Upgradeable child ERC20

contracts/child/ChildToken/ChildERC1155.sol

@@ -27,6 +27,8 @@ contract ChildERC1155 is
         _initializeEIP712(uri_, ERC712_VERSION);
     }
 
+    // This is to support Native meta transactions
+    // never use msg.sender directly, use _msgSender() instead
     function _msgSender()
         internal
         override

contracts/child/ChildToken/ChildERC20.sol

@@ -31,6 +31,8 @@ contract ChildERC20 is
         _initializeEIP712(name_, ERC712_VERSION);
     }
 
+    // This is to support Native meta transactions
+    // never use msg.sender directly, use _msgSender() instead
     function _msgSender()
         internal
         override

contracts/child/ChildToken/ChildERC721.sol

@@ -28,6 +28,8 @@ contract ChildERC721 is
         _initializeEIP712(name_, ERC712_VERSION);
     }
 
+    // This is to support Native meta transactions
+    // never use msg.sender directly, use _msgSender() instead
     function _msgSender()
         internal
         override

contracts/child/ChildToken/ChildMintableERC721.sol

@@ -30,6 +30,8 @@ contract ChildMintableERC721 is
         _initializeEIP712(name_, ERC712_VERSION);
     }
 
+    // This is to support Native meta transactions
+    // never use msg.sender directly, use _msgSender() instead
     function _msgSender()
         internal
         override

contracts/child/ChildToken/UpgradeableChildERC20/ERC20.sol

@@ -0,0 +1,328 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.6.0;
+
+
+import "@openzeppelin/contracts/GSN/Context.sol";
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/math/SafeMath.sol";
+import "@openzeppelin/contracts/utils/Address.sol";
+
+/**
+ * Modified openzeppelin implemtation to add setters for name, symbol and decimals.
+ * This was needed because the variables cannot be set in constructor as the contract is upgradeable.
+ */
+
+/**
+ * @dev openzeppelin Implementation of the {IERC20} interface.
+ *
+ * Modified to add setters for name, symbol and decimals. This was needed
+ * because
+ *
+ * This implementation is agnostic to the way tokens are created. This means
+ * that a supply mechanism has to be added in a derived contract using {_mint}.
+ * For a generic mechanism see {ERC20PresetMinterPauser}.
+ *
+ * TIP: For a detailed writeup see our guide
+ * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
+ * to implement supply mechanisms].
+ *
+ * We have followed general OpenZeppelin guidelines: functions revert instead
+ * of returning `false` on failure. This behavior is nonetheless conventional
+ * and does not conflict with the expectations of ERC20 applications.
+ *
+ * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
+ * This allows applications to reconstruct the allowance for all accounts just
+ * by listening to said events. Other implementations of the EIP may not emit
+ * these events, as it isn't required by the specification.
+ *
+ * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
+ * functions have been added to mitigate the well-known issues around setting
+ * allowances. See {IERC20-approve}.
+ */
+contract ERC20 is Context, IERC20 {
+    using SafeMath for uint256;
+    using Address for address;
+
+    mapping (address => uint256) private _balances;
+
+    mapping (address => mapping (address => uint256)) private _allowances;
+
+    uint256 private _totalSupply;
+
+    string private _name;
+    string private _symbol;
+    uint8 private _decimals;
+
+    /**
+     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
+     * a default value of 18.
+     *
+     * To select a different value for {decimals}, use {_setupDecimals}.
+     *
+     * All three of these values are immutable: they can only be set once during
+     * construction.
+     */
+    constructor (string memory name, string memory symbol) public {
+        _name = name;
+        _symbol = symbol;
+        _decimals = 18;
+    }
+
+    /**
+     * @dev Returns the name of the token.
+     */
+    function name() public view returns (string memory) {
+        return _name;
+    }
+
+    function setName(string memory newName) internal {
+      _name = newName;
+    }
+
+    /**
+     * @dev Returns the symbol of the token, usually a shorter version of the
+     * name.
+     */
+    function symbol() public view returns (string memory) {
+        return _symbol;
+    }
+
+    function setSymbol(string memory newSymbol) internal {
+      _symbol = newSymbol;
+    }
+
+    /**
+     * @dev Returns the number of decimals used to get its user representation.
+     * For example, if `decimals` equals `2`, a balance of `505` tokens should
+     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
+     *
+     * Tokens usually opt for a value of 18, imitating the relationship between
+     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
+     * called.
+     *
+     * NOTE: This information is only used for _display_ purposes: it in
+     * no way affects any of the arithmetic of the contract, including
+     * {IERC20-balanceOf} and {IERC20-transfer}.
+     */
+    function decimals() public view returns (uint8) {
+        return _decimals;
+    }
+
+    function setDecimals(uint8 newDecimals) internal {
+      _decimals = newDecimals;
+    }
+
+    /**
+     * @dev See {IERC20-totalSupply}.
+     */
+    function totalSupply() public view override returns (uint256) {
+        return _totalSupply;
+    }
+
+    /**
+     * @dev See {IERC20-balanceOf}.
+     */
+    function balanceOf(address account) public view override returns (uint256) {
+        return _balances[account];
+    }
+
+    /**
+     * @dev See {IERC20-transfer}.
+     *
+     * Requirements:
+     *
+     * - `recipient` cannot be the zero address.
+     * - the caller must have a balance of at least `amount`.
+     */
+    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
+        _transfer(_msgSender(), recipient, amount);
+        return true;
+    }
+
+    /**
+     * @dev See {IERC20-allowance}.
+     */
+    function allowance(address owner, address spender) public view virtual override returns (uint256) {
+        return _allowances[owner][spender];
+    }
+
+    /**
+     * @dev See {IERC20-approve}.
+     *
+     * Requirements:
+     *
+     * - `spender` cannot be the zero address.
+     */
+    function approve(address spender, uint256 amount) public virtual override returns (bool) {
+        _approve(_msgSender(), spender, amount);
+        return true;
+    }
+
+    /**
+     * @dev See {IERC20-transferFrom}.
+     *
+     * Emits an {Approval} event indicating the updated allowance. This is not
+     * required by the EIP. See the note at the beginning of {ERC20};
+     *
+     * Requirements:
+     * - `sender` and `recipient` cannot be the zero address.
+     * - `sender` must have a balance of at least `amount`.
+     * - the caller must have allowance for ``sender``'s tokens of at least
+     * `amount`.
+     */
+    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
+        _transfer(sender, recipient, amount);
+        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
+        return true;
+    }
+
+    /**
+     * @dev Atomically increases the allowance granted to `spender` by the caller.
+     *
+     * This is an alternative to {approve} that can be used as a mitigation for
+     * problems described in {IERC20-approve}.
+     *
+     * Emits an {Approval} event indicating the updated allowance.
+     *
+     * Requirements:
+     *
+     * - `spender` cannot be the zero address.
+     */
+    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
+        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
+        return true;
+    }
+
+    /**
+     * @dev Atomically decreases the allowance granted to `spender` by the caller.
+     *
+     * This is an alternative to {approve} that can be used as a mitigation for
+     * problems described in {IERC20-approve}.
+     *
+     * Emits an {Approval} event indicating the updated allowance.
+     *
+     * Requirements:
+     *
+     * - `spender` cannot be the zero address.
+     * - `spender` must have allowance for the caller of at least
+     * `subtractedValue`.
+     */
+    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
+        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
+        return true;
+    }
+
+    /**
+     * @dev Moves tokens `amount` from `sender` to `recipient`.
+     *
+     * This is internal function is equivalent to {transfer}, and can be used to
+     * e.g. implement automatic token fees, slashing mechanisms, etc.
+     *
+     * Emits a {Transfer} event.
+     *
+     * Requirements:
+     *
+     * - `sender` cannot be the zero address.
+     * - `recipient` cannot be the zero address.
+     * - `sender` must have a balance of at least `amount`.
+     */
+    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
+        require(sender != address(0), "ERC20: transfer from the zero address");
+        require(recipient != address(0), "ERC20: transfer to the zero address");
+
+        _beforeTokenTransfer(sender, recipient, amount);
+
+        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
+        _balances[recipient] = _balances[recipient].add(amount);
+        emit Transfer(sender, recipient, amount);
+    }
+
+    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
+     * the total supply.
+     *
+     * Emits a {Transfer} event with `from` set to the zero address.
+     *
+     * Requirements
+     *
+     * - `to` cannot be the zero address.
+     */
+    function _mint(address account, uint256 amount) internal virtual {
+        require(account != address(0), "ERC20: mint to the zero address");
+
+        _beforeTokenTransfer(address(0), account, amount);
+
+        _totalSupply = _totalSupply.add(amount);
+        _balances[account] = _balances[account].add(amount);
+        emit Transfer(address(0), account, amount);
+    }
+
+    /**
+     * @dev Destroys `amount` tokens from `account`, reducing the
+     * total supply.
+     *
+     * Emits a {Transfer} event with `to` set to the zero address.
+     *
+     * Requirements
+     *
+     * - `account` cannot be the zero address.
+     * - `account` must have at least `amount` tokens.
+     */
+    function _burn(address account, uint256 amount) internal virtual {
+        require(account != address(0), "ERC20: burn from the zero address");
+
+        _beforeTokenTransfer(account, address(0), amount);
+
+        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
+        _totalSupply = _totalSupply.sub(amount);
+        emit Transfer(account, address(0), amount);
+    }
+
+    /**
+     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
+     *
+     * This is internal function is equivalent to `approve`, and can be used to
+     * e.g. set automatic allowances for certain subsystems, etc.
+     *
+     * Emits an {Approval} event.
+     *
+     * Requirements:
+     *
+     * - `owner` cannot be the zero address.
+     * - `spender` cannot be the zero address.
+     */
+    function _approve(address owner, address spender, uint256 amount) internal virtual {
+        require(owner != address(0), "ERC20: approve from the zero address");
+        require(spender != address(0), "ERC20: approve to the zero address");
+
+        _allowances[owner][spender] = amount;
+        emit Approval(owner, spender, amount);
+    }
+
+    /**
+     * @dev Sets {decimals} to a value other than the default one of 18.
+     *
+     * WARNING: This function should only be called from the constructor. Most
+     * applications that interact with token contracts will not expect
+     * {decimals} to ever change, and may work incorrectly if it does.
+     */
+    function _setupDecimals(uint8 decimals_) internal {
+        _decimals = decimals_;
+    }
+
+    /**
+     * @dev Hook that is called before any transfer of tokens. This includes
+     * minting and burning.
+     *
+     * Calling conditions:
+     *
+     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
+     * will be to transferred to `to`.
+     * - when `from` is zero, `amount` tokens will be minted for `to`.
+     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
+     * - `from` and `to` are never both zero.
+     *
+     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
+     */
+    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
+}