Validate using AJV, parse using typebox

[RobinVdBroeck]

Hello,

Is it possible to validate using AJV by passing the JSON schema generated by typebox while still parsing with typebox? My use case is that I have some advanced schemas that are not supported out of the box with typebox. (For example { type: "string", enum: ["..."] }). Peformance is not really a concern for me, considering that the server time spent on validation is minimal compared to other IO stuff.

Is it recommended that I do something like this?

function myParse(jsonSchema, value) {
  const ajvSchema = ajv(jsonSchema);
  
  const withDefault = Value.Default(jsonSchema, value);
  const cleaned = Value.Clean(jsonSchema, withDefault);
  
  if(!ajvSchema(cleaned)) {
    throw new Error("Validation failed");
  }

  return Value.Decode(cleaned);
}

[sinclairzx81]

@RobinVdBroeck Hi,

Is it recommended that I do something like this?

Yes, this is fine. The Value.* functions can be used to provide additional functionality over Ajv. For parsing, it is recommended to implement a series of Value.* calls in a pipeline. The following is how TypeBox implements Parse internally.

https://github.com/sinclairzx81/typebox/blob/master/src/value/parse/parse.ts#L38-L68

// ------------------------------------------------------------------
// ParseReducer
// ------------------------------------------------------------------
type ReducerFunction = (schema: TSchema, references: TSchema[], value: unknown) => unknown

// prettier-ignore
const ParseReducer: ReducerFunction[] = [
  (_schema, _references, value) => Clone(value),
  (schema, references, value) => Default(schema, references, value),
  (schema, references, value) => Clean(schema, references, value),
  (schema, references, value) => Convert(schema, references, value),
   // replace Assert() with ajv.validate() and throw on error
  (schema, references, value) => { Assert(schema, references, value); return value },
  (schema, references, value) => (HasTransform(schema, references) ? TransformDecode(schema, references, value) : value),
]
// ------------------------------------------------------------------
// ParseValue
// ------------------------------------------------------------------
function ParseValue<T extends TSchema, R = StaticDecode<T>>(schema: T, references: TSchema[], value: unknown): R {
  return ParseReducer.reduce((value, reducer) => reducer(schema, references, value), value) as R
}

You can copy and paste the above to construct your own pipeline using Ajv (and add and remove additional processing stages as necessary)

Hope this helps
S