Implemented min_characters for free text answer

mentoring/answer.py

@@ -29,7 +29,7 @@ from lazy import lazy
 
 from xblock.fragment import Fragment
 
-from .light_children import LightChild, Boolean, Scope, String
+from .light_children import LightChild, Boolean, Scope, String, Integer
 from .models import Answer
 from .utils import render_template
 
@@ -51,6 +51,8 @@ class AnswerBlock(LightChild):
     read_only = Boolean(help="Display as a read-only field", default=False, scope=Scope.content)
     default_from = String(help="If specified, the name of the answer to get the default value from",
                           default=None, scope=Scope.content)
+    min_characters = Integer(help="Minimum number of characters allowed for the answer",
+                             scope=Scope.content)
 
     @lazy
     def student_input(self):
@@ -106,7 +108,11 @@ class AnswerBlock(LightChild):
 
     @property
     def completed(self):
-        return bool(self.read_only or self.student_input)
+        answer_length_ok = self.student_input
+        if self.min_characters > 0:
+            answer_length_ok = len(self.student_input) >= self.min_characters
+
+        return bool(self.read_only or answer_length_ok)
 
     def save(self):
         """

mentoring/public/js/answer.js

 function AnswerBlock(runtime, element) {
     return {
         submit: function() {
-            return $(element).find(':input').serializeArray();
+            var input = $(':input', element),
+                answer_length = input.val().length,
+                data = input.data();
+
+            if (_.isNumber(data.min_characters) &&
+                (data.min_characters > 0) &&
+                (answer_length < data.min_characters)) {
+              throw "The answer has a minimum of " + data.min_characters + " characters.";
+            }
+            return input.serializeArray();
         },
         handleSubmit: function(result) {
             $(element).find('.message').text((result || {}).error || '');

mentoring/public/js/mentoring.js

@@ -77,16 +77,25 @@ function MentoringBlock(runtime, element) {
         var submit_dom = $(element).find('.submit .input-main');
 
         submit_dom.bind('click', function() {
+            var success = true;
             var data = {};
             var children = getChildren(element);
             for (var i = 0; i < children.length; i++) {
                 var child = children[i];
                 if (child.name !== undefined) {
-                    data[child.name] = callIfExists(child, 'submit');
+                    try {
+                        data[child.name] = callIfExists(child, 'submit');
+                    }
+                    catch (error) {
+                      alert(error);
+                      success = false;
+                    }
                 }
             }
-            var handlerUrl = runtime.handlerUrl(element, 'submit');
-            $.post(handlerUrl, JSON.stringify(data)).success(handleSubmitResults);
+            if (success) {
+                var handlerUrl = runtime.handlerUrl(element, 'submit');
+                $.post(handlerUrl, JSON.stringify(data)).success(handleSubmitResults);
+            }
         });
 
         // init children (especially mrq blocks)

mentoring/templates/html/answer_editable.html

-<textarea class="answer editable" cols="50" rows="10" name="input">{{ self.student_input }}</textarea>
+<textarea
+   class="answer editable" cols="50" rows="10" name="input"
+   data-min_characters="{{ self.min_characters }}"
+   >{{ self.student_input }}</textarea>