Fastify validate schema with yup - schema.validateSync is not a function - yup

Question

From the Fastify documentation in the section titled Using other validation libraries I'm trying to get yup to validate my schema but I keep getting schema.validateSync is not a function and I don't know why??
I want the schema to still be valid for creating the swagger document but I want to use yup to give me the validation I need.
const yup = require("yup");
const yupOptions = {
strict: false,
abortEarly: false,
stripUnknown: true,
recursive: true,
};
async function isUsernameAvailable(fastify: any, _options: Object) {
const users = fastify.mongo.db.collection("users");
fastify.get(
"/api/v1/onboarding/isUsernameAvailable/:username",
{
schema: {
params: {
type: "object",
properties: {
username: { type: "string", maxLength: 12, minLength: 1 },
},
required: ["username"],
},
response: {
200: {
type: "object",
properties: {
available: {
type: "boolean",
description: "Returns true if username is available",
},
},
},
},
},
validatorCompiler: ({ schema, method, url, httpPart }: any) => {
return function (data: any) {
try {
const result = schema.validateSync(data, yupOptions);
return { value: result };
} catch (e) {
return { error: e };
}
};
},
},
async (request: any, _reply: any) => {
const { username } = request.params;
const foundNUsernames = await users.countDocuments(
{ username },
{ limit: 1 }
);
const available: boolean = foundNUsernames === 0;
return { available };
}
);
}
export { isUsernameAvailable };
if I use the below, the validation works but the swagger doc doesn't build
schema: {
params: yup.object({
username: yup.string().lowercase().max(12).min(1).required(),
}),
}
if I remove the validatorCompiler then I get no errors, swagger does build but I cant use yup
validatorCompiler: ({ schema, method, url, httpPart }: any) => {
return function (data: any) {
try {
const result = schema.validateSync(data, yupOptions);
return { value: result };
} catch (e) {
return { error: e };
}
};
},
}
how can I satisfy both?
Why do I want to use yup? I want to validate emails and transform values into lowercase.