Pagination normalization for `_per_page=0` is unclear

[Omar-Tnt04]

Description

I noticed an unclear pagination behavior when _per_page=0 is provided.

According to the documentation:

Invalid _page or _per_page values are automatically normalized to valid ranges.

However, the behavior for _per_page=0 is not clearly defined.

The request succeeds and returns paginated results instead of rejecting the value or clearly documenting the normalization rule.

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Environment

• json-server: v1.0.0-beta.6
• Node.js: v24.12.0
• OS: Windows 11

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Steps to reproduce

Run the current repository version with the default fixtures:

pnpm dev

Then send the request:

GET http://localhost:3000/posts?_page=1&_per_page=0

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Observed behavior

The request succeeds and returns a paginated response.

For example, using the default fixtures/db.json, the response includes pagination metadata and returns one item in data.

Example response:

{
  "first": 1,
  "prev": null,
  "next": 2,
  "last": 2,
  "pages": 2,
  "items": 2,
  "data": [
    {
      "id": "1",
      "title": "a title"
    }
  ]
}

This suggests _per_page=0 is internally normalized to a non-zero value.

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Expected behavior

Since the documentation states that invalid values are normalized, it would help clarify what _per_page=0 should normalize to.

Possible expectations could include:

• Normalizing _per_page=0 to 1
• Returning an error (e.g. 400 Bad Request)
• Falling back to the default pagination value

Currently the behavior appears to normalize silently, but the exact rule is not clearly documented.

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Notes

This may be intended behavior, but documenting the normalization rule for _per_page=0 would make the API behavior clearer and more predictable.