add hardhat_getForkedChainId JSON-RPC method

docs/hardhat-network/guides/mainnet-forking.md

@@ -98,6 +98,19 @@ await network.provider.request({
 
 This will reset Hardhat Network, starting a new instance in the state described [here](../hardhat-network/README.md#hardhat-network-initial-state).
 
+## Getting the chainId of the original chain
+
+You can query the original `chainId` of the network that is being forked:
+
+```ts
+await network.provider.request({
+  method: "hardhat_getForkedChainId",
+  params: [],
+)};
+```
+
+Returns the `chanId` of the forked network, or null if this chain is not a fork.
+
 ## Troubleshooting
 
 ### "Project ID does not have access to archive state"

docs/hardhat-network/reference/README.md

@@ -294,6 +294,10 @@ Remove a transaction from the mempool
 #### `hardhat_getStackTraceFailuresCount`
 -->
 
+#### `hardhat_getForkedChainId`
+
+See the [Mainnet Forking guide](../guides/mainnet-forking.md)
+
 #### `hardhat_impersonateAccount`
 
 Hardhat Network allows you to send transactions impersonating specific account and contract addresses.

packages/hardhat-core/src/internal/core/providers/chainId.ts

@@ -11,33 +11,15 @@ export abstract class ProviderWrapperWithChainId extends ProviderWrapper {
   protected async _getChainId(): Promise<number> {
     if (this._chainId === undefined) {
       try {
-        this._chainId = await this._getChainIdFromEthChainId();
+        this._chainId = await getChainIdFromEthChainId(this._wrappedProvider);
       } catch (error) {
         // If eth_chainId fails we default to net_version
-        this._chainId = await this._getChainIdFromEthNetVersion();
+        this._chainId = await getNetworkIdFromNetVersion(this._wrappedProvider);
       }
     }
 
     return this._chainId;
   }
-
-  private async _getChainIdFromEthChainId(): Promise<number> {
-    const id = (await this._wrappedProvider.request({
-      method: "eth_chainId",
-    })) as string;
-
-    return rpcQuantityToNumber(id);
-  }
-
-  private async _getChainIdFromEthNetVersion(): Promise<number> {
-    const id = (await this._wrappedProvider.request({
-      method: "net_version",
-    })) as string;
-
-    // There's a node returning this as decimal instead of QUANTITY.
-    // TODO: Document here which node does that
-    return id.startsWith("0x") ? rpcQuantityToNumber(id) : parseInt(id, 10);
-  }
 }
 
 export class ChainIdValidatorProvider extends ProviderWrapperWithChainId {
@@ -66,3 +48,27 @@ export class ChainIdValidatorProvider extends ProviderWrapperWithChainId {
     return this._wrappedProvider.request(args);
   }
 }
+
+export async function getChainIdFromEthChainId(
+  provider: EIP1193Provider
+): Promise<number> {
+  const id = (await provider.request({
+    method: "eth_chainId",
+  })) as string;
+
+  return rpcQuantityToNumber(id);
+}
+
+export async function getNetworkIdFromNetVersion(
+  provider: EIP1193Provider
+): Promise<number> {
+  const networkId = (await provider.request({
+    method: "net_version",
+  })) as string;
+
+  // There's a node returning this as decimal instead of QUANTITY.
+  // TODO: Document here which node does that
+  return networkId.startsWith("0x")
+    ? rpcQuantityToNumber(networkId)
+    : parseInt(networkId, 10);
+}

packages/hardhat-core/src/internal/hardhat-network/jsonrpc/client.ts

@@ -28,6 +28,7 @@ export class JsonRpcClient {
   constructor(
     private _httpProvider: HttpProvider,
     private _networkId: number,
+    private _chainId: number,
     private _latestBlockNumberOnCreation: number,
     private _maxReorg: number,
     private _forkCachePath?: string
@@ -37,6 +38,10 @@ export class JsonRpcClient {
     return this._networkId;
   }
 
+  public getChainId(): number {
+    return this._chainId;
+  }
+
   public async getDebugTraceTransaction(transactionHash: Buffer): Promise<any> {
     return this._perform(
       "debug_traceTransaction",

packages/hardhat-core/src/internal/hardhat-network/provider/modules/hardhat.ts

@@ -74,6 +74,11 @@ export class HardhatModule {
       case "hardhat_reset":
         return this._resetAction(...this._resetParams(params));
 
+      case "hardhat_getForkedChainId":
+        return this._getForkedChainIdAction(
+          ...this._getForkedChainIdParams(params)
+        );
+
       case "hardhat_setLoggingEnabled":
         return this._setLoggingEnabledAction(
           ...this._setLoggingEnabledParams(params)
@@ -207,6 +212,16 @@ export class HardhatModule {
     return true;
   }
 
+  // hardhat_getForkedChainId
+
+  private _getForkedChainIdParams(params: any[]): [] {
+    return validateParams(params);
+  }
+
+  private async _getForkedChainIdAction(): Promise<number | null> {
+    return (await this._node.getForkedChainId()) ?? null;
+  }
+
   // hardhat_setLoggingEnabled
 
   private _setLoggingEnabledParams(params: any[]): [boolean] {

packages/hardhat-core/src/internal/hardhat-network/provider/node.ts

@@ -140,6 +140,7 @@ export class HardhatNode extends EventEmitter {
     let initialBlockTimeOffset: BN | undefined;
     let nextBlockBaseFeePerGas: BN | undefined;
     let forkNetworkId: number | undefined;
+    let forkChainId: number | undefined;
 
     const initialBaseFeePerGasConfig =
       config.initialBaseFeePerGas !== undefined
@@ -157,6 +158,7 @@ export class HardhatNode extends EventEmitter {
       common = await makeForkCommon(config);
 
       forkNetworkId = forkClient.getNetworkId();
+      forkChainId = forkClient.getChainId();
 
       this._validateHardforks(
         config.forkConfig.blockNumber,
@@ -248,6 +250,7 @@ export class HardhatNode extends EventEmitter {
       genesisAccounts,
       tracingConfig,
       forkNetworkId,
+      forkChainId,
       nextBlockBaseFeePerGas
     );
 
@@ -321,6 +324,7 @@ Hardhat Network's forking functionality only works with blocks from at least spu
     genesisAccounts: GenesisAccount[],
     tracingConfig?: TracingConfig,
     private _forkNetworkId?: number,
+    private _forkChainId?: number,
     nextBlockBaseFee?: BN
   ) {
     super();
@@ -1271,6 +1275,10 @@ Hardhat Network's forking functionality only works with blocks from at least spu
     );
   }
 
+  public async getForkedChainId(): Promise<number | undefined> {
+    return this._forkChainId;
+  }
+
   public async getFeeHistory(
     blockCount: BN,
     newestBlock: BN | "pending",

packages/hardhat-core/src/internal/hardhat-network/provider/utils/makeForkClient.ts

@@ -6,6 +6,10 @@ import {
   numberToRpcQuantity,
   rpcQuantityToNumber,
 } from "../../../core/jsonrpc/types/base-types";
+import {
+  getChainIdFromEthChainId,
+  getNetworkIdFromNetVersion,
+} from "../../../core/providers/chainId";
 import { HttpProvider } from "../../../core/providers/http";
 import { JsonRpcClient } from "../../jsonrpc/client";
 import { ForkConfig } from "../node-types";
@@ -37,7 +41,14 @@ export async function makeForkClient(
     FORK_HTTP_TIMEOUT
   );
 
-  const networkId = await getNetworkId(provider);
+  const networkId = await getNetworkIdFromNetVersion(provider);
+  let chainId;
+  try {
+    chainId = await getChainIdFromEthChainId(provider);
+  } catch (error) {
+    chainId = networkId;
+  }
+
   const actualMaxReorg = getLargestPossibleReorg(networkId);
   const maxReorg = actualMaxReorg ?? FALLBACK_MAX_REORG;
 
@@ -85,6 +96,7 @@ Please use block number ${lastSafeBlock} or wait for the block to get ${
   const forkClient = new JsonRpcClient(
     provider,
     networkId,
+    chainId,
     latestBlock,
     maxReorg,
     cacheToDiskEnabled ? forkCachePath : undefined
@@ -105,13 +117,6 @@ async function getBlockByNumber(
   return rpcBlockOutput;
 }
 
-async function getNetworkId(provider: HttpProvider) {
-  const networkIdString = (await provider.request({
-    method: "net_version",
-  })) as string;
-  return parseInt(networkIdString, 10);
-}
-
 async function getLatestBlockNumber(provider: HttpProvider) {
   const latestBlockString = (await provider.request({
     method: "eth_blockNumber",

packages/hardhat-core/test/internal/core/providers/accounts.ts

@@ -40,7 +40,7 @@ describe("Local accounts provider", () => {
   beforeEach(() => {
     mock = new MockedProvider();
     mock.setReturnValue(
-      "net_version",
+      "eth_chainId",
       numberToRpcQuantity(MOCK_PROVIDER_CHAIN_ID)
     );
     mock.setReturnValue("eth_getTransactionCount", numberToRpcQuantity(0x8));

packages/hardhat-core/test/internal/hardhat-network/jsonrpc/client.ts

@@ -73,6 +73,7 @@ describe("JsonRpcClient", () => {
         clientWithFakeProvider = new JsonRpcClient(
           fakeProvider as any,
           1,
+          1,
           123,
           3
         );
@@ -87,6 +88,7 @@ describe("JsonRpcClient", () => {
         clientWithFakeProvider = new JsonRpcClient(
           fakeProvider as any,
           1,
+          1,
           123,
           3
         );
@@ -101,6 +103,7 @@ describe("JsonRpcClient", () => {
         clientWithFakeProvider = new JsonRpcClient(
           fakeProvider as any,
           1,
+          1,
           123,
           3
         );
@@ -121,6 +124,7 @@ describe("JsonRpcClient", () => {
           clientWithFakeProvider = new JsonRpcClient(
             fakeProvider as any,
             1,
+            1,
             123,
             3,
             this.tmpDir
@@ -148,6 +152,7 @@ describe("JsonRpcClient", () => {
           clientWithFakeProvider = new JsonRpcClient(
             fakeProvider as any,
             1,
+            1,
             123,
             3,
             this.tmpDir
@@ -182,6 +187,7 @@ describe("JsonRpcClient", () => {
         const clientWithFakeProvider = new JsonRpcClient(
           fakeProvider as any,
           1,
+          1,
           123,
           3
         );
@@ -212,6 +218,7 @@ describe("JsonRpcClient", () => {
         const clientWithFakeProvider = new JsonRpcClient(
           fakeProvider as any,
           1,
+          1,
           123,
           3
         );
@@ -241,6 +248,7 @@ describe("JsonRpcClient", () => {
         const clientWithFakeProvider = new JsonRpcClient(
           fakeProvider as any,
           1,
+          1,
           123,
           3
         );
@@ -269,6 +277,7 @@ describe("JsonRpcClient", () => {
         const clientWithFakeProvider = new JsonRpcClient(
           fakeProvider as any,
           1,
+          1,
           123,
           3
         );

packages/hardhat-core/test/internal/hardhat-network/provider/modules/hardhat.ts

@@ -378,6 +378,19 @@ describe("Hardhat module", function () {
         }
       });
 
+      describe("hardhat_getForkedChainId", function () {
+        it("gets correct chainId", async function () {
+          const hardhatChainId = await this.provider.send(
+            "hardhat_getForkedChainId"
+          );
+          if (isFork) {
+            assert.equal(hardhatChainId, 1);
+          } else {
+            assert.isNull(hardhatChainId);
+          }
+        });
+      });
+
       describe("hardhat_setBalance", function () {
         it("should reject an invalid address", async function () {
           await assertInvalidArgumentsError(