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Error Handling

Source: Full executable TypeScript in contract/src/examples/05-error-handling/. This page summarizes the flow — read the source for complete per-step code.

The Story​

Kai is a frontend developer at ArtFund, responsible for building the campaign management interface. Before any transaction is sent to the blockchain, Kai wants to:

  1. Preview the outcome — simulate the transaction against the current chain state to see if it would succeed
  2. Show clear error messages — if the transaction would fail, explain why in plain language and suggest what to do
  3. Estimate the cost — display the gas estimate so users know what they will pay before confirming

Kai also needs to handle edge cases that come up in production: What happens when a user without the right permissions tries to perform a restricted action? What about users browsing the app without a connected wallet? How should the UI handle a read-only session?

These patterns are essential for any production application built on Oak Protocol. A good error handling strategy turns cryptic blockchain reverts into helpful user-facing messages.

Steps​

Step 1: Simulate Before Sending​

Simulation calls the contract against the current chain state without broadcasting a transaction. If the simulation succeeds, the real transaction is safe to send. The simulation result includes the predicted return value and gas estimate.

const campaignParams = {
  creator: process.env.CREATOR_ADDRESS! as `0x${string}`,
  identifierHash,
  selectedPlatformHash: [platformHash],
  campaignData: {
    launchTime: now + 3600n,
    deadline: addDays(now, 30),
    goalAmount: 1_000_000_000n,
    currency: toHex("USD", { size: 32 }),
  },
  nftName: "Test Campaign",
  nftSymbol: "TC",
  nftImageURI: "ipfs://test",
  contractURI: "ipfs://test-meta",
};

// Simulate first
const simulation = await factory.simulate.createCampaign(campaignParams);
console.log("Estimated gas:", simulation.request.gas);

// Safe to send the real transaction
const txHash = await factory.createCampaign(campaignParams);

Step 2: Prepare Transaction for External Signing​

For account-abstraction wallets, Safe multisig, or custom signing flows, use toPreparedTransaction to extract raw transaction parameters (to, data, value, gas) from a simulation result.

import { toPreparedTransaction } from "@oaknetwork/contracts-sdk";

const simulation = await gp.simulate.updatePlatformClaimDelay(
  platformHash,
  604800n, // 7 days
);

const preparedTx = toPreparedTransaction(simulation);
console.log("To:", preparedTx.to);
console.log("Data:", preparedTx.data);
console.log("Gas:", preparedTx.gas);

// Send this to your multisig, bundler, or external signer

Step 3: Catch Typed Errors​

When a transaction reverts, the SDK decodes the raw revert data into a typed error class with a human-readable recovery hint. Three patterns:

import {
  parseContractError,
  getRevertData,
  getRecoveryHint,
} from "@oaknetwork/contracts-sdk";
import {
  CampaignInfoUnauthorizedError,
  CampaignInfoErrorNames,
  SharedErrorNames,
} from "@oaknetwork/contracts-sdk/errors";

try {
  await campaign.cancelCampaign(toHex("cancelled by user", { size: 32 }));
} catch (error) {
  // Pattern 1: instanceof check for a specific error class
  if (error instanceof CampaignInfoUnauthorizedError) {
    console.error("You are not the campaign owner.");
    console.error("Hint:", error.recoveryHint);
  } else {
    // Pattern 2: parse revert data and match by error-name constant
    const revertData = getRevertData(error);
    const parsed = revertData ? parseContractError(revertData) : null;

    if (parsed) {
      switch (parsed.name) {
        case CampaignInfoErrorNames.IsLocked:
          console.error("Campaign is locked — no modifications allowed.");
          break;
        case SharedErrorNames.PausedError:
          console.error("Campaign is currently paused.");
          break;
        default:
          // Pattern 3: generic fallback
          console.error(`Contract error: ${parsed.name}`);
      }

      const hint = getRecoveryHint(parsed);
      if (hint) console.error("Recovery hint:", hint);
    }
  }
}

Step 4: Handle Read-Only Client​

When using a read-only client (no private key), write methods throw immediately with "No signer configured" without making an RPC call. Build your UI to handle this gracefully and prompt the user to connect their wallet.

const readOnlyOak = createOakContractsClient({
  chainId: CHAIN_IDS.CELO_TESTNET_SEPOLIA,
  rpcUrl: process.env.RPC_URL!,
});

const campaign = readOnlyOak.campaignInfo(campaignInfoAddress);

// Reads work fine
const goalAmount = await campaign.getGoalAmount();

// Writes throw immediately
try {
  await campaign.updateGoalAmount(2_000_000_000n);
} catch (error) {
  if ((error as Error).message.startsWith("No signer configured")) {
    console.error("Connect your wallet to perform this action.");
  }
}

Step 5: Safe Transaction Pattern​

A reusable pattern that simulates a transaction, shows the user what will happen, and only sends after simulation passes. Reverts are caught and displayed as user-friendly error messages.

async function safeTransaction(
  description: string,
  simulateFn: () => Promise<unknown>,
  executeFn: () => Promise<`0x${string}`>,
) {
  console.log(`Preparing: ${description}`);

  // Step 1: Simulate
  try {
    await simulateFn();
  } catch (error) {
    const revertData = getRevertData(error);
    const parsed = revertData ? parseContractError(revertData) : null;

    if (parsed) {
      console.error(`Transaction would fail: ${parsed.name}`);
      console.error(parsed.recoveryHint || "No recovery hint available");
    } else {
      console.error("Transaction would fail:", (error as Error).message);
    }
    return null;
  }

  // Step 2: Execute
  const txHash = await executeFn();
  const receipt = await oak.waitForReceipt(txHash);
  return receipt;
}

// Usage
await safeTransaction(
  "Update campaign deadline",
  () => campaign.simulate.updateDeadline(newDeadline),
  () => campaign.updateDeadline(newDeadline),
);

Step 6: Simulate With Error Decode​

simulateWithErrorDecode wraps simulation and error parsing into a single convenience call. If simulation succeeds it returns the SimulationResult; if it reverts it throws a typed error with a recoveryHint property — no manual getRevertData / parseContractError needed.

import { simulateWithErrorDecode } from "@oaknetwork/contracts-sdk";

try {
  const result = await simulateWithErrorDecode(
    () => treasury.simulate.removeReward(rewardName),
  );

  console.log("Simulation passed — safe to send");
  console.log("Gas estimate:", result.request.gas);

  const txHash = await treasury.removeReward(rewardName);
  await oak.waitForReceipt(txHash);
} catch (error) {
  const typedError = error as { name: string; recoveryHint?: string };
  console.error(`Would revert: ${typedError.name}`);
  if (typedError.recoveryHint) {
    console.error("Hint:", typedError.recoveryHint);
  }
}