jtd-validate: Validate JSON Typedef schemas from the shell

JSON Type Definition, aka RFC8927, is an easy-to-learn, standardized way to define a schema for JSON data. You can use JSON Typedef to portably validate data across programming languages, create dummy data, generate code, and more.

jtd-validate is a tool that checks whether an input is valid against a JSON Typedef schema. It's meant to be convenient to use in shell scripts.

# user.jtd.json has the following contents:
#
# {
#   "properties": {
#     "name": { "type": "string" }
#   }
# }
echo '{ "name": 123 }' | jtd-validate user.jtd.json | jq

{
  "instancePath": "/name",
  "schemaPath": "/properties/name/type"
}

Installation

On macOS, you can install jtd-validate via Homebrew:

brew install jsontypedef/jsontypedef/jtd-validate

For all other platforms, you can download and extract the binary yourself from the latest release.

Usage

To invoke jtd-validate, you need a schema to validate and an input or set of inputs to validate. Then, you can use either of these invocations:

# Both of these do the same thing
cat path/to/input_or_inputs.json | jtd-validate path/to/schema.json
jtd-validate path/to/schema.json path/to/input_or_inputs.json

jtd-validate will do the following things:

1. It will validate each of your input(s) against the schema.
2. If there aren't any validation errors, it will print nothing and exit with status code 0.
3. If there are validation errors, it will print each of the validation errors on their own line, and exit with status code 1. jtd-validate will do this on the first bad input it sees.

To customize this behavior, you have a few options:

• The --max-depth (-d) option sets the maximum number of refs to follow during validation (useful if your schema may have cyclical definitions).

• The --max-errors (-e) option sets the maximum number of errors to return. This can improve jtd-validate's performance if your inputs or schemas are large.

• The --quiet (-q) option disables output. This can be useful if you're using jtd-validate in an if in your shell script, such as:

  if jtd-validate -q <(echo "$schema") <(echo "$input"); then
    echo "your input is good"
  else
    echo "your input is not good"
  fi

  This works thanks to the fact that jtd-validate outputs a non-zero status code if there are validation errors. The --quiet option saves you the trouble of redirecting jtd-validate to /dev/null if you don't want to output JSON Typedef validation errors.