What's New in Pyramid 1.6
=========================

This article explains the new features in :app:`Pyramid` version 1.6 as
compared to its predecessor, :app:`Pyramid` 1.5. It also documents backwards
incompatibilities between the two versions and deprecations added to
:app:`Pyramid` 1.6, as well as software dependency changes and notable
documentation additions.


Backwards Incompatibilities
---------------------------

- IPython and BPython support have been removed from pshell in the core. To
  continue using them on Pyramid 1.6+, you must install the binding packages
  explicitly. One way to do this is by adding ``pyramid_ipython`` (or
  ``pyramid_bpython``) to the ``install_requires`` section of your package's
  ``setup.py`` file, then re-running ``setup.py develop``::

    setup(
        #...
        install_requires=[
            'pyramid_ipython',         # new dependency
            'pyramid',
            #...
        ],
    )

- ``request.response`` will no longer be mutated when using the
  :func:`~pyramid.renderers.render_to_response` API. It is now necessary to
  pass in a ``response=`` argument to
  :func:`~pyramid.renderers.render_to_response` if you wish to supply the
  renderer with a custom response object. If you do not pass one, then a
  response object will be created using the current response factory. Almost
  all renderers mutate the ``request.response`` response object (for example,
  the JSON renderer sets ``request.response.content_type`` to
  ``application/json``). However, when invoking ``render_to_response``, it is
  not expected that the response object being returned would be the same one
  used later in the request. The response object returned from
  ``render_to_response`` is now explicitly different from ``request.response``.
  This does not change the API of a renderer. See
  https://github.com/Pylons/pyramid/pull/1563

- In an effort to combat a common issue it is now a
  :class:`~pyramid.exceptions.ConfigurationError` to register a view
  callable that is actually an unbound method when using the default view
  mapper. As unbound methods do not exist in PY3+ possible errors are detected
  by checking if the first parameter is named ``self``. For example,
  `config.add_view(ViewClass.some_method, ...)` should actually be
  `config.add_view(ViewClass, attr='some_method)'`. This was always an issue
  in Pyramid on PY2 but the backward incompatibility is on PY3+ where you may
  not use a function with the first parameter named ``self``. In this case
  it looks too much like a common error and the exception will be raised.
  See https://github.com/Pylons/pyramid/pull/1498


Feature Additions
-----------------

- Python 3.5 and pypy3 compatibility.

- ``pserve --reload`` will no longer crash on syntax errors. See
  https://github.com/Pylons/pyramid/pull/2044

- Cache busting for static resources has been added and is available via a new
  :meth:`pyramid.config.Configurator.add_cache_buster` API. Core APIs are
  shipped for both cache busting via query strings and via asset manifests for
  integrating into custom asset pipelines. See
  https://github.com/Pylons/pyramid/pull/1380 and
  https://github.com/Pylons/pyramid/pull/1583 and
  https://github.com/Pylons/pyramid/pull/2171

- Assets can now be overidden by an absolute path on the filesystem when using
  the :meth:`~pyramid.config.Configurator.override_asset` API. This makes it
  possible to fully support serving up static content from a mutable directory
  while still being able to use the :meth:`~pyramid.request.Request.static_url`
  API and :meth:`~pyramid.config.Configurator.add_static_view`.  Previously it
  was not possible to use :meth:`~pyramid.config.Configurator.add_static_view`
  with an absolute path **and** generate urls to the content. This change
  replaces the call, ``config.add_static_view('/abs/path', 'static')``, with
  ``config.add_static_view('myapp:static', 'static')`` and
  ``config.override_asset(to_override='myapp:static/',
  override_with='/abs/path/')``. The ``myapp:static`` asset spec is completely
  made up and does not need to exist—it is used for generating URLs via
  ``request.static_url('myapp:static/foo.png')``. See
  https://github.com/Pylons/pyramid/pull/1252

- Added :meth:`~pyramid.config.Configurator.set_response_factory` and the
  ``response_factory`` keyword argument to the constructor of
  :class:`~pyramid.config.Configurator` for defining a factory that will return
  a custom ``Response`` class. See https://github.com/Pylons/pyramid/pull/1499

- Added :attr:`pyramid.config.Configurator.root_package` attribute and init
  parameter to assist with includible packages that wish to resolve resources
  relative to the package in which the configurator was created. This is
  especially useful for add-ons that need to load asset specs from settings, in
  which case it may be natural for a developer to define imports or assets
  relative to the top-level package. See
  https://github.com/Pylons/pyramid/pull/1337

- Overall improvements for the ``proutes`` command. Added ``--format`` and
  ``--glob`` arguments to the command, introduced the ``method``
  column for displaying available request methods, and improved the ``view``
  output by showing the module instead of just ``__repr__``. See
  https://github.com/Pylons/pyramid/pull/1488

- ``pserve`` can now take a ``-b`` or ``--browser`` option to open the server
  URL in a web browser. See https://github.com/Pylons/pyramid/pull/1533

- Support keyword-only arguments and function annotations in views in Python 3.
  See https://github.com/Pylons/pyramid/pull/1556

- The ``append_slash`` argument of
  :meth:`~pyramid.config.Configurator.add_notfound_view()` will now accept
  anything that implements the :class:`~pyramid.interfaces.IResponse` interface
  and will use that as the response class instead of the default
  :class:`~pyramid.httpexceptions.HTTPFound`. See
  https://github.com/Pylons/pyramid/pull/1610

- The :class:`~pyramid.config.Configurator` has grown the ability to allow
  actions to call other actions during a commit cycle. This enables much more
  logic to be placed into actions, such as the ability to invoke other actions
  or group them for improved conflict detection. We have also exposed and
  documented the configuration phases that Pyramid uses in order to further
  assist in building conforming add-ons. See
  https://github.com/Pylons/pyramid/pull/1513

- Allow an iterator to be returned from a renderer. Previously it was only
  possible to return bytes or unicode. See
  https://github.com/Pylons/pyramid/pull/1417

- Improve robustness to timing attacks in the
  :class:`~pyramid.authentication.AuthTktCookieHelper` and the
  :class:`~pyramid.session.SignedCookieSessionFactory` classes by using the
  stdlib's ``hmac.compare_digest`` if it is available (such as Python 2.7.7+
  and 3.3+). See https://github.com/Pylons/pyramid/pull/1457

- Improve the readability of the ``pcreate`` shell script output. See
  https://github.com/Pylons/pyramid/pull/1453

- Make it simple to define ``notfound`` and ``forbidden`` views that wish to
  use the default exception-response view, but with altered predicates and
  other configuration options. The ``view`` argument is now optional in
  :meth:`~pyramid.config.Configurator.add_notfound_view` and
  :meth:`~pyramid.config.Configurator.add_forbidden_view` See
  https://github.com/Pylons/pyramid/issues/494

- The ``pshell`` script will now load a ``PYTHONSTARTUP`` file if one is
  defined in the environment prior to launching the interpreter. See
  https://github.com/Pylons/pyramid/pull/1448

- Add new HTTP exception objects for status codes ``428 Precondition
  Required``, ``429 Too Many Requests`` and ``431 Request Header Fields Too
  Large`` in ``pyramid.httpexceptions``. See
  https://github.com/Pylons/pyramid/pull/1372/files

- ``pcreate`` when run without a scaffold argument will now print information
  on the missing flag, as well as a list of available scaffolds. See
  https://github.com/Pylons/pyramid/pull/1566 and
  https://github.com/Pylons/pyramid/issues/1297

- ``pcreate`` will now ask for confirmation if invoked with an argument for a
  project name that already exists or is importable in the current environment.
  See https://github.com/Pylons/pyramid/issues/1357 and
  https://github.com/Pylons/pyramid/pull/1837

- Add :func:`pyramid.request.apply_request_extensions` function which can be
  used in testing to apply any request extensions configured via
  ``config.add_request_method``. Previously it was only possible to test the
  extensions by going through Pyramid's router. See
  https://github.com/Pylons/pyramid/pull/1581

- Make it possible to subclass ``pyramid.request.Request`` and also use
  ``pyramid.request.Request.add_request.method``. See
  https://github.com/Pylons/pyramid/issues/1529

- Additional shells for ``pshell`` can now be registered as entry points. See
  https://github.com/Pylons/pyramid/pull/1891 and
  https://github.com/Pylons/pyramid/pull/2012

- The variables injected into ``pshell`` are now displayed with their
  docstrings instead of the default ``str(obj)`` when possible. See
  https://github.com/Pylons/pyramid/pull/1929


Deprecations
------------

- The ``pserve`` command's daemonization features, as well as
  ``--monitor-restart``, have been deprecated. This includes the
  ``[start,stop,restart,status]`` subcommands, as well as the ``--daemon``,
  ``--stop-daemon``, ``--pid-file``, ``--status``, ``--user``, and ``--group``
  flags. See https://github.com/Pylons/pyramid/pull/2120 and
  https://github.com/Pylons/pyramid/pull/2189 and
  https://github.com/Pylons/pyramid/pull/1641

  Please use a real process manager in the future instead of relying on
  ``pserve`` to daemonize itself. Many options exist, including your operating
  system's services, such as Systemd or Upstart, as well as Python-based
  solutions like Circus and Supervisor.

  See https://github.com/Pylons/pyramid/pull/1641 and
  https://github.com/Pylons/pyramid/pull/2120

- The ``principal`` argument to :func:`pyramid.security.remember` was renamed
  to ``userid``. Using ``principal`` as the argument name still works and will
  continue to work for the next few releases, but a deprecation warning is
  printed.


Scaffolding Enhancements
------------------------

- Added line numbers to the log formatters in the scaffolds to assist with
  debugging. See https://github.com/Pylons/pyramid/pull/1326

- Updated scaffold generating machinery to return the version of :app:`Pyramid`
  and its documentation for use in scaffolds. Updated ``starter``, ``alchemy``
  and ``zodb`` templates to have links to correctly versioned documentation,
  and to reflect which :app:`Pyramid` was used to generate the scaffold.

- Removed non-ASCII copyright symbol from templates, as this was causing the
  scaffolds to fail for project generation.


Documentation Enhancements
--------------------------

- Removed logging configuration from Quick Tutorial ``ini`` files, except for
  scaffolding- and logging-related chapters, to avoid needing to explain it too
  early.

- Improve and clarify the documentation on what :app:`Pyramid` defines as a
  ``principal`` and a ``userid`` in its security APIs. See
  https://github.com/Pylons/pyramid/pull/1399

- Moved the documentation for ``accept`` on
  :meth:`pyramid.config.Configurator.add_view` to no longer be part of the
  predicate list. See https://github.com/Pylons/pyramid/issues/1391 for a bug
  report stating ``not_`` was failing on ``accept``. Discussion with @mcdonc
  led to the conclusion that it should not be documented as a predicate.
  See https://github.com/Pylons/pyramid/pull/1487 for this PR.

- Clarify a previously-implied detail of the ``ISession.invalidate`` API
  documentation.

- Add documentation of command line programs (``p*`` scripts). See
  https://github.com/Pylons/pyramid/pull/2191
