Accepance of `const` and `enum` keys

[JensJelitto]

It appears that the verifier must use _enum and _const for the generation of the presentation definition in the description of the fields, e.g.

constraints: {
  fields: [
    {
       path: ['$.credentialSubject.role'],
       filter: {
         type: 'string',
         _const: 'admin',
       },
    },
  ]
}

or

constraints: {
            fields: [
              {
                path: ['$.vc.credentialSubject.degree.name', '$.credentialSubject.degree.name'],
                filter: {
                  type: 'string',
                  _enum: ['Bachelor of Science and Arts'],
                },
              },
            ],
          },

Why is this necessary, couldn't the keywords enum and const be used directly (even though we understand that these are reserved keywords in Javascript).

[marek5050]

Would also like to point out that in the spec it says ->

The Exchange 1.0 https://identity.foundation/presentation-exchange/spec/v1.0.0/

in-set - Use the enum descriptor. 
For example, to request proof that an attribute is contained in the set of rainbow colors, 
use the following as the value of the filter object:

{  "type": "string", "enum": ["red", "yellow", "blue"] }

[nklomp]

Hi @marek5050 @JensJelitto Yes, you both are correct. The reason is that the PEX library uses autogenerated models from an OpenAPI specification in https://github.com/Sphereon-Opensource/pex-openapi The different language generators typically do not support these keywords. The PEX library does internally replace these values with the correct ones.

I will do some investigation, whether we can create a custom template for Typescript in the generator code, or whether we can re-export a version that removes the underscore version and replaces it with a string based property key.

[nklomp]

It for sure is in the generator, as our OpenAPI spec is explicitly using strings as keys:

  properties:
    "const":
      $ref: './polymorphic_entity.yaml#/one_of_number_string'
      description: A fixed value that is acceptable in this variable
    "enum":
      type: array
      description: Fixed listed values which are acceptable in this variable.
      items:
        $ref: './polymorphic_entity.yaml#/one_of_number_string'

[nklomp]

This is fixed in V2.0.0 of @sphereon/pex-models and @sphereon/pex and as a consequence in @sphereon/did-auth-siop