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Inherit ERC20Wrapper decimals from the underlying #3259

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merged 2 commits into from Mar 22, 2022
Merged

Inherit ERC20Wrapper decimals from the underlying #3259

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73c6598
improve wrapper decimal support
Amxx Mar 10, 2022
f58f39c
Update test/token/ERC20/extensions/ERC20Wrapper.test.js
Amxx Mar 10, 2022
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8 changes: 8 additions & 0 deletions contracts/mocks/ERC20DecimalsMock.sol
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Expand Up @@ -18,4 +18,12 @@ contract ERC20DecimalsMock is ERC20 {
function decimals() public view virtual override returns (uint8) {
return _decimals;
}

function mint(address account, uint256 amount) public {
_mint(account, amount);
}

function burn(address account, uint256 amount) public {
_burn(account, amount);
}
}
11 changes: 11 additions & 0 deletions contracts/token/ERC20/extensions/ERC20Wrapper.sol
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Expand Up @@ -22,6 +22,17 @@ abstract contract ERC20Wrapper is ERC20 {
underlying = underlyingToken;
}

/**
* @dev See {ERC20-decimals}.
*/
function decimals() public view virtual override returns (uint8) {
try IERC20Metadata(address(underlying)).decimals() returns (uint8 value) {
return value;
} catch {
return super.decimals();
}
}

/**
* @dev Allow a user to deposit underlying tokens and mint the corresponding number of wrapped tokens.
*/
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17 changes: 13 additions & 4 deletions test/token/ERC20/extensions/ERC20Wrapper.test.js
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Expand Up @@ -4,7 +4,8 @@ const { ZERO_ADDRESS, MAX_UINT256 } = constants;

const { shouldBehaveLikeERC20 } = require('../ERC20.behavior');

const ERC20Mock = artifacts.require('ERC20Mock');
const NotAnERC20 = artifacts.require('CallReceiverMock');
const ERC20Mock = artifacts.require('ERC20DecimalsMock');
const ERC20WrapperMock = artifacts.require('ERC20WrapperMock');

contract('ERC20', function (accounts) {
Expand All @@ -16,8 +17,10 @@ contract('ERC20', function (accounts) {
const initialSupply = new BN(100);

beforeEach(async function () {
this.underlying = await ERC20Mock.new(name, symbol, initialHolder, initialSupply);
this.underlying = await ERC20Mock.new(name, symbol, 9);
this.token = await ERC20WrapperMock.new(this.underlying.address, `Wrapped ${name}`, `W${symbol}`);

await this.underlying.mint(initialHolder, initialSupply);
});

afterEach(async function () {
Expand All @@ -32,8 +35,14 @@ contract('ERC20', function (accounts) {
expect(await this.token.symbol()).to.equal(`W${symbol}`);
});

it('has 18 decimals', async function () {
expect(await this.token.decimals()).to.be.bignumber.equal('18');
it('has the same decimals as the underlying token', async function () {
expect(await this.token.decimals()).to.be.bignumber.equal('9');
});

it('decimals default back to 18 if token has no metadata', async function () {
const noDecimals = await NotAnERC20.new();
const otherToken = await ERC20WrapperMock.new(noDecimals.address, `Wrapped ${name}`, `W${symbol}`);
expect(await otherToken.decimals()).to.be.bignumber.equal('18');
});

it('has underlying', async function () {
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