A fastify server with type-providers enabled will not be usable as input for the @fastify/aws-lambda plugin, which expects a FastifyInstance parameter.
Types of property 'handler' are incompatible.
Type 'RouteHandlerMethod<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, ... 4 more ..., FastifyBaseLogger>' is not assignable to type 'RouteHandlerMethod<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, any, any, any, FastifyTypeProviderDefault, FastifyBaseLogger>'.
Types of parameters 'request' and 'request' are incompatible.
Type 'FastifyRequest<any, RawServerDefault, IncomingMessage, any, FastifyTypeProviderDefault, any, FastifyBaseLogger, ResolveFastifyRequestType<...>>' is not assignable to type 'FastifyRequest<any, Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, any, TypeBoxTypeProvider, any, FastifyBaseLogger, ResolveFastifyRequestType<...>>'.
Type 'ResolveFastifyRequestType<FastifyTypeProviderDefault, any, any>' is not assignable to type 'ResolveFastifyRequestType<TypeBoxTypeProvider, any, any>'.
+ Type 'FastifyTypeProviderDefault' is not assignable to type 'TypeBoxTypeProvider'.Error: src/index.ts([27](https://github.com/driimus/fastify-instance-assignability/actions/runs/3259362782/jobs/5352129645#step:6:28),41): error TS2769: No overload matches this call.
Overload 1 of 2, '(app: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>, options?: LambdaFastifyOptions | undefined): PromiseHandler<...>', gave the following error.
Argument of type 'FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, TypeBoxTypeProvider>' is not assignable to parameter of type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>'.
The types returned by 'after()' are incompatible between these types.
Type 'FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, TypeBoxTypeProvider> & PromiseLike<...>' is not assignable to type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault> & PromiseLike<...>'.
Type 'FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, TypeBoxTypeProvider> & PromiseLike<...>' is not assignable to type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>'.
Types of property 'register' are incompatible.
Type 'FastifyRegister<FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, TypeBoxTypeProvider> & PromiseLike<...>, RawServerDefault, FastifyTypeProvider>' is not assignable to type 'FastifyRegister<FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault> & PromiseLike<...>, RawServerDefault, FastifyTypeProvider>'.
Type 'FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, TypeBoxTypeProvider> & PromiseLike<...>' is not assignable to type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault> & PromiseLike<...>'.
Type 'FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, TypeBoxTypeProvider> & PromiseLike<...>' is not assignable to type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>'.
The types of 'addSchema(...).addHook' are incompatible between these types.
Type '{ <RouteGeneric extends import("/home/runner/work/fastify-instance-assignability/fastify-instance-assignability/node_modules/.pnpm/fastify@4.8.1/node_modules/fastify/types/route").RouteGenericInterface = import("/home/runner/work/fastify-instance-assignability/fastify-instance-assignability/node_modules/.pnpm/fastif...' is not assignable to type '{ <RouteGeneric extends import("/home/runner/work/fastify-instance-assignability/fastify-instance-assignability/node_modules/.pnpm/fastify@4.8.1/node_modules/fastify/types/route").RouteGenericInterface = import("/home/runner/work/fastify-instance-assignability/fastify-instance-assignability/node_modules/.pnpm/fastif...'. Two different types with this name exist, but they are unrelated.
Types of parameters 'hook' and 'hook' are incompatible.
Types of parameters 'opts' and 'opts' are incompatible.
Type 'RouteOptions<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, ... 4 more ..., FastifyBaseLogger> & { ...; }' is not assignable to type 'RouteOptions<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, any, any, any, FastifyTypeProviderDefault, FastifyBaseLogger> & { ...; }'.
Type 'RouteOptions<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, ... 4 more ..., FastifyBaseLogger> & { ...; }' is not assignable to type 'RouteOptions<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, any, any, any, FastifyTypeProviderDefault, FastifyBaseLogger>'.
Types of property 'handler' are incompatible.
Type 'RouteHandlerMethod<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, ... 4 more ..., FastifyBaseLogger>' is not assignable to type 'RouteHandlerMethod<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, any, any, any, FastifyTypeProviderDefault, FastifyBaseLogger>'.
Types of parameters 'request' and 'request' are incompatible.
Type 'FastifyRequest<any, RawServerDefault, IncomingMessage, any, FastifyTypeProviderDefault, any, FastifyBaseLogger, ResolveFastifyRequestType<...>>' is not assignable to type 'FastifyRequest<any, Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, any, TypeBoxTypeProvider, any, FastifyBaseLogger, ResolveFastifyRequestType<...>>'.
Type 'ResolveFastifyRequestType<FastifyTypeProviderDefault, any, any>' is not assignable to type 'ResolveFastifyRequestType<TypeBoxTypeProvider, any, any>'.
Type 'FastifyTypeProviderDefault' is not assignable to type 'TypeBoxTypeProvider'.
Overload 2 of 2, '(app: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>, options?: LambdaFastifyOptions | undefined): CallbackHandler<...>', gave the following error.
Argument of type 'FastifyInstance<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, TypeBoxTypeProvider>' is not assignable to parameter of type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>'.
Prerequisites
Fastify version
4.7.0
Plugin version
No response
Node.js version
18.1.0
Operating system
Linux
Operating system version (i.e. 20.04, 11.3, 10)
Ubuntu 20.04.5 LTS
Description
Fastify instances with an enabled type-provider are not subtypes of the base
FastifyInstanceinterface.Example
A fastify server with type-providers enabled will not be usable as input for the
@fastify/aws-lambdaplugin, which expects aFastifyInstanceparameter.Cause
A more detailed explanation can be found in the reproduction repo.
In short, the assignability issue stems from certain methods of
FastifyInstancebeing contravariant onTypeProvider. Because of that, the compiler has to flip the assignability check's direction, which boils down to the following outcome:Types of property 'handler' are incompatible. Type 'RouteHandlerMethod<Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, ServerResponse<IncomingMessage>, ... 4 more ..., FastifyBaseLogger>' is not assignable to type 'RouteHandlerMethod<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, any, any, any, FastifyTypeProviderDefault, FastifyBaseLogger>'. Types of parameters 'request' and 'request' are incompatible. Type 'FastifyRequest<any, RawServerDefault, IncomingMessage, any, FastifyTypeProviderDefault, any, FastifyBaseLogger, ResolveFastifyRequestType<...>>' is not assignable to type 'FastifyRequest<any, Server<typeof IncomingMessage, typeof ServerResponse>, IncomingMessage, any, TypeBoxTypeProvider, any, FastifyBaseLogger, ResolveFastifyRequestType<...>>'. Type 'ResolveFastifyRequestType<FastifyTypeProviderDefault, any, any>' is not assignable to type 'ResolveFastifyRequestType<TypeBoxTypeProvider, any, any>'. + Type 'FastifyTypeProviderDefault' is not assignable to type 'TypeBoxTypeProvider'.Steps to Reproduce
"@fastify/aws-lambda": "^3.1.3"plugin.pnpm tsc --noEmitto check for type errorsFrom the CI run: https://github.com/driimus/fastify-instance-assignability/actions/runs/3259362782/jobs/5352129645#step:6:11
Expected Behavior
I would expect specialised versions of the
FastifyInstanceinterface, such as the ones using a custom type provider, to be assignable toFastifyInstance.I am aware of some available workarounds:
FastifyInstance.However, both of them seem inferior to ensuring that subtypes of
FastifyInstanceare assignable to the base interface.I haven't look at the way type providers are being used in details, but it seems possible: 77b7582...driimus:fastify:test/type-provider-contravariance