feat!: Support contracts with no constructor (#5175)

Changes: - **Breaking**: `constructor` is no longer an enshrined function name, it's now required to flag the constructor with `aztec(initializer)`. - Remove need for a function named constructor in noir aztec-macros and yarn-packages - Add `isInitializer` flag to contract artifact - Default the initializer to a function that has the `aztec(initializer)` attribute, if there's more than one, pick one at random, preferring private ones - When there's no initializer, the `initializationHash` of a contract instance is set to zero - Remove empty constructor functions from our contracts, and flag public constructors as initializer where missing cc @AztecProtocol/devrel
AztecProtocol · Mar 14, 2024 · df7fa32 · df7fa32
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diff --git a/boxes/boxes/react/src/contracts/src/main.nr b/boxes/boxes/react/src/contracts/src/main.nr
@@ -8,6 +8,7 @@ contract BoxReact {
     }
 
     #[aztec(private)]
+    #[aztec(initializer)]
     fn constructor(number: Field, owner: AztecAddress) {
         let numbers = storage.numbers;
         let mut new_number = ValueNote::new(number, owner);

diff --git a/boxes/boxes/vanilla/src/contracts/src/main.nr b/boxes/boxes/vanilla/src/contracts/src/main.nr
@@ -8,6 +8,7 @@ contract Vanilla {
     }
 
     #[aztec(private)]
+    #[aztec(initializer)]
     fn constructor(number: Field, owner: AztecAddress) {
         let numbers = storage.numbers;
         let mut new_number = ValueNote::new(number, owner);

diff --git a/docs/docs/misc/migration_notes.md b/docs/docs/misc/migration_notes.md
@@ -6,6 +6,24 @@ keywords: [sandbox, cli, aztec, notes, migration, updating, upgrading]
 
 Aztec is in full-speed development. Literally every version breaks compatibility with the previous ones. This page attempts to target errors and difficulties you might encounter when upgrading, and how to resolve them.
 
+## 0.27.0
+
+### `initializer` macro replaces `constructor`
+
+Before this version, every contract was required to have exactly one `constructor` private function, that was used for deployment. We have now removed this requirement, and made `constructor` a function like any other.
+
+To signal that a function can be used to **initialize** a contract, you must now decorate it with the `#[aztec(initializer)]` attribute. Initializers are regular functions that set an "initialized" flag (a nullifier) for the contract. A contract can only be initialized once, and contract functions can only be called after the contract has been initialized, much like a constructor. However, if a contract defines no initializers, it can be called at any time. Additionally, you can define as many initializer functions in a contract as you want, both private and public.
+
+To migrate from current code, simply add an initializer attribute to your constructor functions. 
+
+```diff
++ #[aztec(initializer)]
+#[aztec(private)]
+fn constructor() { ... }
+```
+
+If your private constructor was used to just call a public internal initializer, then remove the private constructor and flag the public function as initializer. And if your private constructor was an empty one, just remove it.
+
 ## 0.25.0
 
 ### [Aztec.nr] Static calls

diff --git a/l1-contracts/src/core/libraries/ConstantsGen.sol b/l1-contracts/src/core/libraries/ConstantsGen.sol
@@ -92,7 +92,7 @@ library Constants {
   uint256 internal constant DEPLOYER_CONTRACT_INSTANCE_DEPLOYED_MAGIC_VALUE =
     0x85864497636cf755ae7bde03f267ce01a520981c21c3682aaf82a631;
   uint256 internal constant DEPLOYER_CONTRACT_ADDRESS =
-    0x0747a20ed0c86035e44ea5606f30de459f40b55c5e82012640aa554546af9044;
+    0x0bffa876f07f9fe1802579dfef599810202f9c25b9a2f58921064a267d1ad1d3;
   uint256 internal constant L1_TO_L2_MESSAGE_ORACLE_CALL_LENGTH = 17;
   uint256 internal constant MAX_NOTE_FIELDS_LENGTH = 20;
   uint256 internal constant GET_NOTE_ORACLE_RETURN_LENGTH = 23;

diff --git a/noir-projects/noir-contracts/contracts/avm_test_contract/src/main.nr b/noir-projects/noir-contracts/contracts/avm_test_contract/src/main.nr
@@ -29,9 +29,6 @@ contract AvmTest {
     // avm lib
     use dep::aztec::avm::hash::{keccak256, poseidon, sha256};
 
-    #[aztec(private)]
-    fn constructor() {}
-
     struct Storage {
         single: PublicMutable<Field>,
         list: PublicMutable<Note>,

diff --git a/noir-projects/noir-contracts/contracts/benchmarking_contract/src/main.nr b/noir-projects/noir-contracts/contracts/benchmarking_contract/src/main.nr
@@ -18,9 +18,6 @@ contract Benchmarking {
         balances: Map<AztecAddress, PublicMutable<Field>>,
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     // Creates a new value note for the target owner. Use this method to seed an initial set of notes.
     #[aztec(private)]
     fn create_note(owner: AztecAddress, value: Field) {

diff --git a/noir-projects/noir-contracts/contracts/card_game_contract/src/main.nr b/noir-projects/noir-contracts/contracts/card_game_contract/src/main.nr
@@ -18,9 +18,6 @@ contract CardGame {
         games: Map<Field, PublicMutable<Game>>,
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(private)]
     fn buy_pack(seed: Field // The randomness used to generate the cards. Passed in for now.
     ) {

diff --git a/noir-projects/noir-contracts/contracts/child_contract/src/main.nr b/noir-projects/noir-contracts/contracts/child_contract/src/main.nr
@@ -13,9 +13,6 @@ contract Child {
         a_private_value: PrivateSet<ValueNote>,
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     // Returns a sum of the input and the chain id and version of the contract in private circuit public input's return_values.
     #[aztec(private)]
     fn value(input: Field) -> Field {

diff --git a/noir-projects/noir-contracts/contracts/claim_contract/src/main.nr b/noir-projects/noir-contracts/contracts/claim_contract/src/main.nr
@@ -16,20 +16,9 @@ contract Claim {
       reward_token: SharedImmutable<AztecAddress>,
     }
 
-    #[aztec(private)]
-    fn constructor(target_contract: AztecAddress, reward_token: AztecAddress) {
-        let selector = FunctionSelector::from_signature("_initialize((Field),(Field))");
-        context.call_public_function(
-            context.this_address(),
-            selector,
-            [target_contract.to_field(), reward_token.to_field()]
-        );
-    }
-
     #[aztec(public)]
-    #[aztec(internal)]
-    #[aztec(noinitcheck)]
-    fn _initialize(target_contract: AztecAddress, reward_token: AztecAddress) {
+    #[aztec(initializer)]
+    fn constructor(target_contract: AztecAddress, reward_token: AztecAddress) {
         storage.target_contract.initialize(target_contract);
         storage.reward_token.initialize(reward_token);
     }

diff --git a/noir-projects/noir-contracts/contracts/contract_class_registerer_contract/src/main.nr b/noir-projects/noir-contracts/contracts/contract_class_registerer_contract/src/main.nr
@@ -22,9 +22,6 @@ contract ContractClassRegisterer {
 
     use crate::capsule::pop_capsule;
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(private)]
     fn register(artifact_hash: Field, private_functions_root: Field, public_bytecode_commitment: Field) {
         // TODO: Validate public_bytecode_commitment is the correct commitment of packed_public_bytecode

diff --git a/noir-projects/noir-contracts/contracts/contract_instance_deployer_contract/src/main.nr b/noir-projects/noir-contracts/contracts/contract_instance_deployer_contract/src/main.nr
@@ -11,9 +11,6 @@ contract ContractInstanceDeployer {
 
     use crate::events::{instance_deployed::ContractInstanceDeployed};
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(private)]
     fn deploy(
         salt: Field,

diff --git a/noir-projects/noir-contracts/contracts/counter_contract/src/main.nr b/noir-projects/noir-contracts/contracts/counter_contract/src/main.nr
@@ -15,15 +15,16 @@ contract Counter {
     // docs:start:constructor
     #[aztec(private)]
     #[aztec(initializer)]
-    fn constructor(headstart: u64, owner: AztecAddress) {
+    // We can name our initializer anything we want as long as it's marked as aztec(initializer)
+    fn initialize(headstart: u64, owner: AztecAddress) {
         let counters = storage.counters;
         counters.at(owner).add(headstart, owner);
     }
     // docs:end:constructor
 
     // docs:start:increment
     #[aztec(private)]
-      fn increment(owner: AztecAddress) {
+    fn increment(owner: AztecAddress) {
         let counters = storage.counters;
         counters.at(owner).add(1, owner);
     }

diff --git a/noir-projects/noir-contracts/contracts/crowdfunding_contract/src/main.nr b/noir-projects/noir-contracts/contracts/crowdfunding_contract/src/main.nr
@@ -33,24 +33,13 @@ contract Crowdfunding {
         claim_notes: PrivateSet<ValueNote>,
     }
 
-    #[aztec(private)]
-    fn constructor(donation_token: AztecAddress, operator: AztecAddress, deadline: u64) {
-        let selector = FunctionSelector::from_signature("_initialize((Field),(Field),Field)");
-        context.call_public_function(
-            context.this_address(),
-            selector,
-            [donation_token.to_field(), operator.to_field(), deadline as Field]
-        );
-    }
-
     #[aztec(public)]
-    #[aztec(internal)]
-    #[aztec(noinitcheck)]
-    // TODO(#4990): Make deadline a u64 once the neccessary traits are implemented
-    fn _initialize(donation_token: AztecAddress, operator: AztecAddress, deadline: Field) {
+    #[aztec(initializer)]
+    fn constructor(donation_token: AztecAddress, operator: AztecAddress, deadline: u64) {
+        // TODO(#4990): Make deadline a u64 once the neccessary traits are implemented
         storage.donation_token.initialize(donation_token);
         storage.operator.initialize(operator);
-        storage.deadline.initialize(deadline);
+        storage.deadline.initialize(deadline as Field);
     }
 
     #[aztec(public)]

diff --git a/noir-projects/noir-contracts/contracts/delegated_on_contract/src/main.nr b/noir-projects/noir-contracts/contracts/delegated_on_contract/src/main.nr
@@ -13,9 +13,6 @@ contract DelegatedOn {
         a_private_value: PrivateSet<ValueNote>,
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(private)]
     fn private_set_value(new_value: Field, owner: AztecAddress) -> Field {
         let mut note = ValueNote::new(new_value, owner);

diff --git a/noir-projects/noir-contracts/contracts/delegator_contract/src/main.nr b/noir-projects/noir-contracts/contracts/delegator_contract/src/main.nr
@@ -12,9 +12,6 @@ contract Delegator {
         a_private_value: PrivateSet<ValueNote>,
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(private)]
     fn private_delegate_set_value(
         targetContract: AztecAddress,

diff --git a/noir-projects/noir-contracts/contracts/docs_example_contract/src/main.nr b/noir-projects/noir-contracts/contracts/docs_example_contract/src/main.nr
@@ -93,9 +93,6 @@ contract DocsExample {
         }
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(public)]
     fn initialize_shared_immutable(points: u8) {
         let mut new_leader = Leader { account: context.msg_sender(), points };

diff --git a/noir-projects/noir-contracts/contracts/gas_token_contract/src/main.nr b/noir-projects/noir-contracts/contracts/gas_token_contract/src/main.nr
@@ -10,9 +10,6 @@ contract GasToken {
         balances: Map<AztecAddress, PublicMutable<U128>>,
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(public)]
     fn claim_public(to: AztecAddress, amount: Field, canceller: EthAddress, secret: Field) {
         let content_hash = get_bridge_gas_msg_hash(to, amount, canceller);

diff --git a/noir-projects/noir-contracts/contracts/import_test_contract/src/main.nr b/noir-projects/noir-contracts/contracts/import_test_contract/src/main.nr
@@ -11,11 +11,6 @@ contract ImportTest {
         ManyNotesADeepStructTestCodeGenStruct
     };
 
-    // TODO(@spalladino): Delete all empty constructors
-    #[aztec(private)]
-    fn constructor(
-    ) {}
-
     // Calls the testCodeGen on the Test contract at the target address
     // Used for testing calling a function with arguments of multiple types
     // See yarn-project/simulator/src/client/private_execution.ts

diff --git a/noir-projects/noir-contracts/contracts/parent_contract/src/main.nr b/noir-projects/noir-contracts/contracts/parent_contract/src/main.nr
@@ -2,9 +2,6 @@
 contract Parent {
     use dep::aztec::prelude::{AztecAddress, FunctionSelector};
 
-    #[aztec(private)]
-    fn constructor() {}
-
     // Private function to call another private function in the targetContract using the provided selector
     #[aztec(private)]
     fn entryPoint(targetContract: AztecAddress, targetSelector: FunctionSelector) -> Field {

diff --git a/noir-projects/noir-contracts/contracts/pending_note_hashes_contract/src/main.nr b/noir-projects/noir-contracts/contracts/pending_note_hashes_contract/src/main.nr
@@ -18,9 +18,6 @@ contract PendingNoteHashes {
     // TODO(dbanks12): consolidate code into internal helper functions
     // (once Noir's support for this is more robust)
 
-    #[aztec(private)]
-    fn constructor() {}
-
     // Confirm can access pending note hashes by creating / inserting a note and then
     // getting / reading that note all in the same contract function
     // Realistic way to describe this test is "Mint note A, then burn note A in the same transaction"

diff --git a/noir-projects/noir-contracts/contracts/price_feed_contract/src/main.nr b/noir-projects/noir-contracts/contracts/price_feed_contract/src/main.nr
@@ -10,9 +10,6 @@ contract PriceFeed {
         assets: Map<Field, PublicMutable<Asset>>,
     }
 
-    #[aztec(private)]
-    fn constructor() {}
-
     #[aztec(public)]
     fn set_price(asset_id: Field, price: Field) {
         let asset = storage.assets.at(asset_id);

diff --git a/noir-projects/noir-contracts/contracts/schnorr_hardcoded_account_contract/src/main.nr b/noir-projects/noir-contracts/contracts/schnorr_hardcoded_account_contract/src/main.nr
@@ -14,9 +14,6 @@ contract SchnorrHardcodedAccount {
 
     global ACCOUNT_ACTIONS_STORAGE_SLOT = 1;
 
-    #[aztec(private)]
-    fn constructor() {}
-
     // Note: If you globally change the entrypoint signature don't forget to update default_entrypoint.ts
     #[aztec(private)]
     fn entrypoint(app_payload: pub AppPayload, fee_payload: pub FeePayload) {

diff --git a/noir-projects/noir-contracts/contracts/schnorr_single_key_account_contract/src/main.nr b/noir-projects/noir-contracts/contracts/schnorr_single_key_account_contract/src/main.nr
@@ -11,9 +11,6 @@ contract SchnorrSingleKeyAccount {
 
     global ACCOUNT_ACTIONS_STORAGE_SLOT = 1;
 
-    #[aztec(private)]
-    fn constructor() {}
-
     // Note: If you globally change the entrypoint signature don't forget to update default_entrypoint.ts
     #[aztec(private)]
     fn entrypoint(app_payload: pub AppPayload, fee_payload: pub FeePayload) {

diff --git a/noir-projects/noir-contracts/contracts/slow_tree_contract/src/main.nr b/noir-projects/noir-contracts/contracts/slow_tree_contract/src/main.nr
@@ -33,8 +33,6 @@ contract SlowTree {
     }
     // docs:end:constants_and_storage
 
-    #[aztec(private)]
-    fn constructor() {}
     // docs:start:initialize
     #[aztec(public)]
     fn initialize() {

diff --git a/noir-projects/noir-contracts/contracts/test_contract/src/main.nr b/noir-projects/noir-contracts/contracts/test_contract/src/main.nr
@@ -38,12 +38,6 @@ contract Test {
         example_set: PrivateSet<FieldNote>,
     }
 
-    // TODO(@spalladino): Delete all empty constructors
-    #[aztec(private)]
-    // docs:start:empty-constructor
-    fn constructor() {}
-    // docs:end:empty-constructor
-
     #[aztec(private)]
     fn get_public_key(address: AztecAddress) -> [Field; 2] {
         let pub_key = get_public_key_oracle(address);

diff --git a/noir-projects/noir-contracts/contracts/uniswap_contract/src/main.nr b/noir-projects/noir-contracts/contracts/uniswap_contract/src/main.nr
@@ -24,9 +24,6 @@ contract Uniswap {
         // gets incremented each time after use to prevent replay attacks
         nonce_for_burn_approval: PublicMutable<Field>,
     }
-
-    #[aztec(private)]
-    fn constructor() {}
     // docs:end:uniswap_setup
 
     // docs:start:swap_public

diff --git a/noir-projects/noir-protocol-circuits/crates/types/src/constants.nr b/noir-projects/noir-protocol-circuits/crates/types/src/constants.nr
@@ -130,7 +130,7 @@ global REGISTERER_UNCONSTRAINED_FUNCTION_BROADCASTED_MAGIC_VALUE = 0xe7af8166354
 // CONTRACT INSTANCE CONSTANTS
 // sha224sum 'struct ContractInstanceDeployed'
 global DEPLOYER_CONTRACT_INSTANCE_DEPLOYED_MAGIC_VALUE = 0x85864497636cf755ae7bde03f267ce01a520981c21c3682aaf82a631;
-global DEPLOYER_CONTRACT_ADDRESS = 0x0747a20ed0c86035e44ea5606f30de459f40b55c5e82012640aa554546af9044;
+global DEPLOYER_CONTRACT_ADDRESS = 0x0bffa876f07f9fe1802579dfef599810202f9c25b9a2f58921064a267d1ad1d3;
 
 // NOIR CONSTANTS - constants used only in yarn-packages/noir-contracts
 // Some are defined here because Noir doesn't yet support globals referencing other globals yet.

diff --git a/noir/noir-repo/aztec_macros/src/lib.rs b/noir/noir-repo/aztec_macros/src/lib.rs
@@ -179,15 +179,6 @@ fn transform_module(
                 crate_graph.root_file_id,
             ));
         }
-
-        let constructor_defined = module.functions.iter().any(|func| func.name() == "constructor");
-        if !constructor_defined {
-            let crate_graph = &context.crate_graph[crate_id];
-            return Err((
-                AztecMacroError::ContractConstructorMissing { span: Span::default() },
-                crate_graph.root_file_id,
-            ));
-        }
     }
 
     Ok(has_transformed_module)

diff --git a/noir/noir-repo/aztec_macros/src/utils/errors.rs b/noir/noir-repo/aztec_macros/src/utils/errors.rs
@@ -7,7 +7,6 @@ use super::constants::MAX_CONTRACT_PRIVATE_FUNCTIONS;
 pub enum AztecMacroError {
     AztecDepNotFound,
     ContractHasTooManyPrivateFunctions { span: Span },
-    ContractConstructorMissing { span: Span },
     UnsupportedFunctionArgumentType { span: Span, typ: UnresolvedTypeData },
     UnsupportedStorageType { span: Option<Span>, typ: UnresolvedTypeData },
     CouldNotAssignStorageSlots { secondary_message: Option<String> },
@@ -29,11 +28,6 @@ impl From<AztecMacroError> for MacroError {
                 secondary_message: None,
                 span: Some(span),
             },
-            AztecMacroError::ContractConstructorMissing { span } => MacroError {
-                primary_message: "Contract must have a constructor function".to_owned(),
-                secondary_message: None,
-                span: Some(span),
-            },
             AztecMacroError::UnsupportedFunctionArgumentType { span, typ } => MacroError {
                 primary_message: format!("Provided parameter type `{typ:?}` is not supported in Aztec contract interface"),
                 secondary_message: None,

diff --git a/yarn-project/accounts/src/defaults/account_contract.ts b/yarn-project/accounts/src/defaults/account_contract.ts
@@ -11,7 +11,7 @@ import { DefaultAccountInterface } from '../defaults/account_interface.js';
  */
 export abstract class DefaultAccountContract implements AccountContract {
   abstract getAuthWitnessProvider(address: CompleteAddress): AuthWitnessProvider;
-  abstract getDeploymentArgs(): any[];
+  abstract getDeploymentArgs(): any[] | undefined;
 
   constructor(private artifact: ContractArtifact) {}
 

diff --git a/yarn-project/accounts/src/single_key/account_contract.ts b/yarn-project/accounts/src/single_key/account_contract.ts
@@ -18,8 +18,8 @@ export class SingleKeyAccountContract extends DefaultAccountContract {
     super(SchnorrSingleKeyAccountContractArtifact as ContractArtifact);
   }
 
-  getDeploymentArgs(): any[] {
-    return [];
+  getDeploymentArgs(): undefined {
+    return undefined;
   }
 
   getAuthWitnessProvider({ partialAddress }: CompleteAddress): AuthWitnessProvider {

diff --git a/yarn-project/accounts/src/testing/create_account.ts b/yarn-project/accounts/src/testing/create_account.ts
@@ -10,7 +10,7 @@ import { getSchnorrAccount } from '../schnorr/index.js';
  * @returns - A wallet for a fresh account.
  */
 export function createAccount(pxe: PXE): Promise<AccountWalletWithPrivateKey> {
-  return getSchnorrAccount(pxe, GrumpkinScalar.random(), GrumpkinScalar.random()).waitDeploy();
+  return getSchnorrAccount(pxe, GrumpkinScalar.random(), GrumpkinScalar.random()).waitSetup();
 }
 
 /**