Warlock

Common errors

• warlock.core.InvalidOperation: Unable to set 'name' to '5'

  cause An attempt was made to assign a value (e.g., an integer) to a property that is defined as a different type (e.g., string) in the JSON schema.
  fix Ensure the assigned value's type matches the `type` specified in the JSON schema for that property. For example, assign a string for a `string` type property: `obj.name = 'New Name'`.

• warlock.core.InvalidOperation: Unable to set 'overlord' to 'Bears'

  cause This error typically occurs when the schema for the Warlock model includes `'additionalProperties': False`, preventing the creation of properties not explicitly defined in the schema.
  fix If the property is intended to exist, add it to the `properties` section of your JSON schema. If arbitrary properties should be allowed, set `'additionalProperties': True` in your schema.

• ModuleNotFoundError: No module named 'warlock'

  cause The `warlock` library is not installed in the current Python environment or the environment's path is not correctly configured.
  fix Install the library using pip: `pip install warlock`. If using a virtual environment, ensure it is activated.

Warnings

• breaking Warlock 1.3.1 and later versions (including 2.x) upgraded their `jsonschema` dependency to be compatible with `jsonschema` v3+, supporting JSON Schema Draft 7. If your project relies on validation against Draft 4 of JSON Schema, you must explicitly pin your `jsonschema` dependency to `<3`.
  Fix: If your project requires JSON Schema Draft 4, explicitly add `jsonschema<3` to your project's dependencies alongside Warlock. Otherwise, ensure you are using a compatible `jsonschema` version (v3 or later).
• gotcha Attempting to assign a value to an object property that does not conform to the schema's type or constraints (e.g., assigning an `int` to a `string` property) will raise a `warlock.core.InvalidOperation` error.
  Fix: Always ensure that values assigned to Warlock object properties match the type and constraints defined in the JSON Schema. Catch `warlock.core.InvalidOperation` for robust error handling.
• gotcha If your JSON schema includes `'additionalProperties': False`, attempting to set any property on a Warlock object that is not explicitly defined in the schema will raise a `warlock.core.InvalidOperation` error.
  Fix: Review your schema to ensure all expected properties are defined, or set `'additionalProperties': True` in your schema if you intend to allow arbitrary properties. Catch `warlock.core.InvalidOperation` if this behavior is expected.

Install

• pip install warlock Install latest version

Imports

• warlock

  import warlock

  The primary library import is straightforward.
• model_factory

  import warlock
  Country = warlock.model_factory(schema)

  Models are created using the `model_factory` function from the top-level `warlock` module.

Quickstart

This quickstart demonstrates how to define a JSON Schema, create a Warlock model using `warlock.model_factory`, instantiate an object, modify its properties with automatic validation, and generate a JSON Patch document to track changes.

import warlock

# Define your JSON schema
schema = {
    'name': 'Country',
    'properties': {
        'name': {'type': 'string'},
        'abbreviation': {'type': 'string'},
        'population': {'type': 'integer'}
    },
    'additionalProperties': False
}

# Create a Warlock model factory from the schema
Country = warlock.model_factory(schema)

# Create an object using your model
sweden = Country(name='Sweden', abbreviation='SE', population=9453000)

print(f"Country Name: {sweden.name}")
print(f"Population: {sweden.population}")

# Update a property, which is validated against the schema
sweden.population = 10416000
print(f"New Population: {sweden.population}")

# Generate a JSON Patch document to track changes
sweden.population = 9453000 # Reset for patch example
sweden.name = 'Swedish Kingdom'
patch_document = sweden.patch
print(f"Generated JSON Patch: {patch_document}")