Can json schema be used to validate based on input data - jsonschema

Question

I'm just wondering if it is possible to use json schema to do validation of input data BASED on the actual input data itself.
Say I have an object:
{
parts: {
123: {
happy: 'me'
}
},
cells: [{
part_id: 123,
some: 'other property'
}, {
part_id: 124,
some: 'thing else'
}]
}
Can I write a json schema that ensures that the part_id of the cell objects actually corresponds to one of the part objects passed in?
In other words, part_id: 123 would be acceptable, but part_id: 124 wouldn't be.
Thanks!

Answer 1

After doing a bit of research, it looks like JSON Schema v5 has the functionality already via the $data reference attribute.
The following is from the javascript schema validator, ajv:
https://www.npmjs.com/package/ajv#data-reference
$data reference
With v5 option you can use values from the validated data as the values for the schema keywords. See v5 proposal for more information about how it works.
$data reference is supported in the keywords: constant, enum, format, maximum/minimum, exclusiveMaximum / exclusiveMinimum, maxLength / minLength, maxItems / minItems, maxProperties / minProperties, formatMaximum / formatMinimum, formatExclusiveMaximum / formatExclusiveMinimum, multipleOf, pattern, required, uniqueItems.
The value of "$data" should be a relative JSON-pointer.
Examples.
This schema requires that the value in property smaller is less or equal than the value in the property larger:
var schema = {
"properties": {
"smaller": {
"type": number,
"maximum": { "$data": "1/larger" }
},
"larger": { "type": number }
}
};
var validData = {
smaller: 5,
larger: 7
};
This schema requires that the properties have the same format as their field names:
var schema = {
"additionalProperties": {
"type": "string",
"format": { "$data": "0#" }
}
};
var validData = {
'date-time': '1963-06-19T08:30:06.283185Z',
email: 'joe.bloggs#example.com'
}
$data reference is resolved safely - it won't throw even if some property is undefined. If $data resolves to undefined the validation succeeds (with the exclusion of constant keyword). If $data resolves to incorrect type (e.g. not "number" for maximum keyword) the validation fails.