Add deleteAnnotation

CHANGES.txt

@@ -4,8 +4,11 @@ Changes
 1.4 (unreleased)
 ----------------
 
-- Add ``queryAnnotation()`` that will not create an annotation if it didn't
-  exist before, preventing unneccessary databse writes.
+- Add ``queryAnnotation()`` to return an annotation. Return None if it
+  doesn't exists. This helper will never do any write operation in the
+  database.
+
+- Add ``deleteAnnotation()`` to delete an annotation (if it exists).
 
 1.3 (2012-05-01)
 ----------------

README.txt

@@ -75,6 +75,9 @@ Base classes
    interface. Return the annotation if found, None otherwise. This
    will not *make* any write operation.
 
+``deleteAnnotation(model, interface)``
+   Look for the given annotation and delete it from the model.
+
 In addition, the ``grokcore.annotation`` package exposes the
 `grokcore.component`_ API.
 

src/grokcore/annotation/__init__.py

@@ -18,6 +18,7 @@
 
 from grokcore.annotation.components import Annotation, Model
 from grokcore.annotation.components import queryAnnotation
+from grokcore.annotation.components import deleteAnnotation
 
 # BBB These two functions are meant for test fixtures and should be
 # imported from grok.testing, not from grok.

src/grokcore/annotation/components.py

@@ -45,12 +45,19 @@ def __init__(self, factory, name):
         self.factory = factory
         self.name = name
 
-    def get(self, context):
+    def query(self, context):
         """Return None if the annotation doesn't exists.
         """
         annotations = IAnnotations(context)
         return annotations.get(self.name)
 
+    def delete(self, context):
+        annotations = IAnnotations(context)
+        if self.name in annotations:
+            del annotations[self.name]
+            return True
+        return False
+
     def __call__(self, context):
         annotations = IAnnotations(context)
         try:
@@ -71,4 +78,12 @@ def queryAnnotation(context, interface):
     factory = manager.adapters.lookup((providedBy(context),), interface)
     if not IAnnotationFactory.providedBy(factory):
         return None
-    return factory.get(context)
+    return factory.query(context)
+
+
+def deleteAnnotation(context, interface):
+    manager = getSiteManager()
+    factory = manager.adapters.lookup((providedBy(context),), interface)
+    if not IAnnotationFactory.providedBy(factory):
+        return False
+    return factory.delete(context)

src/grokcore/annotation/interfaces.py

@@ -27,11 +27,15 @@ class IAnnotationFactory(interface.Interface):
     factory = interface.Attribute('Class to create a new annotation')
     name = interface.Attribute('Name of the annotation')
 
-    def get(context):
+    def query(context):
         """Return the existing annotation or None if no annotaion
         was created before.
         """
 
+    def delete(context):
+        """Delete the existing annotation on the context.
+        """
+
     def __call__(context):
         """Return the existing annotation or create a new one.
         """
@@ -40,4 +44,5 @@ def __call__(context):
 class IGrokcoreAnnotationAPI(IBaseClasses):
     """grokcore.annotation API description.
     """
-    queryAnnotation = interface.Attribute('Function to query an annotation')
+    queryAnnotation = interface.Attribute('Query an annotation or return None')
+    deleteAnnotation = interface.Attribute('Delete an annotation if it exists')

src/grokcore/annotation/tests/annotation/annotation.py

@@ -42,6 +42,14 @@
   ['mine', 'yours']
   >>>
 
+And you can delete an annotation:
+
+  >>> grok.deleteAnnotation(manfred, IBranding)
+  True
+  >>> grok.queryAnnotation(manfred, IBranding) is None
+  True
+
+
 
 """