morepath 0.8

Morepath: Python web microframework with super powers

Morepath is a Python web framework. An application consists of models. Each type of model is published on a URL path. Content is exposed to the web using views.

Documentation.

0.8 (2014-11-13)

• Breaking change. Reg 0.9 introduces a new, more powerful way to create dispatch functions, and this has resulted in a new, incompatible Reg API.

  Morepath has been adjusted to make use of the new Reg. This won’t affect many Morepath applications, and they should be able to continue unchanged. But some Morepath extensions and advanced applications may break, so you should be aware of the changes.

  • The @App.function directive has changed from this:

    class A(object):
        pass
    
    class B(object):
        pass
    
    @reg.generic
    def dispatch_function(a, b):
        pass
    
    @App.function(dispatch_function, A, B)
    def dispatched_to(a, b):
        return 'dispatched to A and B'

    to this:

    class A(object):
        pass
    
    class B(object):
        pass
    
    @reg.dispatch('a', 'b')
    def dispatch_function(a, b):
        pass
    
    @App.function(dispatch_function, a=A, b=B)
    def dispatched_to(a, b):
        return 'dispatched to A and B'

    The new system in Reg (see its docs) is a lot more flexible than what we had before. When you use function you don’t need to know about the order of the predicates anymore – this is determined by the arguments to @reg.dispatch(). You can now also have function arguments that Reg ignores for dispatch.

  • The @App.predicate and @App.predicate_fallback directive have changed. You can now install custom predicates and fallbacks for any generic function that’s marked with @reg.dispatch_external_predicates(). The Morepath view code has been simplified to be based on this, and is also more powerful as it can now be extended with new predicates that use predicate-style dispatch.

• Introduce the body_model predicate for views. You can give it the class of the request.body_obj you want to handle with this view. In combination with the load_json directive this allows you to write views that respond only to the POSTing or PUTing of a certain type of object.

• Internals refactoring: we had a few potentially overridable dispatch functions in morepath.generic that actually were never overridden in any directives. Simplify this by moving their implementation into morepath.publish and morepath.request. generic.link, generic.consume and generic.response are now gone.

• Introduce a link_prefix directive that allows you to set the URL prefix used by every link generated by the request.

• A bug fix in request.view(); the lookup on the request was not properly updated.

• Another bug fix in request.view(); if deferred_link_app app is used, request.app should be adjusted to the app currently being deferred to.

• request.after behavior is clarified: it does not run for any exceptions raised during the handling of the request, only for the “proper” response. Fix a bug where it did sometimes run.

• Previously if you returned None for a path in a variables function for a path, you would get a path with None in it. Now it is a LinkError.

• If you return a non-dict for variables for a path, you get a proper LinkError now.

• One test related to defer_links did not work correctly in Python 3. Fixed.

• Add API doc for body_obj. Also fix JSON and objects doc to talk about request.body_obj instead of request.obj.

• Extend API docs for security: detail the API an identity policy needs to implement and fix a few bugs.

• Fix ReST error in API docs for autoconfig and autosetup.

• Fix a few ReST links to the API docs in the app reuse document.

0.7 (2014-11-03)

• Breaking change. There has been a change the way the mount directive works. There has also been a change in the way linking between application works. The changes result into a simpler, more powerful API and implementation.

  The relevant changes are:

  • You can now define your own custom __init__ for morepath.App subclasses. Here you can specify the arguments with which your application object should be mounted. The previous variables class attribute is now ignored.

    It’s not necessary to use super() when you subclass from morepath.App directly.

    So, instead of this:

    class MyApp(morepath.App):
        variables = ['mount_id']

    You should now write this:

    class MyApp(morepath.App):
        def __init__(self, mount_id):
            self.mount_id = mount_id

  • The mount directive should now return an instance of the application being mounted, not a dictionary with mount parameters. The application is specified using the app argument to the directive. So instead of this:

    @RootApp.mount(app=MyApp, path='sub/{id}')
    def mount_sub(id):
        return {
           'mount_id': id
        }

    You should now use this:

    @RootApp.mount(app=MyApp, path='sub/{id}')
    def mount_sub(id):
        return MyApp(mount_id=id)

  • The mount directive now takes a variables argument. This works like the variables argument to the path directive and is used to construct links.

    It is given an instance of the app being mounted, and it should reconstruct those variables needed in its path as a dictionary. If omitted, Morepath tries to get them as attributes from the application instance, just like it tries to get attributes of any model instance.

    MyApp above is a good example of where this is required: it does store the correct information, but as the mount_id attribute, not the id attribute. You should add a variables argument to the mount directive to explain to Morepath how to obtain id:

    @RootApp.mount(app=MyApp, path='sub/{id}',
                   variables=lambda app: dict(id=app.mount_id))
    def mount_sub(id):
        return MyApp(mount_id=id)

    The simplest way to avoid having to do this is to name the attributes the same way as the variables in the paths, just like you can do for model classes.

  • In the past you’d get additional mount context variables as extra variables in the function decorated by the path decorator. This does not happen anymore. Instead you can add a special app parameter to this function. This gives you access to the current application object, and you can extract its attributes there.

    So instead of this:

    @MyApp.path(path='models/{id}', model=Model)
    def get_root(mount_id, id):
        return Model(mount_id, id)

    where mount_id is magically retrieved from the way MyApp was mounted, you now write this:

    @MyApp.path(path='models/{id}', model=Model)
    def get_root(app, id):
        return Model(app.mount_id, id)

  • There was an request.mounted attribute. This was a special an instance of a special Mounted class. This Mounted class is now gone – instead mounted applications are simply instances of their class. To access the currently mounted application, use request.app.

  • The Request object had child and sibling methods as well as a parent attribute to navigate to different “link makers”. You’d navigate to the link maker of an application in order to create links to objects in that application. These are now gone. Instead you can do this navigation from the application object directly, and instead of link makers, you get application instances. You can pass an application instance as a special app argument to request.link and request.view.

    So instead of this:

    request.child(foo).link(obj)

    You now write this:

    request.link(obj, app=request.app.child(foo))

    And instead of this:

    request.parent.link(obj)

    You now write this:

    request.link(obj, app=request.app.parent)

    Note that the new defer_links directive can be used to automate this behavior for particular models.

  • The .child method on App can the app class as well as the parameters for the function decorated by the mount directive:

    app.child(MyApp, id='foo')

    This can also be done by name. So, assuming MyApp was mounted under my_app:

    app.child('my_app', id='foo')

    This is how request.child worked already.

    As an alternative you can now instead pass an app instance:

    app.child(MyApp(mount_id='foo'))

    Unlike the other ways to get the child, this takes the parameters need to create the app instance, as opposed to taking the parameters under which the app was mounted.

  Motivation behind these changes:

  Morepath used to have a Mount class separate from the App classes you define. Since Morepath 0.4 application objects became classes, and it made sense to make their instances the same as the mounted application. This unification has now taken place.

  It then also made sense to use its navigation methods (child and friend) to navigate the mount tree, instead of using the rather complicated “link maker” infrastructure we had before.

  This change simplifies the implementation of mounting considerably, without taking away features and actually making the APIs involved more clear. This simplification in turn made it easier to implement the new defer_links directive.

• Breaking change. The arguments to the render function have changed. This is a function you can pass to a view directive. The render function now takes a second argument, the request. You need to update your render functions to take this into account. This only affects code that supplies an explicit render function to the view, json and html directives, and since not a lot of those functions exist, the impact is expected to be minimal.

• Breaking change. In certain circumstances it was useful to access the settings through an application instance using app.settings. This does not work anymore; access the settings through app.registry.settings instead.

• dump_json and load_json directives. This lets you automatically convert an object going to a response to JSON, and converts JSON coming in as a request body from JSON to an object. See http://morepath.readthedocs.org/en/latest/json.html for more information.

• defer_links directive. This directive can be used to declare that a particular mounted application takes care of linking to instances of a class. Besides deferring request.link() it will also defer request.view. This lets you combine applications with more ease. By returning None from it you can also defer links to this app’s parent app.

• app.ancestors() method and app.root attribute. These can be used for convenient access to the ancestor apps of a mounted application. To access from the request, use request.app.root and request.app.ancestors().

• The App class now has a request_class class attribute. This determines the class of the request that is created and can be overridden by subclasses. more.static now makes use of this.

• Several generic functions that weren’t really pulling their weight are now gone as part of the mount simplification: generic.context and generic.traject are not needed anymore, along with generic.link_maker.

• Change documentation to use uppercase class names for App classes everywhere. This reflects a change in 0.4 and should help clarity.

• Added documentation about auto-reloading Morepath during development.

• No longer silently suppress ImportError during scanning: this can hide genuine ImportError in the underlying code.

  We were suppressing ImportError before as it can be triggered by packages that rely on optional dependencies.

  This is a common case in the .tests subdirectory of a package which may import a test runner like pytest. pytest is only a test dependency of the package and not a mainline dependencies, and this can break scanning. To avoid this problem, Morepath’s autosetup and autoconfig now automatically ignore .tests and .test sub-packages.

  Enhanced the API docs for autosetup and autoconfig to describe scenarios which can generate legitimate ImportError exceptions and how to handle them.

• Fix of examples in tween documentation.

• Minor improvement in docstrings.

0.6 (2014-09-08)

• Fix documentation on the with statement; it was not using the local view variable correctly.

• Add #morepath IRC channel to the community docs.

• Named mounts. Instead of referring to the app class when constructing a link to an object in an application mounted elsewhere, you can put in the name of the mount. The name of the mount can be given explicitly in the mount directive but defaults to the mount path.

  This helps when an application is mounted several times and needs to generate different links depending on where it’s mounted; by referring to the application by name this is loosely coupled and will work no matter what application is mounted under that name.

  This also helps when linking to an application that may or may not be present; instead of doing an import while looking for ImportError, you can try to construct the link and you’ll get a LinkError exception if the application is not there. Though this still assumes you can import the model class of what you’re linking to.

  (see issue #197)

• Introduce a sibling method on Request. This combines the .parent.child step in one for convenience when you want to link to a sibling app.

0.5.1 (2014-08-28)

• Drop usage of sphinxcontrib.youtube in favor of raw HTML embedding, as otherwise too many things broke on readthedocs.

0.5 (2014-08-28)

• Add more.static documentation on local components.

• Add links to youtube videos on Morepath: the keynote at PyCon DE 2013, and the talk on Morepath at EuroPython 2014.

• Add a whole bunch of extra code quality tools to buildout.

• verify_identity would be called even if no identity could be established. Now skip calling verify_identity when we already have NO_IDENTITY. See issue #175.

• Fix issue #186: mounting an app that is absorbing paths could sometimes generate the wrong link. Thanks to Ying Zhong for the bug report and test case.

• Upgraded to a newer version of Reg (0.8) for @reg.classgeneric support as well as performance improvements.

• Add a note in the documentation on how to deal with URL parameters that are not Python names (such as foo@, or blah[]). You can use a combination of extra_parameters and get_converters to handle them.

• Document the use of the with statement for directive abbreviation (see the Views document).

• Created a mailing list:

  https://groups.google.com/forum/#!forum/morepath

  Please join!

  Add a new page on community to document this.

0.4.1 (2014-07-08)

• Compatibility for Python 3. I introduced a meta class in Morepath 0.4 and Python 3 did not like this. Now the tests pass again in Python 3.

• remove generic.lookup, unused since Morepath 0.4.

• Increase test coverage back to 100%.

0.4 (2014-07-07)

• BREAKING CHANGE Move to class-based application registries. This breaks old code and it needs to be updated. The update is not difficult and amounts to:

  • subclass morepath.App instead of instantiating it to create a new app. Use subclasses for extension too.

  • To get a WSGI object you can plug into a WSGI server, you need to instantiate the app class first.

  Old way:

  app = morepath.App()

  So, the app object that you use directives on is an instance. New way:

  class app(morepath.App):
      pass

  So, now it’s a class. The directives look the same as before, so this hasn’t changed:

  @app.view(model=Foo)
  def foo_default(self, request):
     ...

  To extend an application with another one, you used to have to pass the extends arguments. Old way:

  sub_app = morepath.App(extends=[core_app])

  This has now turned into subclassing. New way:

  class sub_app(core_app):
      pass

  There was also a variables argument to specify an application that can be mounted. Old way:

  app = morepath.App(variables=['foo'])

  This is now a class attribute. New way:

  class app(morepath.App):
      variables = ['foo']

  The name argument to help debugging is gone; we can look at the class name now. The testing_config argument used internally in the Morepath tests has also become a class attribute.

  In the old system, the application object was both configuration point and WSGI object. Old way:

  app = morepath.App()
  
  # configuration
  @app.path(...)
  ...
  
  # wsgi
  morepath.run(app)

  In the Morepath 0.4 this has been split. As we’ve already seen, the application class serves. To get a WSGI object, you need to first instantiate it. New way:

  class app(morepath.App):
    pass
  
  # configuration
  @app.path(...)
  ...
  
  # wsgi
  morepath.run(app())

  To mount an application manually with variables, we used to need the special mount() method. Old way:

  mounted_wiki_app = wiki_app.mount(wiki_id=3)

  In the new system, mounting is done during instantiation of the app:

  mounted_wiki_app = wiki_app(wiki_id=3)

  Class names in Python are usually spelled with an upper case. In the Morepath docs the application object has been spelled with a lower case. We’ve used lower-case class names for application objects even in the updated docs for example code, but feel free to make them upper-case in your own code if you wish.

  Why this change? There are some major benefits to this change:

  • both extending and mounting app now use natural Python mechanisms: subclassing and instantation.

  • it allows us to expose the facility to create new directives to the API. You can create application-specific directives.

• You can define your own directives on your applications using the directive directive:

  @my_app.directive('my_directive')

  This exposes details of the configuration system which is underdocumented for now; study the morepath.directive module source code for examples.

• Document how to use more.static to include static resources into your application.

• Add a recursive=False option to the config.scan method. This allows the non-recursive scanning of a package. Only its __init__.py will be scanned.

• To support scanning a single module non-recursively we need a feature that hasn’t landed in mainline Venusian yet, so depend on Venusifork for now.

• A small optimization in the publishing machinery. Less work is done to update the generic function lookup context during routing.

0.3 (2014-06-23)

• Ability to absorb paths entirely in path directive, as per issue #132.

• Refactor of config engine to make Venusian and immediate config more clear.

• Typo fix in docs (Remco Wendt).

• Get version number in docs from setuptools.

• Fix changelog so that PyPI page generates HTML correctly.

• Fix PDF generation so that the full content is generated.

• Ability to mark a view as internal. It will be available to request.view() but will give 404 on the web. This is useful for structuring JSON views for reusability where you don’t want them to actually show up on the web.

• A request.child(something).view() that had this view in turn call a request.view() from the context of the something application would fail – it would not be able to look up the view as lookups still occurred in the context of the mounting application. This is now fixed. (thanks Ying Zhong for reporting it)

  Along with this fix refactored the request object so it keeps a simple mounted attribute instead of a stack of mounts; the stack-like nature was not in use anymore as mounts themselves have parents anyway. The new code is simpler.

0.2 (2014-04-24)

• Python 3 support, in particular Python 3.4 (Alec Munro - fudomunro on github).

• Link generation now takes SCRIPT_NAME into account.

• Morepath 0.1 had a security system, but it was undocumented. Now it’s documented (docs now in Morepath Security), and some of its behavior was slightly tweaked:

  • new verify_identity directive.

  • permission directive was renamed to permission_rule.

  • default unauthorized error is 403 Forbidden, not 401 Unauthorized.

  • morepath.remember and morepath.forbet renamed to morepath.remember_identity and morepath.forget_identity.

• Installation documentation tweaks. (Auke Willem Oosterhoff)

• .gitignore tweaks (Auke Willem Oosterhoff)

0.1 (2014-04-08)

• Initial public release.