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import contextlib
import copy
import json
import warnings
from typing import TYPE_CHECKING, Any, Dict, ItemsView, MutableMapping, Optional, ValuesView
from airflow.exceptions import AirflowException, ParamValidationError
from airflow.utils.context import Context
from airflow.utils.types import NOTSET, ArgNotSet
if TYPE_CHECKING:
from airflow.models.dag import DAG
[docs]class Param:
"""
Class to hold the default value of a Param and rule set to do the validations. Without the rule set
it always validates and returns the default value.
:param default: The value this Param object holds
:param description: Optional help text for the Param
:param schema: The validation schema of the Param, if not given then all kwargs except
default & description will form the schema
"""
[docs] CLASS_IDENTIFIER = '__class'
def __init__(self, default: Any = NOTSET, description: Optional[str] = None, **kwargs):
if default is not NOTSET:
self._warn_if_not_json(default)
self.value = default
self.description = description
self.schema = kwargs.pop('schema') if 'schema' in kwargs else kwargs
[docs] def __copy__(self) -> "Param":
return Param(self.value, self.description, schema=self.schema)
@staticmethod
def _warn_if_not_json(value):
try:
json.dumps(value)
except Exception:
warnings.warn(
"The use of non-json-serializable params is deprecated and will be removed in "
"a future release",
DeprecationWarning,
)
[docs] def resolve(self, value: Any = NOTSET, suppress_exception: bool = False) -> Any:
"""
Runs the validations and returns the Param's final value.
May raise ValueError on failed validations, or TypeError
if no value is passed and no value already exists.
We first check that value is json-serializable; if not, warn.
In future release we will require the value to be json-serializable.
:param value: The value to be updated for the Param
:param suppress_exception: To raise an exception or not when the validations fails.
If true and validations fails, the return value would be None.
"""
import jsonschema
from jsonschema import FormatChecker
from jsonschema.exceptions import ValidationError
if value is not NOTSET:
self._warn_if_not_json(value)
final_val = value if value is not NOTSET else self.value
if isinstance(final_val, ArgNotSet):
if suppress_exception:
return None
raise ParamValidationError("No value passed and Param has no default value")
try:
jsonschema.validate(final_val, self.schema, format_checker=FormatChecker())
except ValidationError as err:
if suppress_exception:
return None
raise ParamValidationError(err) from None
self.value = final_val
return final_val
[docs] def dump(self) -> dict:
"""Dump the Param as a dictionary"""
out_dict = {self.CLASS_IDENTIFIER: f'{self.__module__}.{self.__class__.__name__}'}
out_dict.update(self.__dict__)
return out_dict
@property
[docs] def has_value(self) -> bool:
return self.value is not NOTSET
[docs]class ParamsDict(MutableMapping[str, Any]):
"""
Class to hold all params for dags or tasks. All the keys are strictly string and values
are converted into Param's object if they are not already. This class is to replace param's
dictionary implicitly and ideally not needed to be used directly.
"""
[docs] __slots__ = ['__dict', 'suppress_exception']
def __init__(self, dict_obj: Optional[Dict] = None, suppress_exception: bool = False):
"""
:param dict_obj: A dict or dict like object to init ParamsDict
:param suppress_exception: Flag to suppress value exceptions while initializing the ParamsDict
"""
params_dict: Dict[str, Param] = {}
dict_obj = dict_obj or {}
for k, v in dict_obj.items():
if not isinstance(v, Param):
params_dict[k] = Param(v)
else:
params_dict[k] = v
self.__dict = params_dict
self.suppress_exception = suppress_exception
[docs] def __copy__(self) -> "ParamsDict":
return ParamsDict(self.__dict, self.suppress_exception)
[docs] def __deepcopy__(self, memo: Optional[Dict[int, Any]]) -> "ParamsDict":
return ParamsDict(copy.deepcopy(self.__dict, memo), self.suppress_exception)
[docs] def __contains__(self, o: object) -> bool:
return o in self.__dict
[docs] def __len__(self) -> int:
return len(self.__dict)
[docs] def __delitem__(self, v: str) -> None:
del self.__dict[v]
[docs] def __iter__(self):
return iter(self.__dict)
[docs] def __setitem__(self, key: str, value: Any) -> None:
"""
Override for dictionary's ``setitem`` method. This method make sure that all values are of
Param's type only.
:param key: A key which needs to be inserted or updated in the dict
:param value: A value which needs to be set against the key. It could be of any
type but will be converted and stored as a Param object eventually.
"""
if isinstance(value, Param):
param = value
elif key in self.__dict:
param = self.__dict[key]
try:
param.resolve(value=value, suppress_exception=self.suppress_exception)
except ParamValidationError as ve:
raise ParamValidationError(f'Invalid input for param {key}: {ve}') from None
else:
# if the key isn't there already and if the value isn't of Param type create a new Param object
param = Param(value)
self.__dict[key] = param
[docs] def __getitem__(self, key: str) -> Any:
"""
Override for dictionary's ``getitem`` method. After fetching the key, it would call the
resolve method as well on the Param object.
:param key: The key to fetch
"""
param = self.__dict[key]
return param.resolve(suppress_exception=self.suppress_exception)
[docs] def get_param(self, key: str) -> Param:
"""Get the internal :class:`.Param` object for this key"""
return self.__dict[key]
[docs] def items(self):
return ItemsView(self.__dict)
[docs] def values(self):
return ValuesView(self.__dict)
[docs] def update(self, *args, **kwargs) -> None:
if len(args) == 1 and not kwargs and isinstance(args[0], ParamsDict):
return super().update(args[0].__dict)
super().update(*args, **kwargs)
[docs] def dump(self) -> Dict[str, Any]:
"""Dumps the ParamsDict object as a dictionary, while suppressing exceptions"""
return {k: v.resolve(suppress_exception=True) for k, v in self.items()}
[docs] def validate(self) -> Dict[str, Any]:
"""Validates & returns all the Params object stored in the dictionary"""
resolved_dict = {}
try:
for k, v in self.items():
resolved_dict[k] = v.resolve(suppress_exception=self.suppress_exception)
except ParamValidationError as ve:
raise ParamValidationError(f'Invalid input for param {k}: {ve}') from None
return resolved_dict
[docs]class DagParam:
"""
Class that represents a DAG run parameter & binds a simple Param object to a name within a DAG instance,
so that it can be resolved during the run time via ``{{ context }}`` dictionary. The ideal use case of
this class is to implicitly convert args passed to a method which is being decorated by ``@dag`` keyword.
It can be used to parameterize your dags. You can overwrite its value by setting it on conf
when you trigger your DagRun.
This can also be used in templates by accessing ``{{context.params}}`` dictionary.
**Example**:
with DAG(...) as dag:
EmailOperator(subject=dag.param('subject', 'Hi from Airflow!'))
:param current_dag: Dag being used for parameter.
:param name: key value which is used to set the parameter
:param default: Default value used if no parameter was set.
"""
def __init__(self, current_dag: "DAG", name: str, default: Any = NOTSET):
if default is not NOTSET:
current_dag.params[name] = default
self._name = name
self._default = default
[docs] def resolve(self, context: Context) -> Any:
"""Pull DagParam value from DagRun context. This method is run during ``op.execute()``."""
with contextlib.suppress(KeyError):
return context['dag_run'].conf[self._name]
if self._default is not NOTSET:
return self._default
with contextlib.suppress(KeyError):
return context['params'][self._name]
raise AirflowException(f'No value could be resolved for parameter {self._name}')
