Expose `getTotalSupply` RPC method (#370)

web3.js/module.flow.js

@@ -93,6 +93,7 @@ declare module '@solana/web3.js' {
       signature: TransactionSignature,
     ): Promise<SignatureSuccess | TransactionError | null>;
     getTransactionCount(): Promise<number>;
+    getTotalSupply(): Promise<number>;
     getRecentBlockhash(): Promise<[Blockhash, FeeCalculator]>;
     requestAirdrop(
       to: PublicKey,

web3.js/src/connection.js

@@ -214,6 +214,11 @@ const GetSignatureStatusRpcResult = jsonRpcResult(
  */
 const GetTransactionCountRpcResult = jsonRpcResult('number');
 
+/**
+ * Expected JSON RPC response for the "getTotalSupply" message
+ */
+const GetTotalSupplyRpcResult = jsonRpcResult('number');
+
 /**
  * Expected JSON RPC response for the "getRecentBlockhash" message
  */
@@ -524,6 +529,19 @@ export class Connection {
     return Number(res.result);
   }
 
+  /**
+   * Fetch the current total currency supply of the cluster
+   */
+  async getTotalSupply(): Promise<number> {
+    const unsafeRes = await this._rpcRequest('getTotalSupply', []);
+    const res = GetTotalSupplyRpcResult(unsafeRes);
+    if (res.error) {
+      throw new Error(res.error.message);
+    }
+    assert(typeof res.result !== 'undefined');
+    return Number(res.result);
+  }
+
   /**
    * Fetch a recent blockhash from the cluster
    */

web3.js/test/connection.test.js

@@ -199,6 +199,25 @@ test('get transaction count', async () => {
   expect(count).toBeGreaterThanOrEqual(0);
 });
 
+test('get total supply', async () => {
+  const connection = new Connection(url);
+
+  mockRpc.push([
+    url,
+    {
+      method: 'getTotalSupply',
+      params: [],
+    },
+    {
+      error: null,
+      result: 1000000,
+    },
+  ]);
+
+  const count = await connection.getTotalSupply();
+  expect(count).toBeGreaterThanOrEqual(0);
+});
+
 test('get recent blockhash', async () => {
   const connection = new Connection(url);