add getFees with test

web3.js/src/connection.ts

@@ -708,6 +708,17 @@ export type PerfSample = {
   samplePeriodSecs: number;
 };
 
+export type Fees = {
+  /** Recent blockhash */
+  blockhash: Blockhash;
+  /** Calculator for transaction fees */
+  feeCalculator: FeeCalculator;
+  /** @deprecated this value is inaccurate and should not be relied upon */
+  lastValidSlot: number;
+  /** last block height at which a blockhash will be valid */
+  lastValidBlockHeight: number;
+}
+
 function createRpcClient(
   url: string,
   useHttps: boolean,
@@ -1559,6 +1570,20 @@ const GetFeeCalculatorRpcResult = jsonRpcResultAndContext(
   ),
 );
 
+/**
+ * Expected JSON RPC response for the "getFees" message
+ */
+const GetFeesRpcResult = jsonRpcResultAndContext(
+  pick({
+    blockhash: string(),
+    feeCalculator: pick({
+      lamportsPerSignature: number(),
+    }),
+    lastValidSlot: number(),
+    lastValidBlockHeight: number(),
+  }),
+);
+
 /**
  * Expected JSON RPC response for the "requestAirdrop" message
  */
@@ -2935,6 +2960,21 @@ export class Connection {
     };
   }
 
+  /**
+   * Fetch a recent block hash from the ledger, a fee schedule and the last valid block height the block hash is valid for
+   */
+  async getFees(
+    commitment?: Commitment,
+  ): Promise<RpcResponseAndContext<Fees>> {
+    const args = this._buildArgs([], commitment, undefined);
+    const unsafeRes = await this._rpcRequest('getFees', args);
+    const res = create(unsafeRes, GetFeesRpcResult);
+    if ('error' in res) {
+      throw new Error('failed to get fees: ' + res.error.message);
+    }
+    return res.result;
+  }
+
   /**
    * Fetch a recent blockhash from the cluster
    * @return {Promise<{blockhash: Blockhash, feeCalculator: FeeCalculator}>}

web3.js/test/connection.test.ts

@@ -2200,6 +2200,27 @@ describe('Connection', () => {
     expect(feeCalculator.lamportsPerSignature).to.eq(5000);
   });
 
+  it('get fees', async () => {
+    await mockRpcResponse({
+      method: 'getFees',
+      params: [{commitment: 'confirmed'}],
+      value: {
+        blockhash: '57zQNBZBEiHsCZFqsaY6h176ioXy5MsSLmcvHkEyaLGy',
+        feeCalculator: {
+          lamportsPerSignature: 5000,
+        },
+        lastValidSlot: 5678,
+        lastValidBlockHeight: 1234,
+      },
+      withContext: true,
+    });
+
+    const fees = (await connection.getFees('confirmed')).value;
+    expect(fees.feeCalculator).not.to.be.null;
+    expect(fees.lastValidSlot).to.be.greaterThan(0);
+    expect(fees.lastValidBlockHeight).to.be.greaterThan(0);
+  })
+
   it('get block time', async () => {
     await mockRpcResponse({
       method: 'getBlockTime',