Use fastify json schema validation in arbitrary functions - fastify

Question

Fastify has some really awesome json schema support. (Link)
However, I now want to use the schemas which I added with fastify.addSchema(..) inside my business logic as well. For example (pseudo code):
schema = fastify.getSchema("schema1")
if (schema.validate(data)) {
console.log("ok");
} else {
console.log("not ok");
}
How can I achieve that?

Answer 1

Right now, in Fastify, one route has a set of validation functions.
These functions exist only because you set them in the { schema: {} } route
configuration.
So, in the first place, if you don't set those schemas in a route, you will be not able to access them.
The getSchema function retrieves the schema object, not che compiled function.
The relation is not 1:1 because a validation function may use more schemas via the $ref keyword.
The only way to archive what you need is to monkey patch the internal Fastify (highly discouraged)
Or open a feature request to the project.
Here an example, and as you can see, you are limited to get the route's validation functions inside the route's context.
So, it is far from being a flexible usage.
const fastify = require('fastify')({ logger: true })
const {
kSchemaBody: bodySchema
} = require('fastify/lib/symbols')
fastify.post('/', {
schema: {
body: {
$id: '#schema1',
type: 'object',
properties: {
bar: { type: 'number' }
}
}
}
}, async (request, reply) => {
const schemaValidator = request.context[bodySchema]
const result = schemaValidator({ bar: 'not a number' })
if (result) {
return true
}
return schemaValidator.errors
})
fastify.inject({
method: 'POST',
url: '/',
payload: {
bar: 33
}
}, (err, res) => {
console.log(res.json())
})