Add ERC20 preset (#810)

* add erc20 preset

* add tests

* fix formatting

* change preset name

* tidy up tests

* normalize assert msgs

* simplify ZERO, add other transfer tests

* add other transfer tests

* add erc20 preset section

* fix preset sentence

* change initial_supply to fixed_supply

* add code comments

* move preset to API

* Apply suggestions from code review

Co-authored-by: Martín Triay <[email protected]>

* fix preset section sentence

* normalize comments

---------

Co-authored-by: Martín Triay <[email protected]>

docs/modules/ROOT/pages/api/erc20.adoc

@@ -168,7 +168,7 @@ use openzeppelin::token::erc20::ERC20Component;
 ```
 ERC20 component extending <<IERC20,IERC20>> and <<IERC20Metadata,IERC20Metadata>>.
 
-[.contract-index]
+[.contract-index#ERC20Component-Embeddable-Impls]
 .Embeddable implementations
 --
 .ERC20Impl
@@ -189,7 +189,7 @@ ERC20 component extending <<IERC20,IERC20>> and <<IERC20Metadata,IERC20Metadata>
 * xref:#ERC20Component-decrease_allowance[`++decrease_allowance(self, spender, subtracted_value)++`]
 --
 
-[.contract-index]
+[.contract-index#ERC20Component-Embeddable-Impls-camelCase]
 .Embeddable implementations (camelCase)
 --
 .ERC20CamelOnlyImpl
@@ -471,3 +471,43 @@ See <<IERC20-Transfer,IERC20::Transfer>>.
 ==== `[.contract-item-name]#++Approval++#++(owner: ContractAddress, spender: ContractAddress, value: u256)++` [.item-kind]#event#
 
 See <<IERC20-Approval,IERC20::Approval>>.
+
+== Presets
+
+[.contract]
+[[ERC20]]
+=== `++ERC20++` link:https://github.com/OpenZeppelin/cairo-contracts/blob/release-v0.8.0-beta.0/src/presets/erc20.cairo[{github-icon},role=heading-link]
+
+```javascript
+use openzeppelin::presets::ERC20;
+```
+
+Basic ERC20 contract leveraging xref:#ERC20Component[ERC20Component] with a fixed-supply mechanism for token distribution.
+
+[.contract-index]
+.Constructor
+--
+* xref:#ERC20-constructor[`++constructor(self, name, symbol, fixed_supply, recipient)++`]
+--
+
+[.contract-index]
+.Embedded Implementations
+--
+.ERC20Component
+
+* xref:#ERC20Component-Embeddable-Impls[`++ERC20Impl++`]
+* xref:#ERC20Component-Embeddable-Impls[`++ERC20MetadataImpl++`]
+* xref:#ERC20Component-Embeddable-Impls[`++SafeAllowanceImpl++`]
+* xref:#ERC20Component-Embeddable-Impls-camelCase[`++ERC20CamelOnlyImpl++`]
+* xref:#ERC20Component-Embeddable-Impls-camelCase[`++SafeAllowanceCamelImpl++`]
+--
+
+[#ERC20-constructor-section]
+==== Constructor
+
+[.contract-item]
+[[ERC20-constructor]]
+==== `[.contract-item-name]#++constructor++#++(ref self: ContractState, name: felt252, symbol: felt252, fixed_supply: u256, recipient: ContractAddress)++` [.item-kind]#constructor#
+
+Sets the `name` and `symbol`.
+Mints `fixed_supply` tokens to `recipient`.

docs/modules/ROOT/pages/guides/erc20-supply.adoc

@@ -42,20 +42,20 @@ mod MyToken {
     #[constructor]
     fn constructor(
         ref self: ContractState,
-        initial_supply: u256,
+        fixed_supply: u256,
         recipient: ContractAddress
     ) {
         let name = 'MyToken';
         let symbol = 'MTK';
 
         self.erc20.initializer(name, symbol);
-        self.erc20._mint(recipient, initial_supply);
+        self.erc20._mint(recipient, fixed_supply);
     }
 }
 ----
 
 In the constructor, we're first calling the ERC20 initializer to set the token name and symbol.
-Next, we're calling the internal `_mint` function which creates `initial_supply` of tokens and allocates them to `recipient`.
+Next, we're calling the internal `_mint` function which creates `fixed_supply` of tokens and allocates them to `recipient`.
 Since the internal `_mint` is not exposed in our contract, it will not be possible to create any more tokens.
 In other words, we've implemented a fixed token supply!
 

src/presets.cairo

@@ -1,3 +1,5 @@
 mod account;
+mod erc20;
 
 use account::Account;
+use erc20::ERC20;

src/presets/erc20.cairo

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts for Cairo v0.8.0-beta.0 (presets/erc20.cairo)
+
+/// # ERC20 Preset
+///
+/// The ERC20 contract offers basic functionality and provides a
+/// fixed-supply mechanism for token distribution. The fixed supply is
+/// set in the constructor.
+#[starknet::contract]
+mod ERC20 {
+    use openzeppelin::token::erc20::ERC20Component;
+    use starknet::ContractAddress;
+
+    component!(path: ERC20Component, storage: erc20, event: ERC20Event);
+
+    #[abi(embed_v0)]
+    impl ERC20Impl = ERC20Component::ERC20Impl<ContractState>;
+    #[abi(embed_v0)]
+    impl ERC20MetadataImpl = ERC20Component::ERC20MetadataImpl<ContractState>;
+    #[abi(embed_v0)]
+    impl SafeAllowanceImpl = ERC20Component::SafeAllowanceImpl<ContractState>;
+    #[abi(embed_v0)]
+    impl ERC20CamelOnlyImpl = ERC20Component::ERC20CamelOnlyImpl<ContractState>;
+    #[abi(embed_v0)]
+    impl SafeAllowanceCamelImpl =
+        ERC20Component::SafeAllowanceCamelImpl<ContractState>;
+    impl InternalImpl = ERC20Component::InternalImpl<ContractState>;
+
+    #[storage]
+    struct Storage {
+        #[substorage(v0)]
+        erc20: ERC20Component::Storage
+    }
+
+    #[event]
+    #[derive(Drop, starknet::Event)]
+    enum Event {
+        #[flat]
+        ERC20Event: ERC20Component::Event
+    }
+
+    /// Sets the token `name` and `symbol`.
+    /// Mints `fixed_supply` tokens to `recipient`.
+    #[constructor]
+    fn constructor(
+        ref self: ContractState,
+        name: felt252,
+        symbol: felt252,
+        fixed_supply: u256,
+        recipient: ContractAddress
+    ) {
+        self.erc20.initializer(name, symbol);
+        self.erc20._mint(recipient, fixed_supply);
+    }
+}

src/tests/presets.cairo

@@ -1 +1,2 @@
 mod test_account;
+mod test_erc20;