airflow/serialization/json_schema.py

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"""jsonschema for validating serialized DAG and operator."""

import pkgutil
from typing import Iterable

import jsonschema

from airflow.exceptions import AirflowException
from airflow.settings import json
from airflow.typing_compat import Protocol


class Validator(Protocol):
    """
    This class is only used for TypeChecking (for IDEs, mypy, pylint, etc)
    due to the way ``Draft7Validator`` is created. They are created or do not inherit
    from proper classes. Hence you can not have ``type: Draft7Validator``.
    """

    # pylint: disable=unused-argument
    def is_valid(self, instance) -> bool:
        """Check if the instance is valid under the current schema"""
        ...

    def validate(self, instance) -> None:
        """Check if the instance is valid under the current schema, raising validation error if not"""
        ...

    def iter_errors(self, instance) -> Iterable[jsonschema.exceptions.ValidationError]:
        """Lazily yield each of the validation errors in the given instance"""
        ...


def load_dag_schema_dict() -> dict:
    """Load & return Json Schema for DAG as Python dict"""
    schema_file_name = 'schema.json'
    schema_file = pkgutil.get_data(__name__, schema_file_name)

    if schema_file is None:
        raise AirflowException(f"Schema file {schema_file_name} does not exists")

    schema = json.loads(schema_file.decode())
    return schema


def load_dag_schema() -> Validator:
    """Load & Validate Json Schema for DAG"""
    schema = load_dag_schema_dict()
    return jsonschema.Draft7Validator(schema)