Add support for refreshing actions after execution. Needs review.

Update translations, as the change above introduced some new interface description strings.

CHANGES.txt

@@ -5,6 +5,11 @@ CHANGES
 Version 2.0.0 (unreleased)
 --------------------------
 
+- Feature: Add support for refreshing actions after their execution. This
+  is useful when button action conditions are changing as a result of
+  action execution. All you need is to set the ``refreshActions`` flag
+  of the form to True in your action handler.
+
 - Bug: FieldWidgets update where appending keys and values within each
   update call. Now the util.Manager uses a UniqueOrderedKeys implementation
   which will ensure that we can't add duplicted manager keys. The implementation

src/z3c/form/form.py

@@ -160,7 +160,8 @@ class DisplayForm(BaseForm):
 class Form(BaseForm):
     """The Form."""
     zope.interface.implements(
-        interfaces.IInputForm, interfaces.IButtonForm, interfaces.IHandlerForm)
+        interfaces.IInputForm, interfaces.IButtonForm,
+        interfaces.IHandlerForm, interfaces.IActionForm)
 
     buttons = button.Buttons()
 
@@ -169,6 +170,9 @@ class Form(BaseForm):
     acceptCharset = FieldProperty(interfaces.IInputForm['acceptCharset'])
     accept = FieldProperty(interfaces.IInputForm['accept'])
 
+    actions = FieldProperty(interfaces.IActionForm['actions'])
+    refreshActions = FieldProperty(interfaces.IActionForm['refreshActions'])
+
     @property
     def action(self):
         """See interfaces.IInputForm"""
@@ -190,6 +194,8 @@ def update(self):
         super(Form, self).update()
         self.updateActions()
         self.actions.execute()
+        if self.refreshActions:
+            self.updateActions()
 
     def __call__(self):
         self.update()

src/z3c/form/form.txt

@@ -1439,6 +1439,70 @@ In some cases the data converter for a field-widget pair returns the
   <Person u'Roger Ineichen'>
 
 
+Refreshing actions
+------------------
+
+Sometimes, it's useful to update actions again after executing them,
+because some conditions could have changed. For example, imagine
+we have a sequence edit form that has a delete button. We don't
+want to show delete button when the sequence is empty. The button
+condition would handle this, but what if the sequence becomes empty
+as a result of execution of the delete action that was available?
+In that case we want to refresh our actions to new conditions to make
+our delete button not visible anymore. The ``refreshActions`` form
+variable is intended to handle this case.
+
+Let's create a simple form with an action that clears our context
+sequence.
+
+  >>> class SequenceForm(form.Form):
+  ...
+  ...     @button.buttonAndHandler(u'Empty', condition=lambda form:bool(form.context))
+  ...     def handleEmpty(self, action):
+  ...         self.context[:] = []
+  ...         self.refreshActions = True
+
+First, let's illustrate simple cases, when no button is pressed.
+The button will be available when context is not empty. 
+
+  >>> context = [1, 2, 3, 4]
+  >>> request = TestRequest()
+  >>> myForm = SequenceForm(context, request)
+  >>> myForm.update()
+  >>> addTemplate(myForm)
+  >>> print testing.render(myForm, './/xmlns:div[@class="action"]')
+  <div class="action">
+    <input type="submit" id="form-buttons-empty" name="form.buttons.empty"
+           class="submit-widget button-field" value="Empty" />
+  </div>
+
+The button will not be available when the context is empty.
+
+  >>> context = []
+  >>> request = TestRequest()
+  >>> myForm = SequenceForm(context, request)
+  >>> myForm.update()
+  >>> addTemplate(myForm)
+  >>> print testing.render(myForm, './/xmlns:form')
+  <form action=".">
+  </form>
+
+Now, the most interesting case when context is not empty, but becomes
+empty as a result of pressing the "empty" button. We set the
+``refreshActions`` flag in the action handler, so our actions should
+be updated to new conditions.
+
+  >>> context = [1, 2, 3, 4, 5]
+  >>> request = TestRequest(form={
+  ...     'form.buttons.empty': u'Empty'}
+  ...     )
+  >>> myForm = SequenceForm(context, request)
+  >>> myForm.update()
+  >>> addTemplate(myForm)
+  >>> print testing.render(myForm, './/xmlns:form')
+  <form action=".">
+  </form>
+
 Integration tests
 -----------------
 

src/z3c/form/group.py

@@ -95,3 +95,5 @@ def update(self):
         self.groups = tuple(groups)
         self.updateActions()
         self.actions.execute()
+        if self.refreshActions:
+            self.updateActions()

src/z3c/form/interfaces.py

@@ -786,6 +786,23 @@ class IHandlerForm(zope.interface.Interface):
         required=True)
 
 
+class IActionForm(zope.interface.Interface):
+    """A form that stores executable actions"""
+
+    actions = zope.schema.Object(
+        title=_('Actions'),
+        description=_('A list of actons defined on the form'),
+        schema=IActions,
+        required=True)
+
+    refreshActions = zope.schema.Bool(
+        title=_('Refresh actions'),
+        description=_('A flag, when set, causes form actions to be '
+                      'updated again after their execution.'),
+        default=False,
+        required=True)
+
+
 class IContextAware(zope.interface.Interface):
     """Offers a context attribute.