feat: Enable public constructor functions (#4896)

Allow decorating a public function as `initializer`

noir-projects/aztec-nr/aztec/src/initializer.nr

@@ -1,12 +1,20 @@
 use dep::protocol_types::hash::silo_nullifier;
-use crate::context::{PrivateContext, ContextInterface};
+use crate::context::{PrivateContext, PublicContext, ContextInterface};
 use crate::history::nullifier_inclusion::prove_nullifier_inclusion;
 
 pub fn mark_as_initialized(context: &mut PrivateContext) {
   let init_nullifier = compute_unsiloed_contract_initialization_nullifier(*context);
   context.push_new_nullifier(init_nullifier, 0);
 }
 
+// TODO(@spalladino): Using the trait here fails with "No matching impl found for `&mut TContext: ContextInterface`" 
+// on the `push_new_nullifier` call. Remove this method in favor of a single method that uses the trait (and update 
+// the noir compiler macro accordingly) once we sort it out.
+pub fn mark_as_initialized_public(context: &mut PublicContext) {
+  let init_nullifier = compute_unsiloed_contract_initialization_nullifier(*context);
+  context.push_new_nullifier(init_nullifier, 0);
+}
+
 pub fn assert_is_initialized<TContext>(context: &mut TContext) where TContext: ContextInterface {
   let init_nullifier = compute_contract_initialization_nullifier(*context);
   prove_nullifier_inclusion(init_nullifier, *context);

noir-projects/noir-contracts/contracts/stateful_test_contract/src/main.nr

@@ -20,6 +20,13 @@ contract StatefulTest {
         let _res = context.call_private_function(context.this_address(), selector, [owner.to_field(), value]);
     }
 
+    #[aztec(public)]
+    #[aztec(initializer)]
+    fn public_constructor(owner: AztecAddress, value: Field) {
+        let selector = FunctionSelector::from_signature("increment_public_value_no_init_check((Field),Field)");
+        let _res = context.call_public_function(context.this_address(), selector, [owner.to_field(), value]);
+    }
+
     #[aztec(private)]
     fn create_note(owner: AztecAddress, value: Field) {
         if (value != 0) {

noir/noir-repo/aztec_macros/src/lib.rs

@@ -711,16 +711,7 @@ fn transform_function(
 
     // Before returning mark the contract as initialized
     if is_initializer {
-        if ty == "Public" {
-            let error = AztecMacroError::UnsupportedAttributes {
-                span: func.def.name.span(),
-                secondary_message: Some(
-                    "public functions cannot yet be used as initializers".to_owned(),
-                ),
-            };
-            return Err(error);
-        }
-        let mark_initialized = create_mark_as_initialized();
+        let mark_initialized = create_mark_as_initialized(ty);
         func.def.body.0.push(mark_initialized);
     }
 
@@ -1179,9 +1170,10 @@ fn create_init_check() -> Statement {
 /// ```noir
 /// mark_as_initialized(&mut context);
 /// ```
-fn create_mark_as_initialized() -> Statement {
+fn create_mark_as_initialized(ty: &str) -> Statement {
+    let name = if ty == "Public" { "mark_as_initialized_public" } else { "mark_as_initialized" };
     make_statement(StatementKind::Expression(call(
-        variable_path(chained_dep!("aztec", "initializer", "mark_as_initialized")),
+        variable_path(chained_dep!("aztec", "initializer", name)),
         vec![mutable_reference("context")],
     )))
 }

yarn-project/end-to-end/src/e2e_deploy_contract.test.ts

@@ -24,7 +24,7 @@ import {
   deployInstance,
   registerContractClass,
 } from '@aztec/aztec.js/deployment';
-import { ContractClassIdPreimage, Point, PublicKey } from '@aztec/circuits.js';
+import { ContractClassIdPreimage, Point } from '@aztec/circuits.js';
 import { siloNullifier } from '@aztec/circuits.js/hash';
 import { FunctionSelector, FunctionType } from '@aztec/foundation/abi';
 import { StatefulTestContract } from '@aztec/noir-contracts.js';
@@ -258,10 +258,6 @@ describe('e2e_deploy_contract', () => {
         /nullifier witness not found/i,
       );
     });
-
-    it('refuses to call a public function that requires initialization', async () => {
-      // TODO(@spalladino)
-    });
   });
 
   describe('registering a contract class', () => {
@@ -309,16 +305,14 @@ describe('e2e_deploy_contract', () => {
       describe(`deploying a contract instance ${how}`, () => {
         let instance: ContractInstanceWithAddress;
         let initArgs: StatefulContractCtorArgs;
-        let publicKey: PublicKey;
         let contract: StatefulTestContract;
 
-        beforeAll(async () => {
-          initArgs = [accounts[0].address, 42];
+        const deployInstance = async () => {
+          const initArgs = [accounts[0].address, 42] as StatefulContractCtorArgs;
           const salt = Fr.random();
           const portalAddress = EthAddress.random();
-          publicKey = Point.random();
-
-          instance = getContractInstanceFromDeployParams(artifact, initArgs, salt, publicKey, portalAddress);
+          const publicKey = Point.random();
+          const instance = getContractInstanceFromDeployParams(artifact, initArgs, salt, publicKey, portalAddress);
           const { address, contractClassId } = instance;
           logger(`Deploying contract instance at ${address.toString()} class id ${contractClassId.toString()}`);
           await deployFn(instance);
@@ -338,7 +332,12 @@ describe('e2e_deploy_contract', () => {
             publicKey,
           });
           expect(registered.address).toEqual(instance.address);
-          contract = await StatefulTestContract.at(instance.address, wallet);
+          const contract = await StatefulTestContract.at(instance.address, wallet);
+          return { contract, initArgs, instance, publicKey };
+        };
+
+        beforeAll(async () => {
+          ({ instance, initArgs, contract } = await deployInstance());
         }, 60_000);
 
         it('stores contract instance in the aztec node', async () => {
@@ -381,6 +380,32 @@ describe('e2e_deploy_contract', () => {
           const stored = await contract.methods.get_public_value(whom).view();
           expect(stored).toEqual(10n);
         }, 30_000);
+
+        it('refuses to reinitialize the contract', async () => {
+          await expect(
+            contract.methods
+              .public_constructor(...initArgs)
+              .send({ skipPublicSimulation: true })
+              .wait(),
+          ).rejects.toThrow(/dropped/i);
+        }, 30_000);
+
+        it('initializes a new instance of the contract via a public function', async () => {
+          const { contract, initArgs } = await deployInstance();
+          const whom = initArgs[0];
+          logger.info(`Initializing contract at ${contract.address} via a public function`);
+          await contract.methods
+            .public_constructor(...initArgs)
+            .send({ skipPublicSimulation: true })
+            .wait();
+          expect(await contract.methods.get_public_value(whom).view()).toEqual(42n);
+          logger.info(`Calling a public function that requires initialization on ${contract.address}`);
+          await contract.methods.increment_public_value(whom, 10).send().wait();
+          expect(await contract.methods.get_public_value(whom).view()).toEqual(52n);
+          logger.info(`Calling a private function that requires initialization on ${contract.address}`);
+          await contract.methods.create_note(whom, 10).send().wait();
+          expect(await contract.methods.summed_values(whom).view()).toEqual(10n);
+        }, 90_000);
       });
 
     testDeployingAnInstance('from a wallet', async instance => {