Json Schema for Aspect Oriented Json files - json

Question

So my json structure is aspect oriented, meaning that the json is structure in a way that each data is represented by a key and that key will define the structure of its content.
for example:
[
{
"nv": [{ "ln": 123 }]
},
{
"metadata": [{ "name": "nodes" }, { "name": "edges" }]
},
{
"nodes": [{ "#id": 1 }, { "#id": 2 }]
},
{
"edges": [
{ "#id": 1, "nodeId": 1 },
{ "#id": 2, "nodeId": 2 }
]
},
{
"status": [{ "success": true }]
}
]
As shown 3 objects (nv, metadata, status) and based on the name inside of the metadata there will be objects inside the json file.
I tried something like this:
{
"type": "array",
"items": [
{
"type": "object",
"properties": {
"nv": { "type": "array", "items": { "$ref": "#definitions/nv" } }
},
"required": ["nv"]
},
{
"type": "object",
"properties": {
"metaData": {
"type": "array",
"items": { "$ref": "#definitions/metadata" }
}
},
"required": ["metaData"]
},
{
"anyOf": [
{
"type": "object",
"properties": {
"nodes": {
"type": "array",
"items": { "$ref": "#definitions/nodes" }
}
}
},
{
"type": "object",
"properties": {
"edges": {
"type": "array",
"items": { "$ref": "#definitions/edges" }
}
}
},
{
"type": "object",
"properties": {
"edgeAttribute": {
"type": "array",
"items": { "$ref": "#definitions/edgeAttribute" }
}
}
},
{
"type": "object",
"properties": {
"nodeAttribute": {
"type": "array",
"items": { "$ref": "#definitions/nodeAttribute" }
}
}
}
]
},
{
"type": "object",
"properties": {
"status": {
"type": "array",
"items": { "$ref": "#definitions/status" }
}
},
"required": ["status"]
}
],
"definitions": {
"status": {
"type": "object",
"properties": {
"success": { "type": "boolean" }
}
"etc..."
}
}
}
but then if I define an empty array it will be accepted, also it is being accepted if the array only contains one of the 3 required objects.
So is there a way to validate against something like the example using json-schemas?
The real scenario may have more than just 2 objects inside of the metadata that's why I did not use if -> then -> else conditions. if the solution is by using them then please let me know.

Answer 1

The structure of the data makes this a rough one, but there are a few patterns you can use to get the behavior you want. Let's take them one at a time.
Declare an array that can contain any of a number of objects
Generally people use oneOf for this, but I don't recommend that because it can have poor performance and incomprehensible error messages. Usually that means if/then, but in this case you can get good results by defining your items as a single object that only allows one property at a time in each object.
{
"items": {
"type": "object",
"properties": {
"nv": { "$ref": "#/definitions/nv" },
"metadata": { "$ref": "#/definitions/metadata" },
"status": { "$ref": "#/definitions/status" },
"nodes": { "$ref": "#/definitions/nodes" },
"edges": { "$ref": "#/definitions/edges" }
},
"minProperties": 1,
"maxProperties": 1
}
}
Edit: Previously, I recommended dependencies, but then realized that this is better.
Assert that the array contains a required object
To do this, you need to assert that the array contains an object that has a required property.
{ "contains": { "type": "object", "required": ["nv"] } }
You'll have to combine this pattern in allOf to express additional required items.
{
"allOf": [
{ "contains": { "type": "object", "required": ["nv"] } },
{ "contains": { "type": "object", "required": ["metadata"] } },
{ "contains": { "type": "object", "required": ["status"] } }
]
}
Conditionally assert that the array contains a required object
The tricky part here is getting all the nested contains and properties in the if to be able to assert that the "name" is a certain value. The then just uses the same pattern we used above to assert than an object is required in the array.
{
"if": {
"type": "array",
"contains": {
"type": "object",
"properties": {
"metadata": {
"type": "array",
"contains": {
"type": "object",
"properties": {
"name": { "const": "nodes" }
},
"required": ["name"]
}
}
},
"required": ["metadata"]
}
},
"then": { "contains": { "type": "object", "required": ["nodes"] } }
}
The above example shows the "nodes" object being conditionally required. You'll need to repeat this pattern for the "edges" object and combine them with allOf. I suggest making use of definitions to help make this readable.
{
"allOf": [
{ "$ref": "#/definitions/if-metadata-has-nodes-then-require-nodes-object" },
{ "$ref": "#/definitions/if-metadata-has-edges-then-require-edges-object" }
]
}

Answer 2

I would suggest moving each of your "types" into a $defs to be referenced.
{
"$defs": {
"nvObj": {
"type": "object",
"properties": {
"nv": { "type": "array", "items": { "$ref": "#/$defs/nv" } }
},
"required": ["nv"]
},
... // other defitions
}
}
(I've updated the $ref to use $defs instead of definitions as this is the new keyword since draft 7.)
Then you can put many references into a oneOf.
{
"$defs": {
... // from above
},
"type": "array",
"items": {
"oneOf": [
{ "$ref": "#/$defs/nvObj" },
... // all of the other object definitions
]
}
}
You're right to avoid if/then/else for this case. oneOf is the best bet here.