Upgradeable contracts using proxies.

rfcs/0013-contract-proxies.md

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+- Feature Name: `contract_proxies`
+- Start Date: 2024-05-21
+- RFC PR: [FuelLabs/sway-rfcs#0013](https://github.com/FuelLabs/sway-rfcs/pull/39)
+
+# Summary
+
+[summary]: #summary
+
+This proposal introduces a feature to simplify the creation of upgradeable contracts in Sway by enhancing the Forc.toml manifest file.
+
+# Motivation
+
+[motivation]: #motivation
+
+Sway developers want to upgrade their smart contract code post-deployment and need tooling support to facilitate this process. They seek a straightforward method, such as adding a configuration to the Forc.toml file, to enable and manage contract upgradeability seamlessly.
+
+# Guide-level explanation
+
+[guide-level-explanation]: #guide-level-explanation
+
+### Use of the Forc.toml for an upgradeable contact.
+This proposal enhances the Forc.toml file to simplify creating upgradeable contracts. A new `[proxy]` table indicates to `forc-deploy` that this contract is upgradable. During the initial deployment, `forc-deploy` stores the proxy contract's address in the `address` field, streamlining future updates and ensuring the address is stored safely with the project.
+
+```toml
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+entry = "main.sw"
+license = "Apache-2.0"
+name = "implementation"
+
+[proxy]
+enabled = true # Undecided if we really need this flag yet.
+address = # this field gets automatically added and filled in during deployment
+```
+
+## Workflow
+
+The deployment process takes care of generating proxy bytecode, deploying contracts, and updating addresses automatically. The workflow from forc’s perspective could look something like the following:
+
+1. **Forc Deploy**:
+    - Forc deploy checks if the **`proxy.enabled`** field is set to **`true`** in **`Forc.toml`**.
+    - If enabled, it checks the **`proxy.address`** field.
+        - If **`proxy.address`** is empty, it deploys a new proxy contract, updates the **`proxy.address`** field with the deployed proxy's address, and deploys the implementation contract.
+        - If **`proxy.address`** is not empty, it skips deploying a new proxy and proceeds to update the existing proxy's storage to point to the new implementation contract.
+2. **Initial Deployment**:
+    - Generate the proxy contract bytecode.
+    - Deploy the implementation contract.
+    - Deploy the proxy contract.
+    - Update the proxy contract's storage to point to the implementation contract's address.
+    - Store the proxy contract's address in **`Forc.toml`**.
+3. **Subsequent Deployments**:
+    - Check if a proxy address already exists.
+    - Check storage layout consistency between the proxy and the new implementation contract.
+    - Check for breaking changes in the ABI.
+    - If storage layout is consistent and no breaking changes are found in the ABI, deploy the new implementation contract.
+    - Update the existing proxy contract to point to the new implementation contract's address.
+
+```mermaid
+graph TD
+    A[Check Forc.toml] --> B{Proxy Enabled?}
+    B -- No --> C[Deploy Main Contract Normally]
+    B -- Yes --> D{Proxy Address Exists?}
+    D -- No --> E[Generate Proxy Contract Bytecode]
+    E --> F[Deploy Implementation Contract]
+    F --> G[Deploy Proxy Contract]
+    G --> H[Update Proxy Storage with Implementation Address]
+    H --> I[Store Proxy Address in Forc.toml]
+    D -- Yes --> J[Check Storage Layout Consistency]
+    J -- Inconsistent --> X[Abort Deployment]
+    J -- Consistent --> K[Check for ABI Breaking Changes]
+    K -- Breaking Changes --> Y[Abort Deployment]
+    K -- No Breaking Changes --> L[Deploy New Implementation Contract]
+    L --> M[Update Existing Proxy Storage with New Implementation Address]
+```
+
+### **Usability Features**
+
+- **Simplicity**: The system is simple for developers to use. They only need to enable the proxy in **`Forc.toml`**, and the rest is handled automatically.
+- **Automation**: Automatically managing the proxy address in **`Forc.toml`** reduces the risk of errors and ensures consistency.
+- **Deployment Flexibility**: The system handles both initial deployments and subsequent updates seamlessly.
+
+### **Security Considerations**
+
+- **Address Verification**: Ensure the address stored in **`Forc.toml`** is accurate and not tampered with. Use checksums or other verification methods if needed.
+- **State Management**: Ensure the proxy contract's storage is correctly updated to point to the new implementation contract to prevent any potential issues with state consistency.
+- **Access Control**: Implement proper access control in the proxy contract to restrict who can update the implementation address to prevent unauthorized changes.
+- **Storage Layout Consistency**: Ensure that the storage layout between the proxy and the implementation contracts is identical.
+
+### **Example Contract Syntax**
+@IGI-111 to fill out.
+
+
+### **Compiler Features**
+* A function that generates the smallest possible byte code for the proxy contract that can be used by `forc-deploy`