Remove app.use()

[mcollina]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the feature has not already been requested

🚀 Feature Proposal

I think we should be removing app.use() in the next release, i.e.

fastify/fastify.js

Lines 327 to 330 in a174829

	// We are adding `use` to the fastify prototype so the user
	// can still access it (and get the expected error), but `decorate`
	// will not detect it, and allow the user to override it.
	Object.setPrototypeOf(fastify, { use })

.

Motivation

We should not be encouraging people to use middlewares. Both middie and fastify-express will still be there and maintained.

Example

No response

[jsumners]

Please do this. I wouldn't be upset if we also deprecate middie and fastify-express with v4.

[mcollina]

I think they are useful plugins, we should keep having them but reduce their visibility.

[genzyy]

Can I take this? How should I go about this like removing use will do it I guess but deleting entire line will be better or am I missing something here?

[jsumners]

First thing we should probably do is issue a new v3 minor that adds a depreciation warning.

[genzyy]

First thing we should probably do is issue a new v3 minor that adds a depreciation warning.

For this should the docs be updated here?

[jsumners]

That would be part of it. The main thing would be adding a new deprecation error and triggering it when the method is invoked.

[mcollina]

it's already throwing an error, we can just remove it.

[genzyy]

it's already throwing an error, we can just remove it.

Should I make this change on a new branch while keeping next as a base and make a pull request to next branch?

[climba03003]

it's already throwing an error, we can just remove it.

Should I make this change on a new branch while keeping next as a base and make a pull request to next branch?

Yes

[genzyy]

Hey, so to fix this I made a new branch while keeping next as the base. But when I run npm run test, it gives me some errors. How should I commit the changes?

[climba03003]

You need to remove the corresponding test for .use.

fastify/test/middleware.test.js

Lines 10 to 20 in 0ae362b

	test('Should throw if the basic use API has not been overridden', t => {
	t.plan(1)
	const fastify = Fastify()
	try {
	fastify.use()
	t.fail('Should throw')
	} catch (err) {
	t.ok(err instanceof FST_ERR_MISSING_MIDDLEWARE)
	}
	})

fastify/test/middleware.test.js

Lines 50 to 58 in 0ae362b

	fastify.register((instance, opts, done) => {
	try {
	instance.use()
	t.fail('Should throw')
	} catch (err) {
	t.ok(err instanceof FST_ERR_MISSING_MIDDLEWARE)
	}
	done()
	})

[genzyy]

You need to remove the corresponding test for .use.

fastify/test/middleware.test.js

Lines 10 to 20 in 0ae362b

	test('Should throw if the basic use API has not been overridden', t => {
	t.plan(1)
	const fastify = Fastify()
	try {
	fastify.use()
	t.fail('Should throw')
	} catch (err) {
	t.ok(err instanceof FST_ERR_MISSING_MIDDLEWARE)
	}
	})

fastify/test/middleware.test.js

Lines 50 to 58 in 0ae362b

	fastify.register((instance, opts, done) => {
	try {
	instance.use()
	t.fail('Should throw')
	} catch (err) {
	t.ok(err instanceof FST_ERR_MISSING_MIDDLEWARE)
	}
	done()
	})

Removed these tests but I still have errors from multiple test files

[mcollina]

How should I commit the changes?

git commit -n to skip the pre-commit hooks.

---

Looking at your errors, I would recommend to rm -rf node_modules; npm i as it seems you are missing some deps (joi).

As for the rest, you'd need to look why they are failining.

[genzyy]

How should I commit the changes?

git commit -n to skip the pre-commit hooks.

Looking at your errors, I would recommend to rm -rf node_modules; npm i as it seems you are missing some deps (joi).

As for the rest, you'd need to look why they are failining.

Okay, I got here somehow

What about this one?
I removed the two test function mentioned above but I guess more needs to be removed.

[climba03003]

Update the t.plan to match the actual test number.

[genzyy]

Update the t.plan to match the actual test number.

Fixed all of the above
But I got these errors popped up

> fastify@4.0.0-dev test:typescript
> tsc test/types/import.ts && tsd

types/logger.d.ts:18:33 - error TS2694: Namespace 'pino' has no exported member 'SerializerFn'.

18 export type SerializerFn = pino.SerializerFn
                                   ~~~~~~~~~~~~

types/logger.d.ts:23:38 - error TS2694: Namespace 'pino' has no exported member 'BaseLogger'.

23 export type FastifyBaseLogger = pino.BaseLogger & {
                                        ~~~~~~~~~~

types/logger.d.ts:27:34 - error TS2694: Namespace 'pino' has no exported member 'PrettyOptions'.

27 export type PrettyOptions = pino.PrettyOptions & { suppressFlushSyncWarning?: boolean }
                                    ~~~~~~~~~~~~~


Found 3 errors.

[climba03003]

Update the t.plan to match the actual test number.

Fixed all of the above But I got these errors popped up

> fastify@4.0.0-dev test:typescript
> tsc test/types/import.ts && tsd

types/logger.d.ts:18:33 - error TS2694: Namespace 'pino' has no exported member 'SerializerFn'.

18 export type SerializerFn = pino.SerializerFn
                                   ~~~~~~~~~~~~

types/logger.d.ts:23:38 - error TS2694: Namespace 'pino' has no exported member 'BaseLogger'.

23 export type FastifyBaseLogger = pino.BaseLogger & {
                                        ~~~~~~~~~~

types/logger.d.ts:27:34 - error TS2694: Namespace 'pino' has no exported member 'PrettyOptions'.

27 export type PrettyOptions = pino.PrettyOptions & { suppressFlushSyncWarning?: boolean }
                                    ~~~~~~~~~~~~~


Found 3 errors.

It is expected to be fail as pinojs/pino#1195 introduce the type breaking in certain area.
You can submit the PR, it should be fixed in another PR.

[genzyy]

It is expected to be fail as pinojs/pino#1195 introduce the type breaking in certain area. You can submit the PR, it should be fixed in another PR.

Got it!
Also we need to add a note in the current version stating the deprecation of app.use() in the next release right?

[jsumners]

I think they are useful plugins, we should keep having them but reduce their visibility.

Issues like fastify/fastify-express#61 are why I think we should deprecate the middie and fastify-express modules. People are not using them to "migrate" to Fastify. They're keeping their old Express stuff around indefinitely because we continue to support it. This is going to continue to cause problems and maintenance burden as these users continue to try and add more and more new technologies on top.

In short: I think we have given enough lifecycles to facilitate migrating. It's time to move forward.

[Eomm]

Done in #3506