two version of R2R are here HEAD master

1 files changed, 1122 insertions, 0 deletions

diff --git a/.venv/lib/python3.12/site-packages/h11/tests/test_connection.py b/.venv/lib/python3.12/site-packages/h11/tests/test_connection.py
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+from typing import Any, cast, Dict, List, Optional, Tuple, Type
+
+import pytest
+
+from .._connection import _body_framing, _keep_alive, Connection, NEED_DATA, PAUSED
+from .._events import (
+    ConnectionClosed,
+    Data,
+    EndOfMessage,
+    Event,
+    InformationalResponse,
+    Request,
+    Response,
+)
+from .._state import (
+    CLIENT,
+    CLOSED,
+    DONE,
+    ERROR,
+    IDLE,
+    MIGHT_SWITCH_PROTOCOL,
+    MUST_CLOSE,
+    SEND_BODY,
+    SEND_RESPONSE,
+    SERVER,
+    SWITCHED_PROTOCOL,
+)
+from .._util import LocalProtocolError, RemoteProtocolError, Sentinel
+from .helpers import ConnectionPair, get_all_events, receive_and_get
+
+
+def test__keep_alive() -> None:
+    assert _keep_alive(
+        Request(method="GET", target="/", headers=[("Host", "Example.com")])
+    )
+    assert not _keep_alive(
+        Request(
+            method="GET",
+            target="/",
+            headers=[("Host", "Example.com"), ("Connection", "close")],
+        )
+    )
+    assert not _keep_alive(
+        Request(
+            method="GET",
+            target="/",
+            headers=[("Host", "Example.com"), ("Connection", "a, b, cLOse, foo")],
+        )
+    )
+    assert not _keep_alive(
+        Request(method="GET", target="/", headers=[], http_version="1.0")  # type: ignore[arg-type]
+    )
+
+    assert _keep_alive(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    assert not _keep_alive(Response(status_code=200, headers=[("Connection", "close")]))
+    assert not _keep_alive(
+        Response(status_code=200, headers=[("Connection", "a, b, cLOse, foo")])
+    )
+    assert not _keep_alive(Response(status_code=200, headers=[], http_version="1.0"))  # type: ignore[arg-type]
+
+
+def test__body_framing() -> None:
+    def headers(cl: Optional[int], te: bool) -> List[Tuple[str, str]]:
+        headers = []
+        if cl is not None:
+            headers.append(("Content-Length", str(cl)))
+        if te:
+            headers.append(("Transfer-Encoding", "chunked"))
+        return headers
+
+    def resp(
+        status_code: int = 200, cl: Optional[int] = None, te: bool = False
+    ) -> Response:
+        return Response(status_code=status_code, headers=headers(cl, te))
+
+    def req(cl: Optional[int] = None, te: bool = False) -> Request:
+        h = headers(cl, te)
+        h += [("Host", "example.com")]
+        return Request(method="GET", target="/", headers=h)
+
+    # Special cases where the headers are ignored:
+    for kwargs in [{}, {"cl": 100}, {"te": True}, {"cl": 100, "te": True}]:
+        kwargs = cast(Dict[str, Any], kwargs)
+        for meth, r in [
+            (b"HEAD", resp(**kwargs)),
+            (b"GET", resp(status_code=204, **kwargs)),
+            (b"GET", resp(status_code=304, **kwargs)),
+        ]:
+            assert _body_framing(meth, r) == ("content-length", (0,))
+
+    # Transfer-encoding
+    for kwargs in [{"te": True}, {"cl": 100, "te": True}]:
+        kwargs = cast(Dict[str, Any], kwargs)
+        for meth, r in [(None, req(**kwargs)), (b"GET", resp(**kwargs))]:  # type: ignore
+            assert _body_framing(meth, r) == ("chunked", ())
+
+    # Content-Length
+    for meth, r in [(None, req(cl=100)), (b"GET", resp(cl=100))]:  # type: ignore
+        assert _body_framing(meth, r) == ("content-length", (100,))
+
+    # No headers
+    assert _body_framing(None, req()) == ("content-length", (0,))  # type: ignore
+    assert _body_framing(b"GET", resp()) == ("http/1.0", ())
+
+
+def test_Connection_basics_and_content_length() -> None:
+    with pytest.raises(ValueError):
+        Connection("CLIENT")  # type: ignore
+
+    p = ConnectionPair()
+    assert p.conn[CLIENT].our_role is CLIENT
+    assert p.conn[CLIENT].their_role is SERVER
+    assert p.conn[SERVER].our_role is SERVER
+    assert p.conn[SERVER].their_role is CLIENT
+
+    data = p.send(
+        CLIENT,
+        Request(
+            method="GET",
+            target="/",
+            headers=[("Host", "example.com"), ("Content-Length", "10")],
+        ),
+    )
+    assert data == (
+        b"GET / HTTP/1.1\r\n" b"Host: example.com\r\n" b"Content-Length: 10\r\n\r\n"
+    )
+
+    for conn in p.conns:
+        assert conn.states == {CLIENT: SEND_BODY, SERVER: SEND_RESPONSE}
+    assert p.conn[CLIENT].our_state is SEND_BODY
+    assert p.conn[CLIENT].their_state is SEND_RESPONSE
+    assert p.conn[SERVER].our_state is SEND_RESPONSE
+    assert p.conn[SERVER].their_state is SEND_BODY
+
+    assert p.conn[CLIENT].their_http_version is None
+    assert p.conn[SERVER].their_http_version == b"1.1"
+
+    data = p.send(SERVER, InformationalResponse(status_code=100, headers=[]))  # type: ignore[arg-type]
+    assert data == b"HTTP/1.1 100 \r\n\r\n"
+
+    data = p.send(SERVER, Response(status_code=200, headers=[("Content-Length", "11")]))
+    assert data == b"HTTP/1.1 200 \r\nContent-Length: 11\r\n\r\n"
+
+    for conn in p.conns:
+        assert conn.states == {CLIENT: SEND_BODY, SERVER: SEND_BODY}
+
+    assert p.conn[CLIENT].their_http_version == b"1.1"
+    assert p.conn[SERVER].their_http_version == b"1.1"
+
+    data = p.send(CLIENT, Data(data=b"12345"))
+    assert data == b"12345"
+    data = p.send(
+        CLIENT, Data(data=b"67890"), expect=[Data(data=b"67890"), EndOfMessage()]
+    )
+    assert data == b"67890"
+    data = p.send(CLIENT, EndOfMessage(), expect=[])
+    assert data == b""
+
+    for conn in p.conns:
+        assert conn.states == {CLIENT: DONE, SERVER: SEND_BODY}
+
+    data = p.send(SERVER, Data(data=b"1234567890"))
+    assert data == b"1234567890"
+    data = p.send(SERVER, Data(data=b"1"), expect=[Data(data=b"1"), EndOfMessage()])
+    assert data == b"1"
+    data = p.send(SERVER, EndOfMessage(), expect=[])
+    assert data == b""
+
+    for conn in p.conns:
+        assert conn.states == {CLIENT: DONE, SERVER: DONE}
+
+
+def test_chunked() -> None:
+    p = ConnectionPair()
+
+    p.send(
+        CLIENT,
+        Request(
+            method="GET",
+            target="/",
+            headers=[("Host", "example.com"), ("Transfer-Encoding", "chunked")],
+        ),
+    )
+    data = p.send(CLIENT, Data(data=b"1234567890", chunk_start=True, chunk_end=True))
+    assert data == b"a\r\n1234567890\r\n"
+    data = p.send(CLIENT, Data(data=b"abcde", chunk_start=True, chunk_end=True))
+    assert data == b"5\r\nabcde\r\n"
+    data = p.send(CLIENT, Data(data=b""), expect=[])
+    assert data == b""
+    data = p.send(CLIENT, EndOfMessage(headers=[("hello", "there")]))
+    assert data == b"0\r\nhello: there\r\n\r\n"
+
+    p.send(
+        SERVER, Response(status_code=200, headers=[("Transfer-Encoding", "chunked")])
+    )
+    p.send(SERVER, Data(data=b"54321", chunk_start=True, chunk_end=True))
+    p.send(SERVER, Data(data=b"12345", chunk_start=True, chunk_end=True))
+    p.send(SERVER, EndOfMessage())
+
+    for conn in p.conns:
+        assert conn.states == {CLIENT: DONE, SERVER: DONE}
+
+
+def test_chunk_boundaries() -> None:
+    conn = Connection(our_role=SERVER)
+
+    request = (
+        b"POST / HTTP/1.1\r\n"
+        b"Host: example.com\r\n"
+        b"Transfer-Encoding: chunked\r\n"
+        b"\r\n"
+    )
+    conn.receive_data(request)
+    assert conn.next_event() == Request(
+        method="POST",
+        target="/",
+        headers=[("Host", "example.com"), ("Transfer-Encoding", "chunked")],
+    )
+    assert conn.next_event() is NEED_DATA
+
+    conn.receive_data(b"5\r\nhello\r\n")
+    assert conn.next_event() == Data(data=b"hello", chunk_start=True, chunk_end=True)
+
+    conn.receive_data(b"5\r\nhel")
+    assert conn.next_event() == Data(data=b"hel", chunk_start=True, chunk_end=False)
+
+    conn.receive_data(b"l")
+    assert conn.next_event() == Data(data=b"l", chunk_start=False, chunk_end=False)
+
+    conn.receive_data(b"o\r\n")
+    assert conn.next_event() == Data(data=b"o", chunk_start=False, chunk_end=True)
+
+    conn.receive_data(b"5\r\nhello")
+    assert conn.next_event() == Data(data=b"hello", chunk_start=True, chunk_end=True)
+
+    conn.receive_data(b"\r\n")
+    assert conn.next_event() == NEED_DATA
+
+    conn.receive_data(b"0\r\n\r\n")
+    assert conn.next_event() == EndOfMessage()
+
+
+def test_client_talking_to_http10_server() -> None:
+    c = Connection(CLIENT)
+    c.send(Request(method="GET", target="/", headers=[("Host", "example.com")]))
+    c.send(EndOfMessage())
+    assert c.our_state is DONE
+    # No content-length, so Http10 framing for body
+    assert receive_and_get(c, b"HTTP/1.0 200 OK\r\n\r\n") == [
+        Response(status_code=200, headers=[], http_version="1.0", reason=b"OK")  # type: ignore[arg-type]
+    ]
+    assert c.our_state is MUST_CLOSE
+    assert receive_and_get(c, b"12345") == [Data(data=b"12345")]
+    assert receive_and_get(c, b"67890") == [Data(data=b"67890")]
+    assert receive_and_get(c, b"") == [EndOfMessage(), ConnectionClosed()]
+    assert c.their_state is CLOSED
+
+
+def test_server_talking_to_http10_client() -> None:
+    c = Connection(SERVER)
+    # No content-length, so no body
+    # NB: no host header
+    assert receive_and_get(c, b"GET / HTTP/1.0\r\n\r\n") == [
+        Request(method="GET", target="/", headers=[], http_version="1.0"),  # type: ignore[arg-type]
+        EndOfMessage(),
+    ]
+    assert c.their_state is MUST_CLOSE
+
+    # We automatically Connection: close back at them
+    assert (
+        c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+        == b"HTTP/1.1 200 \r\nConnection: close\r\n\r\n"
+    )
+
+    assert c.send(Data(data=b"12345")) == b"12345"
+    assert c.send(EndOfMessage()) == b""
+    assert c.our_state is MUST_CLOSE
+
+    # Check that it works if they do send Content-Length
+    c = Connection(SERVER)
+    # NB: no host header
+    assert receive_and_get(c, b"POST / HTTP/1.0\r\nContent-Length: 10\r\n\r\n1") == [
+        Request(
+            method="POST",
+            target="/",
+            headers=[("Content-Length", "10")],
+            http_version="1.0",
+        ),
+        Data(data=b"1"),
+    ]
+    assert receive_and_get(c, b"234567890") == [Data(data=b"234567890"), EndOfMessage()]
+    assert c.their_state is MUST_CLOSE
+    assert receive_and_get(c, b"") == [ConnectionClosed()]
+
+
+def test_automatic_transfer_encoding_in_response() -> None:
+    # Check that in responses, the user can specify either Transfer-Encoding:
+    # chunked or no framing at all, and in both cases we automatically select
+    # the right option depending on whether the peer speaks HTTP/1.0 or
+    # HTTP/1.1
+    for user_headers in [
+        [("Transfer-Encoding", "chunked")],
+        [],
+        # In fact, this even works if Content-Length is set,
+        # because if both are set then Transfer-Encoding wins
+        [("Transfer-Encoding", "chunked"), ("Content-Length", "100")],
+    ]:
+        user_headers = cast(List[Tuple[str, str]], user_headers)
+        p = ConnectionPair()
+        p.send(
+            CLIENT,
+            [
+                Request(method="GET", target="/", headers=[("Host", "example.com")]),
+                EndOfMessage(),
+            ],
+        )
+        # When speaking to HTTP/1.1 client, all of the above cases get
+        # normalized to Transfer-Encoding: chunked
+        p.send(
+            SERVER,
+            Response(status_code=200, headers=user_headers),
+            expect=Response(
+                status_code=200, headers=[("Transfer-Encoding", "chunked")]
+            ),
+        )
+
+        # When speaking to HTTP/1.0 client, all of the above cases get
+        # normalized to no-framing-headers
+        c = Connection(SERVER)
+        receive_and_get(c, b"GET / HTTP/1.0\r\n\r\n")
+        assert (
+            c.send(Response(status_code=200, headers=user_headers))
+            == b"HTTP/1.1 200 \r\nConnection: close\r\n\r\n"
+        )
+        assert c.send(Data(data=b"12345")) == b"12345"
+
+
+def test_automagic_connection_close_handling() -> None:
+    p = ConnectionPair()
+    # If the user explicitly sets Connection: close, then we notice and
+    # respect it
+    p.send(
+        CLIENT,
+        [
+            Request(
+                method="GET",
+                target="/",
+                headers=[("Host", "example.com"), ("Connection", "close")],
+            ),
+            EndOfMessage(),
+        ],
+    )
+    for conn in p.conns:
+        assert conn.states[CLIENT] is MUST_CLOSE
+    # And if the client sets it, the server automatically echoes it back
+    p.send(
+        SERVER,
+        # no header here...
+        [Response(status_code=204, headers=[]), EndOfMessage()],  # type: ignore[arg-type]
+        # ...but oh look, it arrived anyway
+        expect=[
+            Response(status_code=204, headers=[("connection", "close")]),
+            EndOfMessage(),
+        ],
+    )
+    for conn in p.conns:
+        assert conn.states == {CLIENT: MUST_CLOSE, SERVER: MUST_CLOSE}
+
+
+def test_100_continue() -> None:
+    def setup() -> ConnectionPair:
+        p = ConnectionPair()
+        p.send(
+            CLIENT,
+            Request(
+                method="GET",
+                target="/",
+                headers=[
+                    ("Host", "example.com"),
+                    ("Content-Length", "100"),
+                    ("Expect", "100-continue"),
+                ],
+            ),
+        )
+        for conn in p.conns:
+            assert conn.client_is_waiting_for_100_continue
+        assert not p.conn[CLIENT].they_are_waiting_for_100_continue
+        assert p.conn[SERVER].they_are_waiting_for_100_continue
+        return p
+
+    # Disabled by 100 Continue
+    p = setup()
+    p.send(SERVER, InformationalResponse(status_code=100, headers=[]))  # type: ignore[arg-type]
+    for conn in p.conns:
+        assert not conn.client_is_waiting_for_100_continue
+        assert not conn.they_are_waiting_for_100_continue
+
+    # Disabled by a real response
+    p = setup()
+    p.send(
+        SERVER, Response(status_code=200, headers=[("Transfer-Encoding", "chunked")])
+    )
+    for conn in p.conns:
+        assert not conn.client_is_waiting_for_100_continue
+        assert not conn.they_are_waiting_for_100_continue
+
+    # Disabled by the client going ahead and sending stuff anyway
+    p = setup()
+    p.send(CLIENT, Data(data=b"12345"))
+    for conn in p.conns:
+        assert not conn.client_is_waiting_for_100_continue
+        assert not conn.they_are_waiting_for_100_continue
+
+
+def test_max_incomplete_event_size_countermeasure() -> None:
+    # Infinitely long headers are definitely not okay
+    c = Connection(SERVER)
+    c.receive_data(b"GET / HTTP/1.0\r\nEndless: ")
+    assert c.next_event() is NEED_DATA
+    with pytest.raises(RemoteProtocolError):
+        while True:
+            c.receive_data(b"a" * 1024)
+            c.next_event()
+
+    # Checking that the same header is accepted / rejected depending on the
+    # max_incomplete_event_size setting:
+    c = Connection(SERVER, max_incomplete_event_size=5000)
+    c.receive_data(b"GET / HTTP/1.0\r\nBig: ")
+    c.receive_data(b"a" * 4000)
+    c.receive_data(b"\r\n\r\n")
+    assert get_all_events(c) == [
+        Request(
+            method="GET", target="/", http_version="1.0", headers=[("big", "a" * 4000)]
+        ),
+        EndOfMessage(),
+    ]
+
+    c = Connection(SERVER, max_incomplete_event_size=4000)
+    c.receive_data(b"GET / HTTP/1.0\r\nBig: ")
+    c.receive_data(b"a" * 4000)
+    with pytest.raises(RemoteProtocolError):
+        c.next_event()
+
+    # Temporarily exceeding the size limit is fine, as long as its done with
+    # complete events:
+    c = Connection(SERVER, max_incomplete_event_size=5000)
+    c.receive_data(b"GET / HTTP/1.0\r\nContent-Length: 10000")
+    c.receive_data(b"\r\n\r\n" + b"a" * 10000)
+    assert get_all_events(c) == [
+        Request(
+            method="GET",
+            target="/",
+            http_version="1.0",
+            headers=[("Content-Length", "10000")],
+        ),
+        Data(data=b"a" * 10000),
+        EndOfMessage(),
+    ]
+
+    c = Connection(SERVER, max_incomplete_event_size=100)
+    # Two pipelined requests to create a way-too-big receive buffer... but
+    # it's fine because we're not checking
+    c.receive_data(
+        b"GET /1 HTTP/1.1\r\nHost: a\r\n\r\n"
+        b"GET /2 HTTP/1.1\r\nHost: b\r\n\r\n" + b"X" * 1000
+    )
+    assert get_all_events(c) == [
+        Request(method="GET", target="/1", headers=[("host", "a")]),
+        EndOfMessage(),
+    ]
+    # Even more data comes in, still no problem
+    c.receive_data(b"X" * 1000)
+    # We can respond and reuse to get the second pipelined request
+    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(EndOfMessage())
+    c.start_next_cycle()
+    assert get_all_events(c) == [
+        Request(method="GET", target="/2", headers=[("host", "b")]),
+        EndOfMessage(),
+    ]
+    # But once we unpause and try to read the next message, and find that it's
+    # incomplete and the buffer is *still* way too large, then *that's* a
+    # problem:
+    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(EndOfMessage())
+    c.start_next_cycle()
+    with pytest.raises(RemoteProtocolError):
+        c.next_event()
+
+
+def test_reuse_simple() -> None:
+    p = ConnectionPair()
+    p.send(
+        CLIENT,
+        [Request(method="GET", target="/", headers=[("Host", "a")]), EndOfMessage()],
+    )
+    p.send(
+        SERVER,
+        [
+            Response(status_code=200, headers=[(b"transfer-encoding", b"chunked")]),
+            EndOfMessage(),
+        ],
+    )
+    for conn in p.conns:
+        assert conn.states == {CLIENT: DONE, SERVER: DONE}
+        conn.start_next_cycle()
+
+    p.send(
+        CLIENT,
+        [
+            Request(method="DELETE", target="/foo", headers=[("Host", "a")]),
+            EndOfMessage(),
+        ],
+    )
+    p.send(
+        SERVER,
+        [
+            Response(status_code=404, headers=[(b"transfer-encoding", b"chunked")]),
+            EndOfMessage(),
+        ],
+    )
+
+
+def test_pipelining() -> None:
+    # Client doesn't support pipelining, so we have to do this by hand
+    c = Connection(SERVER)
+    assert c.next_event() is NEED_DATA
+    # 3 requests all bunched up
+    c.receive_data(
+        b"GET /1 HTTP/1.1\r\nHost: a.com\r\nContent-Length: 5\r\n\r\n"
+        b"12345"
+        b"GET /2 HTTP/1.1\r\nHost: a.com\r\nContent-Length: 5\r\n\r\n"
+        b"67890"
+        b"GET /3 HTTP/1.1\r\nHost: a.com\r\n\r\n"
+    )
+    assert get_all_events(c) == [
+        Request(
+            method="GET",
+            target="/1",
+            headers=[("Host", "a.com"), ("Content-Length", "5")],
+        ),
+        Data(data=b"12345"),
+        EndOfMessage(),
+    ]
+    assert c.their_state is DONE
+    assert c.our_state is SEND_RESPONSE
+
+    assert c.next_event() is PAUSED
+
+    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(EndOfMessage())
+    assert c.their_state is DONE
+    assert c.our_state is DONE
+
+    c.start_next_cycle()
+
+    assert get_all_events(c) == [
+        Request(
+            method="GET",
+            target="/2",
+            headers=[("Host", "a.com"), ("Content-Length", "5")],
+        ),
+        Data(data=b"67890"),
+        EndOfMessage(),
+    ]
+    assert c.next_event() is PAUSED
+    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(EndOfMessage())
+    c.start_next_cycle()
+
+    assert get_all_events(c) == [
+        Request(method="GET", target="/3", headers=[("Host", "a.com")]),
+        EndOfMessage(),
+    ]
+    # Doesn't pause this time, no trailing data
+    assert c.next_event() is NEED_DATA
+    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(EndOfMessage())
+
+    # Arrival of more data triggers pause
+    assert c.next_event() is NEED_DATA
+    c.receive_data(b"SADF")
+    assert c.next_event() is PAUSED
+    assert c.trailing_data == (b"SADF", False)
+    # If EOF arrives while paused, we don't see that either:
+    c.receive_data(b"")
+    assert c.trailing_data == (b"SADF", True)
+    assert c.next_event() is PAUSED
+    c.receive_data(b"")
+    assert c.next_event() is PAUSED
+    # Can't call receive_data with non-empty buf after closing it
+    with pytest.raises(RuntimeError):
+        c.receive_data(b"FDSA")
+
+
+def test_protocol_switch() -> None:
+    for (req, deny, accept) in [
+        (
+            Request(
+                method="CONNECT",
+                target="example.com:443",
+                headers=[("Host", "foo"), ("Content-Length", "1")],
+            ),
+            Response(status_code=404, headers=[(b"transfer-encoding", b"chunked")]),
+            Response(status_code=200, headers=[(b"transfer-encoding", b"chunked")]),
+        ),
+        (
+            Request(
+                method="GET",
+                target="/",
+                headers=[("Host", "foo"), ("Content-Length", "1"), ("Upgrade", "a, b")],
+            ),
+            Response(status_code=200, headers=[(b"transfer-encoding", b"chunked")]),
+            InformationalResponse(status_code=101, headers=[("Upgrade", "a")]),
+        ),
+        (
+            Request(
+                method="CONNECT",
+                target="example.com:443",
+                headers=[("Host", "foo"), ("Content-Length", "1"), ("Upgrade", "a, b")],
+            ),
+            Response(status_code=404, headers=[(b"transfer-encoding", b"chunked")]),
+            # Accept CONNECT, not upgrade
+            Response(status_code=200, headers=[(b"transfer-encoding", b"chunked")]),
+        ),
+        (
+            Request(
+                method="CONNECT",
+                target="example.com:443",
+                headers=[("Host", "foo"), ("Content-Length", "1"), ("Upgrade", "a, b")],
+            ),
+            Response(status_code=404, headers=[(b"transfer-encoding", b"chunked")]),
+            # Accept Upgrade, not CONNECT
+            InformationalResponse(status_code=101, headers=[("Upgrade", "b")]),
+        ),
+    ]:
+
+        def setup() -> ConnectionPair:
+            p = ConnectionPair()
+            p.send(CLIENT, req)
+            # No switch-related state change stuff yet; the client has to
+            # finish the request before that kicks in
+            for conn in p.conns:
+                assert conn.states[CLIENT] is SEND_BODY
+            p.send(CLIENT, [Data(data=b"1"), EndOfMessage()])
+            for conn in p.conns:
+                assert conn.states[CLIENT] is MIGHT_SWITCH_PROTOCOL
+            assert p.conn[SERVER].next_event() is PAUSED
+            return p
+
+        # Test deny case
+        p = setup()
+        p.send(SERVER, deny)
+        for conn in p.conns:
+            assert conn.states == {CLIENT: DONE, SERVER: SEND_BODY}
+        p.send(SERVER, EndOfMessage())
+        # Check that re-use is still allowed after a denial
+        for conn in p.conns:
+            conn.start_next_cycle()
+
+        # Test accept case
+        p = setup()
+        p.send(SERVER, accept)
+        for conn in p.conns:
+            assert conn.states == {CLIENT: SWITCHED_PROTOCOL, SERVER: SWITCHED_PROTOCOL}
+            conn.receive_data(b"123")
+            assert conn.next_event() is PAUSED
+            conn.receive_data(b"456")
+            assert conn.next_event() is PAUSED
+            assert conn.trailing_data == (b"123456", False)
+
+        # Pausing in might-switch, then recovery
+        # (weird artificial case where the trailing data actually is valid
+        # HTTP for some reason, because this makes it easier to test the state
+        # logic)
+        p = setup()
+        sc = p.conn[SERVER]
+        sc.receive_data(b"GET / HTTP/1.0\r\n\r\n")
+        assert sc.next_event() is PAUSED
+        assert sc.trailing_data == (b"GET / HTTP/1.0\r\n\r\n", False)
+        sc.send(deny)
+        assert sc.next_event() is PAUSED
+        sc.send(EndOfMessage())
+        sc.start_next_cycle()
+        assert get_all_events(sc) == [
+            Request(method="GET", target="/", headers=[], http_version="1.0"),  # type: ignore[arg-type]
+            EndOfMessage(),
+        ]
+
+        # When we're DONE, have no trailing data, and the connection gets
+        # closed, we report ConnectionClosed(). When we're in might-switch or
+        # switched, we don't.
+        p = setup()
+        sc = p.conn[SERVER]
+        sc.receive_data(b"")
+        assert sc.next_event() is PAUSED
+        assert sc.trailing_data == (b"", True)
+        p.send(SERVER, accept)
+        assert sc.next_event() is PAUSED
+
+        p = setup()
+        sc = p.conn[SERVER]
+        sc.receive_data(b"")
+        assert sc.next_event() is PAUSED
+        sc.send(deny)
+        assert sc.next_event() == ConnectionClosed()
+
+        # You can't send after switching protocols, or while waiting for a
+        # protocol switch
+        p = setup()
+        with pytest.raises(LocalProtocolError):
+            p.conn[CLIENT].send(
+                Request(method="GET", target="/", headers=[("Host", "a")])
+            )
+        p = setup()
+        p.send(SERVER, accept)
+        with pytest.raises(LocalProtocolError):
+            p.conn[SERVER].send(Data(data=b"123"))
+
+
+def test_close_simple() -> None:
+    # Just immediately closing a new connection without anything having
+    # happened yet.
+    for (who_shot_first, who_shot_second) in [(CLIENT, SERVER), (SERVER, CLIENT)]:
+
+        def setup() -> ConnectionPair:
+            p = ConnectionPair()
+            p.send(who_shot_first, ConnectionClosed())
+            for conn in p.conns:
+                assert conn.states == {
+                    who_shot_first: CLOSED,
+                    who_shot_second: MUST_CLOSE,
+                }
+            return p
+
+        # You can keep putting b"" into a closed connection, and you keep
+        # getting ConnectionClosed() out:
+        p = setup()
+        assert p.conn[who_shot_second].next_event() == ConnectionClosed()
+        assert p.conn[who_shot_second].next_event() == ConnectionClosed()
+        p.conn[who_shot_second].receive_data(b"")
+        assert p.conn[who_shot_second].next_event() == ConnectionClosed()
+        # Second party can close...
+        p = setup()
+        p.send(who_shot_second, ConnectionClosed())
+        for conn in p.conns:
+            assert conn.our_state is CLOSED
+            assert conn.their_state is CLOSED
+        # But trying to receive new data on a closed connection is a
+        # RuntimeError (not ProtocolError, because the problem here isn't
+        # violation of HTTP, it's violation of physics)
+        p = setup()
+        with pytest.raises(RuntimeError):
+            p.conn[who_shot_second].receive_data(b"123")
+        # And receiving new data on a MUST_CLOSE connection is a ProtocolError
+        p = setup()
+        p.conn[who_shot_first].receive_data(b"GET")
+        with pytest.raises(RemoteProtocolError):
+            p.conn[who_shot_first].next_event()
+
+
+def test_close_different_states() -> None:
+    req = [
+        Request(method="GET", target="/foo", headers=[("Host", "a")]),
+        EndOfMessage(),
+    ]
+    resp = [
+        Response(status_code=200, headers=[(b"transfer-encoding", b"chunked")]),
+        EndOfMessage(),
+    ]
+
+    # Client before request
+    p = ConnectionPair()
+    p.send(CLIENT, ConnectionClosed())
+    for conn in p.conns:
+        assert conn.states == {CLIENT: CLOSED, SERVER: MUST_CLOSE}
+
+    # Client after request
+    p = ConnectionPair()
+    p.send(CLIENT, req)
+    p.send(CLIENT, ConnectionClosed())
+    for conn in p.conns:
+        assert conn.states == {CLIENT: CLOSED, SERVER: SEND_RESPONSE}
+
+    # Server after request -> not allowed
+    p = ConnectionPair()
+    p.send(CLIENT, req)
+    with pytest.raises(LocalProtocolError):
+        p.conn[SERVER].send(ConnectionClosed())
+    p.conn[CLIENT].receive_data(b"")
+    with pytest.raises(RemoteProtocolError):
+        p.conn[CLIENT].next_event()
+
+    # Server after response
+    p = ConnectionPair()
+    p.send(CLIENT, req)
+    p.send(SERVER, resp)
+    p.send(SERVER, ConnectionClosed())
+    for conn in p.conns:
+        assert conn.states == {CLIENT: MUST_CLOSE, SERVER: CLOSED}
+
+    # Both after closing (ConnectionClosed() is idempotent)
+    p = ConnectionPair()
+    p.send(CLIENT, req)
+    p.send(SERVER, resp)
+    p.send(CLIENT, ConnectionClosed())
+    p.send(SERVER, ConnectionClosed())
+    p.send(CLIENT, ConnectionClosed())
+    p.send(SERVER, ConnectionClosed())
+
+    # In the middle of sending -> not allowed
+    p = ConnectionPair()
+    p.send(
+        CLIENT,
+        Request(
+            method="GET", target="/", headers=[("Host", "a"), ("Content-Length", "10")]
+        ),
+    )
+    with pytest.raises(LocalProtocolError):
+        p.conn[CLIENT].send(ConnectionClosed())
+    p.conn[SERVER].receive_data(b"")
+    with pytest.raises(RemoteProtocolError):
+        p.conn[SERVER].next_event()
+
+
+# Receive several requests and then client shuts down their side of the
+# connection; we can respond to each
+def test_pipelined_close() -> None:
+    c = Connection(SERVER)
+    # 2 requests then a close
+    c.receive_data(
+        b"GET /1 HTTP/1.1\r\nHost: a.com\r\nContent-Length: 5\r\n\r\n"
+        b"12345"
+        b"GET /2 HTTP/1.1\r\nHost: a.com\r\nContent-Length: 5\r\n\r\n"
+        b"67890"
+    )
+    c.receive_data(b"")
+    assert get_all_events(c) == [
+        Request(
+            method="GET",
+            target="/1",
+            headers=[("host", "a.com"), ("content-length", "5")],
+        ),
+        Data(data=b"12345"),
+        EndOfMessage(),
+    ]
+    assert c.states[CLIENT] is DONE
+    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(EndOfMessage())
+    assert c.states[SERVER] is DONE
+    c.start_next_cycle()
+    assert get_all_events(c) == [
+        Request(
+            method="GET",
+            target="/2",
+            headers=[("host", "a.com"), ("content-length", "5")],
+        ),
+        Data(data=b"67890"),
+        EndOfMessage(),
+        ConnectionClosed(),
+    ]
+    assert c.states == {CLIENT: CLOSED, SERVER: SEND_RESPONSE}
+    c.send(Response(status_code=200, headers=[]))  # type: ignore[arg-type]
+    c.send(EndOfMessage())
+    assert c.states == {CLIENT: CLOSED, SERVER: MUST_CLOSE}
+    c.send(ConnectionClosed())
+    assert c.states == {CLIENT: CLOSED, SERVER: CLOSED}
+
+
+def test_sendfile() -> None:
+    class SendfilePlaceholder:
+        def __len__(self) -> int:
+            return 10
+
+    placeholder = SendfilePlaceholder()
+
+    def setup(
+        header: Tuple[str, str], http_version: str
+    ) -> Tuple[Connection, Optional[List[bytes]]]:
+        c = Connection(SERVER)
+        receive_and_get(
+            c, "GET / HTTP/{}\r\nHost: a\r\n\r\n".format(http_version).encode("ascii")
+        )
+        headers = []
+        if header:
+            headers.append(header)
+        c.send(Response(status_code=200, headers=headers))
+        return c, c.send_with_data_passthrough(Data(data=placeholder))  # type: ignore
+
+    c, data = setup(("Content-Length", "10"), "1.1")
+    assert data == [placeholder]  # type: ignore
+    # Raises an error if the connection object doesn't think we've sent
+    # exactly 10 bytes
+    c.send(EndOfMessage())
+
+    _, data = setup(("Transfer-Encoding", "chunked"), "1.1")
+    assert placeholder in data  # type: ignore
+    data[data.index(placeholder)] = b"x" * 10  # type: ignore
+    assert b"".join(data) == b"a\r\nxxxxxxxxxx\r\n"  # type: ignore
+
+    c, data = setup(None, "1.0")  # type: ignore
+    assert data == [placeholder]  # type: ignore
+    assert c.our_state is SEND_BODY
+
+
+def test_errors() -> None:
+    # After a receive error, you can't receive
+    for role in [CLIENT, SERVER]:
+        c = Connection(our_role=role)
+        c.receive_data(b"gibberish\r\n\r\n")
+        with pytest.raises(RemoteProtocolError):
+            c.next_event()
+        # Now any attempt to receive continues to raise
+        assert c.their_state is ERROR
+        assert c.our_state is not ERROR
+        print(c._cstate.states)
+        with pytest.raises(RemoteProtocolError):
+            c.next_event()
+        # But we can still yell at the client for sending us gibberish
+        if role is SERVER:
+            assert (
+                c.send(Response(status_code=400, headers=[]))  # type: ignore[arg-type]
+                == b"HTTP/1.1 400 \r\nConnection: close\r\n\r\n"
+            )
+
+    # After an error sending, you can no longer send
+    # (This is especially important for things like content-length errors,
+    # where there's complex internal state being modified)
+    def conn(role: Type[Sentinel]) -> Connection:
+        c = Connection(our_role=role)
+        if role is SERVER:
+            # Put it into the state where it *could* send a response...
+            receive_and_get(c, b"GET / HTTP/1.0\r\n\r\n")
+            assert c.our_state is SEND_RESPONSE
+        return c
+
+    for role in [CLIENT, SERVER]:
+        if role is CLIENT:
+            # This HTTP/1.0 request won't be detected as bad until after we go
+            # through the state machine and hit the writing code
+            good = Request(method="GET", target="/", headers=[("Host", "example.com")])
+            bad = Request(
+                method="GET",
+                target="/",
+                headers=[("Host", "example.com")],
+                http_version="1.0",
+            )
+        elif role is SERVER:
+            good = Response(status_code=200, headers=[])  # type: ignore[arg-type,assignment]
+            bad = Response(status_code=200, headers=[], http_version="1.0")  # type: ignore[arg-type,assignment]
+        # Make sure 'good' actually is good
+        c = conn(role)
+        c.send(good)
+        assert c.our_state is not ERROR
+        # Do that again, but this time sending 'bad' first
+        c = conn(role)
+        with pytest.raises(LocalProtocolError):
+            c.send(bad)
+        assert c.our_state is ERROR
+        assert c.their_state is not ERROR
+        # Now 'good' is not so good
+        with pytest.raises(LocalProtocolError):
+            c.send(good)
+
+        # And check send_failed() too
+        c = conn(role)
+        c.send_failed()
+        assert c.our_state is ERROR
+        assert c.their_state is not ERROR
+        # This is idempotent
+        c.send_failed()
+        assert c.our_state is ERROR
+        assert c.their_state is not ERROR
+
+
+def test_idle_receive_nothing() -> None:
+    # At one point this incorrectly raised an error
+    for role in [CLIENT, SERVER]:
+        c = Connection(role)
+        assert c.next_event() is NEED_DATA
+
+
+def test_connection_drop() -> None:
+    c = Connection(SERVER)
+    c.receive_data(b"GET /")
+    assert c.next_event() is NEED_DATA
+    c.receive_data(b"")
+    with pytest.raises(RemoteProtocolError):
+        c.next_event()
+
+
+def test_408_request_timeout() -> None:
+    # Should be able to send this spontaneously as a server without seeing
+    # anything from client
+    p = ConnectionPair()
+    p.send(SERVER, Response(status_code=408, headers=[(b"connection", b"close")]))
+
+
+# This used to raise IndexError
+def test_empty_request() -> None:
+    c = Connection(SERVER)
+    c.receive_data(b"\r\n")
+    with pytest.raises(RemoteProtocolError):
+        c.next_event()
+
+
+# This used to raise IndexError
+def test_empty_response() -> None:
+    c = Connection(CLIENT)
+    c.send(Request(method="GET", target="/", headers=[("Host", "a")]))
+    c.receive_data(b"\r\n")
+    with pytest.raises(RemoteProtocolError):
+        c.next_event()
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        b"\x00",
+        b"\x20",
+        b"\x16\x03\x01\x00\xa5",  # Typical start of a TLS Client Hello
+    ],
+)
+def test_early_detection_of_invalid_request(data: bytes) -> None:
+    c = Connection(SERVER)
+    # Early detection should occur before even receiving a `\r\n`
+    c.receive_data(data)
+    with pytest.raises(RemoteProtocolError):
+        c.next_event()
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        b"\x00",
+        b"\x20",
+        b"\x16\x03\x03\x00\x31",  # Typical start of a TLS Server Hello
+    ],
+)
+def test_early_detection_of_invalid_response(data: bytes) -> None:
+    c = Connection(CLIENT)
+    # Early detection should occur before even receiving a `\r\n`
+    c.receive_data(data)
+    with pytest.raises(RemoteProtocolError):
+        c.next_event()
+
+
+# This used to give different headers for HEAD and GET.
+# The correct way to handle HEAD is to put whatever headers we *would* have
+# put if it were a GET -- even though we know that for HEAD, those headers
+# will be ignored.
+def test_HEAD_framing_headers() -> None:
+    def setup(method: bytes, http_version: bytes) -> Connection:
+        c = Connection(SERVER)
+        c.receive_data(
+            method + b" / HTTP/" + http_version + b"\r\n" + b"Host: example.com\r\n\r\n"
+        )
+        assert type(c.next_event()) is Request
+        assert type(c.next_event()) is EndOfMessage
+        return c
+
+    for method in [b"GET", b"HEAD"]:
+        # No Content-Length, HTTP/1.1 peer, should use chunked
+        c = setup(method, b"1.1")
+        assert (
+            c.send(Response(status_code=200, headers=[])) == b"HTTP/1.1 200 \r\n"  # type: ignore[arg-type]
+            b"Transfer-Encoding: chunked\r\n\r\n"
+        )
+
+        # No Content-Length, HTTP/1.0 peer, frame with connection: close
+        c = setup(method, b"1.0")
+        assert (
+            c.send(Response(status_code=200, headers=[])) == b"HTTP/1.1 200 \r\n"  # type: ignore[arg-type]
+            b"Connection: close\r\n\r\n"
+        )
+
+        # Content-Length + Transfer-Encoding, TE wins
+        c = setup(method, b"1.1")
+        assert (
+            c.send(
+                Response(
+                    status_code=200,
+                    headers=[
+                        ("Content-Length", "100"),
+                        ("Transfer-Encoding", "chunked"),
+                    ],
+                )
+            )
+            == b"HTTP/1.1 200 \r\n"
+            b"Transfer-Encoding: chunked\r\n\r\n"
+        )
+
+
+def test_special_exceptions_for_lost_connection_in_message_body() -> None:
+    c = Connection(SERVER)
+    c.receive_data(
+        b"POST / HTTP/1.1\r\n" b"Host: example.com\r\n" b"Content-Length: 100\r\n\r\n"
+    )
+    assert type(c.next_event()) is Request
+    assert c.next_event() is NEED_DATA
+    c.receive_data(b"12345")
+    assert c.next_event() == Data(data=b"12345")
+    c.receive_data(b"")
+    with pytest.raises(RemoteProtocolError) as excinfo:
+        c.next_event()
+    assert "received 5 bytes" in str(excinfo.value)
+    assert "expected 100" in str(excinfo.value)
+
+    c = Connection(SERVER)
+    c.receive_data(
+        b"POST / HTTP/1.1\r\n"
+        b"Host: example.com\r\n"
+        b"Transfer-Encoding: chunked\r\n\r\n"
+    )
+    assert type(c.next_event()) is Request
+    assert c.next_event() is NEED_DATA
+    c.receive_data(b"8\r\n012345")
+    assert c.next_event().data == b"012345"  # type: ignore
+    c.receive_data(b"")
+    with pytest.raises(RemoteProtocolError) as excinfo:
+        c.next_event()
+    assert "incomplete chunked read" in str(excinfo.value)