From f8db2788f42b72dc8d619a7ed4c2d0cc593b1a5a Mon Sep 17 00:00:00 2001
From: Kelvin Fichter <kelvin@optimism.io>
Date: Tue, 10 May 2022 18:35:42 -0400
Subject: [PATCH] fix(sdk): bug causing error when no tx nonce given

Fixes a bug in the SDK that would throw an error when the user did not
provide a nonce along with the transaction (when estimating gas). If no
nonce is provided, will try to find a reasonable nonce or use a default
(large) nonce that will give a good upper bound for the L1 gas cost.
---
 .changeset/smart-readers-remember.md |  5 +++++
 packages/sdk/src/l2-provider.ts      | 25 +++++++++++++++++++++++--
 2 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/smart-readers-remember.md

diff --git a/.changeset/smart-readers-remember.md b/.changeset/smart-readers-remember.md
new file mode 100644
index 0000000000000..bd19d949e5391
--- /dev/null
+++ b/.changeset/smart-readers-remember.md
@@ -0,0 +1,5 @@
+---
+'@eth-optimism/sdk': patch
+---
+
+Fixes a bug in the SDK which would cause the SDK to throw if no tx nonce is provided
diff --git a/packages/sdk/src/l2-provider.ts b/packages/sdk/src/l2-provider.ts
index 5fa2b7a2f4ac9..9b41c7891c095 100644
--- a/packages/sdk/src/l2-provider.ts
+++ b/packages/sdk/src/l2-provider.ts
@@ -11,6 +11,27 @@ import { toProvider, toNumber, toBigNumber } from './utils'
 
 type ProviderTypeIsWrong = any
 
+/**
+ * Gets a reasonable nonce for the transaction.
+ *
+ * @param provider Provider to get the nonce from.
+ * @param tx Requested transaction.
+ * @returns A reasonable nonce for the transaction.
+ */
+const getNonceForTx = async (
+  provider: ProviderLike,
+  tx: TransactionRequest
+): Promise<number> => {
+  if (tx.nonce !== undefined) {
+    return toNumber(tx.nonce as NumberLike)
+  } else if (tx.from !== undefined) {
+    return toProvider(provider).getTransactionCount(tx.from)
+  } else {
+    // Large nonce with lots of non-zero bytes
+    return 0xffffffff
+  }
+}
+
 /**
  * Returns a Contract object for the GasPriceOracle.
  *
@@ -57,7 +78,7 @@ export const estimateL1Gas = async (
       gasPrice: tx.gasPrice,
       type: tx.type,
       gasLimit: tx.gasLimit,
-      nonce: toNumber(tx.nonce as NumberLike),
+      nonce: await getNonceForTx(l2Provider, tx),
     })
   )
 }
@@ -81,7 +102,7 @@ export const estimateL1GasCost = async (
       gasPrice: tx.gasPrice,
       type: tx.type,
       gasLimit: tx.gasLimit,
-      nonce: toNumber(tx.nonce as NumberLike),
+      nonce: await getNonceForTx(l2Provider, tx),
     })
   )
 }