fix: Handle latest block tag in getBlock (#17089)

Fixes #17068

Author: PhilWindle

yarn-project/aztec-node/src/aztec-node/server.test.ts

@@ -11,7 +11,7 @@ import { protocolContractTreeRoot } from '@aztec/protocol-contracts';
 import { computeFeePayerBalanceLeafSlot } from '@aztec/protocol-contracts/fee-juice';
 import type { GlobalVariableBuilder } from '@aztec/sequencer-client';
 import { AztecAddress } from '@aztec/stdlib/aztec-address';
-import type { L2BlockSource } from '@aztec/stdlib/block';
+import { L2Block, type L2BlockSource } from '@aztec/stdlib/block';
 import type { ContractDataSource } from '@aztec/stdlib/contract';
 import { EmptyL1RollupConstants } from '@aztec/stdlib/epoch-helpers';
 import { GasFees } from '@aztec/stdlib/gas';
@@ -321,6 +321,36 @@ describe('aztec node', () => {
         expect(await node.getBlockHeader(3)).toEqual(undefined);
       });
     });
+
+    describe('getBlock', () => {
+      let block1: L2Block;
+      let block2: L2Block;
+
+      beforeEach(() => {
+        block1 = L2Block.empty();
+        block2 = L2Block.empty();
+
+        l2BlockSource.getBlockNumber.mockResolvedValue(2);
+      });
+
+      it('returns requested block number', async () => {
+        l2BlockSource.getBlock.mockResolvedValue(block1);
+        expect(await node.getBlock(1)).toEqual(block1);
+        expect(l2BlockSource.getBlock).toHaveBeenCalledWith(1);
+      });
+
+      it('returns latest block', async () => {
+        l2BlockSource.getBlock.mockResolvedValue(block2);
+        expect(await node.getBlock('latest')).toEqual(block2);
+        expect(l2BlockSource.getBlock).toHaveBeenCalledWith(2);
+      });
+
+      it('returns undefined for non-existent block', async () => {
+        l2BlockSource.getBlock.mockResolvedValue(undefined);
+        expect(await node.getBlock(3)).toEqual(undefined);
+        expect(l2BlockSource.getBlock).toHaveBeenCalledWith(3);
+      });
+    });
   });
 
   describe('simulatePublicCalls', () => {

yarn-project/aztec-node/src/aztec-node/server.ts

@@ -510,8 +510,9 @@ export class AztecNodeService implements AztecNode, AztecNodeAdmin, Traceable {
    * @param number - The block number being requested.
    * @returns The requested block.
    */
-  public async getBlock(number: number): Promise<L2Block | undefined> {
-    return await this.blockSource.getBlock(number);
+  public async getBlock(number: L2BlockNumber): Promise<L2Block | undefined> {
+    const blockNumber = number === 'latest' ? await this.getBlockNumber() : number;
+    return await this.blockSource.getBlock(blockNumber);
   }
 
   /**