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author | Aditi <aditi.iitr@gmail.com> | 2013-06-21 23:09:22 +0530 |
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committer | Aditi <aditi.iitr@gmail.com> | 2013-06-21 23:09:22 +0530 |
commit | 2719d546a57c2332e36cc056ac80ec5d79672c1a (patch) | |
tree | 1f62ab8f761026d4faa5442032df133fc90d47f2 /docs/source/pluginwriter | |
parent | 1a6f065419290b3f4234ce4a89bb2c46b13e8a12 (diff) | |
parent | 92b22e7deac547835f69168f97012b52e87b6de4 (diff) | |
download | mediagoblin-2719d546a57c2332e36cc056ac80ec5d79672c1a.tar.lz mediagoblin-2719d546a57c2332e36cc056ac80ec5d79672c1a.tar.xz mediagoblin-2719d546a57c2332e36cc056ac80ec5d79672c1a.zip |
Merge remote-tracking branch 'cweb/master'
Diffstat (limited to 'docs/source/pluginwriter')
-rw-r--r-- | docs/source/pluginwriter/api.rst | 296 | ||||
-rw-r--r-- | docs/source/pluginwriter/database.rst | 114 | ||||
-rw-r--r-- | docs/source/pluginwriter/foreward.rst | 43 | ||||
-rw-r--r-- | docs/source/pluginwriter/quickstart.rst | 188 | ||||
-rw-r--r-- | docs/source/pluginwriter/tests.rst | 64 |
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diff --git a/docs/source/pluginwriter/api.rst b/docs/source/pluginwriter/api.rst new file mode 100644 index 00000000..66def173 --- /dev/null +++ b/docs/source/pluginwriter/api.rst @@ -0,0 +1,296 @@ +.. MediaGoblin Documentation + + Written in 2013 by MediaGoblin contributors + + To the extent possible under law, the author(s) have dedicated all + copyright and related and neighboring rights to this software to + the public domain worldwide. This software is distributed without + any warranty. + + You should have received a copy of the CC0 Public Domain + Dedication along with this software. If not, see + <http://creativecommons.org/publicdomain/zero/1.0/>. + +.. _plugin-api-chapter: + +========== +Plugin API +========== + +This documents the general plugin API. + +Please note, at this point OUR PLUGIN HOOKS MAY AND WILL CHANGE. +Authors are encouraged to develop plugins and work with the +MediaGoblin community to keep them up to date, but this API will be a +moving target for a few releases. + +Please check the :ref:`release-notes` for updates! + + +How are hooks added? Where do I find them? +------------------------------------------- + +Much of this document talks about hooks, both as in terms of regular +hooks and template hooks. But where do they come from, and how can +you find a list of them? + +For the moment, the best way to find available hooks is to check the +source code itself. (Yes, we should start a more official hook +listing with descriptions soon.) But many hooks you may need do not +exist yet: what to do then? + +The plan at present is that we are adding hooks as people need them, +with community discussion. If you find that you need a hook and +MediaGoblin at present doesn't provide it at present, please +`http://mediagoblin.org/pages/join.html <talk to us>`_! We'll +evaluate what to do from there. + + +:mod:`pluginapi` Module +----------------------- + +.. automodule:: mediagoblin.tools.pluginapi + :members: get_config, register_routes, register_template_path, + register_template_hooks, get_hook_templates, + hook_handle, hook_runall, hook_transform + +Configuration +------------- + +Your plugin may define its own configuration defaults. + +Simply add to the directory of your plugin a config_spec.ini file. An +example might look like:: + + [plugin_spec] + some_string = string(default="blork") + some_int = integer(default=50) + +This means that when people enable your plugin in their config you'll +be able to provide defaults as well as type validation. + + +Context Hooks +------------- + +View specific hooks ++++++++++++++++++++ + +You can hook up to almost any template called by any specific view +fairly easily. As long as the view directly or indirectly uses the +method ``render_to_response`` you can access the context via a hook +that has a key in the format of the tuple:: + + (view_symbolic_name, view_template_path) + +Where the "view symbolic name" is the same parameter used in +``request.urlgen()`` to look up the view. So say we're wanting to add +something to the context of the user's homepage. We look in +mediagoblin/user_pages/routing.py and see:: + + add_route('mediagoblin.user_pages.user_home', + '/u/<string:user>/', + 'mediagoblin.user_pages.views:user_home') + +Aha! That means that the name is ``mediagoblin.user_pages.user_home``. +Okay, so then we look at the view at the +``mediagoblin.user_pages.user_home`` method:: + + @uses_pagination + def user_home(request, page): + # [...] whole bunch of stuff here + return render_to_response( + request, + 'mediagoblin/user_pages/user.html', + {'user': user, + 'user_gallery_url': user_gallery_url, + 'media_entries': media_entries, + 'pagination': pagination}) + +Nice! So the template appears to be +``mediagoblin/user_pages/user.html``. Cool, that means that the key +is:: + + ("mediagoblin.user_pages.user_home", + "mediagoblin/user_pages/user.html") + +The context hook uses ``hook_transform()`` so that means that if we're +hooking into it, our hook will both accept one argument, ``context``, +and should return that modified object, like so:: + + def add_to_user_home_context(context): + context['foo'] = 'bar' + return context + + hooks = { + ("mediagoblin.user_pages.user_home", + "mediagoblin/user_pages/user.html"): add_to_user_home_context} + + +Global context hooks +++++++++++++++++++++ + +If you need to add something to the context of *every* view, it is not +hard; there are two hooks hook that also uses hook_transform (like the +above) but make available what you are providing to *every* view. + +Note that there is a slight, but critical, difference between the two. + +The most general one is the ``'template_global_context'`` hook. This +one is run only once, and is read into the global context... all views +will get access to what are in this dict. + +The slightly more expensive but more powerful one is +``'template_context_prerender'``. This one is not added to the global +context... it is added to the actual context of each individual +template render right before it is run! Because of this you also can +do some powerful and crazy things, such as checking the request object +or other parts of the context before passing them on. + + +Adding static resources +----------------------- + +It's possible to add static resources for your plugin. Say your +plugin needs some special javascript and images... how to provide +them? Then how to access them? MediaGoblin has a way! + + +Attaching to the hook ++++++++++++++++++++++ + +First, you need to register your plugin's resources with the hook. +This is pretty easy actually: you just need to provide a function that +passes back a PluginStatic object. + +.. autoclass:: mediagoblin.tools.staticdirect.PluginStatic + + +Running plugin assetlink +++++++++++++++++++++++++ + +In order for your plugin assets to be properly served by MediaGoblin, +your plugin's asset directory needs to be symlinked into the directory +that plugin assets are served from. To set this up, run:: + + ./bin/gmg assetlink + + +Using staticdirect +++++++++++++++++++ + +Once you have this, you will want to be able to of course link to your +assets! MediaGoblin has a "staticdirect" tool; you want to use this +like so in your templates:: + + staticdirect("css/monkeys.css", "mystaticname") + +Replace "mystaticname" with the name you passed to PluginStatic. The +staticdirect method is, for convenience, attached to the request +object, so you can access this in your templates like: + +.. code-block:: html + + <img alt="A funny bunny" + src="{{ request.staticdirect('images/funnybunny.png', 'mystaticname') }}" /> + + +Additional hook tips +-------------------- + +This section aims to explain some tips in regards to adding hooks to +the MediaGoblin repository. + +WTForms hooks ++++++++++++++ + +We haven't totally settled on a way to tranform wtforms form objects, +but here's one way. In your view:: + + from mediagoblin.foo.forms import SomeForm + + def some_view(request) + form_class = hook_transform('some_form_transform', SomeForm) + form = form_class(request.form) + +Then to hook into this form, do something in your plugin like:: + + import wtforms + + class SomeFormAdditions(wtforms.Form): + new_datefield = wtforms.DateField() + + def transform_some_form(orig_form): + class ModifiedForm(orig_form, SomeFormAdditions) + return ModifiedForm + + hooks = { + 'some_form_transform': transform_some_form} + + +Interfaces +++++++++++ + +If you want to add a pseudo-interface, it's not difficult to do so. +Just write the interface like so:: + + class FrobInterface(object): + """ + Interface for Frobbing. + + Classes implementing this interface should provide defrob and frob. + They may also implement double_frob, but it is not required; if + not provided, we will use a general technique. + """ + + def defrob(self, frobbed_obj): + """ + Take a frobbed_obj and defrob it. Returns the defrobbed object. + """ + raise NotImplementedError() + + def frob(self, normal_obj): + """ + Take a normal object and frob it. Returns the frobbed object. + """ + raise NotImplementedError() + + def double_frob(self, normal_obj): + """ + Frob this object and return it multiplied by two. + """ + return self.frob(normal_obj) * 2 + + + def some_frob_using_method(): + # something something something + frobber = hook_handle(FrobInterface) + frobber.frob(blah) + + # alternately you could have a default + frobber = hook_handle(FrobInterface) or DefaultFrobber + frobber.defrob(foo) + + +It's fine to use your interface as the key instead of a string if you +like. (Usually this is messy, but since interfaces are public and +since you need to import them into your plugin anyway, interfaces +might as well be keys.) + +Then a plugin providing your interface can be like:: + + from mediagoblin.foo.frobfrogs import FrobInterface + from frogfrobber import utils + + class FrogFrobber(FrobInterface): + """ + Takes a frogputer science approach to frobbing. + """ + def defrob(self, frobbed_obj): + return utils.frog_defrob(frobbed_obj) + + def frob(self, normal_obj): + return utils.frog_frob(normal_obj) + + hooks = { + FrobInterface: lambda: return FrogFrobber} diff --git a/docs/source/pluginwriter/database.rst b/docs/source/pluginwriter/database.rst new file mode 100644 index 00000000..603a19eb --- /dev/null +++ b/docs/source/pluginwriter/database.rst @@ -0,0 +1,114 @@ +.. MediaGoblin Documentation + + Written in 2013 by MediaGoblin contributors + + To the extent possible under law, the author(s) have dedicated all + copyright and related and neighboring rights to this software to + the public domain worldwide. This software is distributed without + any warranty. + + You should have received a copy of the CC0 Public Domain + Dedication along with this software. If not, see + <http://creativecommons.org/publicdomain/zero/1.0/>. + + +.. _plugin-database-chapter: + + +=========================== +Database models for plugins +=========================== + + +Accessing Existing Data +======================= + +If your plugin wants to access existing data, this is quite +straight forward. Just import the appropiate models and use +the full power of SQLAlchemy. Take a look at the (upcoming) +database section in the Developer's Chapter. + + +Creating new Tables +=================== + +If your plugin needs some new space to store data, you +should create a new table. Please do not modify core +tables. Not doing so might seem inefficient and possibly +is. It will help keep things sane and easier to upgrade +versions later. + +So if you create a new plugin and need new tables, create a +file named ``models.py`` in your plugin directory. You +might take a look at the core's db.models for some ideas. +Here's a simple one: + +.. code-block:: python + + from mediagoblin.db.base import Base + from sqlalchemy import Column, Integer, Unicode, ForeignKey + + class MediaSecurity(Base): + __tablename__ = "yourplugin__media_security" + + # The primary key *and* reference to the main media_entry + media_entry = Column(Integer, ForeignKey('core__media_entries.id'), + primary_key=True) + get_media_entry = relationship("MediaEntry", + backref=backref("security_rating", cascade="all, delete-orphan")) + + rating = Column(Unicode) + + MODELS = [MediaSecurity] + +That's it. + +Some notes: + +* Make sure all your ``__tablename__`` start with your + plugin's name so the tables of various plugins can't + conflict in the database. (Conflicts in python naming are + much easier to fix later). +* Try to get your database design as good as possible in + the first attempt. Changing the database design later, + when people already have data using the old design, is + possible (see next chapter), but it's not easy. + + +Changing the Database Schema Later +================================== + +If your plugin is in use and instances use it to store some +data, changing the database design is a tricky thing. + +1. Make up your mind how the new schema should look like. +2. Change ``models.py`` to contain the new schema. Keep a + copy of the old version around for your personal + reference later. +3. Now make up your mind (possibly using your old and new + ``models.py``) what steps in SQL are needed to convert + the old schema to the new one. + This is called a "migration". +4. Create a file ``migrations.py`` that will contain all + your migrations and add your new migration. + +Take a look at the core's ``db/migrations.py`` for some +good examples on what you might be able to do. Here's a +simple one to add one column: + +.. code-block:: python + + from mediagoblin.db.migration_tools import RegisterMigration, inspect_table + from sqlalchemy import MetaData, Column, Integer + + MIGRATIONS = {} + + @RegisterMigration(1, MIGRATIONS) + def add_license_preference(db): + metadata = MetaData(bind=db.bind) + + security_table = inspect_table(metadata, 'yourplugin__media_security') + + col = Column('security_level', Integer) + col.create(security_table) + db.commit() diff --git a/docs/source/pluginwriter/foreward.rst b/docs/source/pluginwriter/foreward.rst new file mode 100644 index 00000000..fd3a0c22 --- /dev/null +++ b/docs/source/pluginwriter/foreward.rst @@ -0,0 +1,43 @@ +.. MediaGoblin Documentation + + Written in 2011, 2012 by MediaGoblin contributors + + To the extent possible under law, the author(s) have dedicated all + copyright and related and neighboring rights to this software to + the public domain worldwide. This software is distributed without + any warranty. + + You should have received a copy of the CC0 Public Domain + Dedication along with this software. If not, see + <http://creativecommons.org/publicdomain/zero/1.0/>. + +======== +Foreword +======== + +About the Plugin Writer's Guide +=============================== + +This guide covers writing plugins for GNU MediaGoblin. It's very much +a work in progress partially because we just started writing it and +partially because the plugin API is currently in flux. + + +Improving the Plugin Writer's Guide +=================================== + +There are a few ways---please pick whichever method is convenient for +you! + +1. Write up a bug report in the bug tracker +2. Tell someone on IRC ``#mediagoblin`` on Freenode. +3. Write an email to the devel mailing list. + +Information about the bugtracker, IRC and the mailing list is all on +the `join page`_. + +.. _join page: http://mediagoblin.org/join/ + +Patches are the most helpful, but even feedback on what you think +could be improved and how to improve it is also helpful. + diff --git a/docs/source/pluginwriter/quickstart.rst b/docs/source/pluginwriter/quickstart.rst new file mode 100644 index 00000000..6d45ea36 --- /dev/null +++ b/docs/source/pluginwriter/quickstart.rst @@ -0,0 +1,188 @@ +.. MediaGoblin Documentation + + Written in 2011, 2012 by MediaGoblin contributors + + To the extent possible under law, the author(s) have dedicated all + copyright and related and neighboring rights to this software to + the public domain worldwide. This software is distributed without + any warranty. + + You should have received a copy of the CC0 Public Domain + Dedication along with this software. If not, see + <http://creativecommons.org/publicdomain/zero/1.0/>. + + +=========== +Quick Start +=========== + +This is a quick start. It's not comprehensive, but it walks through +writing a basic plugin called "sampleplugin" which logs "I've been +started!" when ``setup_plugin()`` has been called. + +.. todo: Rewrite this to be a useful plugin + + +Step 1: Files and directories +============================= + +GNU MediaGoblin plugins are Python projects at heart. As such, you should +use a standard Python project directory tree:: + + sampleplugin/ + |- README + |- LICENSE + |- setup.py + |- sampleplugin/ + |- __init__.py + + +The outer ``sampleplugin`` directory holds all the project files. + +The ``README`` should cover what your plugin does, how to install it, +how to configure it, and all the sorts of things a README should +cover. + +The ``LICENSE`` should have the license under which you're +distributing your plugin. + +The inner ``sampleplugin`` directory is the Python package that holds +your plugin's code. + +The ``__init__.py`` denotes that this is a Python package. It also +holds the plugin code and the ``hooks`` dict that specifies which +hooks the sampleplugin uses. + + +Step 2: README +============== + +Here's a rough ``README``. Generally, you want more information +because this is the file that most people open when they want to learn +more about your project. + +:: + + README + ====== + + This is a sample plugin. It logs a line when ``setup__plugin()`` is + run. + + +Step 3: LICENSE +=============== + +GNU MediaGoblin plugins must be licensed under the AGPLv3 or later. So +the LICENSE file should be the AGPLv3 text which you can find at +`<http://www.gnu.org/licenses/agpl-3.0.html>`_ + + +Step 4: setup.py +================ + +This file is used for packaging and distributing your plugin. + +We'll use a basic one:: + + from setuptools import setup, find_packages + + setup( + name='sampleplugin', + version='1.0', + packages=find_packages(), + include_package_data=True, + install_requires=[], + license='AGPLv3', + ) + + +See `<http://docs.python.org/distutils/index.html#distutils-index>`_ +for more details. + + +Step 5: the code +================ + +The code for ``__init__.py`` looks like this: + +.. code-block:: python + :linenos: + :emphasize-lines: 12,23 + + import logging + from mediagoblin.tools.pluginapi import Plugin, get_config + + + # This creates a logger that you can use to log information to + # the console or a log file. + _log = logging.getLogger(__name__) + + + # This is the function that gets called when the setup + # hook fires. + def setup_plugin(): + _log.info("I've been started!") + config = get_config('sampleplugin') + if config: + _log.info('%r' % config) + else: + _log.info('There is no configuration set.') + + + # This is a dict that specifies which hooks this plugin uses. + # This one only uses one hook: setup. + hooks = { + 'setup': setup_plugin + } + + +Line 12 defines the ``setup_plugin`` function. + +Line 23 defines ``hooks``. When MediaGoblin loads this file, it sees +``hooks`` and registers all the callables with their respective hooks. + + +Step 6: Installation and configuration +====================================== + +To install the plugin for development, you need to make sure it's +available to the Python interpreter that's running MediaGoblin. + +There are a couple of ways to do this, but we're going to pick the +easy one. + +Use ``python`` from your MediaGoblin virtual environment and do:: + + python setup.py develop + +Any changes you make to your plugin will be available in your +MediaGoblin virtual environment. + +Then adjust your ``mediagoblin.ini`` file to load the plugin:: + + [plugins] + + [[sampleplugin]] + + +Step 7: That's it! +================== + +When you launch MediaGoblin, it'll load the plugin and you'll see +evidence of that in the log file. + +That's it for the quick start! + + +Where to go from here +===================== + +See the documentation on the :ref:`plugin-api-chapter` for code +samples and other things you can use when building your plugin. If +your plugin needs its own database models, see +:ref:`plugin-database-chapter`. + +See `Hitchhiker's Guide to Packaging +<http://guide.python-distribute.org/>`_ for more information on +packaging your plugin. diff --git a/docs/source/pluginwriter/tests.rst b/docs/source/pluginwriter/tests.rst new file mode 100644 index 00000000..fe99688f --- /dev/null +++ b/docs/source/pluginwriter/tests.rst @@ -0,0 +1,64 @@ +.. MediaGoblin Documentation + + Written in 2013 by MediaGoblin contributors + + To the extent possible under law, the author(s) have dedicated all + copyright and related and neighboring rights to this software to + the public domain worldwide. This software is distributed without + any warranty. + + You should have received a copy of the CC0 Public Domain + Dedication along with this software. If not, see + <http://creativecommons.org/publicdomain/zero/1.0/>. + +============================== +Writing unit tests for plugins +============================== + +Here's a brief guide to writing unit tests for plugins. However, it +isn't really ideal. It also hasn't been well tested... yes, there's +some irony there :) + +Some notes: we're using py.test and webtest for unit testing stuff. +Keep that in mind. + +My suggestion is to mime the behavior of `mediagoblin/tests/` and put +that in your own plugin, like `myplugin/tests/`. Copy over +`conftest.py` and `pytest.ini` to your tests directory, but possibly +change the `test_app` fixture to match your own tests' config needs. +For example:: + + import pkg_resources + # [...] + + @pytest.fixture() + def test_app(request): + return get_app( + request, + mgoblin_config=pkg_resources.resource_filename( + 'myplugin.tests', 'myplugin_mediagoblin.ini')) + +In any test module in your tests directory you can then do:: + + def test_somethingorother(test_app): + # real code goes here + pass + +And you'll get a mediagoblin application wrapped in webtest passed in +to your environment. + +If your plugin needs to define multiple configuration setups, you can +actually set up multiple fixtures very easily for this. You can just +set up multiple fixtures with different names that point to different +configs and pass them in as that named argument. + +To run the tests, from mediagoblin's directory (make sure that your +plugin has been added to your mediagoblin checkout's virtualenv!) do:: + + ./runtests.sh /path/to/myplugin/tests/ + +replacing `/path/to/myplugin/` with the actual path to your plugin. + +NOTE: again, the above is untested, but it should probably work. If +you run into trouble, `contact us +<http://mediagoblin.org/pages/join.html>`_, preferably on IRC! |