Adds basic fieldset support

onegov/form/core.py

@@ -1,17 +1,99 @@
+import weakref
+
+from collections import OrderedDict
+from itertools import groupby
+from operator import itemgetter
 from wtforms import Form as BaseForm
 
 
 class Form(BaseForm):
     """ Extends wtforms.Form with useful methods and integrations needed in
     OneGov applications.
 
+    This form supports fieldsets (which WTForms doesn't recognize). To put
+    fields into a fieldset, add a fieldset attribute to the field during
+    class definition::
+
+        class MyForm(Form):
+            first_name = StringField('First Name', fieldset='Name')
+            last_name = StringField('Last Name', fieldset='Name')
+            comment = StringField('Comment')
+
+    A form created like this will have two fieldsets, one visible fieldset
+    with the legend set to 'Name' and one invisible fieldset containing
+    'comment'.
+
+    Fieldsets with the same name are *not* automatically grouped together.
+    Instead, fields are taken in the order they are defined and put into the
+    same fieldset, if the previous fieldset has the same name.
+
+    That is to say, in this example, we get three fieldsets::
+
+        class MyForm(Form):
+            a = StringField('A', fieldset='1')
+            b = StringField('B', fieldset='2')
+            c = StringField('C', fieldset='1')
+
+    The first fieldset has the label '1' and it contains 'a'. The second
+    fieldset has the label '2' and it contains 'b'. The third fieldset has
+    the label '3' and it contains 'c'.
+
+    This ensures that all fields are in either a visible or an invisible
+    fieldset (see :meth:`Fieldset.is_visible`).
+
     """
 
+    def __init__(self, *args, **kwargs):
+
+        # consume the fieldset attribute of all unbound fields, as WTForms
+        # doesn't know it
+        fields_by_fieldset = [
+            (field.kwargs.pop('fieldset', None), field_id)
+            for field_id, field in self._unbound_fields
+        ]
+
+        super(Form, self).__init__(*args, **kwargs)
+
+        # use the consumed fieldset attribute to build fieldsets
+        self.fieldsets = []
+
+        for label, fields in groupby(fields_by_fieldset, key=itemgetter(0)):
+            self.fieldsets.append(Fieldset(
+                label=label,
+                fields=(self._fields[f[1]] for f in fields)
+            ))
+
     def submitted(self, request):
         """ Returns true if the given request is a successful post request. """
         return request.POST and self.validate()
 
 
+class Fieldset(object):
+    """ Defines a fieldset with a list of fields. """
+
+    def __init__(self, label, fields):
+        """ Initializes the Fieldset.
+
+        :label: Label of the fieldset (None if it's an invisible fieldset)
+        :fields: Iterator of bound fields. Fieldset creates a list of weak
+        references to these fields, as they are defined elsewhere and should
+        not be kept in memory just because a Fieldset references them.
+
+        """
+        self.label = label
+        self.fields = OrderedDict((f.id, weakref.proxy(f)) for f in fields)
+
+    def __len__(self):
+        return len(self.fields)
+
+    def __getitem__(self, key):
+        return self.fields[key]
+
+    @property
+    def is_visible(self):
+        return self.label is not None
+
+
 def with_options(widget_class, **render_options):
     """ Takes a widget class and returns a child-instance of the widget class,
     with the given options set on the render call.

onegov/form/parser/core.py

@@ -23,7 +23,7 @@ class (not an instance of it).
     for block in (i[0] for i in doc.scanString(text)):
 
         if block.type == 'fieldset':
-            raise NotImplementedError
+            builder.set_current_fieldset(block.label or None)
 
         elif block.type == 'button':
             raise NotImplementedError
@@ -77,6 +77,10 @@ class DynamicForm(form_class):
             pass
 
         self.form_class = DynamicForm
+        self.current_fieldset = None
+
+    def set_current_fieldset(self, label):
+        self.current_fieldset = label
 
     def add_field(self, field_class, label, required, **kwargs):
         validators = kwargs.pop('validators', [])
@@ -89,5 +93,6 @@ def add_field(self, field_class, label, required, **kwargs):
         setattr(self.form_class, field_id, field_class(
             label=label,
             validators=validators,
+            fieldset=self.current_fieldset,
             **kwargs
         ))

onegov/form/tests/test_parser.py

@@ -28,3 +28,42 @@ def test_parse_text():
     assert form.comment.label.text == 'Comment'
     assert form.comment.widget(form.comment) == (
         '<textarea id="comment" name="comment" rows="8"></textarea>')
+
+
+def test_parse_fieldsets():
+    text = dedent("""
+        # Name
+        First name = ___
+        Last name = ___
+
+        # Address
+        Street = ___
+
+        # ...
+        Comment = ___
+    """)
+
+    form_class = parse_form(text)
+    form = form_class()
+
+    fields = form._fields.values()
+    assert len(fields) == 4
+
+    fieldsets = form.fieldsets
+    assert len(fieldsets) == 3
+
+    assert len(fieldsets[0]) == 2
+    assert fieldsets[0].label == 'Name'
+    assert fieldsets[0].is_visible
+    assert fieldsets[0]['first_name'].label.text == 'First name'
+    assert fieldsets[0]['last_name'].label.text == 'Last name'
+
+    assert len(fieldsets[1]) == 1
+    assert fieldsets[1].label == 'Address'
+    assert fieldsets[1].is_visible
+    assert fieldsets[1]['street'].label.text == 'Street'
+
+    assert len(fieldsets[2]) == 1
+    assert fieldsets[2].label is None
+    assert not fieldsets[2].is_visible
+    assert fieldsets[2]['comment'].label.text == 'Comment'