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';

Route Guards

getRoutes() resolves to either a RouteResponse (success) or a RouteError (top-level error such as the entire route being paused or exceeding the global USD cap). Use guards.routes to narrow.

const response = await sb.getRoutes({ /* ... */ });

if (guards.routes.isError(response)) {
  // RouteError - discriminate on `type`
  if (response.type === 'Paused') {
    // PausedRouteErrorDto
  }
  if (response.type === 'Disabled') {
    // DisabledRouteErrorDto
  }
  if (response.type === 'SlippageTooHigh') {
    // SlippageTooHighRouteErrorDto - has slippagePercent, maximumSlippagePercent
  }
  return;
}

// guards.routes.isResponse(response) - has `results`
const { results } = response;

Quote Guards

Each entry in RouteResponse.results[] has a result field that is either a QuoteDto (a usable quote with an initiatingTransaction) or a QuoteError (a per-provider error such as AmountTooSmall). Use guards.quotes to narrow.

for (const route of response.results) {
  if (guards.quotes.isQuote(route.result)) {
    // QuoteDto - has initiatingTransaction, fees, steps, receive
  }

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

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

for (const route of response.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'
}

Gas Estimate Guards

TransactionStepNotReadyDto.estimatedGas is shaped per chain family. Narrow on vm.

for (const step of bridge.steps) {
  if (step.type !== 'transaction' || step.transactionStatus !== 'not-ready') {
    continue;
  }

  const gas = step.estimatedGas;

  if (gas.vm === 'evm') {
    // EvmNotReadyStepGasEstimateDto - has gasLimit
  }

  if (gas.vm === 'svm') {
    // SvmNotReadyStepGasEstimateDto - has computeUnitLimit
  }

  if (gas.vm === 'stark') {
    // StarkNotReadyStepGasEstimateDto - has l1GasAmount, l1DataGasAmount, l2GasAmount
  }
}

Narrowing transactions and steps

Initiating transactions and activity steps don't have dedicated guards — narrow on the discriminating property directly.

// Initiating transaction - discriminated by `type`
const { initiatingTransaction } = quote;

if (initiatingTransaction.type === 'evm') {
  // InitiatingTransactionEvmDto - has to, data, value
}
if (initiatingTransaction.type === 'evm-gasless') {
  // InitiatingTransactionEvmGaslessDto - has typedData
}
if (initiatingTransaction.type === 'svm') {
  // InitiatingTransactionSvmDto - has data (base64)
}
if (initiatingTransaction.type === 'starknet') {
  // InitiatingTransactionStarkDto - has calls
}

Steps narrow on type, then on transactionStatus / waitStatus.

for (const step of bridge.steps) {
  if (step.type === 'transaction') {
    if (step.transactionStatus === 'ready') {
      // TransactionStepReadyDto - fetch via getStepTransaction
    }
    if (step.transactionStatus === 'done') {
      // TransactionStepDoneDto - has confirmation
    }
    if (step.transactionStatus === 'not-ready') {
      // TransactionStepNotReadyDto - has estimatedGas
    }
    if (step.transactionStatus === 'auto') {
      // TransactionStepAutoDto - executed automatically
    }
    if (step.transactionStatus === 'invalidated') {
      // TransactionStepInvalidatedDto - has confirmation, invalidatedBy
    }
  }

  if (step.type === 'wait') {
    if (step.waitStatus === 'not-started') {
      // WaitStepNotStartedDto
    }
    if (step.waitStatus === 'in-progress') {
      // WaitStepInProgressDto - has startedAt
    }
    if (step.waitStatus === 'done') {
      // WaitStepDoneDto - has actualDuration
    }
    if (step.waitStatus === 'invalidated') {
      // WaitStepInvalidatedDto - has actualDuration, invalidatedBy
    }
  }

  if (step.type === 'upgrade-event') {
    // UpgradeEventDto - can be referenced by invalidated steps
  }
}