Replace dots with hyphens when generating form id from its name.

CHANGES.txt

@@ -5,6 +5,8 @@ CHANGES
 Version 2.2.0 (unreleased)
 --------------------------
 
+- Bug: Replace dots with hyphens when generating form id from its name.
+
 - Refactored OutputChecker to its own module to allow using 
   ``z3c.form.testing`` without needing to depend on ``lxml``
 

src/z3c/form/form.py

@@ -193,7 +193,9 @@ def name(self):
         """See interfaces.IInputForm"""
         return self.prefix.strip('.')
 
-    id = name
+    @property
+    def id(self):
+        return self.name.replace('.', '-')
 
     def updateActions(self):
         self.actions = zope.component.getMultiAdapter(

src/z3c/form/form.txt

@@ -563,6 +563,14 @@ trailing ".".
   >>> addForm.name
   'form'
 
+The id is computed from the name, replacing dots with hyphens. Let's set
+the prefix to something containing more than one final dot and check how
+it works.
+
+  >>> addForm.prefix = 'person.form.add.'
+  >>> addForm.id
+  'person-form-add'
+
 The template can then use those attributes, if it likes to.
 
 In the examples previously we set the template manually. If no