Type for mixinFn doesn't match docs - mixin doesn't actually get logger parameter

[jason-curtis]

The docs for the mixin option state that it has 3 arguments: https://getpino.io/#/docs/api?id=mixin-function
The first parameter is the value mergeObject or an empty object. The second parameter is the log level number. The third parameter is the logger or child logger itself

However, the type declaration only has two arguments:

pino/pino.d.ts

Line 31 in 91a3505

type MixinFn = (mergeObject: object, level: number) => object;

Which of these versions of reality is correct?

Here's a screenshot of the resultant type error in VS code:

Pino version: 8.15.0

[mcollina]

I think the test are the best form of documentation:

pino/test/mixin.test.js

Lines 164 to 178 in 309cdfb

	test('mixin receives logger as third parameter', async ({ ok, same }) => {
	const stream = sink()
	const instance = pino({
	mixin (context, num, logger) {
	ok(logger !== null, 'logger should be defined')
	ok(logger !== undefined, 'logger should be defined')
	same(logger, instance)
	return { ...context, num }
	}
	}, stream)
	instance.level = name
	instance[name]({
	message: '123'
	}, 'test')
	})

Could you check the behavior and make sure docs and types are correct?

[jason-curtis]

Just as a heads up, my team has worked around this issue for now and I don't expect to have time to check and update the docs.

[andreiwow2]

I encountered the same problem.

Type '(obj: any, num: any, logger: any) => { tags: any; }' is not assignable to type 'MixinFn'.
  Target signature provides too few arguments. Expected 3 or more, but got 2.

[Downster]

When can we expect this fix to be released? What would be the best workaround for now?

[github-actions]

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