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 === 'UsdAmountTooLarge') {
    // UsdAmountTooLargeRouteErrorDto - has amountUsd, maximumUsd
  }
  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 QuoteDto5 (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)) {
    // QuoteDto5 - 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. Use guards.gasEstimate to narrow.

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

  const gas = step.estimatedGas;

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

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

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') {
  // InitiatingTransactionEvmDto5 - has to, data, value
}
if (initiatingTransaction.type === 'evm-gasless') {
  // InitiatingTransactionEvmGaslessDto5 - has typedData
}
if (initiatingTransaction.type === 'svm') {
  // InitiatingTransactionSvmDto5 - has data (base64)
}
if (initiatingTransaction.type === 'starknet') {
  // InitiatingTransactionStarkDto5 - has calls
}

Steps narrow on type, then on transactionType / waitType.

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

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

  if (step.type === 'info') {
    // InfoStepDto - has text, link
  }
}