H2

------------------

Bugfixes
~~~~~~~~

- Reject attempts to push streams on streams that were themselves pushed:
streams can only be pushed on streams that were initiated by the client.
- Correctly allow CONTINUATION frames to extend the header block started by a
PUSH_PROMISE frame.
- Changed our handling of frames received on streams that were reset by the
user.

Previously these would, at best, cause ProtocolErrors to be raised and the
connection to be torn down (rather defeating the point of resetting streams
at all) and, at worst, would cause subtle inconsistencies in state between
hyper-h2 and the remote peer that could lead to header block decoding errors
or flow control blockages.

Now when the user resets a stream all further frames received on that stream
are ignored except where they affect some form of connection-level state,
where they have their effect and are then ignored.
- Fixed a bug whereby receiving a PUSH_PROMISE frame on a stream that was
closed would cause a RST_STREAM frame to be emitted on the closed-stream,
but not the newly-pushed one. Now this causes a ``ProtocolError``.

------------------

Bugfixes
~~~~~~~~

- Added debug representations for all events.
- Fixed problems with setup.py that caused trouble on older setuptools/pip
installs.

------------------

API Changes (Backward-Compatible)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

- Added new field to ``DataReceived``: ``flow_controlled_length``. This is the
length of the frame including padded data, allowing users to correctly track
changes to the flow control window.
- Defined new ``UnsupportedFrameError``, thrown when frames that are known to
hyperframe but not supported by hyper-h2 are received. For
backward-compatibility reasons, this is a ``ProtocolError`` *and* a
``KeyError``.

Bugfixes
~~~~~~~~

- Hyper-h2 now correctly accounts for padding when maintaining flow control
windows.
- Resolved a bug where hyper-h2 would mistakenly apply
SETTINGS_INITIAL_WINDOW_SIZE to the connection flow control window in
addition to the stream-level flow control windows.
- Invalid Content-Length headers now throw ``ProtocolError`` exceptions and
correctly tear the connection down, instead of leaving the connection in an
indeterminate state.
- Invalid header blocks now throw ``ProtocolError``, rather than a grab bag of
possible other exceptions.

------------------

API Changes (Breaking)
~~~~~~~~~~~~~~~~~~~~~~

- Attempts to open streams with invalid stream IDs, either by the remote peer
or by the user, are now rejected as a ``ProtocolError``. Previously these
were allowed, and would cause remote peers to error.
- Receiving frames that have invalid padding now causes the connection to be
terminated with a ``ProtocolError`` being raised. Previously these passed
undetected.
- Settings values set by both the user and the remote peer are now validated
when they're set. If they're invalid, a new ``InvalidSettingsValueError`` is
raised and, if set by the remote peer, a connection error is signaled.
Previously, it was possible to set invalid values. These would either be
caught when building frames, or would be allowed to stand.
- Settings changes no longer require user action to be acknowledged: hyper-h2
acknowledges them automatically. This moves the location where some
exceptions may be thrown, and also causes the ``acknowledge_settings`` method
to be removed from the public API.
- Removed a number of methods on the ``H2Connection`` object from the public,
semantically versioned API, by renaming them to have leading underscores.
Specifically, removed:

- ``get_stream_by_id``
- ``get_or_create_stream``
- ``begin_new_stream``
- ``receive_frame``
- ``acknowledge_settings``

- Added full support for receiving CONTINUATION frames, including policing
logic about when and how they are received. Previously, receiving
CONTINUATION frames was not supported and would throw exceptions.
- All public API functions on ``H2Connection`` except for ``receive_data`` no
longer return lists of events, because these lists were always empty. Events
are now only raised by ``receive_data``.
- Calls to ``increment_flow_control_window`` with out of range values now raise
``ValueError`` exceptions. Previously they would be allowed, or would cause
errors when serializing frames.

API Changes (Backward-Compatible)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

- Added ``PriorityUpdated`` event for signaling priority changes.
- Added ``get_next_available_stream_id`` function.
- Receiving DATA frames on streams not in the OPEN or HALF_CLOSED_LOCAL states
now causes a stream reset, rather than a connection reset. The error is now
also classified as a ``StreamClosedError``, rather than a more generic
``ProtocolError``.
- Receiving HEADERS or PUSH_PROMISE frames in the HALF_CLOSED_REMOTE state now
causes a stream reset, rather than a connection reset.
- Receiving frames that violate the max frame size now causes connection errors
with error code FRAME_SIZE_ERROR, not a generic PROTOCOL_ERROR. This
condition now also raises a ``FrameTooLargeError``, a new subclass of
``ProtocolError``.
- Made ``NoSuchStreamError`` a subclass of ``ProtocolError``.
- The ``StreamReset`` event is now also fired whenever a protocol error from
the remote peer forces a stream to close early. This is only fired once.
- The ``StreamReset`` event now carries a flag, ``remote_reset``, that is set
to ``True`` in all cases where ``StreamReset`` would previously have fired
(e.g. when the remote peer sent a RST_STREAM), and is set to ``False`` when
it fires because the remote peer made a protocol error.
- Hyper-h2 now rejects attempts by peers to increment a flow control window by
zero bytes.
- Hyper-h2 now rejects peers sending header blocks that are ill-formed for a
number of reasons as set out in RFC 7540 Section 8.1.2.
- Attempting to send non-PRIORITY frames on closed streams now raises
``StreamClosedError``.
- Remote peers attempting to increase the flow control window beyond
``2**31 - 1``, either by window increment or by settings frame, are now
rejected as ``ProtocolError``.
- Local attempts to increase the flow control window beyond ``2**31 - 1`` by
window increment are now rejected as ``ProtocolError``.
- The bytes that represent individual settings are now available in
``h2.settings``, instead of needing users to import them from hyperframe.

Bugfixes
~~~~~~~~

- RFC 7540 requires that a separate minimum stream ID be used for inbound and
outbound streams. Hyper-h2 now obeys this requirement.
- Hyper-h2 now does a better job of reporting the last stream ID it has
partially handled when terminating connections.
- Fixed an error in the arguments of ``StreamIDTooLowError``.
- Prevent ``ValueError`` leaking from Hyperframe.
- Prevent ``struct.error`` and ``InvalidFrameError`` leaking from Hyperframe.

------------------

Bugfixes
~~~~~~~~

- Forcibly lowercase all header names to improve compatibility with
implementations that demand lower-case header names.

------------------

API Changes (Backward-Compatible)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

- Added a new ``ConnectionTerminated`` event, which fires when GOAWAY frames
are received.
- Added a subclass of ``NoSuchStreamError``, called ``StreamClosedError``, that
fires when actions are taken on a stream that is closed and has had its state
flushed from the system.
- Added ``StreamIDTooLowError``, raised when the user or the remote peer
attempts to create a stream with an ID lower than one previously used in the
dialog. Inherits from ``ValueError`` for backward-compatibility reasons.

Bugfixes
~~~~~~~~

- Do not throw ``ProtocolError`` when attempting to send multiple GOAWAY
frames on one connection.
- We no longer forcefully change the decoder table size when settings changes
are ACKed, instead waiting for remote acknowledgement of the change.
- Improve the performance of checking whether a stream is open.
- We now attempt to lazily garbage collect closed streams, to avoid having the
state hang around indefinitely, leaking memory.
- Avoid further per-stream allocations, leading to substantial performance
improvements when many short-lived streams are used.