fix: skip calling getFees for sponsored transactions (#37355)

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## **Description**

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1. There is a bug in smart transaction hook that when submitting signed
transaction, it still call `getFees` even though it's not needed. This
leads to sponsored transactions to fail to submit due to `getFees` call
throw errors when users have insufficient funds.
2. To solve this, we'll skip calling `getFees` if transaction is already
signed or it's a batch

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## **Related issues**

Fixes:

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Conditionally bypasses getFees for pre-signed sponsored smart
transactions and updates tests to cover the new behavior and error
handling.
> 
> - **Smart Transactions Logic**:
> - Skip calling `getFees` when `signedTransactionInHex` is present and
`transactionMeta.isGasFeeSponsored` is true.
> - Retain `getFees` try/catch with fallback to regular submission on
error.
>   - Continue normal sign-and-submit flow and status page handling.
> - **Tests**:
> - Add test verifying fees are not fetched for signed, sponsored
transactions and that `submitSignedTransactions` is called.
> - Strengthen error-path test to assert `getFees` was invoked before
fallback.
> - Ensure ASAP tx-hash return behavior remains validated via feature
flag.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
06aeccd. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: tanguyenvn

app/scripts/lib/smart-transaction/smart-transactions.test.ts

@@ -285,13 +285,31 @@ describe('submitSmartTransactionHook', () => {
           throw new Error('Backend call to /getFees failed');
         });
       const result = await submitSmartTransactionHook(request);
+      expect(request.smartTransactionsController.getFees).toHaveBeenCalled();
       expect(endFlowSpy).toHaveBeenCalledWith({
         id: 'approvalId',
       });
       expect(result).toEqual({ transactionHash: undefined });
     });
   });
 
+  it('skips getting fees if the transaction is signed and sponsored', async () => {
+    withRequest(async ({ request }) => {
+      request.transactionMeta.isGasFeeSponsored = true;
+      request.featureFlags.smartTransactions.extensionReturnTxHashAsap = true;
+
+      const result = await submitSmartTransactionHook(request);
+
+      expect(
+        request.smartTransactionsController.getFees,
+      ).not.toHaveBeenCalled();
+      expect(
+        request.smartTransactionsController.submitSignedTransactions,
+      ).toHaveBeenCalled();
+      expect(result).toEqual({ transactionHash: txHash });
+    });
+  });
+
   it('returns a txHash asap if the feature flag requires it', async () => {
     withRequest(async ({ request }) => {
       request.featureFlags.smartTransactions.extensionReturnTxHashAsap = true;

app/scripts/lib/smart-transaction/smart-transactions.ts

@@ -169,20 +169,27 @@ class SmartTransactionHook {
     if (this.#shouldShowStatusPage) {
       await this.#startApprovalFlow();
     }
+
     let getFeesResponse;
-    try {
-      getFeesResponse = await this.#smartTransactionsController.getFees(
-        { ...this.#txParams, chainId: this.#chainId },
-        undefined,
-        { networkClientId: this.#transactionMeta.networkClientId },
-      );
-    } catch (error) {
-      log.error(
-        'Error in smart transaction publish hook, falling back to regular transaction submission',
-        error,
-      );
-      this.#onApproveOrReject();
-      return useRegularTransactionSubmit; // Fallback to regular transaction submission.
+    // Skip getting fees if the tx is signed and sponsored
+    if (
+      !this.#signedTransactionInHex ||
+      !this.#transactionMeta.isGasFeeSponsored
+    ) {
+      try {
+        getFeesResponse = await this.#smartTransactionsController.getFees(
+          { ...this.#txParams, chainId: this.#chainId },
+          undefined,
+          { networkClientId: this.#transactionMeta.networkClientId },
+        );
+      } catch (error) {
+        log.error(
+          'Error in smart transaction publish hook, falling back to regular transaction submission',
+          error,
+        );
+        this.#onApproveOrReject();
+        return useRegularTransactionSubmit; // Fallback to regular transaction submission.
+      }
     }
     try {
       const submitTransactionResponse = await this.#signAndSubmitTransactions({