feat: add support for getGenesisHash RPC (#19732)

web3.js/src/connection.ts

@@ -2963,6 +2963,18 @@ export class Connection {
     return res.result;
   }
 
+  /**
+   * Fetch the genesis hash
+   */
+  async getGenesisHash(): Promise<string> {
+    const unsafeRes = await this._rpcRequest('getGenesisHash', []);
+    const res = create(unsafeRes, jsonRpcResult(string()));
+    if ('error' in res) {
+      throw new Error('failed to get genesis hash: ' + res.error.message);
+    }
+    return res.result;
+  }
+
   /**
    * Fetch a processed block from the cluster.
    */

web3.js/test/connection.test.ts

@@ -2668,6 +2668,17 @@ describe('Connection', () => {
     expect(version['solana-core']).to.be.ok;
   });
 
+  it('getGenesisHash', async () => {
+    await mockRpcResponse({
+      method: 'getGenesisHash',
+      params: [],
+      value: 'GH7ome3EiwEr7tu9JuTh2dpYWBJK3z69Xm1ZE3MEE6JC',
+    });
+
+    const genesisHash = await connection.getGenesisHash();
+    expect(genesisHash).not.to.be.empty;
+  });
+
   it('request airdrop', async () => {
     const account = Keypair.generate();