clear out stale submission fields on resubmit

fixes CNVS-5604

Test plan:
  * set up an assignment that takes online_url and online_text_entry
    submissions
  * make a online_url submission for an assignment
  * have the same student make an online_text_entry submission
  * the api response should now *not* include the url anymore

Change-Id: I2389b0b3e8a565eed01f85ba2bed874c59585a2f
Reviewed-on: https://gerrit.instructure.com/37796
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Anna Koalenz <akoalenz@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>

app/models/assignment.rb

@@ -1130,11 +1130,16 @@ class Assignment < ActiveRecord::Base
     res
   end
 
+  SUBMIT_HOMEWORK_ATTRS = %w[body url attachments submission_type
+                             media_comment_id media_comment_type]
+  ALLOWABLE_SUBMIT_HOMEWORK_OPTS = (SUBMIT_HOMEWORK_ATTRS +
+                                    %w[comment group_comment]).to_set
+
   def submit_homework(original_student, opts={})
     # Only allow a few fields to be submitted.  Cannot submit the grade of a
     # homework assignment, for instance.
     opts.keys.each { |k|
-      opts.delete(k) unless [:body, :url, :attachments, :submission_type, :comment, :media_comment_id, :media_comment_type, :group_comment].include?(k.to_sym)
+      opts.delete(k) unless ALLOWABLE_SUBMIT_HOMEWORK_OPTS.include?(k.to_s)
     }
     raise "Student Required" unless original_student
     comment = opts.delete(:comment)
@@ -1155,6 +1160,11 @@ class Assignment < ActiveRecord::Base
                 end
     transaction do
       find_or_create_submissions(students) do |homework|
+        # clear out attributes from prior submissions
+        if opts[:submission_type].present?
+          SUBMIT_HOMEWORK_ATTRS.each { |attr| homework[attr] = nil }
+        end
+
         student = homework.user
         homework.grade_matches_current_submission = homework.score ? false : true
         homework.attributes = opts.merge({

spec/models/assignment_spec.rb

@@ -583,11 +583,6 @@ describe Assignment do
       s.versions.length.should eql(1)
       s2[0].state.should eql(:graded)
     end
-
-    it "should not mark as submitted if no submission" do
-      s = @a.submit_homework(@user)
-      s.workflow_state.should == "unsubmitted"
-    end
   end
 
   describe  "interpret_grade" do
@@ -611,13 +606,47 @@ describe Assignment do
     end
   end
 
-  it "should create a new version for each submission" do
-    setup_assignment_without_submission
-    @a.submit_homework(@user)
-    @a.submit_homework(@user)
-    @a.submit_homework(@user)
-    @a.reload
-    @a.submissions.first.versions.length.should eql(3)
+  describe '#submit_homework' do
+    before(:once) do
+      course_with_student(active_all: true)
+      @a = @course.assignments.create! title: "blah",
+        submission_types: "online_text_entry,online_url",
+        points_possible: 10
+    end
+
+    it "creates a new version for each submission" do
+      setup_assignment_without_submission
+      @a.submit_homework(@user)
+      @a.submit_homework(@user)
+      @a.submit_homework(@user)
+      @a.reload
+      @a.submissions.first.versions.length.should eql(3)
+    end
+
+    it "doesn't mark as submitted if no submission" do
+      s = @a.submit_homework(@user)
+      s.workflow_state.should == "unsubmitted"
+    end
+
+    it "clears out stale submission information" do
+      s = @a.submit_homework(@user, submission_type: "online_url",
+                             url: "http://example.com")
+      s.submission_type.should == "online_url"
+      s.url.should == "http://example.com"
+
+      s2 = @a.submit_homework(@user, submission_type: "online_text_entry",
+                              body: "blah blah blah blah blah blah blah")
+      s2.submission_type.should == "online_text_entry"
+      s2.body.should == "blah blah blah blah blah blah blah"
+      s2.url.should be_nil
+      s2.workflow_state.should == "submitted"
+
+      # comments shouldn't clear out submission data
+      s3 = @a.submit_homework(@user, comment: "BLAH BLAH")
+      s3.body.should == "blah blah blah blah blah blah blah"
+      s3.submission_comments.first.comment.should == "BLAH BLAH"
+      s3.submission_type.should == "online_text_entry"
+    end
   end
 
   describe "muting" do