🐛 Raises meaningful exception when IPv6 URL is malformed (#1512)

Co-authored-by: J. Nick Koston <[email protected]>

Author: MaelPic

CHANGES/1512.bugfix.rst

@@ -0,0 +1,10 @@
+Started raising a :exc:`ValueError` exception raised for corrupted
+IPv6 URL values.
+
+These fixes the issue where exception :exc:`IndexError` was
+leaking from the internal code because of not being handled and
+transformed into a user-facing error. The problem was happening
+under the following conditions: empty IPv6 URL, brackets in
+reverse order.
+
+-- by :user:`MaelPic`.

tests/test_url.py

@@ -338,9 +338,26 @@ def test_ipv6_missing_right_bracket() -> None:
         URL("http://[1dec:0:0:0::1/")
 
 
-def test_ipv4_brackets_not_allowed() -> None:
-    with pytest.raises(ValueError, match="An IPv4 address cannot be in brackets"):
-        URL("http://[127.0.0.1]/")
+@pytest.mark.parametrize(
+    "url",
+    (
+        "http://[]/",
+        "http://[1]/",
+        "http://[127.0.0.1]/",
+        "http://]1dec:0:0:0::1[/",
+    ),
+    ids=(
+        "empty-IPv6-like-URL",
+        "no-colons-in-IPv6",
+        "IPv4-inside-brackets",
+        "brackets-in-reversed-order",
+    ),
+)
+def test_ipv6_invalid_url(url: str) -> None:
+    with pytest.raises(
+        ValueError, match="The IPv6 content between brackets is not valid"
+    ):
+        URL(url)
 
 
 def test_ipfuture_brackets_not_allowed() -> None:

yarl/_parse.py

@@ -69,11 +69,11 @@ def split_url(url: str) -> SplitURLType:
             # Valid bracketed hosts are defined in
             # https://www.rfc-editor.org/rfc/rfc3986#page-49
             # https://url.spec.whatwg.org/
-            if bracketed_host[0] == "v":
+            if bracketed_host and bracketed_host[0] == "v":
                 if not re.match(r"\Av[a-fA-F0-9]+\..+\Z", bracketed_host):
                     raise ValueError("IPvFuture address is invalid")
             elif ":" not in bracketed_host:
-                raise ValueError("An IPv4 address cannot be in brackets")
+                raise ValueError("The IPv6 content between brackets is not valid")
     if has_hash:
         url, _, fragment = url.partition("#")
     if has_question_mark: