Domain name string type

pydantic_extra_types/domain.py

@@ -0,0 +1,15 @@
+import sys
+
+if sys.version_info < (3, 9):  # pragma: no cover
+    from typing_extensions import Annotated  # pragma: no cover
+else:
+    from typing import Annotated  # pragma: no cover
+
+from pydantic import StringConstraints
+
+DomainStr = Annotated[
+    str,
+    StringConstraints(
+        strip_whitespace=True, to_lower=True, min_length=1, max_length=253, pattern=r'^([a-z0-9-]+(\.[a-z0-9-]+)+)$'
+    ),
+]

tests/test_domain.py

@@ -0,0 +1,40 @@
+import pytest
+from pydantic import BaseModel, ValidationError
+
+from pydantic_extra_types.domain import DomainStr
+
+
+class MyModel(BaseModel):
+    domain: DomainStr
+
+
+very_long_domains_list = [
+    'sub1.sub2.sub3.sub4.sub5.sub6.sub7.sub8.sub9.sub10.sub11.sub12.sub13.sub14.sub15.sub16.sub17.sub18.sub19.sub20.sub21.sub22.sub23.sub24.sub25.sub26.sub27.sub28.sub29.sub30.sub31.sub32.sub33.extremely-long-domain-name-example-to-test-the-253-character-limit.com',
+    'a-very-very-long-subdomain-name-that-continues-forever-and-ever-testing-the-length-limit-of-domains-to-make-sure-it-reaches-beyond-the-maximum-allowed-for-experimentation-and-testing-purposes.extremely-extended-domain-name-example-for-253-characters-limit.net',
+]
+
+
+@pytest.mark.parametrize('domain', ['a.com', 'x.com'])
+def test_single_letter_domain(domain: str):
+    MyModel.model_validate({'domain': domain})
+
+
+@pytest.mark.parametrize('domain', very_long_domains_list)
+def test_domains_over_253_characters(domain: str):
+    assert len(domain) > 253
+    try:
+        MyModel.model_validate({'domain': domain})
+        raise Exception('Domain did not throw an error for having over 253 characters')
+    except ValidationError:
+        # An error is expected on this test
+        pass
+
+
+@pytest.mark.parametrize('domain', [''])
+def test_domains_having_less_than_one_character(domain: str):
+    try:
+        MyModel.model_validate({'domain': domain})
+        raise Exception('Domain did not throw an error for having less than 1 character')
+    except ValidationError:
+        # An error is expected on this test
+        pass