Reference

Type Guards

Type guard helpers for working with discriminated unions

The SDK includes type guard helpers for working with the various discriminated unions returned by the API.

import { guards } from '@superbridge/sdk';

Quote Guards

Each entry in a RouteResponse.results[] has a result field that is either a quote or a quote error. Use guards.quotes to narrow it.

for (const route of routes.results) {
  if (guards.quotes.isQuote(route.result)) {
    // QuoteDto5 - has initiatingTransaction, fees, etc.
  }

  if (guards.quotes.isError(route.result)) {
    // QuoteError - discriminated by `type`
  }
}

Once narrowed to an error, discriminate on type directly — TypeScript will narrow to the specific error DTO.

for (const route of routes.results) {
  if (!guards.quotes.isError(route.result)) continue;

  const error = route.result;

  if (error.type === 'AmountTooLarge') {
    // AmountTooLargeQuoteErrorDto - has maximum
  }

  if (error.type === 'AmountTooSmall') {
    // AmountTooSmallQuoteErrorDto - has minimum
  }

  if (error.type === 'PriceImpactTooHigh') {
    // PriceImpactTooHighQuoteErrorDto - has priceImpactPercent, maximumPriceImpactPercent
  }

  if (error.type === 'GenericError') {
    // GenericQuoteErrorDto - has error
  }

  // 'Paused' | 'Disabled' | 'EscapeHatchNotSupported' | 'ERC777MintToSmartContract'
}

Route Errors

When a request fails (non-2xx response), the SDK throws a SuperbridgeApiError carrying the parsed response body on .data. For /routes, that body is a RouteError — a discriminated union you can narrow by type.

import { SuperbridgeApiError } from '@superbridge/sdk';
import type { RouteError } from '@superbridge/sdk';

try {
  const routes = await sb.getRoutes({ /* ... */ });
} catch (err) {
  if (!(err instanceof SuperbridgeApiError) || err.status !== 400) throw err;

  const error = err.data as RouteError;

  if (error.type === 'UsdAmountTooLarge') {
    // UsdAmountTooLargeRouteErrorDto - has amountUsd, maximumUsd
  }

  if (error.type === 'Paused') {
    // PausedRouteErrorDto
  }

  if (error.type === 'Disabled') {
    // DisabledRouteErrorDto
  }
}

Transaction Guards

Narrow the initiatingTransaction on a quote to a specific chain type.

const { initiatingTransaction } = quote;

if (guards.tx.isEvm(initiatingTransaction)) {
  // InitiatingTransactionEvmDto5 - has to, data, value, chainId
}

if (guards.tx.isEvmGasless(initiatingTransaction)) {
  // InitiatingTransactionEvmGaslessDto5
}

if (guards.tx.isSvm(initiatingTransaction)) {
  // InitiatingTransactionSvmDto5
}

if (guards.tx.isStarknet(initiatingTransaction)) {
  // InitiatingTransactionStarkDto5
}

Step Guards

Narrow steps on a SteppedBridgeDto to their specific types and statuses.

for (const step of bridge.steps) {
  // Narrow by step kind
  if (guards.steps.isTransactionStep(step)) {
    // TransactionStep
  }

  if (guards.steps.isWaitStep(step)) {
    // WaitStep
  }

  if (guards.steps.isInfoStep(step)) {
    // InfoStepDto
  }

  // Narrow transaction steps by status
  if (guards.steps.isTransactionStepReady(step)) {
    // TransactionStepReadyDto - has initiatingTransaction
  }

  if (guards.steps.isTransactionStepDone(step)) {
    // TransactionStepDoneDto - has confirmation
  }

  if (guards.steps.isTransactionStepNotReady(step)) {
    // TransactionStepNotReadyDto - has estimatedGas
  }

  if (guards.steps.isTransactionStepAuto(step)) {
    // TransactionStepAutoDto - executed automatically
  }
}

Wait steps can also be narrowed:

for (const step of bridge.steps) {
  if (!guards.steps.isWaitStep(step)) continue;

  if (guards.steps.isWaitStepNotStarted(step)) {
    // WaitStepNotStartedDto
  }

  if (guards.steps.isWaitStepInProgress(step)) {
    // WaitStepInProgressDto
  }

  if (guards.steps.isWaitStepDone(step)) {
    // WaitStepDoneDto
  }
}

Gas Estimate Guards

Narrow gas estimates to their chain-specific types.

if (guards.gasEstimate.isEvm(gasEstimate)) {
  // EvmGasEstimateDto - has gasLimit
}

if (guards.gasEstimate.isSvm(gasEstimate)) {
  // SvmGasEstimateDto - has computeUnitLimit
}