Support multiple property names in discriminator keyword

[pkuczynski]

What version of Ajv you are you using?

8.6

What problem do you want to solve?

My schema depends on value of two fields, so I wanted to implement something like this:

{
    type: 'object',
    discriminator: { propertyName: ['a', 'b'] }
    required: ['a', 'b'],
    oneOf: [
       {
          properties: {
            a: { const: true }
            b: { const: 'b' }
            c: { type: 'string' }
          }
       },
       {
          properties: {
            a: { const: false }
            b: { const: 'bb' }
            c: { type: 'number' }
          }
       }
       ...
    ]
}

What do you think is the correct solution to problem?

Add ability to define multiple properties in discriminator

Will you be able to implement it?

I am not sure...

[epoberezkin]

You can achieve it by nesting discriminators, or you can define a custom macro keyword to do it for you. discriminator is half-standard so changing it is probably wrong.

[pkuczynski]

I tried nesting discriminator in the following schema:

{
    type: 'object',
    discriminator: { propertyName: 'a' },
    properties: { b: { type: 'string' } },
    required: ['a', 'b'],
    oneOf: [
       {
          properties: {
            a: { const: true }
            c: { type: 'string' }
          }
       }
       {
          properties: {
            a: { const: false }
            c: { type: 'number' }
          },
          discriminator: { propertyName: 'b' },
          oneOf: [
            {
              properties: {
                b: { const: 'b1' }
                d: { type: 'string' }
            },
            {
              properties: {
                b: { const: 'b2' }
                d: { type: 'number' }
            },
          ]
       }
    ]
}

but I am getting the error Error: discriminator: "a" values must be unique string. Seems that discriminator does not really work with boolean? Is this intended?

[epoberezkin]

Yes, it only supports strings

[pkuczynski]

Would you be open for a PR to support other values like numbers and boolean?

[epoberezkin]

Yes - that should be doable I think - thank you!

[epoberezkin]

So effectively any scalar value can be matched with discriminator and you can use the same approach as in select keyword to make them object keys, so true as string is not the same as true as Boolean. Also worth supporting null in this case.

[epoberezkin]

(Select is defined in ajv-keywords for the reference)

[pkuczynski]

I have seen select, but it's deprecated in favor of discriminator. So I will give it a shot next week to extend to other scalar values...

[epoberezkin]

I only meant to use it to support discriminator improvement - not suggesting to use it instead. Let me know if you have any questions.

[pkuczynski]

I am working on extending discriminator with other values then string. Can I use Map object or would it create compatibility issue with older browsers?

[pkuczynski]

Here you go @epoberezkin #1729. Let me know what do you think?