[Proposal] no need to check `type`, if `enum` is provided

[o-alexandrov]

Given:

example: {
      type: `string`,
      enum: [`0`, `1`]
}

The following shouldn't be generated/checked:

• as it will be further checked as part of the enum check for the exact values

if (typeof data1 !== `string`) {
  const err0 = {
    instancePath: instancePath + `/example`,
    schemaPath: `#/properties/example`,
    keyword: `type`,
    params: { type: `string` },
  }
  if (vErrors === null) {
    vErrors = [err0]
  } else {
    vErrors.push(err0)
  }
  errors++
}

What version of Ajv you are you using? 8.11.0

What problem do you want to solve? To have less generated code.

What do you think is the correct solution to problem? Not to check type, if enum is provided.

Will you be able to implement it? Yes

[epoberezkin]

Arguably, in general case it might be more efficient to check for type first, as enum values can have different types, or they can be long strings, so removing type can be at best a micro-optimisation in some cases, but can slow things down in some other cases...

In any case, you can just not include type in the schema if you don't want it compiled - or am I missing something?

[o-alexandrov]

in general case it might be more efficient to check for type first

In general case, the validation would actually pass, so on average the performance would also increase, besides previously mentioned smaller output, hence shorter initialization time.

• so I already named three benefits

Yes, the type can be omitted, but it means the user-developer needs to add a custom post-processing.

• I believe the library should produce a better output by default, not requiring the user-developer to search for options to optimize the output

[epoberezkin]

In general case, the validation would actually pass

excluding any attack scenarios...

Need to think about it.