Add host_subcomponent property (#1159)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

CHANGES/1159.feature.rst

@@ -0,0 +1,3 @@
+Added :attr:`~yarl.URL.host_subcomponent` which returns the :rfc:`3986#section-3.2.2` host subcomponent -- by :user:`bdraco`.
+
+The only current practical difference between :attr:`~yarl.URL.raw_host` and :attr:`~yarl.URL.host_subcomponent` is that IPv6 addresses are returned bracketed.

docs/api.rst

@@ -191,7 +191,22 @@ There are two kinds of properties: *decoded* and *encoded* (with
 
       >>> URL('http://хост.домен').raw_host
       'xn--n1agdj.xn--d1acufc'
+      >>> URL('http://[::1]').raw_host
+      '::1'
+
+.. attribute:: URL.host_subcomponent
+
+   :rfc:`3986#section-3.2.2` host subcomponent part of URL, ``None`` for relative URLs
+   (:ref:`yarl-api-relative-urls`).
+
+   .. doctest::
+
+      >>> URL('http://хост.домен').host_subcomponent
+      'xn--n1agdj.xn--d1acufc'
+      >>> URL('http://[::1]').host_subcomponent
+      '[::1]'
 
+   .. versionadded:: 1.13
 
 .. attribute:: URL.port
 

docs/spelling_wordlist.txt

@@ -42,6 +42,7 @@ runtimes
 sdist
 subclass
 subclasses
+subcomponent
 svetlov
 uncompiled
 v1

tests/test_url.py

@@ -176,6 +176,24 @@ def test_raw_host():
     assert url.raw_host == url._val.hostname
 
 
+@pytest.mark.parametrize(
+    ("host"),
+    [
+        ("example.com"),
+        ("[::1]"),
+        ("xn--gnter-4ya.com"),
+    ],
+)
+def test_host_subcomponent(host: str):
+    url = URL(f"http://{host}")
+    assert url.host_subcomponent == host
+
+
+def test_host_subcomponent_return_idna_encoded_host():
+    url = URL("http://оун-упа.укр")
+    assert url.host_subcomponent == "xn----8sb1bdhvc.xn--j1amh"
+
+
 def test_raw_host_non_ascii():
     url = URL("http://оун-упа.укр")
     assert "xn----8sb1bdhvc.xn--j1amh" == url.raw_host

yarl/_url.py

@@ -647,6 +647,8 @@ def raw_host(self) -> Union[str, None]:
 
         None for relative URLs.
 
+        When working with IPv6 addresses, use the `host_subcomponent` property instead
+        as it will return the host subcomponent with brackets.
         """
         # Use host instead of hostname for sake of shortness
         # May add .hostname prop later
@@ -660,16 +662,35 @@ def host(self) -> Union[str, None]:
         None for relative URLs.
 
         """
-        raw = self.raw_host
-        if raw is None:
+        if (raw := self.raw_host) is None:
             return None
-        if "%" in raw:
-            # Hack for scoped IPv6 addresses like
-            # fe80::2%Перевірка
-            # presence of '%' sign means only IPv6 address, so idna is useless.
+        if raw and raw[-1].isdigit() or ":" in raw:
+            # IP addresses are never IDNA encoded
             return raw
         return _idna_decode(raw)
 
+    @cached_property
+    def host_subcomponent(self) -> Union[str, None]:
+        """Return the host subcomponent part of URL.
+
+        None for relative URLs.
+
+        https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
+
+        `IP-literal = "[" ( IPv6address / IPvFuture  ) "]"`
+
+        Examples:
+        - `http://example.com:8080` -> `example.com`
+        - `http://example.com:80` -> `example.com`
+        - `https://127.0.0.1:8443` -> `127.0.0.1`
+        - `https://[::1]:8443` -> `[::1]`
+        - `http://[::1]` -> `[::1]`
+
+        """
+        if (raw := self.raw_host) is None:
+            return None
+        return f"[{raw}]" if ":" in raw else raw
+
     @cached_property
     def port(self) -> Union[int, None]:
         """Port part of URL, with scheme-based fallback.
@@ -953,7 +974,8 @@ def _encode_host(cls, host: str, human: bool = False) -> str:
             # - 127.0.0.1 (last character is a digit)
             # - 2001:db8::ff00:42:8329 (contains a colon)
             # - 2001:db8::ff00:42:8329%eth0 (contains a colon)
-            # - [2001:db8::ff00:42:8329] (contains a colon)
+            # - [2001:db8::ff00:42:8329] (contains a colon -- brackets should
+            #                             have been removed before it gets here)
             # Rare IP Address formats are not supported per:
             # https://datatracker.ietf.org/doc/html/rfc3986#section-7.4
             #