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"""Triggering DAG runs APIs."""
import json
from datetime import datetime
from typing import List, Optional, Union

from airflow.exceptions import DagNotFound, DagRunAlreadyExists
from airflow.models import DagBag, DagModel, DagRun
from airflow.utils import timezone
from airflow.utils.state import State


def _trigger_dag(
        dag_id: str,
        dag_bag: DagBag,
        dag_run: DagModel,
        run_id: Optional[str],
        conf: Optional[Union[dict, str]],
        execution_date: Optional[datetime],
        replace_microseconds: bool,
) -> List[DagRun]:  # pylint: disable=too-many-arguments
    """Triggers DAG run.

    :param dag_id: DAG ID
    :param dag_bag: DAG Bag model
    :param dag_run: DAG Run model
    :param run_id: ID of the dag_run
    :param conf: configuration
    :param execution_date: date of execution
    :param replace_microseconds: whether microseconds should be zeroed
    :return: list of triggered dags
    """
    dag = dag_bag.get_dag(dag_id)  # prefetch dag if it is stored serialized

    if dag_id not in dag_bag.dags:
        raise DagNotFound("Dag id {} not found".format(dag_id))

    execution_date = execution_date if execution_date else timezone.utcnow()

    if not timezone.is_localized(execution_date):
        raise ValueError("The execution_date should be localized")

    if replace_microseconds:
        execution_date = execution_date.replace(microsecond=0)

    if dag.default_args and 'start_date' in dag.default_args:
        min_dag_start_date = dag.default_args["start_date"]
        if min_dag_start_date and execution_date < min_dag_start_date:
            raise ValueError(
                "The execution_date [{0}] should be >= start_date [{1}] from DAG's default_args".format(
                    execution_date.isoformat(),
                    min_dag_start_date.isoformat()))

    if not run_id:
        run_id = "manual__{0}".format(execution_date.isoformat())

    dag_run_id = dag_run.find(dag_id=dag_id, run_id=run_id)
    if dag_run_id:
        raise DagRunAlreadyExists("Run id {} already exists for dag id {}".format(
            run_id,
            dag_id
        ))

    run_conf = None
    if conf:
        if isinstance(conf, dict):
            run_conf = conf
        else:
            run_conf = json.loads(conf)

    triggers = []
    dags_to_trigger = []
    dags_to_trigger.append(dag)
    while dags_to_trigger:
        dag = dags_to_trigger.pop()
        trigger = dag.create_dagrun(
            run_id=run_id,
            execution_date=execution_date,
            state=State.RUNNING,
            conf=run_conf,
            external_trigger=True,
        )
        triggers.append(trigger)
        if dag.subdags:
            dags_to_trigger.extend(dag.subdags)
    return triggers


def trigger_dag(
        dag_id: str,
        run_id: Optional[str] = None,
        conf: Optional[Union[dict, str]] = None,
        execution_date: Optional[datetime] = None,
        replace_microseconds: bool = True,
) -> Optional[DagRun]:
    """Triggers execution of DAG specified by dag_id

    :param dag_id: DAG ID
    :param run_id: ID of the dag_run
    :param conf: configuration
    :param execution_date: date of execution
    :param replace_microseconds: whether microseconds should be zeroed
    :return: first dag run triggered - even if more than one Dag Runs were triggered or None
    """
    dag_model = DagModel.get_current(dag_id)
    if dag_model is None:
        raise DagNotFound("Dag id {} not found in DagModel".format(dag_id))

    def read_store_serialized_dags():
        from airflow.configuration import conf
        return conf.getboolean('core', 'store_serialized_dags')
    dagbag = DagBag(
        dag_folder=dag_model.fileloc,
        store_serialized_dags=read_store_serialized_dags()
    )
    dag_run = DagRun()
    triggers = _trigger_dag(
        dag_id=dag_id,
        dag_run=dag_run,
        dag_bag=dagbag,
        run_id=run_id,
        conf=conf,
        execution_date=execution_date,
        replace_microseconds=replace_microseconds,
    )

    return triggers[0] if triggers else None

@@ -3128,41 +3128,12 @@
  = %5B
-%5D%0A    dags_to_trigger.append(dag)
+dag%5D
 %0A   

Replace List creation in experimental/trigger_dag.py (#7511)