Add ERC20 _setTokenURI (#1618)

* Add _setTokenURI internal.

* Rename TokenMetadata to ERC20Metadata.

* Add changelog entry for ERC20Metadata.

* Fix linter error.

* Add breaking change changelog notice.

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### New features:
  * `ERC20`: added internal `_approve(address owner, address spender, uint256 value)`, allowing derived contracts to set the allowance of arbitrary accounts.
+ * `ERC20Metadata`: added internal `_setTokenURI(string memory tokenURI)`.
 
 ### Improvements:
  * Upgraded the minimum compiler version to v0.5.2: this removes many Solidity warnings that were false positives.
@@ -14,6 +15,7 @@
 ### Bugfixes:
 
 ### Breaking changes:
+ * `TokenMetadata` (in drafts) has been renamed to `ERC20Metadata`.
 
 ## 2.1.2 (2019-17-01)
  * Removed most of the test suite from the npm package, except `PublicRole.behavior.js`, which may be useful to users testing their own `Roles`.

contracts/drafts/ERC1046/TokenMetadata.sol → contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -7,18 +7,18 @@ import "../../token/ERC20/IERC20.sol";
  * @dev See https://eips.ethereum.org/EIPS/eip-1046
  * @dev tokenURI must respond with a URI that implements https://eips.ethereum.org/EIPS/eip-1047
  */
-contract ERC20TokenMetadata is IERC20 {
-    function tokenURI() external view returns (string memory);
-}
-
-contract ERC20WithMetadata is ERC20TokenMetadata {
+contract ERC20Metadata {
     string private _tokenURI;
 
-    constructor (string memory tokenURI) public {
-        _tokenURI = tokenURI;
+    constructor (string memory tokenURI_) public {
+        _setTokenURI(tokenURI_);
     }
 
     function tokenURI() external view returns (string memory) {
         return _tokenURI;
     }
+
+    function _setTokenURI(string memory tokenURI_) internal {
+        _tokenURI = tokenURI_;
+    }
 }

contracts/mocks/ERC20MetadataMock.sol

@@ -0,0 +1,14 @@
+pragma solidity ^0.5.2;
+
+import "../token/ERC20/ERC20.sol";
+import "../drafts/ERC1046/ERC20Metadata.sol";
+
+contract ERC20MetadataMock is ERC20, ERC20Metadata {
+    constructor (string memory tokenURI) public ERC20Metadata(tokenURI) {
+        // solhint-disable-previous-line no-empty-blocks
+    }
+
+    function setTokenURI(string memory tokenURI) public {
+        _setTokenURI(tokenURI);
+    }
+}

test/drafts/ERC1046/ERC20Metadata.test.js

@@ -0,0 +1,23 @@
+require('openzeppelin-test-helpers');
+
+const ERC20MetadataMock = artifacts.require('ERC20MetadataMock');
+
+const metadataURI = 'https://example.com';
+
+describe('ERC20Metadata', function () {
+  beforeEach(async function () {
+    this.token = await ERC20MetadataMock.new(metadataURI);
+  });
+
+  it('responds with the metadata', async function () {
+    (await this.token.tokenURI()).should.equal(metadataURI);
+  });
+
+  describe('setTokenURI', function () {
+    it('changes the original URI', async function () {
+      const newMetadataURI = 'https://betterexample.com';
+      await this.token.setTokenURI(newMetadataURI);
+      (await this.token.tokenURI()).should.equal(newMetadataURI);
+    });
+  });
+});