Middleware Hooks

beforeAction and afterAction contract details.

Middleware Hooks

Hook argument types

packages/core/src/defineAction.ts

export type BeforeActionArgs<TInput, TContext> = {
  input: TInput;
  ctx: TContext;
};

export type AfterActionArgs<TInput, TOutput, TContext> = {
  input: TInput;
  ctx: TContext;
  result: TOutput;
};

beforeAction

• Runs after input parsing.
• Receives cloned input plus resolved context.
• Best for authorization, policy checks, and auditing.

afterAction

• Runs after handler.
• May return a replacement result.
• Best for output shaping and post-processing.

Example

app/actions.ts

import { defineAction } from "@zapaction/core";
import { z } from "zod";

type AppContext = { userId: string };

export const getProfile = defineAction<{ id: string }, { id: string; owner: string }, AppContext>({
  input: z.object({ id: z.string() }),
  output: z.object({ id: z.string(), owner: z.string() }),
  beforeAction: async ({ ctx }) => {
    if (!ctx.userId) throw new Error("Unauthorized");
  },
  afterAction: async ({ result, ctx }) => ({
    ...result,
    owner: ctx.userId
  }),
  handler: async ({ input }) => ({ id: input.id, owner: "unknown" })
});