fix: add getBlocksSince Connection method

web3.js/src/connection.js

@@ -365,6 +365,11 @@ const GetTotalSupplyRpcResult = jsonRpcResult('number');
  */
 const GetMinimumBalanceForRentExemptionRpcResult = jsonRpcResult('number');
 
+/**
+ * Expected JSON RPC response for the "getBlocksSince" message
+ */
+const GetBlocksSinceRpcResult = jsonRpcResult(struct.list(['number']));
+
 /**
  * Expected JSON RPC response for the "getRecentBlockhash" message
  */
@@ -853,6 +858,19 @@ export class Connection {
     return res.result;
   }
 
+  /**
+   * Fetch a list of rooted blocks from the cluster
+   */
+  async getBlocksSince(slot: number): Promise<Array<number>> {
+    const unsafeRes = await this._rpcRequest('getBlocksSince', [slot]);
+    const res = GetBlocksSinceRpcResult(unsafeRes);
+    if (res.error) {
+      throw new Error(res.error.message);
+    }
+    assert(typeof res.result !== 'undefined');
+    return res.result;
+  }
+
   /**
    * Request an allocation of lamports to the specified account
    */

web3.js/src/transaction.js

@@ -445,7 +445,7 @@ export class Transaction {
     const PUBKEY_LENGTH = 32;
     const SIGNATURE_LENGTH = 64;
 
-    function isCreditDebit(
+    function isWritable(
       i: number,
       numRequiredSignatures: number,
       numReadonlySignedAccounts: number,
@@ -530,7 +530,7 @@ export class Transaction {
           isSigner: transaction.signatures.some(
             keyObj => keyObj.publicKey.toString() === pubkey.toString(),
           ),
-          isWritable: isCreditDebit(
+          isWritable: isWritable(
             j,
             numRequiredSignatures,
             numReadonlySignedAccounts,

web3.js/test/connection.test.js

@@ -419,6 +419,49 @@ test('get minimum balance for rent exemption', async () => {
   expect(count).toBeGreaterThanOrEqual(0);
 });
 
+test('get blocks since slot', async () => {
+  const connection = new Connection(url);
+
+  const expectedBlocks = [0, 1, 3, 4, 7, 8];
+  mockRpc.push([
+    url,
+    {
+      method: 'getBlocksSince',
+      params: [0],
+    },
+    {
+      error: null,
+      result: expectedBlocks,
+    },
+  ]);
+
+  const blocks = await connection.getBlocksSince(0);
+
+  if (mockRpcEnabled) {
+    expect(blocks.length).toEqual(6);
+  } else {
+    // No idea how many blocks since slot 0 on a live cluster
+    expect(blocks.length).toBeGreaterThan(0);
+  }
+
+  const errorMessage = 'Slot 10000: SlotNotRooted';
+  mockRpc.push([
+    url,
+    {
+      method: 'getBlocksSince',
+      params: [10000],
+    },
+    {
+      error: {
+        message: errorMessage,
+      },
+      result: undefined,
+    },
+  ]);
+
+  await expect(connection.getBlocksSince(10000)).rejects.toThrow(errorMessage);
+});
+
 test('get recent blockhash', async () => {
   const connection = new Connection(url);