Support warning messages in SelfHandlingForm

Sometimes we need to show a prominent message at the top of a form to
warn the user about something. One example is trying to snapshot an
in-use volume.

Change-Id: I073fe6bd049eb90b7a6ed45abfad96ebda3510eb
Related-Bug: #1202929

horizon/forms/base.py

@@ -45,6 +45,13 @@ class SelfHandlingForm(SelfHandlingMixin, forms.Form):
         """
         self._errors[NON_FIELD_ERRORS] = self.error_class([message])
 
+    def set_warning(self, message):
+        """Sets a warning on the form.
+
+        Unlike NON_FIELD_ERRORS, this doesn't fail form validation.
+        """
+        self.warnings = self.error_class([message])
+
 
 class DateForm(forms.Form):
     """A simple form for selecting a range of time."""

horizon/templates/horizon/common/_form_fields.html

@@ -1,6 +1,11 @@
 {% for hidden in form.hidden_fields %}
   {{ hidden }}
 {% endfor %}
+{% if form.warnings %}
+  <div class="alert alert-message alert-warning">
+    {{ form.warnings }}
+  </div>
+{% endif %}
 {% if form.non_field_errors %}
   <div class="alert alert-message alert-error">
     {{ form.non_field_errors }}

horizon/test/tests/forms.py

@@ -13,6 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from django import shortcuts
+
 from horizon import forms
 from horizon.test import helpers as test
 
@@ -62,3 +64,39 @@ class FormMixinTests(test.TestCase):
 
             view = self._prepare_view(forms.views.ModalFormView, {})
             self.assertEqual(view.get_template_names(), view.template_name)
+
+
+class TestForm(forms.SelfHandlingForm):
+
+    name = forms.CharField(max_length="255")
+
+    def handle(self, request, data):
+        return True
+
+
+class FormErrorTests(test.TestCase):
+
+    template = 'horizon/common/_form_fields.html'
+
+    def setUp(self):
+        super(FormErrorTests, self).setUp()
+        self.form = TestForm(self.request)
+
+    def _render_form(self):
+        return shortcuts.render(self.request, self.template,
+                                {'form': self.form})
+
+    def test_set_warning(self):
+        warning_text = 'WARNING 29380'
+        self.form.set_warning(warning_text)
+        self.assertEqual([warning_text], self.form.warnings)
+        resp = self._render_form()
+        self.assertIn(warning_text, resp.content)
+
+    def test_api_error(self):
+        error_text = 'ERROR 12938'
+        self.form.full_clean()
+        self.form.api_error(error_text)
+        self.assertEqual([error_text], self.form.non_field_errors())
+        resp = self._render_form()
+        self.assertIn(error_text, resp.content)