refactor: Update function selector computation (#2001)

Fixed #1990. Also adds an oracle to more easily compute selectors from
inside the contracts for improved devex.

yarn-project/acir-simulator/src/acvm/acvm.ts

@@ -32,6 +32,7 @@ export const ONE_ACVM_FIELD: ACVMField = `0x${'00'.repeat(Fr.SIZE_IN_BYTES - 1)}
  * The supported oracle names.
  */
 type ORACLE_NAMES =
+  | 'computeSelector'
   | 'packArguments'
   | 'getSecretKey'
   | 'getNote'

yarn-project/acir-simulator/src/client/private_execution.ts

@@ -72,6 +72,11 @@ export class PrivateFunctionExecution {
     const unencryptedLogs = new FunctionL2Logs([]);
 
     const { partialWitness } = await acvm(await AcirSimulator.getSolver(), acir, initialWitness, {
+      computeSelector: (...args) => {
+        const signature = oracleDebugCallToFormattedStr(args);
+        const returnValue = toACVMField(FunctionSelector.fromSignature(signature).toField());
+        return Promise.resolve(returnValue);
+      },
       packArguments: async args => {
         return toACVMField(await this.context.packedArgsCache.pack(args.map(fromACVMField)));
       },

yarn-project/acir-simulator/src/client/simulator.ts

@@ -1,7 +1,7 @@
-import { CallContext, CircuitsWasm, FunctionData, TxContext } from '@aztec/circuits.js';
+import { CallContext, CircuitsWasm, FunctionData, MAX_NOTE_FIELDS_LENGTH, TxContext } from '@aztec/circuits.js';
 import { computeTxHash } from '@aztec/circuits.js/abis';
 import { Grumpkin } from '@aztec/circuits.js/barretenberg';
-import { ArrayType, FunctionType, encodeArguments } from '@aztec/foundation/abi';
+import { ArrayType, FunctionSelector, FunctionType, encodeArguments } from '@aztec/foundation/abi';
 import { AztecAddress } from '@aztec/foundation/aztec-address';
 import { EthAddress } from '@aztec/foundation/eth-address';
 import { Fr } from '@aztec/foundation/fields';
@@ -15,7 +15,6 @@ import { PackedArgsCache } from '../common/packed_args_cache.js';
 import { ClientTxExecutionContext } from './client_execution_context.js';
 import { DBOracle, FunctionAbiWithDebugMetadata } from './db_oracle.js';
 import { ExecutionResult } from './execution_result.js';
-import { computeNoteHashAndNullifierSelector, computeNoteHashAndNullifierSignature } from './function_selectors.js';
 import { PrivateFunctionExecution } from './private_execution.js';
 import { UnconstrainedFunctionExecution } from './unconstrained_execution.js';
 
@@ -177,12 +176,23 @@ export class AcirSimulator {
     storageSlot: Fr,
     notePreimage: Fr[],
   ) {
-    let abi: FunctionAbiWithDebugMetadata;
-    try {
-      abi = await this.db.getFunctionABI(contractAddress, computeNoteHashAndNullifierSelector);
-    } catch (e) {
+    let abi: FunctionAbiWithDebugMetadata | undefined = undefined;
+
+    // Brute force
+    for (let i = 0; i < MAX_NOTE_FIELDS_LENGTH; i++) {
+      const signature = `compute_note_hash_and_nullifier(Field,Field,Field,[Field;${i}])`;
+      const selector = FunctionSelector.fromSignature(signature);
+      try {
+        abi = await this.db.getFunctionABI(contractAddress, selector);
+        if (abi !== undefined) break;
+      } catch (e) {
+        // ignore
+      }
+    }
+
+    if (abi == undefined) {
       throw new Error(
-        `Mandatory implementation of "${computeNoteHashAndNullifierSignature}" missing in noir contract ${contractAddress.toString()}.`,
+        `Mandatory implementation of "compute_note_hash_and_nullifier" missing in noir contract ${contractAddress.toString()}.`,
       );
     }
 

yarn-project/acir-simulator/src/client/unconstrained_execution.ts

@@ -1,5 +1,5 @@
 import { CallContext, FunctionData } from '@aztec/circuits.js';
-import { DecodedReturn, decodeReturnValues } from '@aztec/foundation/abi';
+import { DecodedReturn, FunctionSelector, decodeReturnValues } from '@aztec/foundation/abi';
 import { AztecAddress } from '@aztec/foundation/aztec-address';
 import { Fr } from '@aztec/foundation/fields';
 import { createDebugLogger } from '@aztec/foundation/log';
@@ -48,6 +48,11 @@ export class UnconstrainedFunctionExecution {
     const initialWitness = toACVMWitness(1, this.args);
 
     const { partialWitness } = await acvm(await AcirSimulator.getSolver(), acir, initialWitness, {
+      computeSelector: (...args) => {
+        const signature = oracleDebugCallToFormattedStr(args);
+        const returnValue = toACVMField(FunctionSelector.fromSignature(signature).toField());
+        return Promise.resolve(returnValue);
+      },
       getSecretKey: ([ownerX], [ownerY]) => this.context.getSecretKey(this.contractAddress, ownerX, ownerY),
       getPublicKey: async ([acvmAddress]) => {
         const address = frToAztecAddress(fromACVMField(acvmAddress));

yarn-project/acir-simulator/src/public/executor.ts

@@ -78,10 +78,13 @@ export class PublicExecutor {
     // We use this cache to hold the packed arguments.
     const packedArgs = await PackedArgsCache.create([]);
     const { partialWitness } = await acvm(await AcirSimulator.getSolver(), acir, initialWitness, {
+      computeSelector: (...args) => {
+        const signature = oracleDebugCallToFormattedStr(args);
+        return Promise.resolve(toACVMField(FunctionSelector.fromSignature(signature).toField()));
+      },
       packArguments: async args => {
         return toACVMField(await packedArgs.pack(args.map(fromACVMField)));
       },
-
       debugLog: (...args) => {
         this.log(oracleDebugCallToFormattedStr(args));
         return Promise.resolve(ZERO_ACVM_FIELD);

yarn-project/end-to-end/src/e2e_lending_contract.test.ts

@@ -54,7 +54,7 @@ describe('e2e_lending_contract', () => {
       logger(`Tx sent with hash ${await tx.getTxHash()}`);
       const receipt = await tx.wait();
       expect(receipt.status).toBe(TxStatus.MINED);
-      logger(`Debt asset deployed to ${receipt.contractAddress}`);
+      logger(`Stable coin asset deployed to ${receipt.contractAddress}`);
       stableCoin = await NativeTokenContract.at(receipt.contractAddress!, wallet);
     }
 

yarn-project/foundation/src/abi/decoder.ts

@@ -1,4 +1,4 @@
-import { ABIType, FunctionAbi } from '@aztec/foundation/abi';
+import { ABIParameter, ABIType, FunctionAbi } from '@aztec/foundation/abi';
 import { Fr } from '@aztec/foundation/fields';
 
 /**
@@ -86,3 +86,53 @@ class ReturnValuesDecoder {
 export function decodeReturnValues(abi: FunctionAbi, returnValues: Fr[]) {
   return new ReturnValuesDecoder(abi, returnValues.slice()).decode();
 }
+
+/**
+ * Decodes the signature of a function from the name and parameters.
+ */
+export class FunctionSignatureDecoder {
+  constructor(private name: string, private parameters: ABIParameter[]) {}
+
+  /**
+   * Decodes a single function parameter for the function signature.
+   * @param param - The parameter to decode.
+   * @returns A string representing the parameter type.
+   */
+  private decodeParameter(param: ABIType): string {
+    switch (param.kind) {
+      case 'field':
+        return 'Field';
+      case 'integer':
+        if (param.sign === 'signed') {
+          throw new Error('Unsupported type: signed integer');
+        }
+        return `u${param.width}`;
+      case 'boolean':
+        return 'bool';
+      case 'array':
+        return `[${this.decodeParameter(param.type)};${param.length}]`;
+      case 'struct':
+        return `(${param.fields.map(field => `${this.decodeParameter(field.type)}`).join(',')})`;
+      default:
+        throw new Error(`Unsupported type: ${param.kind}`);
+    }
+  }
+
+  /**
+   * Decodes all the parameters and build the function signature
+   * @returns The function signature.
+   */
+  public decode(): string {
+    return `${this.name}(${this.parameters.map(param => this.decodeParameter(param.type)).join(',')})`;
+  }
+}
+
+/**
+ * Decodes a function signature from the name and parameters.
+ * @param name - The name of the function-
+ * @param parameters - The parameters of the function.
+ * @returns - The function signature.
+ */
+export function decodeFunctionSignature(name: string, parameters: ABIParameter[]) {
+  return new FunctionSignatureDecoder(name, parameters).decode();
+}

yarn-project/foundation/src/abi/function_selector.ts

@@ -1,4 +1,4 @@
-import { ABIParameter } from '@aztec/foundation/abi';
+import { ABIParameter, decodeFunctionSignature } from '@aztec/foundation/abi';
 import { toBigIntBE, toBufferBE } from '@aztec/foundation/bigint-buffer';
 import { keccak } from '@aztec/foundation/crypto';
 import { Fr } from '@aztec/foundation/fields';
@@ -97,8 +97,11 @@ export class FunctionSelector {
    * @returns A Buffer containing the 4-byte function selector.
    */
   static fromNameAndParameters(name: string, parameters: ABIParameter[]) {
-    const signature = name === 'constructor' ? name : `${name}(${parameters.map(p => p.type.kind).join(',')})`;
-    return FunctionSelector.fromSignature(signature);
+    const signature = decodeFunctionSignature(name, parameters);
+    const selector = FunctionSelector.fromSignature(signature);
+    // If using the debug logger here it kill the typing in the `server_world_state_synchroniser` and jest tests.
+    // console.log(`Function selector for ${signature} is ${selector}`);
+    return selector;
   }
 
   /**

yarn-project/noir-contracts/src/contracts/child_contract/src/main.nr

@@ -5,7 +5,10 @@ contract Child {
     use crate::storage::Storage;
     use dep::aztec::{
         abi::CallContext,
-        oracle::logs::emit_unencrypted_log,
+        oracle::{
+            logs::emit_unencrypted_log,
+            compute_selector::compute_selector,
+        }
     };
     use dep::std::option::Option;
 
@@ -34,7 +37,7 @@ contract Child {
         input + context.chain_id() + context.version()
     }
 
-    // Returns base_value + 42.
+    // Returns base_value + chain_id + version + block_number + timestamp
     #[aztec(public)]
     fn pubGetValue(base_value: Field) -> Field {
         let returnValue = base_value + context.chain_id() + context.version() + context.block_number() + context.timestamp();
@@ -77,7 +80,7 @@ contract Child {
 
     #[aztec(public)]
     fn setValueTwiceWithNestedFirst() {
-        let pubSetValueSelector = 0x5b0f91b0;
+        let pubSetValueSelector = compute_selector("pubSetValue(Field)");
         let _ret = context.call_public_function(context.this_address(), pubSetValueSelector, [10]);
 
         let storage = Storage::init(Option::none(), Option::some(&mut context));
@@ -91,7 +94,7 @@ contract Child {
         storage.current_value.write(20);
         let _hash = emit_unencrypted_log(20);
 
-        let pubSetValueSelector = 0x5b0f91b0;
+        let pubSetValueSelector = compute_selector("pubSetValue(Field)");
         let _ret = context.call_public_function(context.this_address(), pubSetValueSelector, [10]);
     }
 }

yarn-project/noir-contracts/src/contracts/lending_contract/src/interfaces.nr

@@ -7,6 +7,7 @@ use dep::aztec::context::{
 
 use crate::storage::Asset;
 use dep::aztec::constants_gen::RETURN_VALUES_LENGTH;
+use dep::aztec::oracle::compute_selector::compute_selector;
 
 struct PriceFeed {
   address: Field,
@@ -20,7 +21,7 @@ impl PriceFeed {
   fn get_price(self: Self, context: PublicContext) -> u120 {
     let return_values = context.call_public_function(
       self.address, 
-      3359284436,
+      compute_selector("get_price(Field)"),
       [0]
     );
 
@@ -40,23 +41,23 @@ impl Token {
   fn transfer_pub(self: Self, context: PublicContext, to: Field, amount: Field) {
     let _transfer_return_values = context.call_public_function(
       self.address,
-      1012824788, 
+      compute_selector("transfer_pub(Field,Field)"),
       [to, amount]
     );
   }
 
   fn transfer_from_pub(self: Self, context: PublicContext, from: Field, to: Field, amount: Field) {
     let _transfer_return_values = context.call_public_function(
-      self.address, 
-      1602017294, 
+      self.address,
+      compute_selector("transfer_from_pub(Field,Field,Field)"),
       [from, to, amount]
     );
   }
 
   fn owner_mint_pub(self: Self, context: PublicContext, to: Field, amount: Field) {
     let _transfer_return_values = context.call_public_function(
       self.address, 
-      1071038680, 
+      compute_selector("owner_mint_pub(Field,Field)"),
       [to, amount]
     );
   }
@@ -65,7 +66,7 @@ impl Token {
   fn unshield(self: Self, context: &mut PrivateContext, from: Field, to: Field, amount: Field) -> [Field; RETURN_VALUES_LENGTH] {
     context.call_private_function(
       self.address,
-      2423803924, 
+      compute_selector("unshieldTokens(Field,Field,Field)"),
       [from, to, amount]
     )
   }
@@ -82,8 +83,8 @@ impl Lending {
 
   fn update_accumulator(self: Self, context: PublicContext) -> Asset {
     let return_values = context.call_public_function_no_args(
-      self.address, 
-      0x1873b536
+      self.address,
+      compute_selector("update_accumulator()"),
     );
 
     Asset {