Merge remote-tracking branch 'refs/remotes/Pylons/master'

1 files changed, 544 insertions, 191 deletions

diff --git a/docs/narr/assets.rst b/docs/narr/assets.rst
index 8d0e7058c..58f547fc9 100644
--- a/docs/narr/assets.rst
+++ b/docs/narr/assets.rst
@@ -7,8 +7,8 @@
 Static Assets
 =============
 
-An :term:`asset` is any file contained within a Python :term:`package` which
-is *not* a Python source code file.  For example, each of the following is an
+An :term:`asset` is any file contained within a Python :term:`package` which is
+*not* a Python source code file.  For example, each of the following is an
 asset:
 
 - a GIF image file contained within a Python package or contained within any
@@ -20,20 +20,23 @@ asset:
 - a JavaScript source file contained within a Python package or contained
   within any subdirectory of a Python package.
 
-- A directory within a package that does not have an ``__init__.py``
-  in it (if it possessed an ``__init__.py`` it would *be* a package).
+- A directory within a package that does not have an ``__init__.py`` in it (if
+  it possessed an ``__init__.py`` it would *be* a package).
 
 - a :term:`Chameleon` or :term:`Mako` template file contained within a Python
   package.
 
 The use of assets is quite common in most web development projects.  For
 example, when you create a :app:`Pyramid` application using one of the
-available scaffolds, as described in :ref:`creating_a_project`, the
-directory representing the application contains a Python :term:`package`.
-Within that Python package, there are directories full of files which are
-static assets.  For example, there's a ``static`` directory which contains
-``.css``, ``.js``, and ``.gif`` files.  These asset files are delivered when
-a user visits an application URL.
+available scaffolds, as described in :ref:`creating_a_project`, the directory
+representing the application contains a Python :term:`package`. Within that
+Python package, there are directories full of files which are static assets.
+For example, there's a ``static`` directory which contains ``.css``, ``.js``,
+and ``.gif`` files.  These asset files are delivered when a user visits an
+application URL.
+
+.. index::
+   single: asset specifications
 
 .. _asset_specifications:
 
@@ -42,12 +45,11 @@ Understanding Asset Specifications
 
 Let's imagine you've created a :app:`Pyramid` application that uses a
 :term:`Chameleon` ZPT template via the
-:func:`pyramid.renderers.render_to_response` API.  For example, the
-application might address the asset using the :term:`asset specification`
-``myapp:templates/some_template.pt`` using that API within a ``views.py``
-file inside a ``myapp`` package:
+:func:`pyramid.renderers.render_to_response` API.  For example, the application
+might address the asset using the :term:`asset specification`
+``myapp:templates/some_template.pt`` using that API within a ``views.py`` file
+inside a ``myapp`` package:
 
-.. ignore-next-block
 .. code-block:: python
    :linenos:
 
@@ -64,27 +66,28 @@ two parts:
 - The *asset name* (``templates/some_template.pt``), relative to the package
   directory.
 
-The two parts are separated by the colon character.
+The two parts are separated by a colon ``:`` character.
 
-:app:`Pyramid` uses the Python :term:`pkg_resources` API to resolve the
-package name and asset name to an absolute (operating-system-specific) file
-name.  It eventually passes this resolved absolute filesystem path to the
-Chameleon templating engine, which then uses it to load, parse, and execute
-the template file.
+:app:`Pyramid` uses the Python :term:`pkg_resources` API to resolve the package
+name and asset name to an absolute (operating system-specific) file name.  It
+eventually passes this resolved absolute filesystem path to the Chameleon
+templating engine, which then uses it to load, parse, and execute the template
+file.
 
 There is a second form of asset specification: a *relative* asset
 specification.  Instead of using an "absolute" asset specification which
 includes the package name, in certain circumstances you can omit the package
 name from the specification.  For example, you might be able to use
 ``templates/mytemplate.pt`` instead of ``myapp:templates/some_template.pt``.
-Such asset specifications are usually relative to a "current package."  The
+Such asset specifications are usually relative to a "current package".  The
 "current package" is usually the package which contains the code that *uses*
 the asset specification.  :app:`Pyramid` APIs which accept relative asset
-specifications typically describe what the asset is relative to in their
+specifications typically describe to what the asset is relative in their
 individual documentation.
 
 .. index::
    single: add_static_view
+   pair: assets; serving
 
 .. _static_assets_section:
 
@@ -93,15 +96,17 @@ Serving Static Assets
 
 :app:`Pyramid` makes it possible to serve up static asset files from a
 directory on a filesystem to an application user's browser.  Use the
-:meth:`pyramid.config.Configurator.add_static_view` to instruct
-:app:`Pyramid` to serve static assets such as JavaScript and CSS files. This
-mechanism makes a directory of static files available at a name relative to
-the application root URL, e.g. ``/static`` or as an external URL.
+:meth:`pyramid.config.Configurator.add_static_view` to instruct :app:`Pyramid`
+to serve static assets, such as JavaScript and CSS files. This mechanism makes
+a directory of static files available at a name relative to the application
+root URL, e.g., ``/static``, or as an external URL.
+
+.. note::
 
-.. note:: :meth:`~pyramid.config.Configurator.add_static_view` cannot serve a
-   single file, nor can it serve a directory of static files directly
-   relative to the root URL of a :app:`Pyramid` application.  For these
-   features, see :ref:`advanced_static`.
+   :meth:`~pyramid.config.Configurator.add_static_view` cannot serve a single
+   file, nor can it serve a directory of static files directly relative to the
+   root URL of a :app:`Pyramid` application.  For these features, see
+   :ref:`advanced_static`.
 
 Here's an example of a use of
 :meth:`~pyramid.config.Configurator.add_static_view` that will serve files up
@@ -114,13 +119,13 @@ from the ``/var/www/static`` directory of the computer which runs the
    # config is an instance of pyramid.config.Configurator
    config.add_static_view(name='static', path='/var/www/static')
 
-The ``name`` prepresents a URL *prefix*.  In order for files that live in the
+The ``name`` represents a URL *prefix*.  In order for files that live in the
 ``path`` directory to be served, a URL that requests one of them must begin
-with that prefix.  In the example above, ``name`` is ``static``, and ``path``
-is ``/var/www/static``.  In English, this means that you wish to serve the
-files that live in ``/var/www/static`` as sub-URLs of the ``/static`` URL
-prefix.  Therefore, the file ``/var/www/static/foo.css`` will be returned
-when the user visits your application's URL ``/static/foo.css``.
+with that prefix.  In the example above, ``name`` is ``static`` and ``path`` is
+``/var/www/static``.  In English this means that you wish to serve the files
+that live in ``/var/www/static`` as sub-URLs of the ``/static`` URL prefix.
+Therefore, the file ``/var/www/static/foo.css`` will be returned when the user
+visits your application's URL ``/static/foo.css``.
 
 A static directory named at ``path`` may contain subdirectories recursively,
 and any subdirectories may hold files; these will be resolved by the static
@@ -129,16 +134,16 @@ view for each particular type of file is dependent upon its file extension.
 
 By default, all files made available via
 :meth:`~pyramid.config.Configurator.add_static_view` are accessible by
-completely anonymous users.  Simple authorization can be required, however.
-To protect a set of static files using a permission, in addition to passing
-the required ``name`` and ``path`` arguments, also pass the ``permission``
-keyword argument to :meth:`~pyramid.config.Configurator.add_static_view`.
-The value of the ``permission`` argument represents the :term:`permission`
-that the user must have relative to the current :term:`context` when the
-static view is invoked.  A user will be required to possess this permission
-to view any of the files represented by ``path`` of the static view.  If your
-static assets must be protected by a more complex authorization scheme,
-see :ref:`advanced_static`.
+completely anonymous users.  Simple authorization can be required, however. To
+protect a set of static files using a permission, in addition to passing the
+required ``name`` and ``path`` arguments, also pass the ``permission`` keyword
+argument to :meth:`~pyramid.config.Configurator.add_static_view`. The value of
+the ``permission`` argument represents the :term:`permission` that the user
+must have relative to the current :term:`context` when the static view is
+invoked.  A user will be required to possess this permission to view any of the
+files represented by ``path`` of the static view.  If your static assets must
+be protected by a more complex authorization scheme, see
+:ref:`advanced_static`.
 
 Here's another example that uses an :term:`asset specification` instead of an
 absolute path as the ``path`` argument.  To convince
@@ -158,45 +163,47 @@ may be a fully qualified :term:`asset specification` or an *absolute path*.
 
 Instead of representing a URL prefix, the ``name`` argument of a call to
 :meth:`~pyramid.config.Configurator.add_static_view` can alternately be a
-*URL*.  Each of examples we've seen so far have shown usage of the ``name``
-argument as a URL prefix.  However, when ``name`` is a *URL*, static assets
-can be served from an external webserver.  In this mode, the ``name`` is used
-as the URL prefix when generating a URL using :func:`pyramid.url.static_url`.
+*URL*.  Each of the examples we've seen so far have shown usage of the ``name``
+argument as a URL prefix.  However, when ``name`` is a *URL*, static assets can
+be served from an external webserver.  In this mode, the ``name`` is used as
+the URL prefix when generating a URL using
+:meth:`pyramid.request.Request.static_url`.
 
-For example, :meth:`~pyramid.config.Configurator.add_static_view` may
-be fed a ``name`` argument which is ``http://example.com/images``:
+For example, :meth:`~pyramid.config.Configurator.add_static_view` may be fed a
+``name`` argument which is ``http://example.com/images``:
 
 .. code-block:: python
    :linenos:
 
    # config is an instance of pyramid.config.Configurator
-   config.add_static_view(name='http://example.com/images', 
+   config.add_static_view(name='http://example.com/images',
                           path='mypackage:images')
 
-Because :meth:`~pyramid.config.Configurator.add_static_view` is provided with
-a ``name`` argument that is the URL ``http://example.com/images``, subsequent
-calls to :func:`~pyramid.url.static_url` with paths that start with the
-``path`` argument passed to
+Because :meth:`~pyramid.config.Configurator.add_static_view` is provided with a
+``name`` argument that is the URL ``http://example.com/images``, subsequent
+calls to :meth:`~pyramid.request.Request.static_url` with paths that start with
+the ``path`` argument passed to
 :meth:`~pyramid.config.Configurator.add_static_view` will generate a URL
-something like ``http://example.com/images/logo.png``.  The external
-webserver listening on ``example.com`` must be itself configured to respond
-properly to such a request.  The :func:`~pyramid.url.static_url` API is
+something like ``http://example.com/images/logo.png``.  The external webserver
+listening on ``example.com`` must be itself configured to respond properly to
+such a request.  The :meth:`~pyramid.request.Request.static_url` API is
 discussed in more detail later in this chapter.
 
 .. index::
    single: generating static asset urls
    single: static asset urls
+   pair:   assets; generating urls
 
 .. _generating_static_asset_urls:
 
 Generating Static Asset URLs
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-When a :meth:`~pyramid.config.Configurator.add_static_view` method is used to
+When an :meth:`~pyramid.config.Configurator.add_static_view` method is used to
 register a static asset directory, a special helper API named
-:func:`pyramid.url.static_url` can be used to generate the appropriate URL
-for an asset that lives in one of the directories named by the static
-registration ``path`` attribute.
+:meth:`pyramid.request.Request.static_url` can be used to generate the
+appropriate URL for an asset that lives in one of the directories named by the
+static registration ``path`` attribute.
 
 For example, let's assume you create a set of static declarations like so:
 
@@ -206,82 +213,375 @@ For example, let's assume you create a set of static declarations like so:
    config.add_static_view(name='static1', path='mypackage:assets/1')
    config.add_static_view(name='static2', path='mypackage:assets/2')
 
-These declarations create URL-accessible directories which have URLs that
-begin with ``/static1`` and ``/static2``, respectively.  The assets in the
+These declarations create URL-accessible directories which have URLs that begin
+with ``/static1`` and ``/static2``, respectively.  The assets in the
 ``assets/1`` directory of the ``mypackage`` package are consulted when a user
-visits a URL which begins with ``/static1``, and the assets in the
-``assets/2`` directory of the ``mypackage`` package are consulted when a user
-visits a URL which begins with ``/static2``.
+visits a URL which begins with ``/static1``, and the assets in the ``assets/2``
+directory of the ``mypackage`` package are consulted when a user visits a URL
+which begins with ``/static2``.
 
 You needn't generate the URLs to static assets "by hand" in such a
-configuration.  Instead, use the :func:`~pyramid.url.static_url` API to
-generate them for you.  For example:
+configuration.  Instead, use the :meth:`~pyramid.request.Request.static_url`
+API to generate them for you.  For example:
 
 .. code-block:: python
    :linenos:
 
-   from pyramid.url import static_url
-   from pyramid.chameleon_zpt import render_template_to_response
+   from pyramid.renderers import render_to_response
 
    def my_view(request):
-       css_url = static_url('mypackage:assets/1/foo.css', request)
-       js_url = static_url('mypackage:assets/2/foo.js', request)
-       return render_template_to_response('templates/my_template.pt',
-                                          css_url = css_url,
-                                          js_url = js_url)
+       css_url = request.static_url('mypackage:assets/1/foo.css')
+       js_url = request.static_url('mypackage:assets/2/foo.js')
+       return render_to_response('templates/my_template.pt',
+                                 dict(css_url=css_url, js_url=js_url),
+                                 request=request)
 
 If the request "application URL" of the running system is
 ``http://example.com``, the ``css_url`` generated above would be:
-``http://example.com/static1/foo.css``.  The ``js_url`` generated
-above would be ``http://example.com/static2/foo.js``.
+``http://example.com/static1/foo.css``.  The ``js_url`` generated above would
+be ``http://example.com/static2/foo.js``.
 
-One benefit of using the :func:`~pyramid.url.static_url` function rather than
-constructing static URLs "by hand" is that if you need to change the ``name``
-of a static URL declaration, the generated URLs will continue to resolve
-properly after the rename.
+One benefit of using the :meth:`~pyramid.request.Request.static_url` function
+rather than constructing static URLs "by hand" is that if you need to change
+the ``name`` of a static URL declaration, the generated URLs will continue to
+resolve properly after the rename.
 
-URLs may also be generated by :func:`~pyramid.url.static_url` to static assets
-that live *outside* the :app:`Pyramid` application.  This will happen when
-the :meth:`~pyramid.config.Configurator.add_static_view` API associated with
-the path fed to :func:`~pyramid.url.static_url` is a *URL* instead of a view
-name.  For example, the ``name`` argument may be ``http://example.com`` while
-the the ``path`` given may be ``mypackage:images``:
+URLs may also be generated by :meth:`~pyramid.request.Request.static_url` to
+static assets that live *outside* the :app:`Pyramid` application.  This will
+happen when the :meth:`~pyramid.config.Configurator.add_static_view` API
+associated with the path fed to :meth:`~pyramid.request.Request.static_url` is
+a *URL* instead of a view name.  For example, the ``name`` argument may be
+``http://example.com`` while the ``path`` given may be ``mypackage:images``:
 
 .. code-block:: python
    :linenos:
 
-   config.add_static_view(name='http://example.com/images', 
+   config.add_static_view(name='http://example.com/images',
                           path='mypackage:images')
 
-Under such a configuration, the URL generated by ``static_url`` for
-assets which begin with ``mypackage:images`` will be prefixed with
+Under such a configuration, the URL generated by ``static_url`` for assets
+which begin with ``mypackage:images`` will be prefixed with
 ``http://example.com/images``:
 
 .. code-block:: python
    :linenos:
 
-   static_url('mypackage:images/logo.png', request)
+   request.static_url('mypackage:images/logo.png')
    # -> http://example.com/images/logo.png
 
-Using :func:`~pyramid.url.static_url` in conjunction with a
-:meth:`~pyramid.configuration.Configurator.add_static_view` makes it possible
-to put static media on a separate webserver during production (if the
-``name`` argument to :meth:`~pyramid.config.Configurator.add_static_view` is a
-URL), while keeping static media package-internal and served by the
-development webserver during development (if the ``name`` argument to
-:meth:`~pyramid.config.Configurator.add_static_view` is a URL prefix).  To
-create such a circumstance, we suggest using the
-:attr:`pyramid.registry.Registry.settings` API in conjunction with a setting
-in the application ``.ini`` file named ``media_location``.  Then set the
-value of ``media_location`` to either a prefix or a URL depending on whether
-the application is being run in development or in production (use a different
-``.ini`` file for production than you do for development).  This is just a
-suggestion for a pattern; any setting name other than ``media_location``
-could be used.
+Using :meth:`~pyramid.request.Request.static_url` in conjunction with a
+:meth:`~pyramid.config.Configurator.add_static_view` makes it possible to put
+static media on a separate webserver during production (if the ``name``
+argument to :meth:`~pyramid.config.Configurator.add_static_view` is a URL),
+while keeping static media package-internal and served by the development
+webserver during development (if the ``name`` argument to
+:meth:`~pyramid.config.Configurator.add_static_view` is a URL prefix).
+
+For example, we may define a :ref:`custom setting <adding_a_custom_setting>`
+named ``media_location`` which we can set to an external URL in production when
+our assets are hosted on a CDN.
+
+.. code-block:: python
+   :linenos:
+
+   media_location = settings.get('media_location', 'static')
+
+   config = Configurator(settings=settings)
+   config.add_static_view(path='myapp:static', name=media_location)
+
+Now we can optionally define the setting in our ini file:
+
+.. code-block:: ini
+   :linenos:
+
+   # production.ini
+   [app:main]
+   use = egg:myapp#main
+
+   media_location = http://static.example.com/
+
+It is also possible to serve assets that live outside of the source by
+referring to an absolute path on the filesystem. There are two ways to
+accomplish this.
+
+First, :meth:`~pyramid.config.Configurator.add_static_view` supports taking an
+absolute path directly instead of an asset spec. This works as expected,
+looking in the file or folder of files and serving them up at some URL within
+your application or externally. Unfortunately, this technique has a drawback in
+that it is not possible to use the :meth:`~pyramid.request.Request.static_url`
+method to generate URLs, since it works based on an asset specification.
+
+.. versionadded:: 1.6
+
+The second approach, available in Pyramid 1.6+, uses the asset overriding APIs
+described in the :ref:`overriding_assets_section` section. It is then possible
+to configure a "dummy" package which then serves its file or folder from an
+absolute path.
+
+.. code-block:: python
+
+   config.add_static_view(path='myapp:static_images', name='static')
+   config.override_asset(to_override='myapp:static_images/',
+                         override_with='/abs/path/to/images/')
+
+From this configuration it is now possible to use
+:meth:`~pyramid.request.Request.static_url` to generate URLs to the data in the
+folder by doing something like
+``request.static_url('myapp:static_images/foo.png')``. While it is not
+necessary that the ``static_images`` file or folder actually exist in the
+``myapp`` package, it is important that the ``myapp`` portion points to a valid
+package. If the folder does exist, then the overriden folder is given priority,
+if the file's name exists in both locations.
+
+.. index::
+   single: Cache Busting
+
+.. _cache_busting:
+
+Cache Busting
+-------------
+
+.. versionadded:: 1.6
+
+In order to maximize performance of a web application, you generally want to
+limit the number of times a particular client requests the same static asset.
+Ideally a client would cache a particular static asset "forever", requiring it
+to be sent to the client a single time.  The HTTP protocol allows you to send
+headers with an HTTP response that can instruct a client to cache a particular
+asset for an amount of time.  As long as the client has a copy of the asset in
+its cache and that cache hasn't expired, the client will use the cached copy
+rather than request a new copy from the server.  The drawback to sending cache
+headers to the client for a static asset is that at some point the static asset
+may change, and then you'll want the client to load a new copy of the asset.
+Under normal circumstances you'd just need to wait for the client's cached copy
+to expire before they get the new version of the static resource.
+
+A commonly used workaround to this problem is a technique known as
+:term:`cache busting`.  Cache busting schemes generally involve generating a
+URL for a static asset that changes when the static asset changes.  This way
+headers can be sent along with the static asset instructing the client to cache
+the asset for a very long time.  When a static asset is changed, the URL used
+to refer to it in a web page also changes, so the client sees it as a new
+resource and requests the asset, regardless of any caching policy set for the
+resource's old URL.
+
+:app:`Pyramid` can be configured to produce cache busting URLs for static
+assets using :meth:`~pyramid.config.Configurator.add_cache_buster`:
+
+.. code-block:: python
+   :linenos:
+
+   import time
+   from pyramid.static import QueryStringConstantCacheBuster
+
+   # config is an instance of pyramid.config.Configurator
+   config.add_static_view(name='static', path='mypackage:folder/static/')
+   config.add_cache_buster(
+       'mypackage:folder/static/',
+       QueryStringConstantCacheBuster(str(int(time.time()))))
+
+Adding the cachebuster instructs :app:`Pyramid` to add the current time for
+a static asset to the query string in the asset's URL:
+
+.. code-block:: python
+   :linenos:
+
+   js_url = request.static_url('mypackage:folder/static/js/myapp.js')
+   # Returns: 'http://www.example.com/static/js/myapp.js?x=1445318121'
+
+When the web server restarts, the time constant will change and therefore so
+will its URL.
+
+.. note::
+
+   Cache busting is an inherently complex topic as it integrates the asset
+   pipeline and the web application. It is expected and desired that
+   application authors will write their own cache buster implementations
+   conforming to the properties of their own asset pipelines. See
+   :ref:`custom_cache_busters` for information on writing your own.
+
+Disabling the Cache Buster
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+It can be useful in some situations (e.g., development) to globally disable all
+configured cache busters without changing calls to
+:meth:`~pyramid.config.Configurator.add_cache_buster`.  To do this set the
+``PYRAMID_PREVENT_CACHEBUST`` environment variable or the
+``pyramid.prevent_cachebust`` configuration value to a true value.
+
+.. _custom_cache_busters:
+
+Customizing the Cache Buster
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Calls to :meth:`~pyramid.config.Configurator.add_cache_buster` may use
+any object that implements the interface
+:class:`~pyramid.interfaces.ICacheBuster`.
+
+:app:`Pyramid` ships with a very simplistic
+:class:`~pyramid.static.QueryStringConstantCacheBuster`, which adds an
+arbitrary token you provide to the query string of the asset's URL. This
+is almost never what you want in production as it does not allow fine-grained
+busting of individual assets.
+
+In order to implement your own cache buster, you can write your own class from
+scratch which implements the :class:`~pyramid.interfaces.ICacheBuster`
+interface.  Alternatively you may choose to subclass one of the existing
+implementations.  One of the most likely scenarios is you'd want to change the
+way the asset token is generated.  To do this just subclass
+:class:`~pyramid.static.QueryStringCacheBuster` and define a
+``tokenize(pathspec)`` method. Here is an example which uses Git to get
+the hash of the current commit:
+
+.. code-block:: python
+   :linenos:
+
+   import os
+   import subprocess
+   from pyramid.static import QueryStringCacheBuster
+
+   class GitCacheBuster(QueryStringCacheBuster):
+       """
+       Assuming your code is installed as a Git checkout, as opposed to an egg
+       from an egg repository like PYPI, you can use this cachebuster to get
+       the current commit's SHA1 to use as the cache bust token.
+       """
+       def __init__(self, param='x', repo_path=None):
+           super(GitCacheBuster, self).__init__(param=param)
+           if repo_path is None:
+               repo_path = os.path.dirname(os.path.abspath(__file__))
+           self.sha1 = subprocess.check_output(
+               ['git', 'rev-parse', 'HEAD'],
+               cwd=repo_path).strip()
+
+       def tokenize(self, pathspec):
+           return self.sha1
+
+A simple cache buster that modifies the path segment can be constructed as
+well:
+
+.. code-block:: python
+   :linenos:
+
+   import posixpath
+
+   class PathConstantCacheBuster(object):
+       def __init__(self, token):
+           self.token = token
+
+       def __call__(self, request, subpath, kw):
+           base_subpath, ext = posixpath.splitext(subpath)
+           new_subpath = base_subpath + self.token + ext
+           return new_subpath, kw
+
+The caveat with this approach is that modifying the path segment
+changes the file name, and thus must match what is actually on the
+filesystem in order for :meth:`~pyramid.config.Configurator.add_static_view`
+to find the file. It's better to use the
+:class:`~pyramid.static.ManifestCacheBuster` for these situations, as
+described in the next section.
+
+.. _path_segment_cache_busters:
+
+Path Segments and Choosing a Cache Buster
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Many caching HTTP proxies will fail to cache a resource if the URL contains
+a query string.  Therefore, in general, you should prefer a cache busting
+strategy which modifies the path segment rather than methods which add a
+token to the query string.
+
+You will need to consider whether the :app:`Pyramid` application will be
+serving your static assets, whether you are using an external asset pipeline
+to handle rewriting urls internal to the css/javascript, and how fine-grained
+do you want the cache busting tokens to be.
+
+In many cases you will want to host the static assets on another web server
+or externally on a CDN. In these cases your :app:`Pyramid` application may not
+even have access to a copy of the static assets. In order to cache bust these
+assets you will need some information about them.
+
+If you are using an external asset pipeline to generate your static files you
+should consider using the :class:`~pyramid.static.ManifestCacheBuster`.
+This cache buster can load a standard JSON formatted file generated by your
+pipeline and use it to cache bust the assets. This has many performance
+advantages as :app:`Pyramid` does not need to look at the files to generate
+any cache busting tokens, but still supports fine-grained per-file tokens.
+
+Assuming an example ``manifest.json`` like:
+
+.. code-block:: json
+
+   {
+       "css/main.css": "css/main-678b7c80.css",
+       "images/background.png": "images/background-a8169106.png"
+   }
+
+The following code would set up a cachebuster:
+
+.. code-block:: python
+   :linenos:
+
+   from pyramid.static import ManifestCacheBuster
+
+   config.add_static_view(
+       name='http://mycdn.example.com/',
+       path='mypackage:static')
+
+   config.add_cache_buster(
+       'mypackage:static/',
+       ManifestCacheBuster('myapp:static/manifest.json'))
+
+It's important to note that the cache buster only handles generating
+cache-busted URLs for static assets. It does **NOT** provide any solutions for
+serving those assets. For example, if you generated a URL for
+``css/main-678b7c80.css`` then that URL needs to be valid either by
+configuring ``add_static_view`` properly to point to the location of the files
+or some other mechanism such as the files existing on your CDN or rewriting
+the incoming URL to remove the cache bust tokens.
 
 .. index::
    single: static assets view
 
+CSS and JavaScript source and cache busting
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Often one needs to refer to images and other static assets inside CSS and
+JavaScript files. If cache busting is active, the final static asset URL is not
+available until the static assets have been assembled. These URLs cannot be
+handwritten. Below is an example of how to integrate the cache buster into
+the entire stack. Remember, it is just an example and should be modified to
+fit your specific tools.
+
+* First, process the files by using a precompiler which rewrites URLs to their
+  final cache-busted form. Then, you can use the
+  :class:`~pyramid.static.ManifestCacheBuster` to synchronize your asset
+  pipeline with :app:`Pyramid`, allowing the pipeline to have full control
+  over the final URLs of your assets.
+
+Now that you are able to generate static URLs within :app:`Pyramid`,
+you'll need to handle URLs that are out of our control. To do this you may
+use some of the following options to get started:
+
+* Configure your asset pipeline to rewrite URL references inline in
+  CSS and JavaScript. This is the best approach because then the files
+  may be hosted by :app:`Pyramid` or an external CDN without having to
+  change anything. They really are static.
+
+* Templatize JS and CSS, and call ``request.static_url()`` inside their
+  template code. While this approach may work in certain scenarios, it is not
+  recommended because your static assets will not really be static and are now
+  dependent on :app:`Pyramid` to be served correctly. See
+  :ref:`advanced_static` for more information on this approach.
+
+If your CSS and JavaScript assets use URLs to reference other assets it is
+recommended that you implement an external asset pipeline that can rewrite the
+generated static files with new URLs containing cache busting tokens. The
+machinery inside :app:`Pyramid` will not help with this step as it has very
+little knowledge of the asset types your application may use. The integration
+into :app:`Pyramid` is simply for linking those assets into your HTML and
+other dynamic content.
+
 .. _advanced_static:
 
 Advanced: Serving Static Assets Using a View Callable
@@ -289,46 +589,51 @@ Advanced: Serving Static Assets Using a View Callable
 
 For more flexibility, static assets can be served by a :term:`view callable`
 which you register manually.  For example, if you're using :term:`URL
-dispatch`, you may want static assets to only be available as a fallback if
-no previous route matches.  Alternately, you might like to serve a particular
+dispatch`, you may want static assets to only be available as a fallback if no
+previous route matches.  Alternatively, you might like to serve a particular
 static asset manually, because its download requires authentication.
 
-Note that you cannot use the :func:`~pyramid.url.static_url` API to generate
-URLs against assets made accessible by registering a custom static view.
+Note that you cannot use the :meth:`~pyramid.request.Request.static_url` API to
+generate URLs against assets made accessible by registering a custom static
+view.
 
 Root-Relative Custom Static View (URL Dispatch Only)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The :class:`pyramid.view.static` helper class generates a Pyramid view
+The :class:`pyramid.static.static_view` helper class generates a Pyramid view
 callable.  This view callable can serve static assets from a directory.  An
 instance of this class is actually used by the
 :meth:`~pyramid.config.Configurator.add_static_view` configuration method, so
 its behavior is almost exactly the same once it's configured.
 
-.. warning:: The following example *will not work* for applications that use
-   :term:`traversal`, it will only work if you use :term:`URL dispatch`
+.. warning::
+
+   The following example *will not work* for applications that use
+   :term:`traversal`; it will only work if you use :term:`URL dispatch`
    exclusively.  The root-relative route we'll be registering will always be
    matched before traversal takes place, subverting any views registered via
    ``add_view`` (at least those without a ``route_name``).  A
-   :class:`~pyramid.view.static` static view cannot be made root-relative when
-   you use traversal.
+   :class:`~pyramid.static.static_view` static view cannot be made
+   root-relative when you use traversal unless it's registered as a :term:`Not
+   Found View`.
 
 To serve files within a directory located on your filesystem at
 ``/path/to/static/dir`` as the result of a "catchall" route hanging from the
 root that exists at the end of your routing table, create an instance of the
-:class:`~pyramid.view.static` class inside a ``static.py`` file in your
+:class:`~pyramid.static.static_view` class inside a ``static.py`` file in your
 application root as below.
 
-.. ignore-next-block
 .. code-block:: python
    :linenos:
 
-   from pyramid.view import static
-   static_view = static('/path/to/static/dir')
+   from pyramid.static import static_view
+   static_view = static_view('/path/to/static/dir', use_subpath=True)
 
-.. note:: For better cross-system flexibility, use an :term:`asset
-   specification` as the argument to :class:`~pyramid.view.static` instead of
-   a physical absolute filesystem path, e.g. ``mypackage:static`` instead of
+.. note::
+
+   For better cross-system flexibility, use an :term:`asset specification` as
+   the argument to :class:`~pyramid.static.static_view` instead of a physical
+   absolute filesystem path, e.g., ``mypackage:static``, instead of
    ``/path/to/mypackage/static``.
 
 Subsequently, you may wire the files that are served by this view up to be
@@ -345,35 +650,36 @@ application's startup code.
    config.add_view('myapp.static.static_view', route_name='catchall_static')
 
 The special name ``*subpath`` above is used by the
-:class:`~pyramid.view.static` view callable to signify the path of the file
-relative to the directory you're serving.
+:class:`~pyramid.static.static_view` view callable to signify the path of the
+file relative to the directory you're serving.
 
-Registering A View Callable to Serve a "Static" Asset
+Registering a View Callable to Serve a "Static" Asset
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-You can register a simple view callable to serve a single static asset.  To
-do so, do things "by hand".  First define the view callable.
+You can register a simple view callable to serve a single static asset.  To do
+so, do things "by hand".  First define the view callable.
 
 .. code-block:: python
    :linenos:
 
    import os
-   from webob import Response
+   from pyramid.response import FileResponse
 
    def favicon_view(request):
        here = os.path.dirname(__file__)
-       icon = open(os.path.join(here, 'static', 'favicon.ico'))
-       return Response(content_type='image/x-icon', app_iter=icon)
+       icon = os.path.join(here, 'static', 'favicon.ico')
+       return FileResponse(icon, request=request)
 
-The above bit of code within ``favicon_view`` computes "here", which is a
-path relative to the Python file in which the function is defined.  It then
-uses the Python ``open`` function to obtain a file handle to a file within
-"here" named ``static``, and returns a response using the open the file
-handle as the response's ``app_iter``.  It makes sure to set the right
-content_type too.
+The above bit of code within ``favicon_view`` computes "here", which is a path
+relative to the Python file in which the function is defined.  It then creates
+a :class:`pyramid.response.FileResponse` using the file path as the response's
+``path`` argument and the request as the response's ``request`` argument.
+:class:`pyramid.response.FileResponse` will serve the file as quickly as
+possible when it's used this way.  It makes sure to set the right content
+length and content_type, too, based on the file extension of the file you pass.
 
-You might register such a view via configuration as a view callable that
-should be called as the result of a traversal:
+You might register such a view via configuration as a view callable that should
+be called as the result of a traversal:
 
 .. code-block:: python
    :linenos:
@@ -406,13 +712,12 @@ It can often be useful to override specific assets from "outside" a given
 :app:`Pyramid` application more or less unchanged.  However, some specific
 template file owned by the application might have inappropriate HTML, or some
 static asset (such as a logo file or some CSS file) might not be appropriate.
-You *could* just fork the application entirely, but it's often more
-convenient to just override the assets that are inappropriate and reuse the
-application "as is".  This is particularly true when you reuse some "core"
-application over and over again for some set of customers (such as a CMS
-application, or some bug tracking application), and you want to make
-arbitrary visual modifications to a particular application deployment without
-forking the underlying code.
+You *could* just fork the application entirely, but it's often more convenient
+to just override the assets that are inappropriate and reuse the application
+"as is".  This is particularly true when you reuse some "core" application over
+and over again for some set of customers (such as a CMS application, or some
+bug tracking application), and you want to make arbitrary visual modifications
+to a particular application deployment without forking the underlying code.
 
 To this end, :app:`Pyramid` contains a feature that makes it possible to
 "override" one asset with one or more other assets.  In support of this
@@ -420,21 +725,18 @@ feature, a :term:`Configurator` API exists named
 :meth:`pyramid.config.Configurator.override_asset`.  This API allows you to
 *override* the following kinds of assets defined in any Python package:
 
-- Individual :term:`Chameleon` templates.
+- Individual template files.
 
-- A directory containing multiple Chameleon templates.
+- A directory containing multiple template files.
 
 - Individual static files served up by an instance of the
-  ``pyramid.view.static`` helper class.
+  ``pyramid.static.static_view`` helper class.
 
 - A directory of static files served up by an instance of the
-  ``pyramid.view.static`` helper class.
-
-- Any other asset (or set of assets) addressed by code that uses the
-  setuptools :term:`pkg_resources` API.
+  ``pyramid.static.static_view`` helper class.
 
-.. note:: The :term:`ZCML` directive named ``asset`` serves the same purpose
-   as the :meth:`~pyramid.config.Configurator.override_asset` method.
+- Any other asset (or set of assets) addressed by code that uses the setuptools
+  :term:`pkg_resources` API.
 
 .. index::
    single: override_asset
@@ -444,25 +746,23 @@ feature, a :term:`Configurator` API exists named
 The ``override_asset`` API
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-An individual call to :meth:`~pyramid.config.Configurator.override_asset`
-can override a single asset.  For example:
+An individual call to :meth:`~pyramid.config.Configurator.override_asset` can
+override a single asset.  For example:
 
-.. ignore-next-block
 .. code-block:: python
    :linenos:
 
    config.override_asset(
-            to_override='some.package:templates/mytemplate.pt',
-            override_with='another.package:othertemplates/anothertemplate.pt')
+       to_override='some.package:templates/mytemplate.pt',
+       override_with='another.package:othertemplates/anothertemplate.pt')
 
 The string value passed to both ``to_override`` and ``override_with`` sent to
-the ``override_asset`` API is called an :term:`asset specification`.  The
-colon separator in a specification separates the *package name* from the
-*asset name*.  The colon and the following asset name are optional.  If they
-are not specified, the override attempts to resolve every lookup into a
-package from the directory of another package.  For example:
+the ``override_asset`` API is called an :term:`asset specification`.  The colon
+separator in a specification separates the *package name* from the *asset
+name*.  The colon and the following asset name are optional.  If they are not
+specified, the override attempts to resolve every lookup into a package from
+the directory of another package.  For example:
 
-.. ignore-next-block
 .. code-block:: python
    :linenos:
 
@@ -471,51 +771,104 @@ package from the directory of another package.  For example:
 
 Individual subdirectories within a package can also be overridden:
 
-.. ignore-next-block
 .. code-block:: python
    :linenos:
 
    config.override_asset(to_override='some.package:templates/',
                          override_with='another.package:othertemplates/')
 
-
-If you wish to override a directory with another directory, you *must*
-make sure to attach the slash to the end of both the ``to_override``
-specification and the ``override_with`` specification.  If you fail to
-attach a slash to the end of a specification that points to a directory,
-you will get unexpected results.
+If you wish to override a directory with another directory, you *must* make
+sure to attach the slash to the end of both the ``to_override`` specification
+and the ``override_with`` specification.  If you fail to attach a slash to the
+end of a specification that points to a directory, you will get unexpected
+results.
 
 You cannot override a directory specification with a file specification, and
-vice versa: a startup error will occur if you try.  You cannot override an
-asset with itself: a startup error will occur if you try.
+vice versa; a startup error will occur if you try.  You cannot override an
+asset with itself; a startup error will occur if you try.
 
 Only individual *package* assets may be overridden.  Overrides will not
-traverse through subpackages within an overridden package.  This means that
-if you want to override assets for both ``some.package:templates``, and
+traverse through subpackages within an overridden package.  This means that if
+you want to override assets for both ``some.package:templates``, and
 ``some.package.views:templates``, you will need to register two overrides.
 
-The package name in a specification may start with a dot, meaning that
-the package is relative to the package in which the configuration
-construction file resides (or the ``package`` argument to the
-:class:`~pyramid.config.Configurator` class construction).
-For example:
+The package name in a specification may start with a dot, meaning that the
+package is relative to the package in which the configuration construction file
+resides (or the ``package`` argument to the
+:class:`~pyramid.config.Configurator` class construction). For example:
 
-.. ignore-next-block
 .. code-block:: python
    :linenos:
 
    config.override_asset(to_override='.subpackage:templates/',
                          override_with='another.package:templates/')
 
-Multiple calls to ``override_asset`` which name a shared ``to_override`` but
-a different ``override_with`` specification can be "stacked" to form a search
-path.  The first asset that exists in the search path will be used; if no
-asset exists in the override path, the original asset is used.
+Multiple calls to ``override_asset`` which name a shared ``to_override`` but a
+different ``override_with`` specification can be "stacked" to form a search
+path.  The first asset that exists in the search path will be used; if no asset
+exists in the override path, the original asset is used.
 
 Asset overrides can actually override assets other than templates and static
 files.  Any software which uses the
 :func:`pkg_resources.get_resource_filename`,
-:func:`pkg_resources.get_resource_stream` or
+:func:`pkg_resources.get_resource_stream`, or
 :func:`pkg_resources.get_resource_string` APIs will obtain an overridden file
 when an override is used.
 
+.. versionadded:: 1.6
+  As of Pyramid 1.6, it is also possible to override an asset by supplying an
+  absolute path to a file or directory. This may be useful if the assets are
+  not distributed as part of a Python package.
+
+Cache Busting and Asset Overrides
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Overriding static assets that are being hosted using
+:meth:`pyramid.config.Configurator.add_static_view` can affect your cache
+busting strategy when using any cache busters that are asset-aware such as
+:class:`pyramid.static.ManifestCacheBuster`. What sets asset-aware cache
+busters apart is that they have logic tied to specific assets. For example,
+a manifest is only generated for a specific set of pre-defined assets. Now,
+imagine you have overridden an asset defined in this manifest with a new,
+unknown version. By default, the cache buster will be invoked for an asset
+it has never seen before and will likely end up returning a cache busting
+token for the original asset rather than the asset that will actually end up
+being served! In order to get around this issue, it's possible to attach a
+different :class:`pyramid.interfaces.ICacheBuster` implementation to the
+new assets. This would cause the original assets to be served by their
+manifest, and the new assets served by their own cache buster. To do this,
+:meth:`pyramid.config.Configurator.add_cache_buster` supports an ``explicit``
+option. For example:
+
+.. code-block:: python
+   :linenos:
+
+   from pyramid.static import ManifestCacheBuster
+
+   # define a static view for myapp:static assets
+   config.add_static_view('static', 'myapp:static')
+
+   # setup a cache buster for your app based on the myapp:static assets
+   my_cb = ManifestCacheBuster('myapp:static/manifest.json')
+   config.add_cache_buster('myapp:static', my_cb)
+
+   # override an asset
+   config.override_asset(
+       to_override='myapp:static/background.png',
+       override_with='theme:static/background.png')
+
+   # override the cache buster for theme:static assets
+   theme_cb = ManifestCacheBuster('theme:static/manifest.json')
+   config.add_cache_buster('theme:static', theme_cb, explicit=True)
+
+In the above example there is a default cache buster, ``my_cb``, for all
+assets served from the ``myapp:static`` folder. This would also affect
+``theme:static/background.png`` when generating URLs via
+``request.static_url('myapp:static/background.png')``.
+
+The ``theme_cb`` is defined explicitly for any assets loaded from the
+``theme:static`` folder. Explicit cache busters have priority and thus
+``theme_cb`` would be invoked for
+``request.static_url('myapp:static/background.png')``, but ``my_cb`` would
+be used for any other assets like
+``request.static_url('myapp:static/favicon.ico')``.