Legacy Fallback Support for Non EIP-1559 Chains

src/utils/transaction.ts

@@ -1,4 +1,7 @@
 import {
+  Eip1559FeesNotSupportedError,
+  FeeValuesEIP1559,
+  FeeValuesLegacy,
   Hash,
   Hex,
   PublicClient,
@@ -44,17 +47,13 @@ export async function populateTx(
     value: tx.value ?? 0n,
     data: tx.data ?? "0x",
   };
-  const [estimatedGas, { maxFeePerGas, maxPriorityFeePerGas }] =
-    await Promise.all([
-      // Only estimate gas if not provided.
-      tx.gas || provider.estimateGas(transactionData),
-      provider.estimateFeesPerGas(),
-    ]);
+  // Only estimate gas if not provided.
+  const estimatedGas = tx.gas || (await provider.estimateGas(transactionData));
+  const gasValues = await getGasData(provider);
   return {
     ...transactionData,
+    ...gasValues,
     gas: estimatedGas,
-    maxFeePerGas,
-    maxPriorityFeePerGas,
     chainId,
   };
 }
@@ -71,6 +70,20 @@ export function addSignature({
   return serializeTransaction(signedTx);
 }
 
+export async function getGasData(
+  provider: PublicClient
+): Promise<FeeValuesEIP1559 | FeeValuesLegacy> {
+  try {
+    // EIP-1559 transaction
+    return await provider.estimateFeesPerGas();
+  } catch (error: unknown) {
+    if (error instanceof Eip1559FeesNotSupportedError) {
+      console.warn(`${error.shortMessage} Using Legacy Gas Fees`);
+    }
+    return { gasPrice: await provider.getGasPrice() };
+  }
+}
+
 /**
  * Relays signed transaction to Ethereum mem-pool for execution.
  * @param serializedTransaction - Signed Ethereum transaction.

tests/unit/utils.transaction.test.ts

@@ -1,4 +1,4 @@
-import { zeroAddress } from "viem";
+import { serializeTransaction, zeroAddress } from "viem";
 import { Network, TransactionWithSignature } from "../../src";
 import {
   buildTxPayload,
@@ -54,4 +54,13 @@ describe("Transaction Builder Functions", () => {
     expect(tx.to).toEqual(zeroAddress);
     expect(tx.value).toEqual(0n);
   });
+
+  it.only("populate Non EIP-1559 Transaction", async () => {
+    const baseTx = {
+      chainId: 3776,
+      to: zeroAddress,
+    };
+    const tx = await populateTx(baseTx, zeroAddress);
+    console.log("Build Transaction", serializeTransaction(tx));
+  });
 });