Add getRoleMembers method to return all accounts that have role

.changeset/violet-moons-tell.md

@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`AccessControlEnumerable`: add `getRoleMembers` method to return all accounts that have `role`

contracts/access/extensions/AccessControlEnumerable.sol

@@ -46,6 +46,18 @@ abstract contract AccessControlEnumerable is IAccessControlEnumerable, AccessCon
         return _roleMembers[role].length();
     }
 
+    /**
+     * @dev Return all accounts that have `role`
+     *
+     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
+     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
+     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
+     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
+     */
+    function getRoleMembers(bytes32 role) public view virtual returns (address[] memory) {
+        return _roleMembers[role].values();
+    }
+
     /**
      * @dev Overload {AccessControl-_grantRole} to track enumerable memberships
      */

test/access/AccessControl.behavior.js

@@ -242,6 +242,8 @@ function shouldBehaveLikeAccessControlEnumerable(admin, authorized, other, other
       }
 
       expect(bearers).to.have.members([authorized, otherAuthorized]);
+
+      expect(await this.accessControl.getRoleMembers(ROLE)).to.be.deep.equal([authorized, otherAuthorized]);
     });
     it('role enumeration should be in sync after renounceRole call', async function () {
       expect(await this.accessControl.getRoleMemberCount(ROLE)).to.bignumber.equal('0');