Introduce instance-wide setting that specifies if previous answers to

MCQs are shown when users revisit them.

problem_builder/mentoring.py

@@ -63,6 +63,10 @@ _default_theme_config = {
     'locations': ['public/themes/lms.css']
 }
 
+_default_options_config = {
+    'pb_mcq_hide_previous_answer': False
+}
+
 
 # Make '_' a no-op so we can scrape strings
 def _(text):
@@ -121,6 +125,7 @@ class BaseMentoringBlock(
     icon_class = 'problem'
     block_settings_key = 'mentoring'
     theme_key = 'theme'
+    options_key = 'options'
 
     @property
     def url_name(self):
@@ -156,18 +161,28 @@ class BaseMentoringBlock(
             return [self.display_name]
         return []
 
-    def get_theme(self):
+    def get_settings(self, settings_key, default):
         """
-        Gets theme settings from settings service. Falls back to default (LMS) theme
-        if settings service is not available, xblock theme settings are not set or does
-        contain mentoring theme settings.
+        Get settings identified by `settings_key` from settings service.
+
+        Fall back on `default` if settings service is unavailable
+        or settings have not been customized.
         """
         settings_service = self.runtime.service(self, "settings")
         if settings_service:
             xblock_settings = settings_service.get_settings_bucket(self)
-            if xblock_settings and self.theme_key in xblock_settings:
-                return xblock_settings[self.theme_key]
-        return _default_theme_config
+            if xblock_settings and settings_key in xblock_settings:
+                return xblock_settings[settings_key]
+        return default
+
+    def get_theme(self):
+        """
+        Get theme settings for this block from settings service.
+
+        Fall back on default (LMS) theme if settings service is not available,
+        or theme has not been customized.
+        """
+        return self.get_settings(self.theme_key, _default_theme_config)
 
     def include_theme_files(self, fragment):
         theme = self.get_theme()
@@ -175,6 +190,18 @@ class BaseMentoringBlock(
         for theme_file in theme_files:
             fragment.add_css(ResourceLoader(theme_package).load_unicode(theme_file))
 
+    def get_options(self):
+        """
+        Get options settings for this block from settings service.
+
+        Fall back on default options if settings service is not available
+        or options have not been customized.
+        """
+        return self.get_settings(self.options_key, _default_options_config)
+
+    def get_option(self, option):
+        return self.get_options()[option]
+
     @XBlock.json_handler
     def view(self, data, suffix=''):
         """
@@ -368,6 +395,8 @@ class MentoringBlock(BaseMentoringBlock, StudioContainerXBlockMixin, StepParentM
         return Score(score, int(round(score * 100)), correct, incorrect, partially_correct)
 
     def student_view(self, context):
+        from .mcq import MCQBlock  # Import here to avoid circular dependency
+
         # Migrate stored data if necessary
         self.migrate_fields()
 
@@ -379,6 +408,8 @@ class MentoringBlock(BaseMentoringBlock, StudioContainerXBlockMixin, StepParentM
         fragment = Fragment()
         child_content = u""
 
+        mcq_hide_previous_answer = self.get_option('pb_mcq_hide_previous_answer')
+
         for child_id in self.children:
             child = self.runtime.get_block(child_id)
             if child is None:  # child should not be None but it can happen due to bugs or permission issues
@@ -388,6 +419,10 @@ class MentoringBlock(BaseMentoringBlock, StudioContainerXBlockMixin, StepParentM
                     if self.is_assessment and isinstance(child, QuestionMixin):
                         child_fragment = child.render('assessment_step_view', context)
                     else:
+                        if mcq_hide_previous_answer and isinstance(child, MCQBlock):
+                            context['hide_prev_answer'] = True
+                        else:
+                            context['hide_prev_answer'] = False
                         child_fragment = child.render('mentoring_view', context)
                 except NoSuchViewError:
                     if child.scope_ids.block_type == 'html' and getattr(self.runtime, 'is_author_mode', False):

problem_builder/public/js/questionnaire.js

@@ -138,6 +138,8 @@ function MCQBlock(runtime, element) {
                 var choiceResultDOM = $('.choice-result', choiceDOM);
                 var choiceTipsDOM = $('.choice-tips', choiceDOM);
 
+                if (choiceInputDOM.prop('checked')) {  // We're showing previous answers,
+                                                       // so go ahead and display results as well
                     if (result.status === "correct" && choiceInputDOM.val() === result.submission) {
                         choiceDOM.addClass('correct');
                         choiceResultDOM.addClass('checkmark-correct icon-ok fa-check');
@@ -156,6 +158,7 @@ function MCQBlock(runtime, element) {
                             messageView.showMessage(choiceTipsDOM);
                         }
                     });
+                }
             });
 
             if (_.isNull(result.submission)) {