catapult/third_party/WebOb/docs/differences.txt

Differences Between WebOb and Other Systems
+++++++++++++++++++++++++++++++++++++++++++

This document points out some of the API differences between the
Request and Response object, and the objects in other systems.

.. contents::

paste.wsgiwrappers and Pylons
=============================

The Pylons ``request`` and ``response`` object are based on
``paste.wsgiwrappers.WSGIRequest`` and ``WSGIResponse``

There is no concept of ``defaults`` in WebOb.  In Paste/Pylons these
serve as threadlocal settings that control certain policies on the
request and response object.  In WebOb you should make your own
subclasses to control policy (though in many ways simply being
explicit elsewhere removes the need for this policy).

Request
-------

``body``:
    This is a file-like object in WSGIRequest.  In WebOb it is a
    string (to match Response.body) and the file-like object is
    available through ``req.body_file``

``languages()``:
    This is available through ``req.accept_language``, particularly
    ``req.accept_language.best_match(supported_languages)``

``match_accept(mimetypes)``:
    This is available through ``req.accept.first_match(mimetypes)``;
    or if you trust the client's quality ratings, you can use
    ``req.accept.best_match(mimetypes)``

``errors``:
    This controls how unicode decode errors are handled; it is now
    named ``unicode_errors``

There are also many extra methods and attributes on WebOb Request
objects.

Response
--------

``determine_charset()``:
    Is now available as ``res.charset``

``has_header(header)``:
    Should be done with ``header in res.headers``

``get_content()`` and ``wsgi_response()``:
    These are gone; you should use ``res.body`` or ``res(environ,
    start_response)``

``write(content)``:
    Available in ``res.body_file.write(content)``.

``flush()`` and ``tell()``:
    Not available.

There are also many extra methods and attributes on WebOb Response
objects.

Django
======

This is a quick summary from reading `the Django documentation
<http://www.djangoproject.com/documentation/request_response/>`_.

Request
-------

``encoding``:
    Is ``req.charset``

``REQUEST``:
    Is ``req.params``

``FILES``:
    File uploads are ``cgi.FieldStorage`` objects directly in
    ``res.POST``

``META``:
    Is ``req.environ``

``user``:
    No equivalent (too connected to application model for WebOb).
    There is ``req.remote_user``, which is only ever a string.

``session``:
    No equivalent

``raw_post_data``:
    Available with ``req.body``

``__getitem__(key)``:
    You have to use ``req.params``

``is_secure()``:
    No equivalent; you could use ``req.scheme == 'https'``.

QueryDict
---------

QueryDict is the way Django represents the multi-key dictionary-like
objects that are request variables (query string and POST body
variables).  The equivalent in WebOb is MultiDict.

Mutability:
    WebOb dictionaries are sometimes mutable (req.GET is,
    req.params is not)

Ordering:
    I believe Django does not order the keys fully; MultiDict is a
    full ordering.  Methods that iterate over the parameters iterate
    over keys in their order in the original request.

``keys()``, ``items()``, ``values()`` (plus ``iter*``):
    These return all values in MultiDict, but only the last value for
    a QueryDict.  That is, given ``a=1&a=2`` with MultiDict
    ``d.items()`` returns ``[('a', '1'), ('a', '2')]``, but QueryDict
    returns ``[('a', '1')]``

``getlist(key)``:
    Available as ``d.getall(key)``

``setlist(key)``:
    No direct equivalent

``appendlist(key, value)``:
    Available as ``d.add(key, value)``

``setlistdefault(key, default_list)``:
    No direct equivalent

``lists()``:
    Is ``d.dict_of_lists()``

The MultiDict object has a ``d.getone(key)`` method, that raises
KeyError if there is not exactly one key.  There is a method
``d.mixed()`` which returns a version where values are lists *if*
there are multiple values for a list.  This is similar to how many
cgi-based request forms are represented.

Response
--------

Constructor:
    Somewhat different.  WebOb takes any keyword arguments as
    attribute assignments.  Django only takes a couple arguments.  The
    ``mimetype`` argument is ``content_type``, and ``content_type`` is
    the entire ``Content-Type`` header (including charset).

dictionary-like:
    The Django response object is somewhat dictionary-like, setting
    headers.  The equivalent dictionary-like object is
    ``res.headers``.  In WebOb this is a MultiDict.

``has_header(header)``:
    Use ``header in res.headers``

``flush()``, ``tell()``:
    Not available

``content``:
    Use ``res.body`` for the ``str`` value, ``res.text`` for
    the ``unicode`` value

Response Subclasses
-------------------

These are generally like ``webob.exc`` objects.
``HttpResponseNotModified`` is ``HTTPNotModified``; this naming
translation generally works.

CherryPy/TurboGears
===================

The `CherryPy request object
<http://www.cherrypy.org/wiki/RequestObject>`_ is also used by
TurboGears 1.x.

Request
-------

``app``:
    No equivalent

``base``:
    ``req.application_url``

``close()``:
    No equivalent

``closed``:
    No equivalent

``config``:
    No equivalent

``cookie``:
    A ``SimpleCookie`` object in CherryPy; a dictionary in WebOb
    (``SimpleCookie`` can represent cookie parameters, but cookie
    parameters are only sent with responses not requests)

``dispatch``:
    No equivalent (this is the object dispatcher in CherryPy).

``error_page``, ``error_response``, ``handle_error``:
    No equivalent

``get_resource()``:
    Similar to ``req.get_response(app)``

``handler``:
    No equivalent

``headers``, ``header_list``:
    The WSGI environment represents headers as a dictionary, available
    through ``req.headers`` (no list form is available in the request).

``hooks``:
    No equivalent

``local``:
    No equivalent

``methods_with_bodies``:
    This represents methods where CherryPy will automatically try to
    read the request body.  WebOb lazily reads POST requests with the
    correct content type, and no other bodies.

``namespaces``:
    No equivalent

``protocol``:
    As ``req.environ['SERVER_PROTOCOL']``

``query_string``:
    As ``req.query_string``

``remote``:
    ``remote.ip`` is like ``req.remote_addr``.  ``remote.port`` is not
    available.  ``remote.name`` is in
    ``req.environ.get('REMOTE_HOST')``

``request_line``:
    No equivalent

``respond()``:
    A method that is somewhat similar to ``req.get_response()``.

``rfile``:
    ``req.body_file``

``run``:
    No equivalent

``server_protocol``:
    As ``req.environ['SERVER_PROTOCOL']``

``show_tracebacks``:
    No equivalent

``throw_errors``:
    No equivalent

``throws``:
    No equivalent

``toolmaps``:
    No equivalent

``wsgi_environ``:
    As ``req.environ``

Response
--------

From information `from the wiki
<http://www.cherrypy.org/wiki/ResponseObject>`_.

``body``:
    This is an iterable in CherryPy, a string in WebOb;
    ``res.app_iter`` gives an iterable in WebOb.

``check_timeout``:
    No equivalent

``collapse_body()``:
    This turns a stream/iterator body into a single string.  Accessing
    ``res.body`` will do this automatically.

``cookie``:
    Accessible through ``res.set_cookie(...)``, ``res.delete_cookie``,
    ``res.unset_cookie()``

``finalize()``:
    No equivalent

``header_list``:
    In ``res.headerlist``

``stream``:
    This can make CherryPy stream the response body out directory.
    There is direct no equivalent; you can use a dynamically generated
    iterator to do something similar.

``time``:
    No equivalent

``timed_out``:
    No equivalent

Yaro
====

`Yaro <http://lukearno.com/projects/yaro/>`_ is a small wrapper around
the WSGI environment, much like WebOb in scope.

The WebOb objects have many more methods and attributes.  The Yaro
Response object is a much smaller subset of WebOb's Response.

Request
-------

``query``:
    As ``req.GET``

``form``:
    As ``req.POST``

``cookie``:
    A ``SimpleCookie`` object in Yaro; a dictionary in WebOb
    (``SimpleCookie`` can represent cookie parameters, but cookie
    parameters are only sent with responses not requests)

``uri``:
    Returns a URI object, no equivalent (only string URIs available).

``redirect``:
    Not available (response-related).  ``webob.exc.HTTPFound()`` can
    be useful here.

``forward(yaroapp)``, ``wsgi_forward(wsgiapp)``:
    Available with ``req.get_response(app)`` and
    ``req.call_application(app)``.  In both cases it is a WSGI
    application in WebOb, there is no special kind of communication;
    ``req.call_application()`` just returns a ``webob.Response`` object.

``res``:
    The request object in WebOb *may* have a ``req.response``
    attribute.

Werkzeug
========

An offshoot of `Pocoo <http://pocoo.org>`_,
this library is based around WSGI, similar to Paste and Yaro.

This is taken from the `wrapper documentation
<http://werkzeug.pocoo.org/documentation/wrappers>`_.

Request
-------

path:
    As ``req.path_info``
args:
    As ``req.GET``
form:
    As ``req.POST``
values:
    As ``req.params``
files:
    In ``req.POST`` (as FieldStorage objects)
data:
    In ``req.body_file``

Response
--------

response:
    In ``res.body`` (settable as ``res.body`` or ``res.app_iter``)
status:
    In ``res.status_code``
mimetype:
    In ``res.content_type``

Zope 3
======

From the Zope 3 interfaces for the `Request
<http://apidoc.zope.org/++apidoc++/Interface/zope.publisher.interfaces.browser.IBrowserRequest/index.html>`_
and `Response
<http://apidoc.zope.org/++apidoc++/Interface/zope.publisher.interfaces.http.IHTTPResponse/index.html>`_.

Request
-------

``locale``, ``setupLocale()``:
    This is not fully calculated, but information is available in
    ``req.accept_languages``.

``principal``, ``setPrincipal(principal)``:
    ``req.remote_user`` gives the username, but there is no standard
    place for a user *object*.

``publication``, ``setPublication()``,
    These are associated with the object publishing system in Zope.
    This kind of publishing system is outside the scope of WebOb.

``traverse(object)``, ``getTraversalStack()``, ``setTraversalStack()``:
    These all relate to traversal, which is part of the publishing
    system.

``processInputs()``, ``setPathSuffix(steps)``:
    Also associated with traversal and preparing the request.

``environment``:
    In ``req.environ``

``bodyStream``:
    In ``req.body_file``

``interaction``:
    This is the security context for the request; all the possible
    participants or principals in the request.  There's no
    equivalent.

``annotations``:
    Extra information associated with the request.  This would
    generally go in custom keys of ``req.environ``, or if you set
    attributes those attributes are stored in
    ``req.environ['webob.adhoc_attrs']``.

``debug``:
    There is no standard debug flag for WebOb.

``__getitem__(key)``, ``get(key)``, etc:
    These treat the request like a dictionary, which WebOb does not
    do.  They seem to take values from the environment, not
    parameters.  Also on the Zope request object is ``items()``,
    ``__contains__(key)``, ``__iter__()``, ``keys()``, ``__len__()``,
    ``values()``.

``getPositionalArguments()``:
    I'm not sure what the equivalent would be, as there are no
    positional arguments during instantiation (it doesn't fit into
    WSGI).  Maybe ``wsgiorg.urlvars``?

``retry()``, ``supportsRetry()``:
    Creates a new request that can be used to retry a request.
    Similar to ``req.copy()``.

``close()``, ``hold(obj)``:
    This closes resources associated with the request, including any
    "held" objects.  There's nothing similar.

Response
--------

``authUser``:
    Not sure what this is or does.

``reset()``:
    No direct equivalent; you'd have to do ``res.headers = [];
    res.body = ''; res.status = 200``

``setCookie(name, value, **kw)``:
    Is ``res.set_cookie(...)``.

``getCookie(name)``:
    No equivalent.  Hm.

``expireCookie(name)``:
    Is ``res.delete_cookie(name)``.

``appendToCookie(name, value)``:
    This appends the value to any existing cookie (separating values
    with a colon).  WebOb does not do this.

``setStatus(status)``:
    Availble by setting ``res.status`` (can be set to an integer or a
    string of "code reason").

``getHeader(name, default=None)``:
    Is ``res.headers.get(name)``.

``getStatus()``:
    Is ``res.status_code`` (or ``res.status`` to include reason)

``addHeader(name, value)``:
    Is ``res.headers.add(name, value)`` (in Zope and WebOb, this does
    not clobber any previous value).

``getHeaders()``:
    Is ``res.headerlist``.

``setHeader(name, value)``:
    Is ``res.headers[name] = value``.

``getStatusString()``:
    Is ``res.status``.

``consumeBody()``:
    This consumes any non-string body to turn the body into a single
    string.  Any access to ``res.body`` will do this (e.g., when you
    have set the ``res.app_iter``).

``internalError()``:
    This is available with ``webob.exc.HTTP*()``.

``handleException(exc_info)``:
    This is provided with a tool like ``paste.exceptions``.

``consumeBodyIter()``:
    This returns the iterable for the body, even if the body was a
    string.  Anytime you access ``res.app_iter`` you will get an
    iterable.  ``res.body`` and ``res.app_iter`` can be interchanged
    and accessed as many times as you want, unlike the Zope
    equivalents.

``setResult(result)``:
    You can achieve the same thing through ``res.body = result``, or
    ``res.app_iter = result``.  ``res.body`` accepts None, a unicode
    string (*if* you have set a charset) or a normal string.
    ``res.app_iter`` only accepts None and an interable.  You can't
    update all of a response with one call.

    Like in Zope, WebOb updates Content-Length.  Unlike Zope, it does
    not automatically calculate a charset.


mod_python
==========

Some key attributes from the `mod_python
<http://modpython.org/live/current/doc-html/pyapi-mprequest-mem.html>`_
request object.

Request
-------

``req.uri``:
    In ``req.path``.

``req.user``:
    In ``req.remote_user``.

``req.get_remote_host()``:
    In ``req.environ['REMOTE_ADDR']`` or ``req.remote_addr``.

``req.headers_in.get('referer')``:
    In ``req.headers.get('referer')`` or ``req.referer`` (same pattern
    for other request headers, presumably).

Response
--------

``util.redirect`` or ``req.status = apache.HTTP_MOVED_TEMPORARILY``:

.. code-block:: python

    from webob.exc import HTTPTemporaryRedirect
    exc = HTTPTemporaryRedirect(location=url)
    return exc(environ, start_response)

``req.content_type = "application/x-csv"`` and
``req.headers_out.add('Content-Disposition', 'attachment;filename=somefile.csv')``:

.. code-block:: python

    res = req.ResponseClass()
    res.content_type = 'application/x-csv'
    res.headers.add('Content-Disposition', 'attachment;filename=somefile.csv')
    return res(environ, start_response)

webapp Response
===============

The Google App Engine `webapp
<http://code.google.com/appengine/docs/python/tools/webapp/>`_
framework uses the WebOb Request object, but does not use its Response
object.

The constructor for ``webapp.Response`` does not take any arguments.
The response is created by the framework, so you don't use it like
``return Response(...)``, instead you use ``self.response``.  Also the
response object automatically has ``Cache-Control: no-cache`` set,
while the WebOb response does not set any cache headers.

``resp.set_status(code, message=None)``:
    This is handled by setting the ``resp.status`` attribute.

``resp.clear()``:
    You'd do ``resp.body = ""``

``resp.wsgi_write(start_response)``:
    This writes the response using the ``start_response`` callback,
    and using the ``start_response`` writer.  The WebOb response
    object is called as a WSGI app (``resp(environ, start_response)``)
    to do the equivalent.

``resp.out.write(text)``:
    This writes to an internal ``StringIO`` instance of the response.
    This uses the ability of the standard StringIO object to hold
    either unicode or ``str`` text, and so long as you are always
    consistent it will encode your content (but it does not respect
    your preferred encoding, it always uses UTF-8).  The WebOb method
    ``resp.write(text)`` is basically equivalent, and also accepts
    unicode (using ``resp.charset`` for the encoding).  You can also
    write to ``resp.body_file``, but it does not allow unicode.

Besides exposing a ``.headers`` attribute (based on
`wsgiref.headers.Headers
<http://docs.python.org/library/wsgiref.html#wsgiref.headers.Headers>`_)
there is no other API for the webapp response object.  This means the
response lacks:

* A usefully readable body or status.
* A useful constructor that makes it easy to treat responses like
  objects.
* Providing a non-string ``app_iter`` for the body (like a generator).
* Parsing of the Content-Type charset.
* Getter/setters for parsed forms of headers, specifically
  cache_control and last_modified.
* The ``cache_expires`` method
* ``set_cookie``, ``delete_cookie``, and ``unset_cookie``.  Instead
  you have to simply manually set the Set-Cookie header.
* ``encode_content`` and ``decode_content`` for handling gzip encoding.
* ``md5_etag()`` for generating an etag from the body.
* Conditional responses that will return 304 based on the response and
  request headers.
* The ability to serve Range request automatically.

PHP
===

PHP does not have anything really resembling a request and response
object.  Instead these are encoded in a set of global objects for the
request and functions for the response.

``$_POST``, ``$_GET``, ``$_FILES``
----------------------------------

These represent ``req.POST`` and ``req.GET``.

PHP uses the variable names to tell whether a variable can hold
multiple values.  For instance ``$_POST['name[]']``, which will be an
array.  In WebOb any variable can have multiple values, and you can
get these through ``req.POST.getall('name')``.

The files in ``$_FILES`` are simply in ``req.POST`` in WebOb, as
FieldStorage instances.

``$_COOKIES``
-------------

This is in ``req.cookies``.

``$_SERVER``, ``$_REQUEST``, ``$_ENV``
--------------------------------------

These are all in ``req.environ``.  These are not split up like they
are in PHP, it's all just one dictionary.  Everything that would
typically be in ``$_ENV`` is technically optional, and outside of a
couple CGI-standard keys in ``$_SERVER`` most of those are also
optional, but it is common for WSGI servers to populate the request
with similar information as PHP.

``$HTTP_RAW_POST_DATA``
-----------------------

This contains the unparsed data in the request body.  This is in
``req.body``.

The response
------------

Response headers in PHP are sent with ``header("Header-Name:
value")``.  In WebOb there is a dictionary in ``resp.headers`` that
can have values set; the headers aren't actually sent until you send
the response.  You can add headers without overwriting (the equivalent
of ``header("...", false)``) with ``resp.headers.add('Header-Name',
'value')``.

The status in PHP is sent with ``http_send_status(code)``.  In WebOb
this is ``resp.status = code``.

The body in PHP is sent implicitly through the rendering of the PHP
body (or with ``echo`` or any other functions that send output).