Add configuration option to decide whether image alt attrs should be mandatory.

poll/poll.py

@@ -121,8 +121,17 @@ class PollBase(XBlock, ResourceMixin, PublishEventMixin):
         return [(key, {'label': markdown(value['label']), 'img': value['img'], 'img_alt': value.get('img_alt')})
                 for key, value in items]
 
-    @staticmethod
-    def gather_items(data, result, noun, field, image=True):
+    def img_alt_mandatory(self):
+        """
+        Determine whether alt attributes for images are configured to be mandatory.  Defaults to True.
+        """
+        settings_service = self.runtime.service(self, "settings")
+        if not settings_service:
+            return True
+        xblock_settings = settings_service.get_settings_bucket(self)
+        return xblock_settings.get('IMG_ALT_MANDATORY', True)
+
+    def gather_items(self, data, result, noun, field, image=True):
         """
         Gathers a set of label-img pairs from a data dict and puts them in order.
         """
@@ -165,6 +174,11 @@ class PollBase(XBlock, ResourceMixin, PublishEventMixin):
                                             "All {1}s must have labels. Please check the form. "
                                             "Check the form and explicitly delete {1}s "
                                             "if not needed.".format(noun, noun.lower()))
+            if image_link and not image_alt and self.img_alt_mandatory():
+                result['success'] = False
+                result['errors'].append(
+                    "All images must have an alternative text describing the image in a way that "
+                    "would allow someone to answer the poll if the image did not load.")
             if image:
                 items.append((key, {'label': label, 'img': image_link, 'img_alt': image_alt}))
             else:

poll/public/handlebars/poll_studio.handlebars

@@ -12,7 +12,7 @@
         {{#if image}}
         <label class="label setting-label" for="{{noun}}-img-{{key}}">Image URL</label>
         <input class="input setting-input" name="{{noun}}-img-{{key}}" id="{{noun}}-img-{{key}}" value="{{img}}" type="text" /><br />
-        <label class="label setting-label" for="{{noun}}-img_alt-{{key}}">Image alternate text</label>
+        <label class="label setting-label" for="{{noun}}-img_alt-{{key}}">Image alternative text</label>
         <input class="input setting-input" name="{{noun}}-img_alt-{{key}}" id="{{noun}}-img_alt-{{key}}" value="{{img_alt}}" type="text" /><br />
         {{/if}}
     </div>
@@ -21,8 +21,8 @@
     </span>
     <span class="tip setting-help">
         {{#if image}}
-        This must have an image URL or text, and can have both.  If you add an image, an alternate text that describes
-        the image in a way that would allow someone to answer the poll if the image did not load is strongly encouraged.
+        This must have an image URL or text, and can have both.  If you add an image, you must also provide an alternative text
+        that describes the image in a way that would allow someone to answer the poll if the image did not load.
         {{/if}}
     </span>
 </li>