Add integration-test for possible migration pattern

integration-tests/upgradeable-contracts/.gitignore

@@ -0,0 +1,2 @@
+**/target/
+Cargo.lock

integration-tests/upgradeable-contracts/README.md

@@ -12,6 +12,21 @@ This is exactly what `set_code_hash()` function does.
 However, developers needs to be mindful of storage compatibility.
 You can read more about storage compatibility on [use.ink](https://use.ink/basics/upgradeable-contracts#replacing-contract-code-with-set_code_hash)
 
+## [`set-code-hash`](set-code-hash-migration/)
+
+When upgrading a contract, the new code may have a different storage layout. This example illustrates a method to 
+migrate the storage from the old layout to the new layout. It does so by using an intermediate `migration` contract
+which performs the storage upgrade. The workflow is as follows:
+
+
+1. Upload a `migration` contract with a message `migrate` which performs the storage migration.
+2. Set code hash to the `migration` contract.
+3. Upload the upgraded version of the original contract.
+4. Call `migrate` on the `migration` contract, passing the code hash of the new updated incrementer contract from `3.` 
+This must happen as a single message, because following the storage migration, the contract will not be able to be 
+called again, since it will fail to load the migrated storage.
+
+
 ## [Delegator](delegator/)
 
 Delegator patter is based around a low level cross contract call function `delegate_call`.

integration-tests/upgradeable-contracts/set-code-hash-migration/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "incrementer"
+version = "5.0.0-alpha"
+authors = ["Parity Technologies <[email protected]>"]
+edition = "2021"
+publish = false
+
+[dependencies]
+ink = { path = "../../../crates/ink", default-features = false }
+
+migration = { path = "./migration", default-features = false, features = ["ink-as-dependency"] }
+updated-incrementer = { path = "./updated-incrementer", default-features = false, features = ["ink-as-dependency"] }
+
+[dev-dependencies]
+ink_e2e = { path = "../../../crates/e2e" }
+
+[lib]
+path = "lib.rs"
+
+[features]
+default = ["std"]
+std = [
+    "ink/std",
+    "migration/std",
+    "updated-incrementer/std",
+]
+ink-as-dependency = []
+e2e-tests = []

integration-tests/upgradeable-contracts/set-code-hash-migration/e2e_tests.rs

@@ -0,0 +1,94 @@
+use super::incrementer::*;
+use ink_e2e::ContractsBackend;
+
+type E2EResult<T> = std::result::Result<T, Box<dyn std::error::Error>>;
+
+#[ink_e2e::test]
+async fn migration_works<Client: E2EBackend>(mut client: Client) -> E2EResult<()> {
+    // Given
+    let mut constructor = IncrementerRef::new();
+    let contract = client
+        .instantiate("incrementer", &ink_e2e::alice(), &mut constructor)
+        .submit()
+        .await
+        .expect("instantiate failed");
+    let mut call_builder = contract.call_builder::<Incrementer>();
+
+    let get = call_builder.get();
+    let get_res = client.call(&ink_e2e::alice(), &get).dry_run().await?;
+    assert_eq!(get_res.return_value(), 0);
+
+    let inc = call_builder.inc();
+    let _inc_result = client
+        .call(&ink_e2e::alice(), &inc)
+        .submit()
+        .await
+        .expect("`inc` failed");
+
+    let get = call_builder.get();
+    let get_res = client.call(&ink_e2e::alice(), &get).dry_run().await?;
+    let pre_migration_value = get_res.return_value();
+    assert_eq!(pre_migration_value, 1);
+
+    // Upload the code for the contract to be updated to after the migration.
+    let new_code_hash = client
+        .upload("updated-incrementer", &ink_e2e::alice())
+        .submit()
+        .await
+        .expect("uploading `updated-incrementer` failed")
+        .code_hash;
+    let new_code_hash = new_code_hash.as_ref().try_into().unwrap();
+
+    // Upload the code for the migration contract.
+    let migration_contract = client
+        .upload("migration", &ink_e2e::alice())
+        .submit()
+        .await
+        .expect("uploading `migration` failed");
+    let migration_code_hash = migration_contract.code_hash.as_ref().try_into().unwrap();
+
+    // When
+
+    // Set the code hash to the migration contract
+    let set_code = call_builder.set_code(migration_code_hash);
+    let _set_code_result = client
+        .call(&ink_e2e::alice(), &set_code)
+        .submit()
+        .await
+        .expect("`set_code` failed");
+
+    // Call the migration contract with a new value for `inc_by` and the code hash
+    // of the updated contract.
+    const NEW_INC_BY: u8 = 4;
+    let migrate = contract
+        .call_builder::<migration::incrementer::Incrementer>()
+        .migrate(NEW_INC_BY, new_code_hash);
+
+    let _migration_result = client
+        .call(&ink_e2e::alice(), &migrate)
+        .submit()
+        .await
+        .expect("`migrate` failed");
+
+    // Then
+    let inc = contract
+        .call_builder::<updated_incrementer::incrementer::Incrementer>()
+        .inc();
+
+    let _inc_result = client
+        .call(&ink_e2e::alice(), &inc)
+        .submit()
+        .await
+        .expect("`inc` failed");
+
+    let get = call_builder.get();
+    let get_res = client.call(&ink_e2e::alice(), &get).dry_run().await?;
+
+    // Remember, we updated our incrementer contract to increment by `4`.
+    assert_eq!(
+        get_res.return_value(),
+        pre_migration_value + NEW_INC_BY as u32
+    );
+
+    Ok(())
+}

integration-tests/upgradeable-contracts/set-code-hash-migration/lib.rs

@@ -0,0 +1,69 @@
+#![cfg_attr(not(feature = "std"), no_std, no_main)]
+
+//! Demonstrates how to use [`set_code_hash`](https://docs.rs/ink_env/latest/ink_env/fn.set_code_hash.html)
+//! to swap out the `code_hash` of an on-chain contract.
+//!
+//! We will swap the code of our `Incrementer` contract with that of the `Incrementer`
+//! found in the `updated_incrementer` folder.
+//!
+//! See the included End-to-End tests an example update workflow.
+
+#[ink::contract]
+pub mod incrementer {
+    /// Track a counter in storage.
+    ///
+    /// # Note
+    ///
+    /// Is is important to realize that after the call to `set_code_hash` the contract's
+    /// storage remains the same.
+    ///
+    /// If you change the storage layout in your storage struct you may introduce
+    /// undefined behavior to your contract!
+    #[ink(storage)]
+    #[derive(Default)]
+    pub struct Incrementer {
+        count: u32,
+    }
+
+    impl Incrementer {
+        /// Creates a new counter smart contract initialized with the given base value.
+        #[ink(constructor)]
+        pub fn new() -> Self {
+            Default::default()
+        }
+
+        /// Increments the counter value which is stored in the contract's storage.
+        #[ink(message)]
+        pub fn inc(&mut self) {
+            self.count = self.count.checked_add(1).unwrap();
+            ink::env::debug_println!(
+                "The new count is {}, it was modified using the original contract code.",
+                self.count
+            );
+        }
+
+        /// Returns the counter value which is stored in this contract's storage.
+        #[ink(message)]
+        pub fn get(&self) -> u32 {
+            self.count
+        }
+
+        /// Modifies the code which is used to execute calls to this contract address
+        /// (`AccountId`).
+        ///
+        /// We use this to upgrade the contract logic. We don't do any authorization here,
+        /// any caller can execute this method.
+        ///
+        /// In a production contract you would do some authorization here!
+        #[ink(message)]
+        pub fn set_code(&mut self, code_hash: Hash) {
+            self.env().set_code_hash(&code_hash).unwrap_or_else(|err| {
+                panic!("Failed to `set_code_hash` to {code_hash:?} due to {err:?}")
+            });
+            ink::env::debug_println!("Switched code hash to {:?}.", code_hash);
+        }
+    }
+}
+
+#[cfg(all(test, feature = "e2e-tests"))]
+mod e2e_tests;

integration-tests/upgradeable-contracts/set-code-hash-migration/migration/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "migration"
+version = "5.0.0-alpha"
+authors = ["Parity Technologies <[email protected]>"]
+edition = "2021"
+publish = false
+
+[dependencies]
+ink = { path = "../../../../crates/ink", default-features = false }
+
+[lib]
+path = "lib.rs"
+
+[features]
+default = ["std"]
+std = [
+    "ink/std",
+]
+ink-as-dependency = []

integration-tests/upgradeable-contracts/set-code-hash-migration/migration/lib.rs

@@ -0,0 +1,70 @@
+#![cfg_attr(not(feature = "std"), no_std, no_main)]
+#![allow(clippy::new_without_default)]
+
+#[ink::contract]
+pub mod incrementer {
+
+    /// Storage struct matches exactly that of the original `incrementer` contract, from
+    /// which we are migrating.
+    #[ink(storage)]
+    pub struct Incrementer {
+        count: u32,
+    }
+
+    #[ink::storage_item]
+    pub struct IncrementerNew {
+        count: u64,
+        inc_by: u8,
+    }
+
+    impl Incrementer {
+        /// Creates a new counter smart contract initialized with the given base value.
+        ///
+        /// # Note
+        ///
+        /// When upgrading using the `set_code_hash` workflow we only need to point to a
+        /// contract's uploaded code hash, **not** an instantiated contract's
+        /// `AccountId`.
+        ///
+        /// Because of this we will never actually call the constructor of this contract.
+        #[ink(constructor)]
+        pub fn new() -> Self {
+            unreachable!(
+                "Constructors are not called when upgrading using `set_code_hash`."
+            )
+        }
+
+        /// Run the migration to the data layout for the upgraded contract.
+        /// Once the storage migration has successfully completed, the contract will be
+        /// upgraded to the supplied code hash.
+        ///
+        /// In a production contract you would do some authorization here!
+        ///
+        /// # Note
+        ///
+        /// This function necessarily accepts a `&self` instead of a `&mut self` because
+        /// we are modifying storage directly for the migration.
+        ///
+        /// The `self` in `&mut self` is the original `Incrementer` storage struct, and
+        /// would be implicitly written to storage following the function execution,
+        /// overwriting the migrated storage.
+        #[ink(message)]
+        pub fn migrate(&self, inc_by: u8, code_hash: Hash) {
+            let incrementer_new = IncrementerNew {
+                count: self.count as u64,
+                inc_by,
+            };
+
+            // overwrite the original storage struct with the migrated storage struct,
+            // which has a layout compatible with the new contract code.
+            const STORAGE_KEY: u32 =
+                <Incrementer as ink::storage::traits::StorageKey>::KEY;
+            ink::env::set_contract_storage(&STORAGE_KEY, &incrementer_new);
+
+            ink::env::set_code_hash::<<Self as ink::env::ContractEnv>::Env>(&code_hash)
+                .unwrap_or_else(|err| {
+                    panic!("Failed to `set_code_hash` to {code_hash:?} due to {err:?}")
+                })
+        }
+    }
+}

integration-tests/upgradeable-contracts/set-code-hash-migration/updated-incrementer/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "updated-incrementer"
+version = "5.0.0-alpha"
+authors = ["Parity Technologies <[email protected]>"]
+edition = "2021"
+publish = false
+
+[dependencies]
+ink = { path = "../../../../crates/ink", default-features = false }
+
+[lib]
+path = "lib.rs"
+
+[features]
+default = ["std"]
+std = [
+    "ink/std",
+]
+ink-as-dependency = []