Draft: restore original form list generation and support dynamic form lists Fixes #220

formtools/wizard/views.py

@@ -165,8 +165,6 @@ def get_initkwargs(cls, form_list=None, initial_dict=None, instance_dict=None,
 
         computed_form_list = OrderedDict()
 
-        assert len(form_list) > 0, 'at least one form is needed'
-
         # walk through the passed form list
         for i, form in enumerate(form_list):
             if isinstance(form, (list, tuple)):
@@ -401,18 +399,32 @@ def get_form_kwargs(self, step=None):
         """
         return {}
 
-    def get_form(self, step=None, data=None, files=None):
+    def get_form_class(self, step):
+        """
+        Returns the form class for step.
+
+        If self.form_list is not empty then it is assumed the wizard has been
+        implemented according to the original form list generation strategy and the form
+        class is taken from there. If self.form_list is empty, however, then get the
+        form class from the dynamically generated list provided by get_form_list().
+        """
+        return self.form_list[step] if self.form_list else self.get_form_list()[step]
+
+    def get_form(self, step=None, data=None, files=None, form_cls=None):
         """
         Constructs the form for a given `step`. If no `step` is defined, the
         current step will be determined automatically.
 
         The form will be initialized using the `data` argument to prefill the
         new form. If needed, instance or queryset (for `ModelForm` or
         `ModelFormSet`) will be added too.
+
+        If form_cls is provided, this class will be instantiated rather than trying to
+        retrieve the class from the form list.
         """
         if step is None:
             step = self.steps.current
-        form_class = self.get_form_list()[step]
+        form_class = form_cls or self.get_form_class(step)
         # prepare the kwargs for the form instance.
         kwargs = self.get_form_kwargs(step)
         kwargs.update({
@@ -490,21 +502,27 @@ def get_all_cleaned_data(self):
                     cleaned_data.update(form_obj.cleaned_data)
         return cleaned_data
 
-    def get_cleaned_data_for_step(self, step):
+    def get_cleaned_data_for_step(self, step, form_cls=None):
         """
         Returns the cleaned data for a given `step`. Before returning the
         cleaned data, the stored values are revalidated through the form.
         If the data doesn't validate, None will be returned.
+
+        A form_cls can be provided to avoid having to query the class by calling
+        get_form_list(). This is useful when overriding get_form_list() to create a
+        dynamic form list but data from other steps is required.
         """
-        if step in self.form_list:
-            form_obj = self.get_form(
-                step=step,
-                data=self.storage.get_step_data(step),
-                files=self.storage.get_step_files(step),
-            )
-            if form_obj.is_valid():
-                return form_obj.cleaned_data
-        return None
+        if self.form_list and step not in self.form_list:
+            return None
+        form_obj = self.get_form(
+            step=step,
+            data=self.storage.get_step_data(step),
+            files=self.storage.get_step_files(step),
+            form_cls=form_cls,
+        )
+        if not form_obj.is_valid():
+            return None
+        return form_obj.cleaned_data
 
     def get_next_step(self, step=None):
         """

tests/wizard/test_forms.py

@@ -1,4 +1,5 @@
 import sys
+from collections import OrderedDict
 from importlib import import_module
 
 from django import forms, http
@@ -93,11 +94,11 @@ def done(self, form_list, **kwargs):
 
 
 class TestWizardWithCustomGetFormList(TestWizard):
-
-    form_list = [Step1]
-
     def get_form_list(self):
-        return {'start': Step1, 'step2': Step2}
+        form_list = OrderedDict([('start', Step1), ('step2', Step2)])
+        self.get_cleaned_data_for_step("step2", form_cls=Step2)
+        form_list["step3"] = Step3
+        return form_list
 
 
 class FormTests(TestCase):
@@ -159,21 +160,41 @@ def test_form_condition(self):
         response, instance = testform(request)
         self.assertEqual(instance.get_next_step(), 'step2')
 
-    def test_form_condition_avoid_recursion(self):
+    def test_form_condition_can_check_prior_step_data(self):
+        def step_check(wizard):
+            wizard.get_cleaned_data_for_step('start')
+            return False
+
+        testform = TestWizard.as_view(
+            [('start', Step1), ('step2', Step2), ('step3', Step3)],
+            condition_dict={'step2': step_check}
+        )
+        request = get_request()
+        old_limit = sys.getrecursionlimit()
+        sys.setrecursionlimit(80)
+        try:
+            response, instance = testform(request)
+            self.assertEqual(instance.get_next_step(), 'step3')
+        except RecursionError:
+            self.fail("RecursionError happened during wizard test.")
+        finally:
+            sys.setrecursionlimit(old_limit)
+
+    def test_form_condition_future_can_check_future_step_data(self):
         def subsequent_step_check(wizard):
             data = wizard.get_cleaned_data_for_step('step3') or {}
             return data.get('foo')
 
         testform = TestWizard.as_view(
             [('start', Step1), ('step2', Step2), ('step3', Step3)],
-            condition_dict={'step3': subsequent_step_check}
+            condition_dict={'step2': subsequent_step_check}
         )
         request = get_request()
         old_limit = sys.getrecursionlimit()
         sys.setrecursionlimit(80)
         try:
             response, instance = testform(request)
-            self.assertEqual(instance.get_next_step(), 'step2')
+            self.assertEqual(instance.get_next_step(), 'step3')
         except RecursionError:
             self.fail("RecursionError happened during wizard test.")
         finally:
@@ -298,11 +319,18 @@ def test_get_form_list_default(self):
 
     def test_get_form_list_custom(self):
         request = get_request()
-        testform = TestWizardWithCustomGetFormList.as_view([('start', Step1)])
+        testform = TestWizardWithCustomGetFormList.as_view()
         response, instance = testform(request)
 
-        form_list = instance.get_form_list()
-        self.assertEqual(form_list, {'start': Step1, 'step2': Step2})
+        old_limit = sys.getrecursionlimit()
+        sys.setrecursionlimit(80)
+        try:
+            form_list = instance.get_form_list()
+        except RecursionError:
+            self.fail("RecursionError happened during wizard test.")
+        finally:
+            sys.setrecursionlimit(old_limit)
+        self.assertEqual(form_list, {'start': Step1, 'step2': Step2, 'step3': Step3})
         self.assertIsInstance(instance.get_form('step2'), Step2)