Fix error pointer on linebreaks

CHANGES/7468.bugfix

@@ -0,0 +1 @@
+Fixed output of parsing errors on `\n`. -- by :user:`Dreamsorcerer`

aiohttp/_http_parser.pyx

@@ -548,8 +548,8 @@ cdef class HttpParser:
                 else:
                     after = cparser.llhttp_get_error_pos(self._cparser)
                     before = data[:after - <char*>self.py_buf.buf]
-                    after_b = after.split(b"\n", 1)[0]
-                    before = before.rsplit(b"\n", 1)[-1]
+                    after_b = after.split(b"\r\n", 1)[0]
+                    before = before.rsplit(b"\r\n", 1)[-1]
                     data = before + after_b
                     pointer = " " * (len(repr(before))-1) + "^"
                     ex = parser_error_from_errno(self._cparser, data, pointer)

tests/test_http_parser.py

@@ -131,7 +131,27 @@ def test_invalid_character(loop: Any, protocol: Any, request: Any) -> None:
     error_detail = re.escape(
         r""":
 
-    b'Set-Cookie: abc\x01def\r'
+    b'Set-Cookie: abc\x01def'
+                     ^"""
+    )
+    with pytest.raises(http_exceptions.BadHttpMessage, match=error_detail):
+        parser.feed_data(text)
+
+
+@pytest.mark.skipif(NO_EXTENSIONS, reason="Only tests C parser.")
+def test_invalid_linebreak(loop: Any, protocol: Any, request: Any) -> None:
+    parser = HttpRequestParserC(
+        protocol,
+        loop,
+        2**16,
+        max_line_size=8190,
+        max_field_size=8190,
+    )
+    text = b"GET /world HTTP/1.1\r\nHost: 127.0.0.1\n\r\n"
+    error_detail = re.escape(
+        r""":
+
+    b'Host: 127.0.0.1\n'
                      ^"""
     )
     with pytest.raises(http_exceptions.BadHttpMessage, match=error_detail):