fix subdomain_matching=False behavior

tests/test_basic.py

@@ -4,6 +4,7 @@ import typing as t
 import uuid
 import warnings
 import weakref
+from contextlib import nullcontext
 from datetime import datetime
 from datetime import timezone
 from platform import python_implementation
@@ -1483,6 +1484,48 @@ def test_request_locals():
     assert not flask.g
 
 
+@pytest.mark.parametrize(
+    ("subdomain_matching", "host_matching", "expect_base", "expect_abc", "expect_xyz"),
+    [
+        (False, False, "default", "default", "default"),
+        (True, False, "default", "abc", "<invalid>"),
+        (False, True, "default", "abc", "default"),
+    ],
+)
+def test_server_name_matching(
+    subdomain_matching: bool,
+    host_matching: bool,
+    expect_base: str,
+    expect_abc: str,
+    expect_xyz: str,
+) -> None:
+    app = flask.Flask(
+        __name__,
+        subdomain_matching=subdomain_matching,
+        host_matching=host_matching,
+        static_host="example.test" if host_matching else None,
+    )
+    app.config["SERVER_NAME"] = "example.test"
+
+    @app.route("/", defaults={"name": "default"}, host="<name>")
+    @app.route("/", subdomain="<name>", host="<name>.example.test")
+    def index(name: str) -> str:
+        return name
+
+    client = app.test_client()
+
+    r = client.get(base_url="http://example.test")
+    assert r.text == expect_base
+
+    r = client.get(base_url="http://abc.example.test")
+    assert r.text == expect_abc
+
+    with pytest.warns() if subdomain_matching else nullcontext():
+        r = client.get(base_url="http://xyz.other.test")
+
+    assert r.text == expect_xyz
+
+
 def test_server_name_subdomain():
     app = flask.Flask(__name__, subdomain_matching=True)
     client = app.test_client()