Compatibility issues with Type.Number and @nestjs/swagger (exclusiveMaximum, exclusiveMinimum)

[Dev-Drew]

I'm defining a TypeBox schema then using it generate documentation with nestjs/swagger.

@sinclair/typebox defines Number with exclusiveMaximum and exclusiveMinimum as type number

nestjs/swagger is based on open-api-spec and has a SchemaObject which contains exclusiveMaximum and exclusiveMinimum as type boolean.

This of course causes an error, consider the following

import { Type } from '@sinclair/typebox'
import { ApiResponse } from '@nestjs/swagger';

  @ApiResponse({
    schema: Type.Number({ example: 201 }),
  })

Which results in

Type 'TNumber' is not assignable to type 'SchemaObject & Partial<ReferenceObject>'.
  Type 'TNumber' is not assignable to type 'SchemaObject'.
    Types of property 'exclusiveMaximum' are incompatible.
      Type 'number | undefined' is not assignable to type 'boolean | undefined'.
        Type 'number' is not assignable to type 'boolean | undefined

Just curious what the reason is for making exclusiveMaximum / exclusiveMinimum a number and how others may have solved.

[sinclairzx81]

@Dev-Drew Hi,

Just curious what the reason is for making exclusiveMaximum / exclusiveMinimum a number and how others may have solved.

The nestjs/swagger package is in error. The exclusiveMaximum and exclusiveMinimum keywords are of type number not boolean.

https://json-schema.org/draft/2020-12/json-schema-validation#name-exclusivemaximum

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6.2.3. exclusiveMaximum

The value of "exclusiveMaximum" MUST be a number, representing an exclusive upper limit for a numeric instance. If the instance is a number, then the instance is valid only if it has a value strictly less than (not equal to) "exclusiveMaximum".

6.2.5. exclusiveMinimum

The value of "exclusiveMinimum" MUST be a number, representing an exclusive lower limit for a numeric instance. If the instance is a number, then the instance is valid only if it has a value strictly greater than (not equal to) "exclusiveMinimum".

---

nestjs/swagger is based on open-api-spec

The OpenAPI 3.1 and above adheres to the Json Schema specification (specifically 2020-12) for type representation. The exclusiveMinimum and exclusiveMaximum keywords are formally of the Json Schema specification used to express range conditions of the following form.

https://json-schema.org/understanding-json-schema/reference/numeric#range

x ≥ minimum
x > exclusiveMinimum
x ≤ maximum
x < exclusiveMaximum

Historically, OpenAPI has had various interpretations of the Json Schema specification and it's possible the authors of nestjs/swagger are attempting to express older versions of the specification. As of OpenAPI 3.1, there is a claim it aligns to Json Schema 2020-12 for
compatibility. The nestjs/swagger project should align with that, even if it means making these fields number | boolean.

The correct type is number though.

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This would be a good thing to submit to the nestjs/swagger project as an issue. Feel free to link back to here for relevant links and information.

Hope this helps
S