Source: oafp 35a922f9. See documentation baseline for availability and verification.

JSON Schema

Validate an input map against a schema file, or obtain the schema from a command that prints JSON:

oafp in=json file=data.json jsonschema=schema.json out=json
oafp in=json file=data.json jsonschemacmd="cat schema.json" out=json

Use one schema source per invocation. Validation supports input maps and schema maps. Successful validation returns {"valid":true,"errors":null}. Invalid data returns {"valid":false,"errors":[...]} as ordinary output; it does not by itself cause a nonzero exit status. Invalid schemas, unsupported dialects, unresolved references and invalid options are command errors.

With OpenAF’s Ajv 8 upgrade, errors are the compiled validator’s raw Ajv v8 errors: instancePath is a JSON Pointer such as /age, alongside schemaPath, keyword, params and usually message. Consumers of the old dataPath or exact v6 message wording must adapt. Messages commonly use “must” instead of “should”.

Options

jsonschemaoptions accepts a JSON or SLON map (or a map when calling oafp(params)):

oafp in=json file=data.json jsonschema=schema.json jsonschemaoptions='(format: full)' out=json
oafp in=json file=data.json jsonschema=schema.json jsonschemaoptions='{"allErrors":false,"strict":true}' out=json

Options are merged with {allErrors:true}; explicit values override it. Existing defaults remain: collect all errors, use fast format validation, allow non-strict schemas, and leave default insertion, type coercion and $data references disabled. To enable them explicitly, use useDefaults:true, coerceTypes:true or $data:true. Mutating options can change the input while validation runs, though the output remains the validation result.

OpenAF installs standard formats automatically. format:full selects full format checks; format:false disables format validation. Unknown formats normally cause a compilation error. OpenAF handles compatibility aliases for legacy Ajv options and rejects removed options with an explanation. See OpenAF’s JSON Schema guide for the supported API and compatibility details.

OpenAF initializes its schema engine once per process: the first schemaInit call wins. In a long-running process invoking oafp(params) repeatedly, choose consistent options before the first validation. Separate CLI invocations initialize independently.

Schema drafts

On OpenAF with the Ajv 8 upgrade, the root $schema selects draft-07, draft-2019-09 or draft-2020-12. Omitting $schema uses draft-07. For example, save this as schema.json and validate {"values":["first",2]}:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "required": ["values"],
  "properties": {
    "values": {
      "type": "array",
      "prefixItems": [{"type":"string"},{"type":"integer"}],
      "items": false
    }
  }
}

Older OpenAF runtimes do not gain newer draft support by updating oafp alone. Use canonical draft URIs; unsupported drafts fail rather than silently falling back. External references must already be registered in the OpenAF process; oafp does not fetch remote schemas automatically.

Generation

# Infer a draft-07 schema from an example map
oafp in=json file=data.json jsonschemagen=true out=json
# Try to generate sample data from a schema map
oafp in=jsonschema file=schema.json out=json

jsonschemagen delegates to OpenAF’s schema generator and continues to emit draft-07. in=jsonschema delegates to the sample generator, not Ajv validation. It is a best-effort generator and does not guarantee valid samples for all constraints or newer draft keywords. jsonschemaoptions applies only to validation with jsonschema or jsonschemacmd. Validate generated samples explicitly when correctness matters.

Read this guide locally with oafp help=jsonschema (or out=raw for plain Markdown).