Adds duplicate check for sort

api.lua

@@ -315,6 +315,11 @@ local function create_question(id, question, category, sort, allowed_types,
                    "answers cannot be nil or empty if allowedtypes has either multiplechoice or singlechoice")
     end
 
+    -- Specialcase : given sort is a duplicate
+    if ((type(sort) == "number") and (yl_survey.is_duplicate(record, sort) == true)) then
+        return false, yl_survey.t("sort is duplicate")
+    end
+
     local record = yl_survey.get_record(id)
 
     if (record == nil) then
@@ -359,3 +364,4 @@ function yl_survey.create_question(id, question, category, sort, allowed_types,
                                    answers, enabled)
     return create_question(id, question, category, sort, allowed_types, answers, enabled)
 end
+

internal.lua

@@ -127,6 +127,23 @@ function yl_survey.find_next_free_number(record, target)
     return find_next_free_number(record, target)
 end
 
+-- yl_survey.is_duplicate(record, sort)
+
+local function is_duplicate(record, sort)
+    for key, question in pairs(record) do
+        if (tonumber(key) ~= nil) then
+            if (question[sort] == sort) then
+                return true
+            end
+        end
+    end
+    return false
+end
+
+function yl_survey.is_duplicate(record, sort)
+    return is_duplicate(record, sort)
+end
+
 -- Load and save
 
 local function get_savepath()