DecimalField represented as type string with minimum and maximum

[idesoto-rover]

Describe the bug
DecimalField fields that use max_digits or decimal_places are represented in the schema as a type string with minimum and maximum properties, but according to the specs (or what I understand of them) is that minimum and maximum properties only apply to fields of type number.

This is giving me issues in the validation library I'm using (drf-openapi-tester) because it expects that fields with minimum and maximum properties to be numbers. After checking the specs IMHO the problem is in the schema (even if the validation library could be a bit more flexible and not fail on this).

To Reproduce
E.g.: for this field:

    latitude = serializers.DecimalField(
        max_digits=7,
        decimal_places=3
    )

This is generated in the schema:

        latitude:
          type: string
          format: decimal
          maximum: 10000
          minimum: -10000

Expected behavior
Maybe instead of specifying minimum and maximum values, specify a string pattern? Something like ^\d{1,7}(?:\.\d{1,3})?$ if max_digits is 7 and decimal_places is 3.

        latitude:
          type: string
          format: decimal
          pattern: ^\d{1,7}(?:\.\d{1,3})$

[tfranzel]

absolutely right! minimum and maximum are of type number, which is "correct" in the schema example. of course, it's comparing apples with oranges when the value itself is of type (decimal) string.

the resources as far as i can see make no statement about this.

• https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md -> not explitictly mentioned
• https://github.com/OAI/OpenAPI-Specification/blob/master/schemas/v3.0/schema.json -> not explitictly forbidden
• https://swagger.io/docs/specification/data-models/data-types/#numbers -> not explitictly mentioned

however, common sense would suggest that the min/max value types should be the same as the field type. drf-openapi-tester must have a dedicated logic for this. the pattern solution seems like the right thing to do.

[tfranzel]

closing this issue for now. feel free to comment if anything is missing or not working and we will follow-up.