Type Utilities

next-safe-action exports several utility types for inferring types from action functions, clients, and middleware. These are useful when you need to reference action types in other parts of your code.

All type utilities are imported from the main entry point:

import type {
	InferSafeActionFnInput,
	InferSafeActionFnResult,
	InferMiddlewareFnNextCtx,
	InferCtx,
	InferMetadata,
	InferServerError,
} from "next-safe-action";

`InferSafeActionFnInput`

Infer the input types (both client-side and parsed) from an action function.

type InferSafeActionFnInput<T extends Function>

Produces:

{
	clientInput: StandardSchemaV1.InferInput<S>;
	bindArgsClientInputs: InferInputArray<BAS>;
	parsedInput: StandardSchemaV1.InferOutput<S>;
	bindArgsParsedInputs: InferOutputArray<BAS>;
}

Works with: SafeActionFn, SafeStateActionFn

import type { InferSafeActionFnInput } from "next-safe-action";
import { myAction } from "./actions";

type MyInput = InferSafeActionFnInput<typeof myAction>;
// MyInput.clientInput — what you pass to execute()
// MyInput.parsedInput — what the server code receives
// MyInput.bindArgsClientInputs — bound arg types (input side)
// MyInput.bindArgsParsedInputs — bound arg types (parsed side)

`InferSafeActionFnResult`

Infer the result type from an action function.

type InferSafeActionFnResult<T extends Function>

Produces: SafeActionResult<ServerError, S, CVE, Data>

Works with: SafeActionFn, SafeStateActionFn

import type { InferSafeActionFnResult } from "next-safe-action";
import { myAction } from "./actions";

type MyResult = InferSafeActionFnResult<typeof myAction>;
// MyResult.data — the successful return type
// MyResult.serverError — the server error type
// MyResult.validationErrors — the validation errors type

`InferMiddlewareFnNextCtx`

Infer the next context type that a middleware function provides via next({ ctx }).

type InferMiddlewareFnNextCtx<T>

Produces: The NextCtx type parameter from MiddlewareFn.

Works with: MiddlewareFn

import type { InferMiddlewareFnNextCtx } from "next-safe-action";
import { authMiddleware } from "./middleware";

type AuthCtx = InferMiddlewareFnNextCtx<typeof authMiddleware>;
// { user: { id: string; role: string } }

`InferCtx`

Infer the current context type from a safe action client or middleware function.

type InferCtx<T>

Produces: The Ctx type, the accumulated context up to that point in the chain.

Works with: SafeActionClient, MiddlewareFn

import type { InferCtx } from "next-safe-action";
import { authClient } from "./safe-action";

type AuthClientCtx = InferCtx<typeof authClient>;
// { user: { id: string; role: string } }

`InferMetadata`

Infer the metadata type from a safe action client or middleware function.

type InferMetadata<T>

Produces: The MD type, inferred from the metadata schema or undefined if none.

Works with: SafeActionClient, MiddlewareFn

import type { InferMetadata } from "next-safe-action";
import { actionClient } from "./safe-action";

type MyMetadata = InferMetadata<typeof actionClient>;
// { actionName: string } (if defineMetadataSchema was set)
// undefined (if no metadata schema)

`InferServerError`

Infer the server error type from a client, middleware, or action function.

type InferServerError<T>

Produces: The ServerError type, which defaults to string unless customized via handleServerError.

Works with: SafeActionClient, MiddlewareFn, SafeActionFn, SafeStateActionFn

import type { InferServerError } from "next-safe-action";
import { actionClient } from "./safe-action";
import { myAction } from "./actions";

type ClientError = InferServerError<typeof actionClient>; // string (default)
type ActionError = InferServerError<typeof myAction>; // string (inherited)

Hook inference types

These are imported from next-safe-action/hooks:

import type {
	InferUseActionHookReturn,
	InferUseOptimisticActionHookReturn,
	InferUseStateActionHookReturn,
} from "next-safe-action/hooks";

`InferUseActionHookReturn`

Infer the return type of useAction for a given action function.

type InferUseActionHookReturn<T extends Function>

Works with: SafeActionFn

`InferUseOptimisticActionHookReturn`

Infer the return type of useOptimisticAction for a given action function and state type.

type InferUseOptimisticActionHookReturn<T extends Function, State = any>

Works with: SafeActionFn

`InferUseStateActionHookReturn` (deprecated)

Infer the return type of useStateAction for a given stateful action function.

type InferUseStateActionHookReturn<T extends Function>

Works with: SafeStateActionFn