oneOf returns unwanted errors

[VasudhaMathur]

What version of Ajv you are you using?
8.12.0

What problem do you want to solve?

Schema:
var schema = { type: 'object', additionalProperties: false, properties: { children: { type: 'array', items: { oneOf: [{ type: 'object', properties: { a: { type: 'string' } }, required: ['a'], additionalProperties: false }, { type: 'object', properties: { b: { type: 'string' } }, required: ['b'], additionalProperties: false }] } } } };

Data:
const data = { "children": [ { a: 'a' }, { b: 'b' }, { c: 'c' } ] };

Code:
var Ajv = require('ajv'); var ajv = new Ajv(); ajv.validate(schema, data); console.log('Errors:', ajv.errors);

Errors:
Array of 3 items:
0: Object instancePath: "/children/2" schemaPath: "#/properties/children/items/oneOf/0/required" keyword: "required" params: Object {missingProperty: "a"} message: "must have required property 'a'"

1: Object instancePath: "/children/2" schemaPath: "#/properties/children/items/oneOf/1/required" keyword: "required" params: Object {missingProperty: "b"} message: "must have required property 'b'"

2: Object instancePath: "/children/2" schemaPath: "#/properties/children/items/oneOf" keyword: "oneOf" params: Object {passingSchemas: null} message: "must match exactly one schema in oneOf"

In real use case I have 20+ properties. And if in the data there's a typo, I get 20+ errors, when I'm looking for only "must match exactly one schema in oneOf". Is there a way to update the schema such that I get only the oneOf error?

[jasoniangreen]

I am still getting to grips with all the details of AJV but I do know that oneOf is one of (no pun intended) the most misunderstood and misused features of AJV. The most common advice I hear when dealing with oneOf is that you probably want to actually use anyOf. If the types in your oneOf have no overlap, then I think it's equivalent, but more efficient since it doesn't need to check ALL of the different types when it finds a match.

As for the error reporting I think that what you want may have once been the behaviour according to this response by EP so I can only assume it was changed to report all of the schemas that didn't match for good reasons.

So AFAIK this is not something that we'll be open to changing.