Add L1-L2 communication docs guide

docs/guide.rst

@@ -7,5 +7,6 @@ Guide
     guide/using_existing_contracts
     guide/resolving_proxy_contracts
     guide/deploying_contracts
+    guide/mocking_interaction_with_l1
     guide/serialization
     guide/signing

docs/guide/mocking_interaction_with_l1.rst

@@ -0,0 +1,64 @@
+Mocking interaction with L1
+===========================
+
+Abstract
+--------
+
+In order to test interaction with L1 contracts, devnet client provides a way to mock the L1 interaction.
+Before taking a look at the examples, please get faimiliar with the `devnet postman docs <https://0xspaceshard.github.io/starknet-devnet-rs/docs/postman>`_ and messaging mechanism:
+
+- `Writing messaging contracts <https://book.cairo-lang.org/ch16-04-L1-L2-messaging.html>`_
+- `Mechanism overview <https://docs.starknet.io/architecture-and-concepts/network-architecture/messaging-mechanism/>`_
+- `StarkGate example <https://docs.starknet.io/architecture-and-concepts/network-architecture/messaging-mechanism/>`_
+
+L1 network setup
+----------------
+
+First of all you should deploy `messaging contract <https://github.com/0xSpaceShard/starknet-devnet-rs/blob/138120b355c44ae60269167b326d1a267f7af0a8/contracts/l1-l2-messaging/solidity/src/MockStarknetMessaging.sol>`_ on ethereum network.
+
+.. codesnippet:: ../../starknet_py/tests/e2e/docs/guide/test_postman_load.py
+    :language: python
+    :dedent: 4
+
+
+L2 -> L1
+--------
+
+Deploying L2 interaction contract
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Interaction with L1 is done by sending a message using `send_message_to_l1_syscall` function.
+So in order to test this functionality, you need to deploy a contract that has this functionality.
+Example contract: `l1_l2.cairo <https://github.com/0xSpaceShard/starknet-devnet-js/blob/5069ec3397f31a408d3df2734ae40d93b42a0f7f/test/data/l1_l2.cairo>`_
+
+.. codesnippet:: ../../starknet_py/tests/e2e/docs/guide/test_postman_load.py
+    :language: python
+    :dedent: 4
+    :start-after: docs: messaging-contract-start
+    :end-before: docs: messaging-contract-end
+
+
+Consuming message
+^^^^^^^^^^^^^^^^^
+
+After deploying the contract, you need to flush the messages to the L1 network.
+And then you can consume the message on the L1 network.
+
+.. codesnippet:: ../../starknet_py/tests/e2e/docs/guide/test_postman_load.py
+    :language: python
+    :dedent: 4
+    :start-after: docs: flush-1-start
+    :end-before: docs: flush-1-end
+
+L1 -> L2
+--------
+
+Sending mock transactions from L1 to L2 does not require L1 node to be running.
+
+.. codesnippet:: ../../starknet_py/tests/e2e/docs/guide/test_postman_load.py
+    :language: python
+    :dedent: 4
+    :start-after: docs: send-l2-start
+    :end-before: docs: send-l2-end
+
+

starknet_py/tests/e2e/client_devnet/fixtures/contracts.py

@@ -24,3 +24,21 @@ async def deploy_string_contract(
         contract_name="MyString",
         class_hash=f_string_contract_class_hash,
     )
+
+
+@pytest_asyncio.fixture(scope="package", name="l1_l2_contract_class_hash")
+async def declare_l1_l2_contract(account) -> int:
+    contract = load_contract("l1_l2")
+    class_hash, _ = await declare_cairo1_contract(
+        account, contract["sierra"], contract["casm"]
+    )
+    return class_hash
+
+
+@pytest_asyncio.fixture(scope="package", name="l1_l2_contract")
+async def deploy_l1_l2_contract(account, l1_l2_contract_class_hash) -> Contract:
+    return await deploy_v1_contract(
+        account=account,
+        contract_name="l1_l2",
+        class_hash=l1_l2_contract_class_hash,
+    )

starknet_py/tests/e2e/docs/guide/test_postman_load.py

@@ -0,0 +1,83 @@
+import pytest
+
+from starknet_py.hash.selector import get_selector_from_name
+
+
+@pytest.mark.asyncio
+async def test_postman_load(devnet_client, l1_l2_contract, account):
+    # pylint: disable=import-outside-toplevel
+
+    eth_account_address = 1390849295786071768276380950238675083608645509734
+
+    # docs: start
+    from starknet_py.devnet_utils.devnet_client import DevnetClient
+
+    client = DevnetClient(node_url="http://127.0.0.1:5050")
+
+    # docs: end
+    client: DevnetClient = devnet_client
+    # docs: start
+    # Load the messaging contract on ETH network
+    # e.g. anvil eth devnet https://github.com/foundry-rs/foundry/tree/master/crates/anvil
+
+    await client.postman_load(network_url="http://127.0.0.1:8545")
+    # docs: end
+
+    # docs: messaging-contract-start
+    from starknet_py.contract import Contract
+
+    # Address of your contract that is emitting messages
+    contract_address = "0x12345"
+
+    # docs: messaging-contract-end
+    contract_address = l1_l2_contract.address
+
+    # docs: messaging-contract-start
+    contract = await Contract.from_address(address=contract_address, provider=account)
+
+    await contract.functions["increase_balance"].invoke_v1(
+        user=account.address, amount=100, max_fee=int(1e16)
+    )
+
+    # docs: messaging-contract-end
+    assert await contract.functions["get_balance"].call(user=account.address) == (100,)
+
+    # docs: messaging-contract-start
+    # Invoking function that is emitting message
+    await contract.functions["withdraw"].invoke_v1(
+        user=account.address,
+        amount=100,
+        l1_address=eth_account_address,
+        max_fee=int(1e16),
+    )
+    # docs: messaging-contract-end
+    assert await contract.functions["get_balance"].call(user=account.address) == (0,)
+
+    # docs: flush-1-start
+    # Sending messages from L2 to L1.
+    flush_response = await client.postman_flush()
+
+    message = flush_response.messages_to_l1[0]
+
+    message_hash = await client.consume_message_from_l2(
+        from_address=message.from_address,
+        to_address=message.to_address,
+        payload=message.payload,
+    )
+    # docs: flush-1-end
+
+    # docs: send-l2-start
+    await client.send_message_to_l2(
+        l2_contract_address=contract_address,
+        entry_point_selector=get_selector_from_name("deposit"),
+        l1_contract_address="0xa000000000000000000000000000000000000001",
+        payload=[account.address, 420],
+        nonce="0x0",
+        paid_fee_on_l1="0xfffffffffff",
+    )
+
+    # Sending messages from L1 to L2.
+    flush_response = await client.postman_flush()
+    # docs: send-l2-end
+
+    assert await contract.functions["get_balance"].call(user=account.address) == (420,)

starknet_py/tests/e2e/mock/contracts_v2/src/l1_l2.cairo

@@ -0,0 +1,110 @@
+//! L1 L2 messaging demo contract.
+//! Rewrite in Cairo 1 of the contract from previous Devnet version:
+//! https://github.com/0xSpaceShard/starknet-devnet/blob/e477aa1bbe2348ba92af2a69c32d2eef2579d863/test/contracts/cairo/l1l2.cairo
+//!
+//! This contract does not use interface to keep the code as simple as possible.
+//!
+
+#[starknet::contract]
+mod l1_l2 {
+    const MESSAGE_WITHDRAW: felt252 = 0;
+
+    #[storage]
+    struct Storage {
+        // Balances (users) -> (amount).
+        balances: LegacyMap<felt252, felt252>,
+    }
+
+    #[event]
+    #[derive(Drop, starknet::Event)]
+    enum Event {
+        DepositFromL1: DepositFromL1,
+    }
+
+    #[derive(Drop, starknet::Event)]
+    struct DepositFromL1 {
+        #[key]
+        user: felt252,
+        #[key]
+        amount: felt252,
+    }
+
+    /// Gets the balance of the `user`.
+    #[external(v0)]
+    fn get_balance(self: @ContractState, user: felt252) -> felt252 {
+        self.balances.read(user)
+    }
+
+    /// Increases the balance of the `user` for the `amount`.
+    #[external(v0)]
+    fn increase_balance(ref self: ContractState, user: felt252, amount: felt252) {
+        let balance = self.balances.read(user);
+        self.balances.write(user, balance + amount);
+    }
+
+    /// Withdraws the `amount` for the `user` and sends a message to `l1_address` to
+    /// send the funds.
+    #[external(v0)]
+    fn withdraw(ref self: ContractState, user: felt252, amount: felt252, l1_address: felt252) {
+        assert(amount.is_non_zero(), 'Amount must be positive');
+
+        let balance = self.balances.read(user);
+        assert(balance.is_non_zero(), 'Balance is already 0');
+
+        // We need u256 to make comparisons.
+        let balance_u: u256 = balance.into();
+        let amount_u: u256 = amount.into();
+        assert(balance_u >= amount_u, 'Balance will be negative');
+
+        let new_balance = balance - amount;
+
+        self.balances.write(user, new_balance);
+
+        let payload = array![MESSAGE_WITHDRAW, user, amount,];
+
+        starknet::send_message_to_l1_syscall(l1_address, payload.span()).unwrap();
+    }
+
+    /// Withdraws the `amount` for the `user` and sends a message to `l1_address` to
+    /// send the funds.
+    #[external(v0)]
+    fn withdraw_from_lib(
+        ref self: ContractState, user: felt252, amount: felt252, l1_address: felt252, message_sender_class_hash: starknet::ClassHash,
+    ) {
+        assert(amount.is_non_zero(), 'Amount must be positive');
+
+        let balance = self.balances.read(user);
+        assert(balance.is_non_zero(), 'Balance is already 0');
+
+        // We need u256 to make comparisons.
+        let balance_u: u256 = balance.into();
+        let amount_u: u256 = amount.into();
+        assert(balance_u >= amount_u, 'Balance will be negative');
+
+        let new_balance = balance - amount;
+
+        self.balances.write(user, new_balance);
+
+        let calldata = array![user, amount, l1_address];
+
+        starknet::SyscallResultTrait::unwrap_syscall(
+            starknet::library_call_syscall(
+                message_sender_class_hash,
+                selector!("send_withdraw_message"),
+                calldata.span(),
+            )
+        );
+    }
+
+    /// Deposits the `amount` for the `user`. Can only be called by the sequencer itself,
+    /// after having fetched some messages from the L1.
+    #[l1_handler]
+    fn deposit(ref self: ContractState, from_address: felt252, user: felt252, amount: felt252) {
+        // In a real case scenario, here we would assert from_address value
+
+        let balance = self.balances.read(user);
+        self.balances.write(user, balance + amount);
+
+        self.emit(DepositFromL1 { user, amount });
+    }
+}

starknet_py/tests/e2e/mock/contracts_v2/src/lib.cairo

@@ -9,3 +9,4 @@ mod test_contract;
 mod test_enum;
 mod test_option;
 mod token_bridge;
+mod l1_l2;