yet.

mswezey23 · 2018-10-09T03:43:16Z

contracts/token/ERC20/ERC20Snapshot.sol

+  {
+    updateSnapshot(from);
+    updateSnapshot(to);
+    return super.transferFrom(from, to, value);


Again, super.transferFrom() should be called first.

mswezey23 · 2018-10-09T03:43:35Z

contracts/token/ERC20/ERC20Snapshot.sol

+   */
+  function _mint(address account, uint256 amount) internal {
+    updateSnapshot(account);
+    super._mint(account, amount);


super._mint() should be called first

mswezey23 · 2018-10-09T03:43:54Z

contracts/token/ERC20/ERC20Snapshot.sol

+   */
+  function _burn(address account, uint256 amount) internal {
+    updateSnapshot(account);
+    super._burn(account, amount);


super._burn() should be called first

mswezey23 · 2018-10-09T03:46:20Z

contracts/token/ERC20/ERC20Snapshot.sol

+  function updateSnapshot(address account) private {
+    if (lastSnapshotId(account) < currentSnapshotId) {
+      snapshotIds[account].push(currentSnapshotId);
+      snapshotBalances[account].push(balanceOf(account));


balanceOf(account) will have the previous amount recorded. Perhaps this was a desired effect to have the history always behind and not current due to the nature of having to iterate a new snapshot manually.

A discussion is to be had about having snapshots with an on/off feature or have snapshots that are always active.

It's desired flow to have history always behind. If you want to have snapshots off then use regular ERC20.

In your implementation, snapshots are off until another iteration is called upon. It is not an always on feature.

I have to know which snapshot id I want to query, instead of using timestamp or blockNumber, you use a trivial number starting at 1 (0 == no snapshot exists yet). This will make it hard for user adoption as now I have to look up which snapshot id I want in relation to blockNumber/timestamp.

Also, one needs to define which state of the balance do you care about at a specific block number? The balance before the block has been applied to the state or after?

mswezey23 · 2018-10-09T03:48:43Z

contracts/token/ERC20/ERC20Snapshot.sol

+ * @dev An ERC20 token which enables taking snapshots of account balances.
+ * This can be useful to safely implement voting weighed by balance.
+ */
+contract ERC20Snapshot is ERC20 {


There is no tracking of the total supply history of the token if it was mintable or burnable

I don't see the reason to keep racking total supply. Could you elaborate ?

Voting power and dividend payments require knowing the proper ratio of tokens held against the current token supply at a specified time in history.

Small typo in the comment here, should be "weighted" by balance.

mswezey23

Please see my comments below I've included inline per file.
Noted, this PR was submitted awhile back and OZ's repo has been updated since then.

No tracking of totalSupply() history
Does not follow OZ's fail early standard
Not using SafeMath
Requires an external actor to trigger a snapshot (a discussion should be had about this)

Require reason message removed Inline documentation in NatSpec added Snapshot added to _mint and _burn method

….com/jbogacz/openzeppelin-solidity into fix/ERC20-token-with-snapshots-#1209

jbogacz · 2018-10-13T05:53:33Z

@mswezey23 your comments sounds reasonable but with my coding I based on @frangio instructions and @nventuro comments so before any change it's kind to ask guys what do they think about it. @frangio @nventuro could you put your comments here ?

Anyway @mswezey23 implemented #1398 which pretty much covers snapshoting for particular block number and keep total supply as well. I did some research due devident payment and voting power and it follows these requirements so I'm fine to close this my PR and track work on SnapshotToken @mswezey23's PR #1398.

mswezey23 · 2018-11-06T15:30:03Z

Hey everyone - just checking in to see if there has been any updates in regards to this and the PR:
#1398

Thanks!

thomasvds · 2018-11-15T17:04:13Z

contracts/token/ERC20/ERC20Snapshot.sol

+ * @dev An ERC20 token which enables taking snapshots of account balances.
+ * This can be useful to safely implement voting weighed by balance.
+ */
+contract ERC20Snapshot is ERC20 {


Small typo in the comment here, should be "weighted" by balance.

thomasvds · 2018-11-15T17:07:08Z

contracts/token/ERC20/ERC20Snapshot.sol

+  event Snapshot(uint256 id);
+
+  /**
+   * @dev Increments current snapshot. Emites Snapshot event.


Should be "Emits Snapshot event." instead of "Emites".

nventuro · 2019-01-15T19:25:33Z

Hey @jbogacz, sorry for taking so long to review this! We intend to include snapshots in the upcoming release, which is scheduled for next week. Sadly it looks like the diff got too large, due to commits, etc. on master. Could you git rebase so that we get a cleaner changeset? Thanks!

frangio · 2019-02-06T19:28:55Z

The equivalent #1617 was just merged.

nventuro requested a review from frangio September 18, 2018 20:21

nventuro added feature New contracts, functions, or helpers. contracts Smart contract code. labels Sep 18, 2018

frangio reviewed Sep 20, 2018

View reviewed changes

Jakub Bogacz and others added 2 commits September 23, 2018 11:53

Add ERC20 token with snapshoting mechanism (OpenZeppelin#1209)

3b66e70

Methods visibility corrected

1302e6a

Require reason message removed Inline documentation in NatSpec added Snapshot added to _mint and _burn method

jbogacz force-pushed the fix/ERC20-token-with-snapshots-#1209 branch from 61e76c4 to 1302e6a Compare September 23, 2018 09:56

nventuro and others added 9 commits September 26, 2018 11:36

Roles now emit events in construction and when renouncing. (OpenZeppe…

21198bf

…lin#1329) * release candidate v2.0.0-rc.1 * fix linter error (cherry picked from commit c12a1c6) * Roles now emit events in construction and when renouncing.

Add the missing test for ERC721Holder (OpenZeppelin#1249)

396680b

* Add the missing test for ERC721Holder * fix lint * Move the holder test to a separate file

Removed assertions from Escrow and SplitPayment. (OpenZeppelin#1349)

db2e1d2

Removed mintingFinished. (OpenZeppelin#1351)

5fdeaa8

* Removed mintingFinished from ERC20Mintable. * Removed MintingFinished from ERC721Mintable. * Removed MintingFinished event.

Improved bounty tests. (OpenZeppelin#1350)

ae109f6

* Improved bounty tests. * Fixed linter errors. * Addressed review comments.

Add SignatureBouncer test for when msg.data is too short (OpenZeppeli…

1a4e534

…n#1360) * add test for msg.data too short * fix test to hit that branch * Update SignatureBouncer.test.js

nventuro self-assigned this Sep 28, 2018

nventuro reviewed Sep 28, 2018

View reviewed changes

nventuro added the on hold Put on hold for some reason that must be specified in a comment. label Sep 28, 2018

nventuro and others added 3 commits September 28, 2018 19:20

Dangling commas are now required. (OpenZeppelin#1359)

a688977

nventuro added 3 commits October 2, 2018 07:07

Merged latestTime, increaseTime and duration into a time helper. (Ope…

34bc709

…nZeppelin#1364)

Created test utils directory

269981e

Fixed test path.

f4d6f40

Added a constructor to BreakInvariantBounty. (OpenZeppelin#1395)

3acc2b4

mswezey23 reviewed Oct 9, 2018

View reviewed changes

mswezey23 suggested changes Oct 9, 2018

View reviewed changes

Jakub Bogacz and others added 4 commits October 9, 2018 06:55

Add ERC20 token with snapshoting mechanism (OpenZeppelin#1209)

aa6b6d0

Methods visibility corrected

7f59f86

Require reason message removed Inline documentation in NatSpec added Snapshot added to _mint and _burn method

Use SafeMath.

360c85e

Merge branch 'fix/ERC20-token-with-snapshots-#1209' of https://github…

474ec3d

….com/jbogacz/openzeppelin-solidity into fix/ERC20-token-with-snapshots-#1209

nventuro removed the on hold Put on hold for some reason that must be specified in a comment. label Oct 9, 2018

thomasvds suggested changes Nov 15, 2018

View reviewed changes

frangio added this to the v2.1 milestone Nov 28, 2018

nventuro assigned frangio and unassigned nventuro Dec 10, 2018

frangio modified the milestones: v2.1, v2.2 Dec 11, 2018

nventuro assigned nventuro and unassigned frangio Jan 15, 2019

frangio closed this Feb 6, 2019

dependabot-preview bot mentioned this pull request Apr 17, 2019

Bump eslint-plugin-import from 2.13.0 to 2.17.2 buypolarbear/openzeppelin-solidity#39

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Bump eslint-plugin-import from 2.13.0 to 2.17.3 buypolarbear/openzeppelin-solidity#53

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Add ERC20 token with snapshoting mechanism (#1209) #1331

Add ERC20 token with snapshoting mechanism (#1209) #1331

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Add ERC20 token with snapshoting mechanism (#1209) #1331

Add ERC20 token with snapshoting mechanism (#1209) #1331

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