Change dataset URI validation to raise warning instead of error in Airflow 2.9 (apache#39670)

Closes: apache#39486

# Context

Valid DAGs that worked in Airflow 2.8.x  and had tasks with outlets with specific URIs, such as `Dataset("postgres://postgres:5432/postgres.dbt.stg_customers")`, stopped working in Airflow 2.9.0 & Airflow 2.9.1, after apache#37005 was merged.

This was a breaking change in an Airflow minor version. We should avoid this.

Airflow < 3.0 should raise a warning, and from Airflow 3.0, we can make errors by default. We can have a feature flag to allow users who want to see this in advance to enable errors in Airflow 2. x, but this should not be the default behaviour.

The DAGs should continue working on Airflow 2.x minor/micro releases without errors (unless the user opts in via configuration).

# How to reproduce

By running the following DAG with `apache-airflow==2.9.1` and `apache-airflow-providers-postgres==5.11.0`, as an example:
```
from datetime import datetime

from airflow import DAG
from airflow.datasets import Dataset
from airflow.operators.empty import EmptyOperator



with DAG(dag_id='empty_operator_example', start_date=datetime(2022, 1, 1), schedule_interval=None) as dag:

    task1 = EmptyOperator(
        task_id='empty_task1',
        dag=dag,
        outlets=[Dataset("postgres://postgres:5432/postgres.dbt.stg_customers")]
    )

    task2 = EmptyOperator(
        task_id='empty_task2',
        dag=dag
    )

    task1 >> task2
```

Causes to the exception:
```
Broken DAG: [/usr/local/airflow/dags/example_issue.py]
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/airflow/datasets/__init__.py", line 81, in _sanitize_uri
    parsed = normalizer(parsed)
             ^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/airflow/providers/postgres/datasets/postgres.py", line 34, in sanitize_uri
    raise ValueError("URI format postgres:// must contain database, schema, and table names")
ValueError: URI format postgres:// must contain database, schema, and table names
```

# About the changes introduced

This PR introduces the following:

1. A boolean configuration within `[core],` named `strict_dataset_uri_validation,` which should be `False` by default.

2. When this configuration is `False,` Airflow should raise a warning saying:
```
From Airflow 3, Airflow will be more strict with Dataset URIs, and the URI xx will no longer be valid. Please, follow the expected standard as documented in XX.
```

3. If this configuration is `True,` Airflow should raise the exception, as it does now in Airflow 2.9.0 and 2.9.1

4. From Airflow 3.0, we change this configuration to be `True` by default.

Author: tatiana

airflow/config_templates/config.yml

@@ -464,6 +464,15 @@ core:
       sensitive: true
       default: ~
       example: '{"some_param": "some_value"}'
+    strict_dataset_uri_validation:
+      description: |
+        Dataset URI validation should raise an exception if it is not compliant with AIP-60.
+        By default this configuration is false, meaning that Airflow 2.x only warns the user.
+        In Airflow 3, this configuration will be enabled by default.
+      default: "False"
+      example: ~
+      version_added: 2.9.2
+      type: boolean
     database_access_isolation:
       description: (experimental) Whether components should use Airflow Internal API for DB connectivity.
       version_added: 2.6.0

airflow/datasets/__init__.py

@@ -27,6 +27,9 @@
 if TYPE_CHECKING:
     from urllib.parse import SplitResult
 
+
+from airflow.configuration import conf
+
 __all__ = ["Dataset", "DatasetAll", "DatasetAny"]
 
 
@@ -87,7 +90,18 @@ def _sanitize_uri(uri: str) -> str:
         fragment="",  # Ignore any fragments.
     )
     if (normalizer := _get_uri_normalizer(normalized_scheme)) is not None:
-        parsed = normalizer(parsed)
+        try:
+            parsed = normalizer(parsed)
+        except ValueError as exception:
+            if conf.getboolean("core", "strict_dataset_uri_validation", fallback=False):
+                raise exception
+            else:
+                warnings.warn(
+                    f"The dataset URI {uri} is not AIP-60 compliant. "
+                    f"In Airflow 3, this will raise an exception. More information: {repr(exception)}",
+                    UserWarning,
+                    stacklevel=3,
+                )
     return urllib.parse.urlunsplit(parsed)
 
 

tests/datasets/test_dataset.py

@@ -20,15 +20,17 @@
 import os
 from collections import defaultdict
 from typing import Callable
+from unittest.mock import patch
 
 import pytest
 from sqlalchemy.sql import select
 
-from airflow.datasets import BaseDataset, Dataset, DatasetAll, DatasetAny
+from airflow.datasets import BaseDataset, Dataset, DatasetAll, DatasetAny, _sanitize_uri
 from airflow.models.dataset import DatasetDagRunQueue, DatasetModel
 from airflow.models.serialized_dag import SerializedDagModel
 from airflow.operators.empty import EmptyOperator
 from airflow.serialization.serialized_objects import BaseSerialization, SerializedDAG
+from tests.test_utils.config import conf_vars
 
 
 @pytest.fixture
@@ -441,3 +443,31 @@ def test_datasets_expression_error(expression: Callable[[], None], error: str) -
     with pytest.raises(TypeError) as info:
         expression()
     assert str(info.value) == error
+
+
+def mock_get_uri_normalizer(normalized_scheme):
+    def normalizer(uri):
+        raise ValueError("Incorrect URI format")
+
+    return normalizer
+
+
+@patch("airflow.datasets._get_uri_normalizer", mock_get_uri_normalizer)
+@patch("airflow.datasets.warnings.warn")
+def test__sanitize_uri_raises_warning(mock_warn):
+    _sanitize_uri("postgres://localhost:5432/database.schema.table")
+    msg = mock_warn.call_args.args[0]
+    assert "The dataset URI postgres://localhost:5432/database.schema.table is not AIP-60 compliant." in msg
+    assert (
+        "In Airflow 3, this will raise an exception. More information: ValueError('Incorrect URI format')"
+        in msg
+    )
+
+
+@patch("airflow.datasets._get_uri_normalizer", mock_get_uri_normalizer)
+@conf_vars({("core", "strict_dataset_uri_validation"): "True"})
+def test__sanitize_uri_raises_exception():
+    with pytest.raises(ValueError) as e_info:
+        _sanitize_uri("postgres://localhost:5432/database.schema.table")
+    assert isinstance(e_info.value, ValueError)
+    assert str(e_info.value) == "Incorrect URI format"