JSON-Schema oneOf for option under root area - json

Question

I am trying to get the "oneof" to allow for options in root items but can't find an example and what I try gives an error.
I can get it to work if it is under another item but not under the root {'s
Example - a Job Payment that has required fields (jobNum, payee, amount, type, ) and an option for the payment type (checkInfo or dollarAmt). I know this could be done other ways, but I need this method for a more complex schema.
{
"jobNum": "x216",
"payee": "John Doe",
"type": "check",
"amount": "112.25",
"checkInfo": {
"number": "386"
}
}
{
"JobNum": "x216",
"Payee": "John Doe",
"type" : "Cash",
"amount" : "112.25",
"cashInfo" : {
"dollarAmt" : "112",
"coinAmt" : "0.25"
}
}
The following gives me this error - "Unexpected token encountered when reading value for 'oneOf'. Expected StartObject, Boolean, got StartArray"
{
"description": "Job Payment",
"type": "object",
"required": [ "jobNum", "payee", "amount", "type"],
"properties": {
"jobNum": {
"type": "string"
},
"payee": {
"type": "string"
},
"amount": {
"type": "string"
},
"type": {"enum": [ "check", "cash" ]
},
"oneOf": [
{ "$ref": "#/definitions/ptCash" },
{ "$ref": "#/definitions/ptCheck" }
]
},
"definitions": {
"ptCash": {
"properties": {
"checkInfo": {
"number": "string"
}
},
"required": [ "checkInfo" ],
"additionalProperties": false
},
"ptCheck": {
"properties": {
"dollarAmt": {
"type": "string"
},
"coinAmt": {
"type": "string"
}
},
"required": [ "dollarAmt", "coinAmt" ],
"additionalProperties": false
}
},
"additionalProperties": false
}

Answer 1

There are a a few issues with your schema. I fixed it for you below. I won't explain all the changes I made because I think it is mostly pretty clear by reading the schema. If you want more detail on anything, just ask and I'll update the answer with more details.
The oneOf keyword can only appear in a schema. The properties keyword is an object whose values are schemas. When you put "oneOf" directly under properties, it's not interpreted as a keyword, it's interpreted as a property called "oneOf". The validator then complains because the value of property "oneOf" is expected to be a schema, not an array of schemas like the oneOf keyword.
Your use of additionalProperties doesn't work. This keyword doesn't work the way people often assume that it does. JSON Schema keywords are not aware of any state outside of the schema they are in. Let's look at the "ptCheck" branch of your oneOf first. This describes the property "number", says it is required and that there may be no keywords other than "number". Then your top level defines a the properties "jobNum", "payee", "amount", and "type", requires them all and allows no other properties. These two things can never be true at the same time. Even though your schema is valid, there is no JSON value that can ever be valid against this schema. That's why I moved the definitions of "checkInfo" and "cashInfo" to the top level and only put the required part in oneOf. The only downside to this approach is that you can pass both a "checkInfo" and a "cachInfo" object and it will validate. The extraneous property gets ignored. There are ways around this, but they are problematic enough that I don't advise using them.
I always advise people not to use "additionalProperties": false and to ignore unknown properties instead. The reason is that JSON Schema is a constraint system. Any valid JSON is valid against the empty schema ({}) and each keyword in the schema adds some constraint. This is a different approach to what people are used to when defining classes. An empty class describes nothing and valid values are added. We use "additionalProperties": false to get JSON Schema to behave more like defining a class, but trying to get JSON Schema to behave like something it isn't causes challenges like the one you see here.
{
"description": "Job Payment",
"type": "object",
"required": ["jobNum", "payee", "amount", "type"],
"properties": {
"jobNum": { "type": "string" },
"payee": { "type": "string" },
"amount": { "type": "string" },
"type": { "enum": ["check", "cash"] },
"checkInfo": {
"type": "object",
"properties": {
"number": { "type": "string" }
},
"required": ["number"]
},
"cashInfo": {
"type": "object",
"properties": {
"dollarAmt": { "type": "string" },
"coinAmt": { "type": "string" }
},
"required": ["dollarAmt", "coinAmt"]
}
},
"oneOf": [
{ "$ref": "#/definitions/ptCash" },
{ "$ref": "#/definitions/ptCheck" }
],
"definitions": {
"ptCheck": {
"type": "object",
"properties": {
"type": { "enum": ["check"] }
},
"required": ["checkInfo"]
},
"ptCash": {
"type": "object",
"properties": {
"type": { "enum": ["cash"] }
},
"required": ["cashInfo"]
}
},
"additionalProperties": false
}

Answer 2

oneOf should be placed in prope
Have to re-write rule for both ptCash and ptCheck by using type: object
Following schema should work with ptCheck:
{
"description": "Job Payment",
"type": "object",
"required": [ "jobNum", "payee", "amount", "type"],
"properties": {
"jobNum": {
"type": "string"
},
"payee": {
"type": "string"
},
"amount": {
"type": "string"
},
"type": {"enum": [ "check", "cash" ]
}
},
"oneOf": [
{ "$ref": "#/definitions/ptCash" },
{ "$ref": "#/definitions/ptCheck" }
],
"definitions": {
"ptCash": {
"properties": {
"checkInfo": {
"type": "object",
"required": ["number"],
"properties": {
"number": {
"type": "string"
}
}
}
},
"required": [ "checkInfo" ]
},
"ptCheck": {
"properties": {
"cashInfo": {
"type": "object",
"properties": {
"dollarAmt": {
"type": "string"
},
"coinAmt": {
"type": "string"
}
},
"required": ["dollarAmt", "coinAmt"]
}
},
"required": ["cashInfo"]
}
}
}
Provide some example as below:
import jsonschema
import simplejson as json
schema_filename = '47926398.json'
with open(schema_filename, 'r') as f:
schema_data = f.read()
schema = json.loads(schema_data)
# validate with checkInfo
json_obj = {
"jobNum": "x216",
"payee": "John Doe",
"type": "check",
"amount": "112.25",
"checkInfo": {
"number": "386"
}
}
jsonschema.validate(json_obj, schema)
# invalidate
json_obj = {
"jobNum": "x216",
"payee": "John Doe",
"type": "check",
"amount": "112.25",
"checkInfox": {
"number": "386"
}
}
jsonschema.validate(json_obj, schema)
# validate with cashInfo
json_obj = {
"jobNum": "x216",
"payee": "John Doe",
"type": "check",
"amount": "112.25",
"cashInfo": {
"dollarAmt": "400",
"coinAmt": "30"
}
}
jsonschema.validate(json_obj, schema)
# invalidate with cashInfo
json_obj = {
"jobNum": "x216",
"payee": "John Doe",
"type": "check",
"amount": "112.25",
"cashInfox": {
"dollarAmt": "400",
"coinAmt": "30"
}
}
jsonschema.validate(json_obj, schema)
# invalidate with cashInfo.dollarAmtx
json_obj = {
"jobNum": "x216",
"payee": "John Doe",
"type": "check",
"amount": "112.25",
"cashInfo": {
"dollarAmtx": "400",
"coinAmt": "30"
}
}
jsonschema.validate(json_obj, schema)