How do I declare dependencies of nested properties?

Question

I am using Draft-04 of JSON Schema. Is it possible to set dependencies based on the existence of a sub-property, and/or depend on a sub-property? Or am I forced to use allOf to manage these kinds of dependencies?

I have the following (you can play with it at https://repl.it/@neverendingqs/JsonSchemaNestedDependencies):

'use strict';

const Ajv = require('ajv');
const assert = require('chai').assert;

// Using ajv@5.5.1
const draft4 = require('ajv/lib/refs/json-schema-draft-04.json');

const schema = {
  "$schema": "http://json-schema.org/draft-04/schema#",
  "type": "object",
  "properties": {
    "foo1": {
      "type": [ "object" ],
      "properties": {
        "bar1": { "type": "string" }
      }
    },
    "foo2": {
      "type": [ "object" ],
      "properties": {
        "bar2": { "type": "string" }
      }
    }
  },
  "dependencies": {
    "foo1": ["foo2"],
    
    // Is this possible?
    "foo1/bar1": ["foo2/bar2"]
  }
};

const schemaName = 'my-schema';

const ajv = new Ajv();
ajv.addMetaSchema(draft4);
ajv.addSchema(schema, schemaName);


assert.isTrue(
  ajv.validate(schemaName, {
    "foo1": { "bar1": "a" },
    "foo2": { "bar2": "c" }
  }),
  ajv.errorsText(ajv.errors, { dataVar: 'event' })
);

assert.isFalse(ajv.validate(schemaName, {
  "foo1": { "bar1": "a" }
}));

// Looking to cause this to pass
assert.isFalse(ajv.validate(schemaName, {
  "foo1": { "bar1": "a" },
  "foo2": {}
}));

I am looking for Draft-04 answers, but am also interested in answers using later specifications.

EDIT: Draft-04 refers to the specifications under http://json-schema.org/specification-links.html#draft-4. Specifically, I am using dependencies which is defined under the Validation specification (https://datatracker.ietf.org/doc/html/draft-fge-json-schema-validation-00)

score 1 · Answer 1 · answered Mar 16 '18 at 02:43

It would be nice if dependencies supported a JSON Pointer, but it doesn't. You have to solve this using implication. I've broken it down using definitions to help make it more clear what is happening.

First I define schemas for the cases we are checking for: /foo1/bar1 is present and /foo2/bar2 is present. With those two definitions, I use anyOf to say either /foo1/bar1 is not present, or /foo2/bar2 is required. In other words, /foo1/bar1 implies /foo2/bar2.

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "type": "object",
  "properties": {
    "foo1": {
      "type": [ "object" ],
      "properties": {
        "bar1": { "type": "string" }
      }
    },
    "foo2": {
      "type": [ "object" ],
      "properties": {
        "bar2": { "type": "string" }
      }
    }
  },
  "allOf": [{ "$ref": "#/definitions/foo1-bar1-implies-foo2-bar2" }],
  "dependencies": {
    "foo1": ["foo2"]
  },
  "definitions": {
    "foo1-bar1-implies-foo2-bar2": {
      "anyOf": [
        { "not": { "$ref": "#/definitions/foo1-bar1" } },
        { "$ref": "#/definitions/foo2-bar2" }
      ]
    },
    "foo1-bar1": {
      "properties": {
        "foo1": { "required": ["bar1"] }
      },
      "required": ["foo1"]
    },
    "foo2-bar2": {
      "properties": {
        "foo2": { "required": ["bar2"] }
      },
      "required": ["foo2"]
    }
  }
}

score 0 · Answer 2 · answered Mar 15 '18 at 09:25

0

It's pretty tricky to achive this in draft 4! You can use required in draft 4 to make a property required in an object...

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "type": "object",
  "properties": {
    "foo1": {
      "type": [ "object" ],
      "properties": {
        "bar1": { "type": "string" }
      }
    },
    "foo2": {
      "type": [ "object" ],
      "properties": {
        "bar2": { "type": "string" }
      },
      "required": [ "bar2" ]
    }
  }
}

I can't make this change re-run in repl.it, but I checked it against the schema you want to fail using https://www.jsonschemavalidator.net

For draft-7 (which is latest at the time of writing), you can use if, then, else, which might be more intuative, but I think you'd still need to use required to achive this, as you want the subschema in if to pass or fail. Keywords for Applying Subschemas Conditionally.

answered Mar 15 '18 at 09:25

Relequestual

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I tried `{ "foo1": {}, "foo2": {} }`. It passes for the schema in the question, but fails for the schema in your answer. (Is your answer to draft 4 basically "no"?) – neverendingqs Mar 15 '18 at 15:24
I didn't anticipate that was JSON you would want to pass. I don't think I fully understand your requirements. Could you maybe write some sudo logic to add to your question? `dependencies` isn't a thing in JSON Schema, so your use of it in your example schema has no meaning to me. – Relequestual Mar 15 '18 at 15:35
I have added an edit around `dependencies` and which specification it appears in. I don't have a good example I can post here yet that's different / anonymized enough from what I'm looking into. – neverendingqs Mar 15 '18 at 17:23
Sorry, it seems like in all the times I've read through JSON Schema, I've missed `dependencies`. Looks like other answers my be more what you're looking for. – Relequestual Mar 16 '18 at 09:39

How do I declare dependencies of nested properties?

2 Answers2