Better validation of Dataset URI during dag parse (#26389)

Previously we had the validation on the Dataset model, but we since
moved the "dag" facing class to a separate one. This adds validation to
the public class, and extends the validation to not allow space-only
strings

(cherry picked from commit bd181da)

Author: ashb

airflow/datasets/__init__.py

@@ -17,6 +17,7 @@
 from __future__ import annotations
 
 from typing import Any
+from urllib.parse import urlparse
 
 import attr
 
@@ -25,5 +26,17 @@
 class Dataset:
     """A Dataset is used for marking data dependencies between workflows."""
 
-    uri: str
+    uri: str = attr.field(validator=[attr.validators.min_len(1), attr.validators.max_len(3000)])
     extra: dict[str, Any] | None = None
+
+    @uri.validator
+    def _check_uri(self, attr, uri: str):
+        if uri.isspace():
+            raise ValueError(f'{attr.name} cannot be just whitespace')
+        try:
+            uri.encode('ascii')
+        except UnicodeEncodeError:
+            raise ValueError(f'{attr.name!r} must be ascii')
+        parsed = urlparse(uri)
+        if parsed.scheme and parsed.scheme.lower() == 'airflow':
+            raise ValueError(f'{attr.name!r} scheme `airflow` is reserved')

tests/datasets/test_dataset.py

@@ -0,0 +1,48 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+
+import pytest
+
+from airflow.datasets import Dataset
+from airflow.operators.empty import EmptyOperator
+
+
+@pytest.mark.parametrize(
+    ["uri"],
+    [
+        pytest.param("", id="empty"),
+        pytest.param("\n\t", id="whitespace"),
+        pytest.param("a" * 3001, id="too_long"),
+        pytest.param("airflow:" * 3001, id="reserved_scheme"),
+        pytest.param("😊" * 3001, id="non-ascii"),
+    ],
+)
+def test_invalid_uris(uri):
+    with pytest.raises(ValueError):
+        Dataset(uri=uri)
+
+
+def test_uri_with_scheme():
+    dataset = Dataset(uri="s3://example_dataset")
+    EmptyOperator(task_id="task1", outlets=[dataset])
+
+
+def test_uri_without_scheme():
+    dataset = Dataset(uri="example_dataset")
+    EmptyOperator(task_id="task1", outlets=[dataset])