Domain name string type

pydantic_extra_types/domain.py

@@ -0,0 +1,5 @@
+from pydantic import StringConstraints
+from typing import Annotated
+
+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 +1,35 @@
+from pydantic_extra_types.domain import DomainStr
+from pydantic import BaseModel, ValidationError
+import pytest
+
+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_over_253_characters(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