How do I use check-jsonschema in my application?#

check-jsonschema is only a CLI application, not a library for import and use within python applications.

It is powered by the jsonschema library. Most users looking to integrate JSON Schema in their applications should look into using jsonschema directly.

It is also safe and supported to run check-jsonschema in a process, invoking it with correct CLI arguments and checking the output.

Python Subprocess Invocation#

The following snippet for python applications ensures that you are running with the current interpreter and runs the equivalent of check-jsonschema --version:

import subprocess
import sys

result = subprocess.check_output([sys.executable, "-m", "check_jsonschema", "--version"])

Non-Python Considerations#

When invoking check-jsonschema from another language in a process, make sure you control the installation of check-jsonschema. For example, the following Ruby snippet may look safe:

require 'json'

raw_data = `check-jsonschema -o JSON --schemafile #{schema} #{instance}`
data = JSON.parse(raw_data)

However, it could be problematic if run in environments with different versions of check-jsonschema installed.

One way to handle this is to install check-jsonschema into a virtualenv and always invoke it explicitly from that virtualenv, as in

require 'json'

raw_data = `venv/bin/check-jsonschema -o JSON --schemafile #{schema} #{instance}`
data = JSON.parse(raw_data)

GitHub Actions Workflows#

Using Self-Hosted Runners#

The GitHub Actions Workflow schema defined in SchemaStore does not allow all valid workflows, but rather a specific subset of workflows.

For self-hosted runners, the schema will reject runs-on with an unrecognized string value. In order to use a custom runner runs-on value, put it into an array with self-hosted, like so:

name: self-hosted job

    runs-on: [self-hosted, spot-self-hosted]
      - run: echo 'hi'