Merge schemas

When we define a schema using Guard, the schema will be added to a route. But it will be overridden if the route provides a schema:

import { Elysia, t } from 'elysia'

new Elysia()
  .guard({
    body: t.Object({
      age: t.Number()
    })
  })
  .post(
    '/user',
    {
      // This will override the guard schema
      body: t.Object({
        name: t.String()
      })
    }, ({ body }) => body
  )
  .listen(3000)

If we want a schema to co-exist with route schema, we can define it as merged guard schema:

import { Elysia, t } from 'elysia'

new Elysia()
  .guard({
    schema: 'merge',
    body: t.Object({
      age: t.Number()
    })
  })
  .post(
    '/user',
    // body will have both age and name property
    {
      body: t.Object({
        name: t.String()
      })
    }, ({ body }) => body
  )
  .listen(3000)

Schema library interoperability

Schemas between merged guard schemas can be from different validation libraries.

For example you can define a merged guard schema using zod, and a local schema using t from elysia, and both will works interchangeably.

Assignment

Let’s make both age and name properties required in the request body by using merged guard schema.

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Standalone schema
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Let's make POST '/user' endpoint accept a body with `name` as string and `age` as number by modifying a guard schema to use `schema: 'merge'`

We can define a merged guard schema by adding schema: 'merge' in the guard options.

import { Elysia, t } from 'elysia'
import { z } from 'zod'

new Elysia()
  .guard({
    schema: 'merge',
    body: z.object({
      age: z.number()
    })
  })
  .post(
    '/user',
    {
      body: t.Object({
        name: t.String()
      })
    }, ({ body }) => body
  )
  .listen(3000)

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Standalone schema