trycat is a lightweight, type-safe, zero-dependency implementation of the Result type in Rust.
It provides utilities to replace try-catch error handling with Result that provides various methods to
handle errors in a more type-safe, explicit manner.
trycat provides two functions, trys and tryp, that returns results of throwable synchronous and asynchronous operations as either Ok or Err respectively.
import * as fs from "node:fs"
import { type Result, trys } from "trycat"
function readTextFileSync(path: string): Result<string, string> {
return trys(() => {
return fs.readFileSync(path, "utf-8")
}).mapErr((err) => {
if (err instance of Error) {
return err.message
}
return "unknown"
})
}
const rows = readTextFileSync("./data.csv")
.mapOr([], (content) => content.split('\n').map((line) => line.split(" ")))You can also use the ok and err functions manually to create an Ok value or an Err value:
import * as fs from "node:fs"
import { type Result, ok, err } from "trycat"
function readTextFileSync(path: string): Result<string, string> {
try {
const content = fs.readFileSync(path, "utf-8")
return ok(content)
} catch (err: unknown) {
if (err instanceof Error) {
return err(err.message)
}
return err("unknown")
}
}
const rows = readTextFileSync("./data.csv")
.mapOr([], (content) => content.split('\n').map((line) => line.split(" ")))tryp is an asynchronous version of trys:
type ApiError = "InternalError" | "NetworkError" | "ServerError" | "UnexpectedResponse"
const WeatherSchema = z.object({ ... })
type Weather = z.infer<typeof WeatherSchema>
async function fetchWeather(): Promise<Result<Weather, ApiError>> {
const res = await tryp(fetch("/api/weather"))
if (res.isErr()) {
return err("NetworkError")
}
if (res.value.status === 500) {
return err("ServerError")
}
const json = await tryp(res.json())
if (json.isErr()) {
return err("UnexpectedResponse")
}
const weather = trys(() => WeatherSchema.parse(json)).mapErr((error): ApiError => {
if (error instanceof ZodError) {
return "UnexpectedResponse"
}
return "InternalError"
})
if (weather.isErr()) {
return err(weather.error)
}
return ok(weather.value)
}The goal of this library is to match Rust's Result as close as possible. If there is anything missing, please file an issue.