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ErrorPolicy type

The ErrorPolicy type determines which errors should be handled for example in resilience middlewares like retry 6or fallback.

info

The ErrorPolicy will also apply when a function returns a failed Result.

Predicate as ErrorPolicy​

A predicate function can be used to dynamically determine if an error should be handled:

import { fallback } from "@daiso-tech/core/async";
import { AsyncHooks } from "@daiso-tech/core/utilities";

class CustomError extends Error {
    constructor(
        readonly errorCode: string,
        message: string,
        cause?: unknown,
    ) {
        super(message, { cause });
        this.name = CustomError.name;
    }
}
const func = new AsyncHooks((): string => {
    return "asd";
}, [
    fallback({
        fallbackValue: "DEFAULT_VALUE",
        errorPolicy: (error) => error instanceof CustomError,
    }),
]).toFunc();

Classes as ErrorPolicy:​

You can directly pass an class to match if errors are instance of the class:

const func = new AsyncHooks((): string => {
    return "asd";
}, [
    fallback({
        fallbackValue: "DEFAULT_VALUE",
        errorPolicy: CustomError,
    }),
]).toFunc();

Standard Schema as ErrorPolicy​

You can use any standard schema as error policy:

import { z } from "zod";

const func = new AsyncHooks((): string => {
    return "asd";
}, [
    fallback({
        fallbackValue: "DEFAULT_VALUE",
        errorPolicy: z.object({
            code: z.liter("e20"),
            message: z.string(),
        }),
    }),
]).toFunc();

False return values as error​

You can treat false return values as errors. This useful when you want to retry functions that return boolean.

import { AsyncHooks } from "@daiso-tech/core/utillities";
import { retry } from "@daiso-tech/async";

await new AsyncHooks((): Promise<boolean> => {
    // Will be
    console.log("EXECUTING");
    return false;
}, [
    retry({
        maxAttempts: 4,
        errorPolicy: {
            treatFalseAsError: true,
        },
    }),
]).invoke();

Further information​

For further information refer to @daiso-tech/core/utilities API docs.