feat: introduce getInflationReward to connection (#16807)

* feat: introduce getInflationReward to connection

* fix: only run getInflationReward test in mock mode

web3.js/src/connection.ts

@@ -321,6 +321,36 @@ const GetInflationGovernorResult = pick({
   terminal: number(),
 });
 
+/**
+ * The inflation reward for an epoch
+ */
+export type InflationReward = {
+  /** epoch for which the reward occurs */
+  epoch: number;
+  /** the slot in which the rewards are effective */
+  effectiveSlot: number;
+  /** reward amount in lamports */
+  amount: number;
+  /** post balance of the account in lamports */
+  postBalance: number;
+};
+
+/**
+ * Expected JSON RPC response for the "getInflationReward" message
+ */
+const GetInflationRewardResult = jsonRpcResult(
+  array(
+    nullable(
+      pick({
+        epoch: number(),
+        effectiveSlot: number(),
+        amount: number(),
+        postBalance: number(),
+      }),
+    ),
+  ),
+);
+
 /**
  * Information about the current epoch
  */
@@ -2516,6 +2546,30 @@ export class Connection {
     return res.result;
   }
 
+  /**
+   * Fetch the inflation reward for a list of addresses for an epoch
+   */
+  async getInflationReward(
+    addresses: PublicKey[],
+    epoch?: number,
+    commitment?: Commitment,
+  ): Promise<(InflationReward | null)[]> {
+    const args = this._buildArgs(
+      [addresses.map(pubkey => pubkey.toBase58())],
+      commitment,
+      undefined,
+      {
+        epoch,
+      },
+    );
+    const unsafeRes = await this._rpcRequest('getInflationReward', args);
+    const res = create(unsafeRes, GetInflationRewardResult);
+    if ('error' in res) {
+      throw new Error('failed to get inflation reward: ' + res.error.message);
+    }
+    return res.result;
+  }
+
   /**
    * Fetch the Epoch Info parameters
    */

web3.js/test/connection.test.ts

@@ -588,6 +588,42 @@ describe('Connection', () => {
     }
   });
 
+  it('get inflation reward', async () => {
+    if (mockServer) {
+      await mockRpcResponse({
+        method: 'getInflationReward',
+        params: [
+          [
+            '7GHnTRB8Rz14qZQhDXf8ox1Kfu7mPcPLpKaBJJirmYj2',
+            'CrinLuHjVGDDcQfrEoCmM4k31Ni9sMoTCEEvNSUSh7Jg',
+          ],
+          {
+            epoch: 0,
+          },
+        ],
+        value: [
+          {
+            amount: 3646143,
+            effectiveSlot: 432000,
+            epoch: 0,
+            postBalance: 30504783,
+          },
+          null,
+        ],
+      });
+
+      const inflationReward = await connection.getInflationReward(
+        [
+          new PublicKey('7GHnTRB8Rz14qZQhDXf8ox1Kfu7mPcPLpKaBJJirmYj2'),
+          new PublicKey('CrinLuHjVGDDcQfrEoCmM4k31Ni9sMoTCEEvNSUSh7Jg'),
+        ],
+        0,
+      );
+
+      expect(inflationReward).to.have.lengthOf(2);
+    }
+  });
+
   it('get epoch info', async () => {
     await mockRpcResponse({
       method: 'getEpochInfo',