Switch event classes to dataclasses

The _EventBundle used previously dynamically creates the Event
classes, which makes typing hard. As the Event classes are now stable
the dynamic creation isn't required, and as h11 supports Python3.6+
dataclasses can be used instead.

This now makes the Events frozen (and almost imutable) which better
matches the intended API. In turn it requires the `object.__setattr__`
usage and the alteration to the
`_clean_up_response_headers_for_sending` method.

This change also improves the performance a little, using the
benchmark,

Before: 6.7k requests/sec
After: 6.9k requests/sec

Notes:

The test response-header changes are required as the previous version
would mutate the response object.

The init for the Data event is required as slots and defaults aren't
possible with dataclasses.

Author: pgjones

h11/_connection.py

@@ -483,7 +483,7 @@ def send_with_data_passthrough(self, event):
             raise LocalProtocolError("Can't send data when our state is ERROR")
         try:
             if type(event) is Response:
-                self._clean_up_response_headers_for_sending(event)
+                event = self._clean_up_response_headers_for_sending(event)
             # We want to call _process_event before calling the writer,
             # because if someone tries to do something invalid then this will
             # give a sensible error message, while our writers all just assume
@@ -528,8 +528,7 @@ def send_failed(self):
     #
     # This function's *only* responsibility is making sure headers are set up
     # right -- everything downstream just looks at the headers. There are no
-    # side channels. It mutates the response event in-place (but not the
-    # response.headers list object).
+    # side channels.
     def _clean_up_response_headers_for_sending(self, response):
         assert type(response) is Response
 
@@ -582,4 +581,9 @@ def _clean_up_response_headers_for_sending(self, response):
             connection.add(b"close")
             headers = set_comma_header(headers, b"connection", sorted(connection))
 
-        response.headers = headers
+        return Response(
+            headers=headers,
+            status_code=response.status_code,
+            http_version=response.http_version,
+            reason=response.reason,
+        )

h11/_events.py

@@ -6,13 +6,17 @@
 # Don't subclass these. Stuff will break.
 
 import re
+from abc import ABC
+from dataclasses import dataclass, field
+from typing import Any, cast, Dict, List, Tuple, Union
 
-from . import _headers
 from ._abnf import request_target
+from ._headers import Headers, normalize_and_validate
 from ._util import bytesify, LocalProtocolError, validate
 
 # Everything in __all__ gets re-exported as part of the h11 public API.
 __all__ = [
+    "Event",
     "Request",
     "InformationalResponse",
     "Response",
@@ -24,72 +28,16 @@
 request_target_re = re.compile(request_target.encode("ascii"))
 
 
-class _EventBundle:
-    _fields = []
-    _defaults = {}
-
-    def __init__(self, **kwargs):
-        _parsed = kwargs.pop("_parsed", False)
-        allowed = set(self._fields)
-        for kwarg in kwargs:
-            if kwarg not in allowed:
-                raise TypeError(
-                    "unrecognized kwarg {} for {}".format(
-                        kwarg, self.__class__.__name__
-                    )
-                )
-        required = allowed.difference(self._defaults)
-        for field in required:
-            if field not in kwargs:
-                raise TypeError(
-                    "missing required kwarg {} for {}".format(
-                        field, self.__class__.__name__
-                    )
-                )
-        self.__dict__.update(self._defaults)
-        self.__dict__.update(kwargs)
-
-        # Special handling for some fields
-
-        if "headers" in self.__dict__:
-            self.headers = _headers.normalize_and_validate(
-                self.headers, _parsed=_parsed
-            )
-
-        if not _parsed:
-            for field in ["method", "target", "http_version", "reason"]:
-                if field in self.__dict__:
-                    self.__dict__[field] = bytesify(self.__dict__[field])
-
-            if "status_code" in self.__dict__:
-                if not isinstance(self.status_code, int):
-                    raise LocalProtocolError("status code must be integer")
-                # Because IntEnum objects are instances of int, but aren't
-                # duck-compatible (sigh), see gh-72.
-                self.status_code = int(self.status_code)
-
-        self._validate()
-
-    def _validate(self):
-        pass
-
-    def __repr__(self):
-        name = self.__class__.__name__
-        kwarg_strs = [
-            "{}={}".format(field, self.__dict__[field]) for field in self._fields
-        ]
-        kwarg_str = ", ".join(kwarg_strs)
-        return "{}({})".format(name, kwarg_str)
-
-    # Useful for tests
-    def __eq__(self, other):
-        return self.__class__ == other.__class__ and self.__dict__ == other.__dict__
+class Event(ABC):
+    """
+    Base class for h11 events.
+    """
 
-    # This is an unhashable type.
-    __hash__ = None
+    __slots__ = ()
 
 
-class Request(_EventBundle):
+@dataclass(init=False, frozen=True)
+class Request(Event):
     """The beginning of an HTTP request.
 
     Fields:
@@ -123,10 +71,38 @@ class Request(_EventBundle):
 
     """
 
-    _fields = ["method", "target", "headers", "http_version"]
-    _defaults = {"http_version": b"1.1"}
+    __slots__ = ("method", "headers", "target", "http_version")
+
+    method: bytes
+    headers: Headers
+    target: bytes
+    http_version: bytes
+
+    def __init__(
+        self,
+        *,
+        method: Union[bytes, str],
+        headers: Union[Headers, List[Tuple[bytes, bytes]], List[Tuple[str, str]]],
+        target: Union[bytes, str],
+        http_version: Union[bytes, str] = b"1.1",
+        _parsed: bool = False,
+    ) -> None:
+        super().__init__()
+        if isinstance(headers, Headers):
+            object.__setattr__(self, "headers", headers)
+        else:
+            object.__setattr__(
+                self, "headers", normalize_and_validate(headers, _parsed=_parsed)
+            )
+        if not _parsed:
+            object.__setattr__(self, "method", bytesify(method))
+            object.__setattr__(self, "target", bytesify(target))
+            object.__setattr__(self, "http_version", bytesify(http_version))
+        else:
+            object.__setattr__(self, "method", method)
+            object.__setattr__(self, "target", target)
+            object.__setattr__(self, "http_version", http_version)
 
-    def _validate(self):
         # "A server MUST respond with a 400 (Bad Request) status code to any
         # HTTP/1.1 request message that lacks a Host header field and to any
         # request message that contains more than one Host header field or a
@@ -143,12 +119,58 @@ def _validate(self):
 
         validate(request_target_re, self.target, "Illegal target characters")
 
+    # This is an unhashable type.
+    __hash__ = None  # type: ignore
+
+
+@dataclass(init=False, frozen=True)
+class _ResponseBase(Event):
+    __slots__ = ("headers", "http_version", "reason", "status_code")
+
+    headers: Headers
+    http_version: bytes
+    reason: bytes
+    status_code: int
+
+    def __init__(
+        self,
+        *,
+        headers: Union[Headers, List[Tuple[bytes, bytes]], List[Tuple[str, str]]],
+        status_code: int,
+        http_version: Union[bytes, str] = b"1.1",
+        reason: Union[bytes, str] = b"",
+        _parsed: bool = False,
+    ) -> None:
+        super().__init__()
+        if isinstance(headers, Headers):
+            object.__setattr__(self, "headers", headers)
+        else:
+            object.__setattr__(
+                self, "headers", normalize_and_validate(headers, _parsed=_parsed)
+            )
+        if not _parsed:
+            object.__setattr__(self, "reason", bytesify(reason))
+            object.__setattr__(self, "http_version", bytesify(http_version))
+            if not isinstance(status_code, int):
+                raise LocalProtocolError("status code must be integer")
+            # Because IntEnum objects are instances of int, but aren't
+            # duck-compatible (sigh), see gh-72.
+            object.__setattr__(self, "status_code", int(status_code))
+        else:
+            object.__setattr__(self, "reason", reason)
+            object.__setattr__(self, "http_version", http_version)
+            object.__setattr__(self, "status_code", status_code)
+
+        self.__post_init__()
+
+    def __post_init__(self) -> None:
+        pass
 
-class _ResponseBase(_EventBundle):
-    _fields = ["status_code", "headers", "http_version", "reason"]
-    _defaults = {"http_version": b"1.1", "reason": b""}
+    # This is an unhashable type.
+    __hash__ = None  # type: ignore
 
 
+@dataclass(init=False, frozen=True)
 class InformationalResponse(_ResponseBase):
     """An HTTP informational response.
 
@@ -179,14 +201,18 @@ class InformationalResponse(_ResponseBase):
 
     """
 
-    def _validate(self):
+    def __post_init__(self) -> None:
         if not (100 <= self.status_code < 200):
             raise LocalProtocolError(
                 "InformationalResponse status_code should be in range "
                 "[100, 200), not {}".format(self.status_code)
             )
 
+    # This is an unhashable type.
+    __hash__ = None  # type: ignore
+
 
+@dataclass(init=False, frozen=True)
 class Response(_ResponseBase):
     """The beginning of an HTTP response.
 
@@ -216,16 +242,20 @@ class Response(_ResponseBase):
 
     """
 
-    def _validate(self):
+    def __post_init__(self) -> None:
         if not (200 <= self.status_code < 600):
             raise LocalProtocolError(
                 "Response status_code should be in range [200, 600), not {}".format(
                     self.status_code
                 )
             )
 
+    # This is an unhashable type.
+    __hash__ = None  # type: ignore
+
 
-class Data(_EventBundle):
+@dataclass(init=False, frozen=True)
+class Data(Event):
     """Part of an HTTP message body.
 
     Fields:
@@ -258,16 +288,30 @@ class Data(_EventBundle):
 
     """
 
-    _fields = ["data", "chunk_start", "chunk_end"]
-    _defaults = {"chunk_start": False, "chunk_end": False}
+    __slots__ = ("data", "chunk_start", "chunk_end")
+
+    data: bytes
+    chunk_start: bool
+    chunk_end: bool
+
+    def __init__(
+        self, data: bytes, chunk_start: bool = False, chunk_end: bool = False
+    ) -> None:
+        object.__setattr__(self, "data", data)
+        object.__setattr__(self, "chunk_start", chunk_start)
+        object.__setattr__(self, "chunk_end", chunk_end)
+
+    # This is an unhashable type.
+    __hash__ = None  # type: ignore
 
 
 # XX FIXME: "A recipient MUST ignore (or consider as an error) any fields that
 # are forbidden to be sent in a trailer, since processing them as if they were
 # present in the header section might bypass external security filters."
 # https://svn.tools.ietf.org/svn/wg/httpbis/specs/rfc7230.html#chunked.trailer.part
 # Unfortunately, the list of forbidden fields is long and vague :-/
-class EndOfMessage(_EventBundle):
+@dataclass(init=False, frozen=True)
+class EndOfMessage(Event):
     """The end of an HTTP message.
 
     Fields:
@@ -284,11 +328,32 @@ class EndOfMessage(_EventBundle):
 
     """
 
-    _fields = ["headers"]
-    _defaults = {"headers": []}
+    __slots__ = ("headers",)
+
+    headers: Headers
+
+    def __init__(
+        self,
+        *,
+        headers: Union[
+            Headers, List[Tuple[bytes, bytes]], List[Tuple[str, str]], None
+        ] = None,
+        _parsed: bool = False,
+    ) -> None:
+        super().__init__()
+        if headers is None:
+            headers = Headers([])
+        elif not isinstance(headers, Headers):
+            headers = normalize_and_validate(headers, _parsed=_parsed)
+
+        object.__setattr__(self, "headers", headers)
+
+    # This is an unhashable type.
+    __hash__ = None  # type: ignore
 
 
-class ConnectionClosed(_EventBundle):
+@dataclass(frozen=True)
+class ConnectionClosed(Event):
     """This event indicates that the sender has closed their outgoing
     connection.
 

h11/tests/helpers.py

@@ -26,11 +26,13 @@ def normalize_data_events(in_events):
     out_events = []
     for event in in_events:
         if type(event) is Data:
-            event.data = bytes(event.data)
-            event.chunk_start = False
-            event.chunk_end = False
+            event = Data(data=bytes(event.data), chunk_start=False, chunk_end=False)
         if out_events and type(out_events[-1]) is type(event) is Data:
-            out_events[-1].data += event.data
+            out_events[-1] = Data(
+                data=out_events[-1].data + event.data,
+                chunk_start=out_events[-1].chunk_start,
+                chunk_end=out_events[-1].chunk_end,
+            )
         else:
             out_events.append(event)
     return out_events