Add tutorial working with workspaces

docs/build/guides/conventions/workspace.mdx

@@ -0,0 +1,357 @@
+---
+title: Workspaces
+hide_table_of_contents: true
+description: Organize contracts using Cargo workspaces
+---
+
+### Initializing workspace project
+
+Using Cargo's workspace [feature](https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html) makes it very convenient to organize your smart contracts in subdirectories of your project's root.
+
+It's very simple to get started using the cli:
+
+```
+stellar contract init . --name add_contract
+```
+
+Running this command will create a root project directory (`soroban-project`) and then initialize a project workspace with a single contract named `add_contract`.
+
+Adding one more contract template to the project can be done using the same command:
+
+```
+stellar contract init . --name main_contract
+```
+
+The project tree will look like this:
+
+```
+$ tree
+.
+├── Cargo.toml
+├── contracts
+│   ├── add-contract
+│   │   ├── Cargo.toml
+│   │   ├── Makefile
+│   │   └── src
+│   │       ├── lib.rs
+│   │       └── test.rs
+│   └── main-contract
+│       ├── Cargo.toml
+│       ├── Makefile
+│       └── src
+│           ├── lib.rs
+│           └── test.rs
+└── README.md
+```
+
+Running `stellar contract init` command created a sample contracts subdirectories (located in `./contracts), each contains:
+
+1. Cargo.toml file with all (minimal) necessary dependencies
+2. `Makefile` to easily build contract using `make` command
+3. `src` directory with an example hello-world contract and a simple test.
+
+We can now build our workspace's contracts with
+
+```
+stellar contract build
+```
+
+command and check the build directory `target/wasm32-unknown-unknown/release/`
+
+### Cross-contract call between workspaces
+
+With the given project structure, cross-contract calls can be easily made. Starting with modifying the sample hello world contract into an add contract:
+
+```rust title="contracts/add_contract/src/lib.rs"
+#![no_std]
+use soroban_sdk::{contract, contractimpl};
+
+#[contract]
+pub struct ContractAdd;
+
+#[contractimpl]
+impl ContractAdd {
+    pub fn add(x: u32, y: u32) -> u32 {
+        x.checked_add(y).expect("no overflow")
+    }
+}
+```
+
+The `ContractAdd` can now be referenced and used from another contracts in the same workspace using [`contractimport`](https://docs.rs/soroban-sdk/latest/soroban_sdk/macro.contractimport.html) macros. Note that the `contractimport` requires relative path of the compiled wasm file, so first it's required to recompile the contract with:
+
+```
+stellar contract build
+```
+
+As seen previously, target wasm file is located in
+
+```
+$PROJECT_ROOT/target/wasm32-unknown-unknown/release/
+```
+
+In order to reference this wasm file from `contracts/main_contract/src/lib.rs`, we need to first construct the path to the project root: `../..` (relative to second contract's Cargo.toml file location) followed by path to the wasm file:
+
+```
+../../../target/wasm32-unknown-unknown/release/add_contract.wasm
+```
+
+It can now be used in the rust code:
+
+```rust title="contracts/main_contract/src/lib.rs"
+#![no_std]
+
+use soroban_sdk::{contract, contractimpl, Address, Env};
+
+mod contract_add {
+    soroban_sdk::contractimport!(
+        file = "../../../target/wasm32-unknown-unknown/release/add_contract.wasm"
+    );
+}
+
+#[contract]
+pub struct ContractMain;
+
+#[contractimpl]
+impl ContractMain {
+    pub fn add_with(env: Env, contract: Address, x: u32, y: u32) -> u32 {
+        let client = contract_add::Client::new(&env, &contract);
+        client.add(&x, &y)
+    }
+}
+
+mod test;
+```
+
+Here, main contract will invoke `ContractAdd`'s `add` function to calculate the sum of 2 numbers. It's a good idea to update tests for our main contract as well:
+
+```rust title="contracts/main_contract/src/test.rs"
+#![cfg(test)]
+
+use crate::{contract_add, ContractMain, ContractMainClient};
+use soroban_sdk::Env;
+
+#[test]
+fn test_adding_cross_contract() {
+    let env = Env::default();
+
+    // Register add contract using the imported WASM.
+    let contract_add_id = env.register_contract_wasm(None, contract_add::WASM);
+
+    // Register main contract defined in this crate.
+    let contract_main_id = env.register_contract(None, ContractMain);
+
+    // Create a client for calling main contract.
+    let client = ContractMainClient::new(&env, &contract_main_id);
+
+    // Invoke main contract via its client. Main contract will invoke add contract.
+    let sum = client.add_with(&contract_add_id, &5, &7);
+    assert_eq!(sum, 12);
+}
+```
+
+Contracts can now be re-complied running the following command from the project root:
+
+```
+stellar contract build
+```
+
+And check that the test is working correctly, running tests in `contracts/main_contract`:
+
+```
+cargo test
+
+running 1 test
+test test::test_adding_cross_contract ... ok
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.01s
+```
+
+Finally, let's deploy this contracts and call our main contract using cli. If you haven't already, set up an account (alice) first
+
+```bash
+stellar keys generate alice --fund --network testnet
+STELLAR_SOURCE_ACCOUNT=alice
+```
+
+Second is to deploy the contracts:
+
+```bash
+stellar contract deploy --network testnet --wasm target/wasm32-unknown-unknown/release/add_contract.wasm --alias add_contract
+stellar contract deploy --network testnet --wasm target/wasm32-unknown-unknown/release/main_contract.wasm --alias main_contract
+```
+
+And finally call the main contract:
+
+```
+$ stellar contract invoke --id main_contract --network testnet -- add_with --contract add_contract --x 9 --y 10
+ℹ️ Send skipped because simulation identified as read-only. Send by rerunning with `--send=yes`.
+19
+```
+
+### Adding contract interfaces
+
+As the next step, we can abstract away add contract and allow it to have multiple implementations. Main contract will in turn use the contract interface that is not bound to its implementation.
+
+```
+stellar contract init . --name adder_interface
+stellar contract init . --name add_extra_contract
+```
+
+First, let's create an interface and change our existing implementation to use this interface:
+
+```rust title="contracts/adder_interface/src/lib.rs"
+#![no_std]
+
+use soroban_sdk::contractclient;
+
+#[contractclient(name = "ContractAClient")]
+pub trait ContractAInterface {
+    fn add(x: u32, y: u32) -> u32;
+}
+```
+
+To use the interface definition our workspace members will now have an `adder_interface` as a dependency:
+
+```toml title="./Cargo.toml"
+# <...>
+[workspace.dependencies]
+soroban-sdk = "21.0.0"
+adder-interface = { path = "contracts/adder_interface" }
+# <...>
+```
+
+```toml title="./contracts/add_contract/Cargo.toml"
+# <...>
+[dependencies]
+soroban-sdk = { workspace = true }
+adder-interface = {workspace = true}
+# <...>
+```
+
+```toml title="./contracts/main_contract/Cargo.toml"
+# <...>
+[dependencies]
+soroban-sdk = { workspace = true }
+adder-interface = {workspace = true}
+# <...>
+```
+
+```toml title="./contracts/add_extra_contract/Cargo.toml"
+# <...>
+[dependencies]
+soroban-sdk = { workspace = true }
+adder-interface = {workspace = true}
+# <...>
+```
+
+And change lib type of `adder_interface` crate:
+
+```toml title="./contracts/adder_interface/Cargo.toml"
+# <...>
+[lib]
+crate-type = ["rlib"]
+# <...>
+```
+
+```rust title="./contracts/adder_interface/src/lib.rs"
+#![no_std]
+
+use soroban_sdk::contractclient;
+
+#[contractclient(name = "AdderClient")]
+pub trait Adder {
+    fn add(x: u32, y: u32) -> u32;
+}
+
+```
+
+```rust title="contracts/add_contract/src/lib.rs"
+#![no_std]
+use soroban_sdk::{contract, contractimpl};
+use adder_interface::Adder;
+
+#[contract]
+pub struct ContractAdd;
+
+#[contractimpl]
+impl Adder for ContractAdd {
+    fn add(x: u32, y: u32) -> u32 {
+        x.checked_add(y).expect("no overflow")
+    }
+}
+
+```
+
+```rust title="contracts/main_contract/src/lib.rs"
+#![no_std]
+
+use soroban_sdk::{contract, contractimpl, Address, Env};
+use adder_interface::AdderClient;
+
+#[contract]
+pub struct ContractMain;
+
+#[contractimpl]
+impl ContractMain {
+    pub fn add_with(env: Env, contract: Address, x: u32, y: u32) -> u32 {
+        let client = AdderClient::new(&env, &contract);
+        client.add(&x, &y)
+    }
+}
+
+mod test;
+```
+
+And update test imports:
+
+```rust title="contracts/main_contract/src/test.rs"
+#![cfg(test)]
+
+use crate::{ContractMain, ContractMainClient};
+use soroban_sdk::Env;
+
+mod contract_add {
+    soroban_sdk::contractimport!(
+        file = "../../target/wasm32-unknown-unknown/release/my_contract.wasm"
+    );
+}
+// <...>
+```
+
+As the final step we can create an alternative `Adder` implementation that adds an extra 1:
+
+```rust title="contracts/add_extra_contract/src/lib.rs"
+#![no_std]
+use soroban_sdk::{contract, contractimpl};
+use adder_interface::Adder;
+
+#[contract]
+pub struct ContractAdd;
+
+#[contractimpl]
+impl Adder for ContractAdd {
+    fn add(x: u32, y: u32) -> u32 {
+        x.checked_add(y).expect("no overflow").checked_add(1).expect("no overflow")
+    }
+}
+```
+
+We can now deploy this contracts and test the new behavior:
+
+```bash
+stellar contract build
+stellar contract deploy --network testnet --wasm target/wasm32-unknown-unknown/release/add_contract.wasm --alias add_contract
+stellar contract deploy --network testnet --wasm target/wasm32-unknown-unknown/release/add_extra_contract.wasm --alias wrong_math_contract
+stellar contract deploy --network testnet --wasm target/wasm32-unknown-unknown/release/main_contract.wasm --alias main_contract
+```
+
+Now let's try to do sum 2 unsigned integers causing an overflow:
+
+```
+$ stellar contract invoke --id main_contract --network testnet -- add_with --contract add_contract --x 2 --y 2
+ℹ️ Send skipped because simulation identified as read-only. Send by rerunning with `--send=yes`.
+4
+$ stellar contract invoke --id main_contract --network testnet -- add_with --contract wrong_math_contract --x 2 --y 2
+ℹ️ Send skipped because simulation identified as read-only. Send by rerunning with `--send=yes`.
+5
+```