fix: add missing getSlot API

web3.js/module.flow.js

@@ -94,6 +94,7 @@ declare module '@solana/web3.js' {
     getClusterNodes(): Promise<Array<ContactInfo>>;
     getEpochVoteAccounts(): Promise<Array<VoteAccountInfo>>;
     confirmTransaction(signature: TransactionSignature): Promise<boolean>;
+    getSlot(): Promise<number>;
     getSlotLeader(): Promise<string>;
     getSignatureStatus(
       signature: TransactionSignature,

web3.js/src/connection.js

@@ -160,6 +160,11 @@ const GetProgramAccountsRpcResult = jsonRpcResult(
  */
 const ConfirmTransactionRpcResult = jsonRpcResult('boolean');
 
+/**
+ * Expected JSON RPC response for the "getSlot" message
+ */
+const GetSlot = jsonRpcResult('number');
+
 /**
  * Expected JSON RPC response for the "getSlotLeader" message
  */
@@ -535,6 +540,20 @@ export class Connection {
     return res.result;
   }
 
+ /**
+   * Fetch the current slot that the node is processing
+   */
+  async getSlot(): Promise<number> {
+    const unsafeRes = await this._rpcRequest('getSlot', []);
+    const res = GetSlot(unsafeRes);
+    if (res.error) {
+      throw new Error(res.error.message);
+    }
+    assert(typeof res.result !== 'undefined');
+    return res.result;
+  }
+
+
   /**
    * Fetch the current slot leader of the cluster
    */

web3.js/test/connection.test.js

@@ -128,6 +128,31 @@ test('get balance', async () => {
   expect(balance).toBeGreaterThanOrEqual(0);
 });
 
+test('get slot', async () => {
+  const connection = new Connection(url);
+
+  mockRpc.push([
+    url,
+    {
+      method: 'getSlot',
+    },
+    {
+      error: null,
+      result: 123,
+    },
+  ]);
+
+  const slotLeader = await connection.getSlot();
+  if (mockRpcEnabled) {
+    expect(slotLeader).toBe(123);
+  } else {
+    // No idea what the correct slot value should be on a live cluster, so
+    // just check the type
+    expect(typeof slotLeader).toBe('number');
+  }
+});
+
+
 test('get slot leader', async () => {
   const connection = new Connection(url);