feat: decorate fastify instance with addittional properties by DemonHa · Pull Request #5093 · fastify/fastify

DemonHa · 2023-10-13T22:21:03Z

Proposal regarding to #5061

We are decorating the FastifyInstance to take into account decorators so it can work together with fastifyPlugin in order to have to end to end type safe apis.

This PR is a draft so any suggestion will be highly appreciated.

Checklist

run npm run test and npm run benchmark
tests and/or benchmarks are included
documentation is changed or added
commit message and code follows the Developer's Certification of Origin
and the Code of conduct

Uzlopak · 2023-10-13T22:27:21Z

It feels kind of wrong to change the FastifyInstance to a type. Doesnt this result in potential issues because you maybe cant extend from a type?

Also i think AppInstance or app is a term of expressjs. A AppInstance or App in fastify is the FastifyInstance.

DemonHa · 2023-10-13T22:33:25Z

@Uzlopak Actually you can extend a type the same way you do with an interface

DemonHa · 2023-10-13T22:40:14Z

@Uzlopak If you are talking about declaration merging then you are correct, but this is the thing we are trying to avoid

mcollina · 2024-05-02T07:51:57Z

@DemonHa what can we do to help you ship this?

DemonHa · 2024-05-02T10:01:21Z

@DemonHa what can we do to help you ship this?

Getting feedback as early as possible would be a great help.

DemonHa · 2024-05-04T16:58:06Z

Was thinking how would it work with a plugin like autoload or even when defining routes on a separate function.

We would probably need a generic to tell us which plugins have been registered. Wdyt @mcollina ?

rozzilla

Good approach overall! We should just avoid breaking changes 😉

rozzilla · 2024-11-25T11:04:37Z

examples/typescript-plugin-safety.ts

+// Used to type plugins written in javascript
+export type GetPluginTypes<Decorators extends FastifyPluginDecorators = { decorators: {}, dependencies: [] }> = FastifyPluginCallback<{}, RawServerBase, FastifyTypeProviderDefault, FastifyBaseLogger,  Decorators["decorators"] & ExtractSixGeneric<ExtractFirstFunctionParameter<Decorators["dependencies"][number] extends undefined ? {} : Decorators["dependencies"][number]>>>;
+
+// Testing types


Typescript tests should live in test/types folder 😉

Actually GetPluginTypes should not be living on the test folder at all, I just put it there for demo purposes. I think I should move it on the type definitions, since it will be exported and used by the libraries written in javascript (no library should be written in javascript IMO) or they can still use the declaration merging we currently have

rozzilla · 2024-11-25T11:06:30Z

examples/typescript-plugin-safety.ts

+    RawServer extends RawServerBase = RawServerDefault,
+    TypeProvider extends FastifyTypeProvider = FastifyTypeProviderDefault,
+    Logger extends FastifyBaseLogger = FastifyBaseLogger,
+    Fn extends FastifyPluginCallback<Options, RawServer, TypeProvider, Logger,  Decorators["decorators"]> | FastifyPluginAsync<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> = FastifyPluginCallback<Options, RawServer, TypeProvider, Logger,  Decorators["decorators"]>


nit (formatting)

Suggested change

Fn extends FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> | FastifyPluginAsync<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> = FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]>

Fn extends FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> | FastifyPluginAsync<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> = FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]>

rozzilla · 2024-11-25T11:07:38Z

examples/typescript-plugin-safety.ts

+): Fn;
+
+// Used to type plugins written in javascript
+export type GetPluginTypes<Decorators extends FastifyPluginDecorators = { decorators: {}, dependencies: [] }> = FastifyPluginCallback<{}, RawServerBase, FastifyTypeProviderDefault, FastifyBaseLogger,  Decorators["decorators"] & ExtractSixGeneric<ExtractFirstFunctionParameter<Decorators["dependencies"][number] extends undefined ? {} : Decorators["dependencies"][number]>>>;


nit (formatting)

Suggested change

export type GetPluginTypes<Decorators extends FastifyPluginDecorators = { decorators: {}, dependencies: [] }> = FastifyPluginCallback<{}, RawServerBase, FastifyTypeProviderDefault, FastifyBaseLogger, Decorators["decorators"] & ExtractSixGeneric<ExtractFirstFunctionParameter<Decorators["dependencies"][number] extends undefined ? {} : Decorators["dependencies"][number]>>>;

export type GetPluginTypes<Decorators extends FastifyPluginDecorators = { decorators: {}, dependencies: [] }> = FastifyPluginCallback<{}, RawServerBase, FastifyTypeProviderDefault, FastifyBaseLogger, Decorators["decorators"] & ExtractSixGeneric<ExtractFirstFunctionParameter<Decorators["dependencies"][number] extends undefined ? {} : Decorators["dependencies"][number]>>>;

types/instance.d.ts

types/reply.d.ts

types/request.d.ts

DemonHa · 2024-12-26T03:23:39Z

Hi guys!

I have been away for quite some times since a lot of things have been going on lately.
Anyways, I found a way to keep everything as an interface so we don't introduce breaking changes. That means that people can still use declaration merging. Let me know what you guys think.

@mcollina @Uzlopak @rozzilla

rozzilla · 2024-12-26T10:00:16Z

I found a way to keep everything as an interface so we don't introduce breaking changes. That means that people can still use declaration merging. Let me know what you guys think.

I love that approach! We keep compatibility with old code while allowing new types to be introduced. Since declaration merging will still be allowed, we will probably have to mark it as deprecated. Anyway, one thing at the time. I think we should proceed that way you're suggesting 😀

rozzilla

We need to fix conflicts, but now this change LGTM!

DemonHa · 2024-12-26T13:22:03Z

We need to fix conflicts, but now this change LGTM!

Yes, there might be quite some conflicts since this is a really old PR. I'll try to fix them today.

gurgunday

Yeah I thought about this again and it is looking pretty good to me now!

mcollina · 2025-01-12T10:08:54Z

@DemonHa what is missing?

DemonHa · 2025-01-15T23:35:53Z

@DemonHa what is missing?

I am creating the PR on the other projects as well and I am also going to create a little test application

rozzilla · 2025-02-09T10:54:24Z

examples/typescript-plugin-safety.ts

+import fastify, { FastifyBaseLogger, FastifyPluginAsync, FastifyPluginCallback, FastifyPluginOptions, FastifyTypeProvider, FastifyTypeProviderDefault, RawServerBase, RawServerDefault } from '../fastify'
+import { FastifyDecorators, FastifyInstance } from '../types/instance'
+
+type ExtractSixGeneric<T> = T extends FastifyInstance<any, any, any, any, any, infer U> ? U : void


Can we use other types and avoid any's?

Eomm · 2026-01-17T13:42:29Z

Closing as too old

DemonHa added 2 commits October 13, 2023 23:49

feat: decorate fastify instance with addittional properties

040c0c3

feat: type javascript plugins

8653101

chore: use the right terminology

4e07627

DemonHa marked this pull request as draft November 4, 2023 13:05

feat: merge decorators when registering plugins

83b070e

DemonHa mentioned this pull request May 1, 2024

Removal of declaration merging #5061

Open

mcollina self-requested a review May 1, 2024 14:58

Eomm added the typescript TypeScript related label May 5, 2024

nemanja-tosic mentioned this pull request Sep 8, 2024

Type improvements #5672

Closed

4 tasks

rozzilla suggested changes Nov 25, 2024

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chore: support backwards compatibility

477c377

rozzilla approved these changes Dec 26, 2024

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gurgunday reviewed Dec 26, 2024

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DemonHa mentioned this pull request Jan 3, 2025

feat: support decorators on plugin definition fastify/fastify-plugin#259

Draft

4 tasks

Merge branch 'main' into type-safe-plugin-definitions

089b793

feat: export FastifyInstanceWithPlugins type

5ff3307

rozzilla reviewed Feb 9, 2025

View reviewed changes

fix: correctly get fastify decorators

9a438e8

Eomm closed this Jan 17, 2026

	Fn extends FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> \| FastifyPluginAsync<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> = FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]>
	Fn extends FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> \| FastifyPluginAsync<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]> = FastifyPluginCallback<Options, RawServer, TypeProvider, Logger, Decorators["decorators"]>

	export type GetPluginTypes<Decorators extends FastifyPluginDecorators = { decorators: {}, dependencies: [] }> = FastifyPluginCallback<{}, RawServerBase, FastifyTypeProviderDefault, FastifyBaseLogger, Decorators["decorators"] & ExtractSixGeneric<ExtractFirstFunctionParameter<Decorators["dependencies"][number] extends undefined ? {} : Decorators["dependencies"][number]>>>;
	export type GetPluginTypes<Decorators extends FastifyPluginDecorators = { decorators: {}, dependencies: [] }> = FastifyPluginCallback<{}, RawServerBase, FastifyTypeProviderDefault, FastifyBaseLogger, Decorators["decorators"] & ExtractSixGeneric<ExtractFirstFunctionParameter<Decorators["dependencies"][number] extends undefined ? {} : Decorators["dependencies"][number]>>>;

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DemonHa commented Oct 13, 2023

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