Fix plone.memoize.view to support unhashable types in function argume…

…nts.

Fixes: #36

news/36.bugfix

@@ -0,0 +1,3 @@
+Fix plone.memoize.view to support unhashable types in function arguments.
+
+Fixes: #36

plone/memoize/view.py

@@ -6,6 +6,8 @@
 from zope.annotation.interfaces import IAnnotations
 from zope.globalrequest import getRequest
 
+import json
+
 
 class ViewMemo:
     key = "plone.memoize"
@@ -44,7 +46,7 @@ def memogetter(*args, **kwargs):
                 instance.__class__.__name__,
                 func.__name__,
                 args[1:],
-                frozenset(kwargs.items()),
+                frozenset(json.dumps(kwargs)),
             )
             if key not in cache:
                 cache[key] = func(*args, **kwargs)
@@ -73,7 +75,7 @@ def memogetter(*args, **kwargs):
                 instance.__class__.__name__,
                 func.__name__,
                 args[1:],
-                frozenset(kwargs.items()),
+                frozenset(json.dumps(kwargs)),
             )
             if key not in cache:
                 cache[key] = func(*args, **kwargs)

plone/memoize/view.rst

@@ -81,14 +81,24 @@ Even though we've twiddled txt1, txt2 is not recalculated::
     >>> msg.txt2
     'hello world'
 
-We support memoization of multiple signatures as long as all signature values are hashable::
+We support memoization of multiple signatures.
+The signature values just need to be able to be converted into a JSON string::
 
     >>> print(msg.getMsg('Ernest'))
     Ernest: goodbye cruel world!
 
     >>> print(msg.getMsg('J.D.', **{'raise':'roofbeams'}))
     J.D.: goodbye cruel world! raise--roofbeams
 
+We also support unhashable types like lists and dicts::
+
+    >>> print(msg.getMsg('J.D.', lower=['shields', 'engines']))
+    J.D.: goodbye cruel world! lower--['shields', 'engines']
+
+    >>> print(msg.getMsg('J.D.', actions={'open': ['gates']}))
+    J.D.: goodbye cruel world! actions--{'open': ['gates']}
+
+
 We can alter data underneath, but nothing changes::
 
     >>> msg.txt1 = 'sound and fury'