Add eth_chainId (#791)

* Add eth_chainId to supported methods handler

* add test

Author: acolytec3

packages/cli/src/rpc/modules/eth.ts

@@ -1,6 +1,6 @@
 import type { PrefixedHexString } from '@ethereumjs/util'
 import { bigIntToHex, hexToBytes, intToHex, toBytes } from '@ethereumjs/util'
-import { GET_LOGS_BLOCK_RANGE_LIMIT, NetworkId, NetworkIdByChain, getLogs } from 'portalnetwork'
+import { ChainId, GET_LOGS_BLOCK_RANGE_LIMIT, NetworkId, NetworkIdByChain, getLogs } from 'portalnetwork'
 
 import { INTERNAL_ERROR, INVALID_PARAMS } from '../error-code.js'
 import { jsonRpcLog } from '../types.js'
@@ -86,6 +86,7 @@ export class eth {
       [validators.transaction(['to'])],
       [validators.blockOption],
     ])
+    this.chainId = middleware(callWithStackTrace(this.chainId.bind(this), false), 0, [])
   }
 
   async getBalance(params: [string, string]) {
@@ -130,7 +131,12 @@ export class eth {
    * @returns The chain ID.
    */
   async chainId(_params = []) {
-    return '0x01'
+    switch (this._client.chainId) {
+      case ChainId.MAINNET:
+        return '0x1'
+      case ChainId.SEPOLIA:
+        return '0xaa36a7'
+    }
   }
 
   /**

packages/cli/test/rpc/eth/chainId.spec.ts

@@ -0,0 +1,26 @@
+import { assert, afterAll, beforeAll, describe, it } from 'vitest'
+
+import { startRpc } from '../util.js'
+const method = 'eth_chainId'
+describe(`${method} tests`, () => {
+    describe(`${method} tests`, () => {
+        let ul
+        let rp
+        beforeAll(async () => {
+            const { ultralight, rpc } = await startRpc({
+                networks: ['history'],
+                rpcPort: 8547,
+                port: 9002,
+            })
+            ul = ultralight
+            rp = rpc
+        })
+        it('should return the correct chainId', async () => {
+            const res = await rp.request(method, [])
+            assert.equal(res.result, '0x1')
+        })
+        afterAll(() => {
+            ul.kill()
+        })
+    })
+})