fix(plugin-nested-docs): add generics to generate function types

[lachieh]

Description

Noticed that I had to cast some types while writing the functions in the options for @payload/plugin-nested-docs. Took a page from @payload/plugin-seo and updated the types for these functions to accept generics, with a default that matches the previous type.

• [x] I have read and understand the CONTRIBUTING.md document in this repository.

Details

Problem: can't determine return type from function param

nestedDocsPlugin({
  generateLabel: (_, doc) => doc.title,
                           // ^--- Type 'unknown' is not assignable to type 'string'.
}),

Fix: provide param type New Problem: function doesn't match GenerateLabel signature

nestedDocsPlugin({
  generateLabel: (_, doc: Page) => doc.title,
// ^--- Type '(_: Record<string, unknown>[], doc: Page) => string' is not assignable to type 'GenerateLabel'.
}),

Temp fix: cast function

import { GenerateLabel } from '@payloadcms/plugin-nested-docs/types'
// ...
nestedDocsPlugin({
  generateLabel: ((_, doc: Page) => doc.title) as unknown as GenerateLabel,
                                               // ^-- no more ts error but ew.
}),

Solution

After this type is updated, the first solution works:

nestedDocsPlugin({
  generateLabel: (_, doc: Page) => doc.title
}),

Alternatively a function assignment also works:

import { GenerateLabel } from '@payloadcms/plugin-nested-docs/types'
// ...
const generateLabel: GenerateLabel<Page>: (_, doc) => doc.title
nestedDocsPlugin({
  generateLabel
}),

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Checklist:

• [x] I have added tests that prove my fix is effective or that my feature works
• [x] Existing test suite passes locally with my changes
• [x] ~~I have made corresponding changes to the documentation~~ No docs update required