Resolvers

Resolvers

Pass preds, meta, and resolver in one route() call:

import {route, err, type ResolverFor} from 'callspec';
import {predicates as p} from 'runtyp';

const product = p.object({id: p.string(), name: p.string(), priceCents: p.number()});

const products = [
    {id: 'sku-1', name: 'Widget', priceCents: 999},
    {id: 'sku-2', name: 'Gadget', priceCents: 1299},
];

export const getProductById = route({
    input: p.object({id: p.string()}),
    output: product,
    meta: {summary: 'Get product by ID', tags: ['catalog']},
    auth: 'none',
    mcp: true,
    resolver: async (input, _ctx) => {
        const found = products.find((item) => item.id === input.id);
        if (!found) return err.NOT_FOUND();
        return found;
    },
});

Separate resolver binding (optional):

const preds = { input, output, meta, auth: 'none' } as const;

const impl: ResolverFor<typeof preds, Ctx> = async (input, _ctx) => {
    return {id: input.id, name: '…', priceCents: 0};
};

export const getProductById = route({...preds, resolver: impl});

Export	Purpose
route({ …, resolver })	Wired route for spec; resolver also on .resolver for tests
ResolverFor<typeof preds, Ctx?>	Explicit resolver type for a separate binding

Domain-specific errors: defineErrors() + errors: on the route — see Error handling. Builtins like err.NOT_FOUND() work without declaring errors.

Private routes: annotate auth context on the resolver — resolver: async (input, ctx: Ctx) => …. See Authentication and Request context.

Testing resolvers

Call .resolver(input, ctx) on the wired route — no HTTP. Full guide: Unit testing.

import {test} from 'kizu';
import {isRouteFailure} from 'callspec';
import {getProductById} from '../routes/getProductById';

test('getProductById: NOT_FOUND', async (assert) => {
    const missing = await getProductById.resolver({id: 'missing'}, undefined);
    assert.equal(isRouteFailure(missing) && missing.code, 'NOT_FOUND');
});

Export the wired route from the route module when tests live in another file.

← API reference