Send emails from Plone to interested members (watchers)
collective.watcherlist is a package that enables you to keep a list of people who want to receive emails when an item gets updated. The main use case is something like Products.Poi, which is an issue tracker for Plone. That product lets you create an issue tracker. In this tracker people can add issues. The tracker has managers. Everytime a new issue is posted, the managers should receive an email. When a manager responds to an issue, the original poster (and the other managers) should get an email. Anyone interested in following the issue, should be able to add themselves to the list of people who get an email. The functionality for this was in Poi, but has now been factored out into this collective.watcherlist package.
Who should use this package?
This is not a package for end users. Out of the box it does nothing. It is a package for integrators or developers. You need to write some python and zcml in your own package (like Poi now does) to hook collective.watcherlist up in your code.
We gladly use the ZCA (Zope Component Architecture) to allow others to register their own adapters and own email texts, so outside of Zope the package does not make much sense. And we import some code from Plone too, so you will need that. If you want to use it in bare Zope or CMF, contact me: we can probably do some conditional imports instead.
collective.watcherlist might also be usable as a basis for a newsletter product. If you feel Singing and Dancing is overkill for you, or too hard to adapt to your specific needs, you could try writing some code around collective.watcherlist instead.
Basic integration steps
In its simplest form, the integration that is needed, is this:
- Register an adapter from your content type to collective.watcherlist.interfaces.IWatcherList. In a lot of cases using the default implementation as factory for this adapter is fine: collective.watcherlist.watchers.WatcherList
- Create an html form where people can add themselves to the watcher list. This could also be PloneFormGen form with a custom script adapter as action.
- Register a BrowserView for your content type, inheriting from collective.watcherlist.browser.BaseMail and override its properties subject, plain and/or html.
- Create an event handler or some other code that gets the adapter for your content type and uses that to send an email with the subject and contents defined in the browser view you created.
This addons play well with zope’s event and plone’s contentrules. It triggers a zope event on all basic actions done on the watcherlist:
Those events are registred to be useable as content rule trigger so you can create a rule based on it.
It also provides a content rule action so you can create an action that’s add or remove the current user to or from the watcherlist attached to the context.
Let’s give an example of what you need to do in your own code to use this package. We define a class that holds some info about a party:
>>> class Party(object): ... def __init__(self, reason): ... self.reason = reason ... self.invited = 
We tell the ZCA how to adapt a Party to a watcher list: how to turn it into an object that holds a list of interested people and knows how to send them an email. Normally you would define an interface IParty, say that the Party class implements it and use zcml to register an adapter for that, something like this:
<adapter for=".interfaces.IParty" factory="collective.watcherlist.watchers.WatcherList" />
Let’s ignore the interface and use python (as that is a bit easier to use in tests). We will use the default implementation of a watcherlist as provided by the package:
>>> from zope.component import getGlobalSiteManager >>> from collective.watcherlist.watchers import WatcherList >>> sm = getGlobalSiteManager() >>> sm.registerAdapter(WatcherList, (Party, ))
Now we create a Party and invite people:
>>> birthday = Party("Maurits' birthday") >>> birthday.invited.append('Fred') >>> birthday.invited.append('Mirella')
We see if we can get a watcherlist for it:
>>> from collective.watcherlist.interfaces import IWatcherList >>> watcherlist = IWatcherList(birthday) >>> watcherlist <collective.watcherlist.watchers.WatcherList object at ...>
We can ask several things of this list:
>>> watcherlist.watchers  >>> watcherlist.send_emails True >>> watcherlist.addresses ()
We can add watchers. These should be email addresses or (at least in a Plone context) the ids of members in the site. In your package you would either create a button or other small form that people can use to add themselves to the list, or create some code that automatically adds some people, as Poi does for the creator of a new issue. The code is simple:
>>> watcherlist.watchers.append('email@example.com') >>> watcherlist.watchers.append('firstname.lastname@example.org') >>> watcherlist.watchers ['email@example.com', 'firstname.lastname@example.org'] >>> watcherlist.addresses ('email@example.com', 'firstname.lastname@example.org')
You can always switch off email sending. This has the effect that no addresses are reported:
>>> watcherlist.send_emails = False >>> watcherlist.watchers ['email@example.com', 'firstname.lastname@example.org'] >>> watcherlist.addresses ()
>>> watcherlist.send_emails = True >>> watcherlist.watchers ['email@example.com', 'firstname.lastname@example.org'] >>> watcherlist.addresses ('email@example.com', 'firstname.lastname@example.org')
Now we send an email. We get the email text and subject simply from a browser view that we define. In the test this means we need to give the Party a request object:
>>> from zope.publisher.browser import TestRequest >>> birthday.REQUEST = TestRequest()
We now send an invitation email, but this fails:
>>> watcherlist.send('invitation') Traceback (most recent call last): ... ComponentLookupError...
This means we need to create a browser view with that name. As the basis we should take the base browser view defined in the collective.watcherlist package. It contains three properties that you would normally override: subject, plain and html:
>>> from collective.watcherlist.browser import BaseMail >>> class PartyMail(BaseMail): ... @property ... def subject(self): ... return self.context.reason ... @property ... def plain(self): ... return "Invited are %s" % self.context.invited ... @property ... def html(self): ... return "<p>%s</p>" % self.plain
You would normally register this with zcml, just like any other browser view. But here we do that in python code:
>>> from zope.interface import Interface >>> sm.registerAdapter(PartyMail, (Party, TestRequest), Interface, 'invitation')
And we send the invitation again, in both plain text and html. In this test we have no proper mail host setup, so we simply print the relevant info so we can see what would happen:
>>> watcherlist.send('invitation') Subject = Maurits' birthday Addresses = ('email@example.com', 'firstname.lastname@example.org') Message = From... Content-Type: multipart/alternative;... ... Content-Type: text/plain; charset="us-ascii" ... Invited are ['Fred', 'Mirella'] ... Content-Type: text/html; charset="us-ascii" ... <p>Invited are ['Fred', 'Mirella']</p> ...
Let’s skip the html and see if that simplifies the mail:
>>> PartyMail.html = '' >>> watcherlist.send('invitation') Subject = Maurits' birthday Addresses = ('email@example.com', 'firstname.lastname@example.org') Message = From... MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit <BLANKLINE> Invited are ['Fred', 'Mirella']
If there is neither plain text nor html, we do not send anything:
>>> PartyMail.plain = '' >>> watcherlist.send('invitation')
Let’s add a bit of html again to see that only html goes fine too:
>>> PartyMail.html = '<p>You are invited.</p>' >>> watcherlist.send('invitation') Subject = Maurits' birthday Addresses = ('email@example.com', 'firstname.lastname@example.org') Message = From... MIME-Version: 1.0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: 7bit <BLANKLINE> <p>You are invited.</p>
If we switch off email sending for this watcherlist… no emails are sent:
>>> watcherlist.send_emails = False >>> watcherlist.send('invitation')
>>> watcherlist.send_emails = True
Look at Products.Poi for some more examples of what you can do.
- Pass immediate=False by default. This used to be True. The original idea was to send emails immediately, so that we could catch any errors ourselves and continue with a warning. But since Plone 4.1 the emails are by default sent at the end of the transaction, and exceptions are caught. For immediate mails they are not caught there. So for our uses cases it makes most sense to not send emails immediately, as then Plone does what we want already. You can still pass immediate=True to mailer.simple_send_mail or now also to watchers.send if you want the old behavior back. This fixes issue #8. [maurits]
- Check allow_recursive on the watcher list. The default value is true, which gives the same behavior as before. When the value is false, the addresses property only looks for watchers on the current item, not on the parent. A sample usage would be in Products.Poi to only allow recursive if an issue is not yet assigned. (I am going to use this in custom code for a client). [maurits]
- Strip the email address that we get from a member or the site. I have a site where some email addresses are email@example.com\r\n, which gives an error when sending. [maurits]
- Removed backwards compatibility code for Plone 3.3 and 4.0. We already were not testing on 3.3 anymore, and 4.0 is too hard to keep working too. [maurits]
- Fixed Plone 5 email sending. Improved code quality. Fixed Travis tests. [maurits]
- When the internal watchers list is of type list (instead of tuple), make sure its updated when toggling a watcher [skurfer]
- Added events, triggers and action for content rules. [Gagaro]
- Made compatible with Plone 4.3 (keeping compatibility with Plone 3). [maurits]
- Moved to https://github.com/collective/collective.watcherlist [maurits]
- When showing the plain text in the browser as test, force text/plain as content-type. [maurits]
- Catch MailHostErrors when sending email. [maurits]
- You can now add only_these_addresses as an argument to the send method. This forces sending only to those addresses and ignoring all others. [maurits]
- Fixed possible UnicodeDecodeError when the plain text or html part of the email was not unicode. [maurits]
- Initial release