Cross-platform fetch error classification

Fetch-happened.ts

/**
 * Uses various heurisitics to determine if an error is a connection error.
 */
export function isConnectionError(err: unknown): boolean {
  if (typeof err !== "object" || err == null) {
    return false;
  }

  // Covers fetch in Deno as well
  const isBrowserErr =
    err instanceof TypeError &&
    err.message.toLowerCase().startsWith("failed to fetch");

  const isNodeErr =
    err instanceof TypeError &&
    err.message.toLowerCase().startsWith("fetch failed");

  const isBunErr = "name" in err && err.name === "ConnectionError";

  const isGenericErr =
    "code" in err &&
    typeof err.code === "string" &&
    err.code.toLowerCase() === "econnreset";

  return isBrowserErr || isNodeErr || isGenericErr || isBunErr;
}

/**
 * Uses various heurisitics to determine if an error is a timeout error.
 */
export function isTimeoutError(err: unknown): boolean {
  if (typeof err !== "object" || err == null) {
    return false;
  }

  // Fetch in browser, Node.js, Bun, Deno
  const isNative = "name" in err && err.name === "TimeoutError";
  const isLegacyNative = "code" in err && err.code === 23;

  // Node.js HTTP client and Axios
  const isGenericErr =
    "code" in err &&
    typeof err.code === "string" &&
    err.code.toLowerCase() === "econnaborted";

  return isNative || isLegacyNative || isGenericErr;
}

/**
 * Uses various heurisitics to determine if an error is a abort error.
 */
export function isAbortError(err: unknown): boolean {
  if (typeof err !== "object" || err == null) {
    return false;
  }

  // Fetch in browser, Node.js, Bun, Deno
  const isNative = "name" in err && err.name === "AbortError";
  const isLegacyNative = "code" in err && err.code === 20;

  // Node.js HTTP client and Axios
  const isGenericErr =
    "code" in err &&
    typeof err.code === "string" &&
    err.code.toLowerCase() === "econnaborted";

  return isNative || isLegacyNative || isGenericErr;
}