check in some skeletal code + notes, nothing concrete or working yet
svn path=/plone.app.discussion/trunk/; revision=26892
This commit is contained in:
Martin Aspeli
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=================================
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plone.app.discussion design notes
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=================================
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This document contains design notes for plone.app.discussion.
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The Comment class
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-----------------
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The inheritance tree for DiscussionItem is shown below. Classes we want to
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mix in and interface we want to implement in the Comment class are marked
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with [x].
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[ ] DiscussionItem
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[ ] Document
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[ ] PortalContent = [ ] IContentish
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[ ] DynamicType = [ ] IDynamicType
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[ ] CMFCatalogAware = [ ] <no interface>
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[ ] SimpleItem = [ ] ISimpleItem
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[ ] Item [ ]
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[?] Base = [ ] <no interface>
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[ ] Resource = [ ] <no interface>
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[ ] CopySource = [ ] ICopySource
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[ ] Tabs = [ ] <no interface>
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[x] Traversable = [ ] ITraversable
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[ ] Element = [ ] <no interface>
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[x] Owned = [ ] IOwned
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[ ] UndoSupport = [ ] IUndoSupport
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[ ] Persistent [ ]
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[ ] Implicit [ ]
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[x] RoleManager = [ ] IRoleManager
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[ ] RoleManager = [ ] IPermissionMappingSupport
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[ ] DefaultDublinCoreImpl = [ ] IDublinCore
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[ ] ICatalogableDublinCore
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[ ] IMutableDublinCore
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[ ] PropertyManager = [ ] IPropertyManager
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Thus, we want:
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* Traversable, to get absolute_url() and friends
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- this requires a good acquisition chain at all times
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* Acquisition.Explicit, to support acquisition
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- we do not want implicit acquisition
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* Owned, to be able to track ownership
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* RoleManager, to support permissions and local roles
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We also want to use a number of custom indexers for most of the standard
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metadata such as creator, effective date etc.
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Finally, we'll need event handlers to perform the actual indexing.
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The Discussable class
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---------------------
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To obtain comments for a content item, we adapt the content to IDiscussable.
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This has a 'replies' BTree.
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To support __parent__ pointer integrity and stable URLs, we will implement
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IDiscussable as a persistent object stored in an annotation. Comments directly
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in reply to the content item have a __parent__ pointing to this, which in turn
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has a __parent__ pointing at the content item.
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The IDiscussable interface also maintains information about the total number
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of comments and the unique set of commenters' usernames. These are indexed in
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the catalog, allowing queries like "recently commented-upon content items",
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"my comments", or "all comments by user X". These values need to be stored and
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maintained by event handlers, not calculated on the fly.
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See collective.discussionplus for inspiration.
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Traversal and acquisition
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--------------------------
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A comment may have a URL such as:
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http://localhost:8080/site/content/++comments++/1/2/3
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For this traversal to work, we have:
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- a namespace traversal adapter for ++comments++ that looks up an
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IDiscussable adapter on the context and returns this
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- an IPublishTraverse adapter for IHasReplies (inherited by IDiscussable
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and IComment), which looks up values in the 'replies' dictionary and
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acquisition-wraps them.
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- the IDiscussable adapter needs to have an id of ++comment++
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XXX: unrestrictedTraverse() does not take IPublishTraverse adapters into
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account. This may mean we need to implement __getitem__ on comments instead
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of/in addition to using a custom IPublishTraverse for IHasReplies.
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Discussion settings
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-------------------
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Discussion can be enabled per-type and per-instance, via values in the FTI
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(allow_discussion) and on the object. These will remain unchanged. The
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IDiscussable object's 'enabled' property should consult these.
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Global settings should be managed using plone.registry. A control panel
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can be generated from this as well, using the helper class in
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plone.app.registry.
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Note that some settings, notably those to do with permissions and workflow,
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will need to be wired up as custom form fields with custom data mangers
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or similar.
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Workflow and permissions
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------------------------
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Where possible, we should use existing permissions:
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* View
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* Reply to Item
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* Modify Portal Content
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* Request Review
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In addition, we'll need a 'Moderator' role and a moderation permission,
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* Moderate comment
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* Bypass moderation
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To control whether Anonymous can post comments, we manage the 'Reply to Item'
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permission. To control whether moderation is required for various roles, we
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could manage the 'Bypass moderation' permission.
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These could work in a workflow like this:
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* --> [posted] -- {publish} --> [published]--> *
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| ^
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+----- {auto-publish} -----+
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+----- {auto-moderate} ----+
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The 'posted' state is the initial state. 'published' is the state where the
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comment is visible to non-reviewers.
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The 'publish' transition would be protected by the 'Moderate comment'
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permission. We could have states and transition for 'rejected', etc, but it
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is probably just as good to delete comments that are rejected.
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The 'auto-publish' transition would be an automatic transition protected by
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the 'Bypass moderation' permission.
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The 'auto-moderate' transition would be another automatic transition protected
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by an expression (e.g. calling a view) that returns True if the user is on
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an auto-moderation 'white-list', e.g. by email address or username.
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Forms and UI
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------------
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The basic commenting display/reply form should be placed in a viewlet.
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Ideally, the reply form should be inline, perhaps revealed with JavaScript
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if enabled. This allows full contextualisation of replies. The current
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solution, with a separate form that shows some context, is brittle and
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over-complicated.
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If we support quoting of comments in replies, we can load the text to quote
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using JavaScript as well.
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As a fall-back for non-JavaScript enabled browsers, it is probably OK not to
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support quoting and/or viewing of context, e.g. the user is taken to a standalone
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'comment reply' form.
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All actual forms should be handled using z3c.form and plone.z3cform's
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ExtensibleForm support. This makes it possible to plug in additional fields
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declaratively, e.g. to include spam protection.
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@@ -0,0 +1,77 @@
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=============================================
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plone.app.discussion architectural principles
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=============================================
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This document outlines architectural principles used in the design of
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plone.app.discussion.
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Discussion items have a portal_type
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This makes it easier to search for them and manage them using existing
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CMF and Plone UI constructs.
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Discussion items are cataloged
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It should be possible to search for discussion items like any other
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type of content.
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Discussion items are subject to workflow and permission
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Moderation, anonymous commenting, and auto approve/reject should be
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handled using workflow states, automatic and manual transitions, and
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permissions.
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Discussion items are light weight objects
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All discussion item objects should be as light weight as possible.
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Ideally, a discussion item should be as lightweight as a catalog brain.
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This may mean that we forego convenience base classes and re-implement
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certain interfaces. Comments should not provide the full set of dublin
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core metadata, though custom indexers can be used to provide values for
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standard catalog indexes.
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Optimise for retrival speed
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HTML filtering and other processing should happen on save, not on render,
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to make rendering quick.
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Settings are stored using plone.registry
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Any global setting should be stored in plone.registry records
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Forms are constructed using extensible z3c.form forms
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This allows plugins (such as spam protection algorithms) to provide
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additional validation
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Discussion items are stored in a BTree container
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This allows faster lookup and manipulation
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Discussion items are accessed using a dict-like interface
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This makes iteration and manipulation more natural. Even if comments are
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not stored threaded, the dict interface should act as if they are, i.e.
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calling items() on a comment should return the replies to that comment
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(in order).
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Discussion items are retrieved in reverse creation date order
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Discussion items do not need to support explicit ordering. They should
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always be retrieved in reverse creation date order (most recent for).
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They can be stored with keys so that this is always true.
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Discussion items do not need readable ids
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Ids can be based on the creation date.
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Discussion items send events
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The usual zope.lifecycleevent and zope.app.container events should be
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fired when discussion items are added, removed, or modified.
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Outstanding questions
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---------------------
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* Should comments use the 'talkback' URL structure currently used in CMF,
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or a ++comments++ namespace?
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* Should discussion items be stored in one container, maintaining parent
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pointers as references or attributes, or in a nested structure?
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- it may be possible to use the navtree algorithm to turn a search of
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comments into a nested structure
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* How can we ensure that discussion items are not removed from the catalog
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when the user initiates a "clear and rebuild"?
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* Can we find a way to avoid having to explicitly migrate all existing
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comments?
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@@ -0,0 +1 @@
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<configure
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xmlns="http://namespaces.zope.org/zope"
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xmlns:browser="http://namespaces.zope.org/browser"
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i18n_domain="plone.app.discussion">
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</configure>
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"""Implement an IPublishTraverse adapter for discussion items that allows
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traversal into the 'replies' dictionary, as well as the ++comments++ traversal
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namespace.
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"""
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"""Catalog indexers, using plone.indexer. These will populate standard catalog
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indexes with values based on the IComment interface.
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Also provide event handlers to actually catalog the comments.
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"""
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"""Discussion items and replies
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"""
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from zope.interface import implements, alsoProvides
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from BTrees.OOBTree import OOBTree
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from Acquisition import Explicit
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from OFS.Traversable import Traversable
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from AccessControl.Role import RoleManager
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from AccessControl.Owned import Owned
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from plone.app.discussion.interfaces import IReplies, IComment
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def Replies():
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"""Create a new replies object. Acts like a constructor, but actually
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returns a BTree marked with an interface. We do this because subclassing
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an OOBTree does not work properly.
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"""
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replies = OOBTree()
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alsoProvides(replies, IReplies)
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return replies
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class Comment(Explicit, Traversable, RoleManager, Owned):
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"""A comment.
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This object attempts to be as lightweight as possible. We implement a
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number of standard methods instead of subclassing, to have total control
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over what goes into the object.
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"""
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implements(IComment)
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meta_type = portal_type = 'Discussion Item'
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__parent__ = None
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__name__ = None
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ancestor = None
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title = u""
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mime_type = "text/plain"
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text = u""
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creator = None
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creation_date = None
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modification_date = None
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author_username = None
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author_name = None
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author_email = None
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replies = None
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def __init__(self, id, ancestor, parent, **kw):
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self.__name__ = id
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self.__parent__ = parent
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self.ancestor = ancestor
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for k, v in kw:
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setattr(self, k, v)
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replies = Replies()
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# convenience functions
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@property
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def id(self):
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return self.__name__
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def getId(self):
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return self.__name__
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@@ -0,0 +1,6 @@
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<configure
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xmlns="http://namespaces.zope.org/zope"
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i18n_domain="plone.app.discussion">
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</configure>
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@@ -0,0 +1,3 @@
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"""Default implementation of the IDiscussable adapter.
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"""
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@@ -0,0 +1,68 @@
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from zope.interface import Interface
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from zope.interface.common.mapping import IIterableMapping, IWriteMapping
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from zope import schema
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from zope.i18nmessageid import MessageFactory
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_ = MessageFactory('plone.app.discussion')
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class IReplies(IIterableMapping, IWriteMapping):
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"""A set of related comments
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This acts as a mapping (dict) with string keys and values being other
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discussion items in reply to this discussion item.
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"""
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class IHasReplies(Interface):
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"""Common interface for objects that have replies.
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"""
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replies = schema.Object(title=_(u"Replies"), schema=IReplies)
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class IComment(IHasReplies):
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"""A comment
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"""
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portal_type = schema.ASCIILine(title=_(u"Portal type"), default="Discussion Item")
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__parent__ = schema.Object(title=_(u"In reply to"), description=_(u"Another comment or a content item"), schema=Interface)
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__name__ = schema.TextLine(title=_(u"Name"))
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ancestor = schema.Object(title=_(u"The original content object the comment is for"), schema=Interface)
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title = schema.TextLine(title=_(u"Subject"))
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mime_type = schema.ASCIILine(title=_(u"MIME type"), default="text/plain")
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text = schema.Text(title=_(u"Comment text"))
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creator = schema.TextLine(title=_(u"Author name (for display)"))
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creation_date = schema.Date(title=_(u"Creation date"))
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modification_date = schema.Date(title=_(u"Modification date"))
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# for logged in comments - set to None for anonymous
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author_username = schema.TextLine(title=_(u"Author username"), required=False)
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# for anonymous comments only, set to None for logged in comments
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author_name = schema.TextLine(title=_(u"Author name"), required=False)
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author_email = schema.TextLine(title=_(u"Author email address"), required=False)
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class IDiscussable(IHasReplies):
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"""Adapt a content item to this interface to determine whether discussions
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are currently enabled, and obtain a list of comments.
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"""
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enabled = schema.Bool(title=_(u"Is commenting enabled?"))
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total_comments = schema.Int(title=_(u"Total number of comments on this item"), min=0, readonly=True)
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last_comment_date = schema.Date(title=_(u"Date of the most recent comment"), readonly=True)
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commentators = schema.Set(title=_(u"The set of unique commentators (usernames)"), readonly=True)
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class IDiscussionSettings(Interface):
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"""Global discussion settings. This describes records stored in the
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configuration registry and obtainable via plone.registry.
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"""
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globally_enabled = schema.Bool(title=_(u"Globally enabled"),
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description=_(u"Use this setting to enable or disable comments globally"),
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default=True)
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@@ -0,0 +1,3 @@
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<metadata>
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<version>1.0a1</version>
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</metadata>
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@@ -0,0 +1 @@
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1.0a1
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Reference in New Issue
Block a user