Add ERC1155.totalSupply that returns overall supply count (#3962)

.changeset/chilled-spiders-attack.md

@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': major
+---
+
+`ERC1155Supply`: add a `totalSupply()` function that returns the total amount of token circulating, this change will restrict the total tokens minted across all ids to 2\*\*256-1 .

contracts/token/ERC1155/extensions/ERC1155Supply.sol

@@ -15,6 +15,7 @@ import "../ERC1155.sol";
  */
 abstract contract ERC1155Supply is ERC1155 {
     mapping(uint256 => uint256) private _totalSupply;
+    uint256 private _totalSupplyAll;
 
     /**
      * @dev Total amount of tokens in with a given id.
@@ -23,6 +24,13 @@ abstract contract ERC1155Supply is ERC1155 {
         return _totalSupply[id];
     }
 
+    /**
+     * @dev Total amount of tokens.
+     */
+    function totalSupply() public view virtual returns (uint256) {
+        return _totalSupplyAll;
+    }
+
     /**
      * @dev Indicates whether any token exist with a given id, or not.
      */
@@ -41,20 +49,32 @@ abstract contract ERC1155Supply is ERC1155 {
         bytes memory data
     ) internal virtual override {
         if (from == address(0)) {
+            uint256 totalMintAmount = 0;
             for (uint256 i = 0; i < ids.length; ++i) {
-                _totalSupply[ids[i]] += amounts[i];
+                uint256 amount = amounts[i];
+                _totalSupply[ids[i]] += amount;
+                totalMintAmount += amount;
             }
+            _totalSupplyAll += totalMintAmount;
         }
 
         if (to == address(0)) {
+            uint256 totalBurnAmount = 0;
             for (uint256 i = 0; i < ids.length; ++i) {
                 uint256 id = ids[i];
                 uint256 amount = amounts[i];
                 uint256 supply = _totalSupply[id];
                 require(supply >= amount, "ERC1155: burn amount exceeds totalSupply");
                 unchecked {
+                    // Overflow not possible: amounts[i] <= totalSupply(i)
                     _totalSupply[id] = supply - amount;
+                    // Overflow not possible: sum(amounts[i]) <= sum(totalSupply(i)) <= totalSupplyAll
+                    totalBurnAmount += amount;
+                }
             }
+            unchecked {
+                // Overflow not possible: totalBurnAmount = sum(amounts[i]) <= sum(totalSupply(i)) <= totalSupplyAll
+                _totalSupplyAll -= totalBurnAmount;
             }
         }
         super._update(from, to, ids, amounts, data);

test/token/ERC1155/extensions/ERC1155Supply.test.js

@@ -1,7 +1,9 @@
-const { BN } = require('@openzeppelin/test-helpers');
+const { BN, constants } = require('@openzeppelin/test-helpers');
 
 const { expect } = require('chai');
 
+const { ZERO_ADDRESS } = constants;
+
 const ERC1155Supply = artifacts.require('$ERC1155Supply');
 
 contract('ERC1155Supply', function (accounts) {
@@ -25,7 +27,8 @@ contract('ERC1155Supply', function (accounts) {
     });
 
     it('totalSupply', async function () {
-      expect(await this.token.totalSupply(firstTokenId)).to.be.bignumber.equal('0');
+      expect(await this.token.methods['totalSupply(uint256)'](firstTokenId)).to.be.bignumber.equal('0');
+      expect(await this.token.methods['totalSupply()']()).to.be.bignumber.equal('0');
     });
   });
 
@@ -40,7 +43,8 @@ contract('ERC1155Supply', function (accounts) {
       });
 
       it('totalSupply', async function () {
-        expect(await this.token.totalSupply(firstTokenId)).to.be.bignumber.equal(firstTokenAmount);
+        expect(await this.token.methods['totalSupply(uint256)'](firstTokenId)).to.be.bignumber.equal(firstTokenAmount);
+        expect(await this.token.methods['totalSupply()']()).to.be.bignumber.equal(firstTokenAmount);
       });
     });
 
@@ -60,8 +64,13 @@ contract('ERC1155Supply', function (accounts) {
       });
 
       it('totalSupply', async function () {
-        expect(await this.token.totalSupply(firstTokenId)).to.be.bignumber.equal(firstTokenAmount);
-        expect(await this.token.totalSupply(secondTokenId)).to.be.bignumber.equal(secondTokenAmount);
+        expect(await this.token.methods['totalSupply(uint256)'](firstTokenId)).to.be.bignumber.equal(firstTokenAmount);
+        expect(await this.token.methods['totalSupply(uint256)'](secondTokenId)).to.be.bignumber.equal(
+          secondTokenAmount,
+        );
+        expect(await this.token.methods['totalSupply()']()).to.be.bignumber.equal(
+          firstTokenAmount.add(secondTokenAmount),
+        );
       });
     });
   });
@@ -78,7 +87,8 @@ contract('ERC1155Supply', function (accounts) {
       });
 
       it('totalSupply', async function () {
-        expect(await this.token.totalSupply(firstTokenId)).to.be.bignumber.equal('0');
+        expect(await this.token.methods['totalSupply(uint256)'](firstTokenId)).to.be.bignumber.equal('0');
+        expect(await this.token.methods['totalSupply()']()).to.be.bignumber.equal('0');
       });
     });
 
@@ -99,9 +109,20 @@ contract('ERC1155Supply', function (accounts) {
       });
 
       it('totalSupply', async function () {
-        expect(await this.token.totalSupply(firstTokenId)).to.be.bignumber.equal('0');
-        expect(await this.token.totalSupply(secondTokenId)).to.be.bignumber.equal('0');
+        expect(await this.token.methods['totalSupply(uint256)'](firstTokenId)).to.be.bignumber.equal('0');
+        expect(await this.token.methods['totalSupply(uint256)'](secondTokenId)).to.be.bignumber.equal('0');
+        expect(await this.token.methods['totalSupply()']()).to.be.bignumber.equal('0');
+      });
+    });
+  });
+
+  context('other', function () {
+    it('supply unaffected by no-op', async function () {
+      this.token.safeTransferFrom(ZERO_ADDRESS, ZERO_ADDRESS, firstTokenId, firstTokenAmount, '0x', {
+        from: ZERO_ADDRESS,
       });
+      expect(await this.token.methods['totalSupply(uint256)'](firstTokenId)).to.be.bignumber.equal('0');
+      expect(await this.token.methods['totalSupply()']()).to.be.bignumber.equal('0');
     });
   });
 });