API documentation

This is the API documentation of the program. It should explain how to create new plugins and navigate the code.

Controller module

This is the core modules that processes all feeds and talks to the storage. It’s where most of the logic lies, althought the parsing is still currently done inside the model. It dispatches the plugin logic to the plugin module.

fast feed parser that offloads tasks to plugins and commands

class feed2exec.controller.FeedManager(conf_path, db_path, pattern=None, session=None)

a feed manager fetches and stores feeds.

this is a “controller” in a “model-view-controller” pattern. it derives the “model” (feed2exec.model.FeedConfStorage) for simplicity’s sake, and there is no real “view” (except maybe __main__).

on intialization, a new requests.Session object is created to be used across all requests. it is passed to plugins during dispatch as a session parameter so it can be reused.

sessionConfig()

our custom session configuration

we change the user agent and set the file:// hanlder. extra configuration may be performed in the future and will override your changes.

this can be used to configure sessions used externally, for example by plugins.

property session

the session property

fetch(parallel=False, force=False, catchup=False)

main entry point for the feed fetch routines.

this iterates through all feeds configured in the linked feed2exec.model.FeedConfStorage that match the given pattern, fetches the feeds and dispatches the parsing, which in turn dispatches the plugins.

Parameters

• parallel (bool) – parse feeds in parallel, using multiprocessing

• force (bool) – force plugin execution even if entry was already seen. passed to feed2exec.feeds.parse as is

• catchup (bool) – set the catchup flag on the feed, so that output plugins can avoid doing any permanent changes.

fetch_one(feed)

fetch the feed content and return the body, in binary

This will call logging.warning() for exceptions requests.exceptions.Timeout and requests.exceptions.ConnectionError as they are transient errors and the user may want to ignore those.

Other exceptions raised from requests.exceptions (like TooManyRedirects or HTTPError but basically any other exception) may be a configuration error or a more permanent failure so will be signaled with logging.error().

this will return the body on success or None on failure and cached entries

dispatch(feed, data, lock=None, force=False)

process parsed entries and execute plugins

This handles locking, caching, and filter and output plugins.

This calls the plugins configured in the feed (using feed2exec.plugins.output() and feed2exec.plugins.filter()). It also updates the cache with the found items if the output plugin succeeds (returns True) and if the filter plugin doesn’t set the skip element in the feed item.

Parameters

• lock (object) – a multiprocessing.Lock object previously initialized. if None, the global LOCK variable will be used: this is used in the test suite to avoid having to pass locks all the way through the API. this lock is in turn passed to plugin calls.

• force (bool) – force plugin execution even if entry was already seen. passed to feed2exec.feeds.parse as is

opml_import(opmlfile)

import a file stream as an OPML feed in the feed storage

Model

The “model” keeps track of feeds and their items. It handles configuration and cache storage.

data structures and storage for feed2exec

class feed2exec.model.Feed(name, *args, **kwargs)

basic data structure representing a RSS or Atom feed.

it derives from the base feedparser.FeedParserDict but forces the element to have a name, which is the unique name for that feed in the feed2exec.controller.FeedManager. We also add convenience functions to parse (in parallel) and normalize feed items.

For all intents and purposes, this can be considered like a dict() unless otherwise noted.

normalize(item=None)

normalize feeds a little more than what feedparser provides.

we do the following operation:

1. add more defaults to item dates (issue #113)

2. missing GUID in some feeds (issue #112)

3. link normalization fails on some feeds, particilarly GitHub, where feeds are /foo instead of https://github.com/foo. unreported for now.

parse(body)

parse the body of the feed

this parses the given body using feedparser and returns the parsed data.

Todo

this could be moved to a plugin, but then we’d need to take out the cache checking logic, which would remove most of the code here…

Parameters

• body (bytes) – the body of the feed, as returned by :func:fetch

• self (dict) – a feed object used to pass to plugins and debugging

Return dict

the parsed data

class feed2exec.model.FeedConfStorage(path, pattern=None)

Feed configuration stored in a config file.

This derives from configparser.RawConfigParser and uses the .ini file set in the path member to read and write settings.

Changes are committed immediately, and no locking is performed so loading here should be safe but not editing.

The particular thing about this configuration is that there is an iterator that will yield entries matching the pattern substring provided in the constructor.

add(name, url, output=None, args=None, filter=None, filter_args=None, folder=None, mailbox=None)

add the designated feed to the configuration

this is not thread-safe.

set(section, option, value=None)

override parent to make sure we immediately write changes

not thread-safe

remove_option(section, option)

override parent to make sure we immediately write changes

not thread-safe

remove(name)

convenient alias for configparser.RawConfigParser.remove_section()

not thread-safe

commit()

write the feed configuration

see configparser.RawConfigParser.write()

Main entry point

The main entry point of the program is in the feed2exec.__main__ module. This is to make it possible to call the program directly from the source code through the Python interpreter with:

python -m feed2exec

All this code is here rather than in __init__.py to avoid requiring too many dependencies in the base module, which contains useful metadata for setup.py.

This uses the click module to define the base command and options.

fast feed parser that offloads tasks to plugins and commands

Plugins

Plugin interface

In this context, a “plugin” is simply a Python module with a defined interface.

feed2exec.plugins.output(feed, item, lock=None, session=None)

load and run the given plugin with the given arguments

an “output plugin” is a simple Python module with an output callable defined which will process arguments and should output them somewhere, for example by email or through another command. the plugin is called (from feed2exec.feeds.parse()) when a new item is found, unless cache is flushed or ignored.

The “callable” can be a class, in which case only the constructor is called or a function. The *args and **kwargs parameter SHOULD be used in the function definition for forward-compatibility (ie. to make sure new parameters added do not cause a regression).

Plugins should also expect to be called in parallel and should use the provided lock (a multiprocessor.Lock object) to acquire and release locks around contentious resources.

Finally, the FeedManager will pass along his own session that should be reused by plugins to do requests. This allows plugins to be unit-tested and leverages the built-in cache as well.

The following keywords are usually replaced in the arguments:

• {item.link}

• {item.title}

• {item.description}

• {item.published}

• {item.updated}

• {item.guid}

The full list of such parameters is determined by the :module:feedparser module.

Similarly, feed parameters from the configuration file are accessible.

Caution

None of those parameters are sanitized in any way other than what feedparser does, so plugins writing files, executing code or talking to the network should be careful to sanitize the input appropriately.

The feed and items are also passed to the plugin as keyword arguments. Plugins should especially respect the catchup argument that, when set, forbids plugins to do any permanent activity. For example, plugins MUST NOT run commands, write files, or make network requests. In general, “catchup mode” should be fast: it allows users to quickly catchup with new feeds without firing plugins, but it should also allow users to test configurations so plugins SHOULD give information to the user about what would have been done by the plugin without catchup.

Parameters

• feed (dict) – the feed metadata

• item (dict) – the updated item

Return object

the loaded plugin

Note

more information about plugin design is in the Writing new plugins document.

feed2exec.plugins.filter(feed, item, lock=None, session=None)

call filter plugins.

very similar to the output plugin, but just calls the filter module member instead of output

Todo

common code with output() should be factored out, but output() takes arguments…

feed2exec.plugins.resolve(plugin)

resolve a short plugin name to a loadable plugin path

Some parts of feed2exec allow shorter plugin names. For example, on the commandline, users can pass maildir instead of feed2exec.plugins.maildir.

Plugin resolution works like this:

1. search for the module in the feed2exec.plugins namespace

2. if that fails, consider the module to be an absolute path

Note

actual plugins are documented in the Plugins document.

Utilities

Those are various utilities reused in multiple modules that did not fit anywhere else.

various reusable utilities

feed2exec.utils.slug(text)

Make a URL-safe, human-readable version of the given text

This will do the following:

1. decode unicode characters into ASCII

2. shift everything to lowercase

3. strip whitespace

4. replace other non-word characters with dashes

5. strip extra dashes

This somewhat duplicates the Google.slugify() function but slugify is not as generic as this one, which can be reused elsewhere.

>>> slug('test')
'test'
>>> slug('Mørdag')
'mordag'
>>> slug("l'été c'est fait pour jouer")
'l-ete-c-est-fait-pour-jouer'
>>> slug(u"çafe au lait (boisson)")
'cafe-au-lait-boisson'
>>> slug(u"Multiple  spaces -- and symbols! -- merged")
'multiple-spaces-and-symbols-merged'

This is a simpler, one-liner version of the slugify module.

taken from ecdysis

feed2exec.utils.make_dirs_helper(path)

Create the directory if it does not exist

Return True if the directory was created, false if it was already present, throw an OSError exception if it cannot be created

>>> import tempfile
>>> import os
>>> import os.path as p
>>> d = tempfile.mkdtemp()
>>> make_dirs_helper(p.join(d, 'foo'))
True
>>> make_dirs_helper(p.join(d, 'foo'))
False
>>> make_dirs_helper('')
False
>>> make_dirs_helper(p.join('/dev/null', 'foo')) 
Traceback (most recent call last):
    ...
NotADirectoryError: [Errno 20] Not a directory: ...
>>> os.rmdir(p.join(d, 'foo'))
>>> os.rmdir(d)
>>>

feed2exec.utils.find_test_file(name='.')

need to be updated from ecdysis

See also https://pypi.org/project/pytest-datadir/

feed2exec.utils.find_parent_module()

find the name of a the first module calling this module

if we cannot find it, we return the current module’s name (__name__) instead.

taken from ecdysis