Allow arbitrarily setting the entry point in a workflow.

Change-Id: I45fed66f368305ffc60ca4cd1c4d1296c5351b02

horizon/tests/workflows_tests.py

@@ -251,3 +251,11 @@ class WorkflowsTests(test.TestCase):
                                  ['<TestStepOne: test_action_one>',
                                   '<AdminStep: admin_action>',
                                   '<TestStepTwo: test_action_two>'])
+
+    def test_entry_point(self):
+        req = self.factory.get("/foo")
+        flow = TestWorkflow(req)
+        self.assertEqual(flow.get_entry_point(), "test_action_one")
+
+        flow = TestWorkflow(req, entry_point="test_action_two")
+        self.assertEqual(flow.get_entry_point(), "test_action_two")

horizon/workflows/base.py

@@ -497,6 +497,13 @@ class Workflow(html.HTMLElement):
         In general the default common template should be used. Default:
         ``"horizon/common/_workflow.html"``.
 
+    .. attribute:: entry_point
+
+        The slug of the step which should initially be active when the
+        workflow is rendered. This can be passed in upon initialization of
+        the workflow, or set anytime after initialization but before calling
+        either ``get_entry_point`` or ``render``.
+
     .. attribute:: redirect_param_name
 
         The name of a parameter used for tracking the URL to redirect to upon
@@ -519,7 +526,8 @@ class Workflow(html.HTMLElement):
     def __repr__(self):
         return "<%s: %s>" % (self.__class__.__name__, self.slug)
 
-    def __init__(self, request=None, context_seed=None, *args, **kwargs):
+    def __init__(self, request=None, context_seed=None, entry_point=None,
+                 *args, **kwargs):
         super(Workflow, self).__init__(*args, **kwargs)
         if self.slug is None:
             raise AttributeError("The workflow %s must have a slug."
@@ -528,6 +536,7 @@ class Workflow(html.HTMLElement):
         self.request = request
         self.depends_on = set([])
         self.contributions = set([])
+        self.entry_point = entry_point
 
         # Put together our steps in order. Note that we pre-register
         # non-default steps so that we can identify them and subsequently
@@ -616,6 +625,11 @@ class Workflow(html.HTMLElement):
         This method takes into account both already-available data and errors
         within the steps.
         """
+        # If we have a valid specified entry point, use it.
+        if self.entry_point:
+            if self.get_step(self.entry_point):
+                return self.entry_point
+        # Otherwise fall back to calculating the appropriate entry point.
         for step in self.steps:
             if step.has_errors:
                 return step.slug
@@ -623,6 +637,8 @@ class Workflow(html.HTMLElement):
                 step._verify_contributions(self.context)
             except exceptions.WorkflowError:
                 return step.slug
+        # If nothing else, just return the first step.
+        return self.steps[0].slug
 
     def _trigger_handlers(self, key):
         responses = []

horizon/workflows/views.py

@@ -70,8 +70,10 @@ class WorkflowView(generic.TemplateView):
     def get_workflow(self):
         """ Returns the instanciated workflow class. """
         extra_context = self.get_initial()
+        entry_point = self.request.GET.get("step", None)
         workflow = self.workflow_class(self.request,
-                                       context_seed=extra_context)
+                                       context_seed=extra_context,
+                                       entry_point=entry_point)
         return workflow
 
     def get_context_data(self, **kwargs):