Consider only relevant discussions when evaluating CMPs

Context module progressions should only consider items that a user
is able to view when evaluating a module's completion status. Ungraded
discussions can be posted to only certain sections within a course, so
only discussions in section(s) where the student is enrolled should be
considered. This is normally the case, however, when evaluating all of
the progressions within a course, we cache the item visibilities to
prevent recalculating the same thing repeatedly (see
ContextModule#evaluate_all_progressions). This codepath is not
frequently followed, but is, for example, when a module itelf is
edited. In the caching process, we get all of the sections (and
associated discussions) visible to a list of users. This was an issue
becuase the list of users might contain users with different section
visibilities. This patchset considers section visibilities for each
user in the list individually, ensuring that module progressions
evaluate appropriately for all users.

closes LS-3245
flag = none

Test plan:
 - Create a course with 2 sections
 - Create a module in the course
 - Create 2 discussions in the module - both ungraded; assign one to
   the first section, and one to the second section
 - Create a page in the module
 - Edit module requirements - set "contribute to the page" on both
   discussions and "view" on the page
 - Enroll a student in one of the sections and publish the course
 - As the student, view the page and reply to the visible discussion
 - Expect the module to be marked as completed
 - As the teacher, create a new (empty) module, move it to the top of
   the page, then delete it
 - As the student, view the modules page; expect the module to still
   be marked as completed

Change-Id: I4d9a57dae0cf521a46953f4c5217df7358b08835
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/296104
Tested-by: Service Cloud Jenkins <[email protected]>
QA-Review: Luis Oliveira <[email protected]>
Reviewed-by: Luis Oliveira <[email protected]>
Product-Review: Jackson Howe <[email protected]>

lib/submittable.rb

@@ -42,8 +42,9 @@ def self.included(klass)
 
   module ClassMethods
     def visible_ids_by_user(opts)
-      # pluck id, assignment_id, and user_id from items joined with the SQL view
+      # Items with an assignment: pluck id, assignment_id, and user_id from items joined with the SQL view
       plucked_visibilities = pluck_visibilities(opts).group_by { |_, _, user_id| user_id }
+
       # Assignment-less items are *normally* visible to all -- the exception is
       # section-specific discussions, so here get the ones visible to everyone in the
       # course, and below get the ones that are visible to the right section.
@@ -55,18 +56,33 @@ def visible_ids_by_user(opts)
 
       # Now get the section-specific discussions that are in the proper sections.
       ids_visible_to_sections = if opts[:item_type] == :discussion
-                                  user_sections = Enrollment.active.where(
-                                    course_id: opts[:course_id], user_id: opts[:user_id]
-                                  ).pluck(:course_section_id)
-                                  DiscussionTopicSectionVisibility.active.where(course_section_id: user_sections).pluck(:discussion_topic_id).uniq
+                                  # build hash of user_ids to array of section ids
+                                  sections_per_user = {}
+                                  Enrollment.active.where(course_id: opts[:course_id], user_id: opts[:user_id])
+                                            .pluck(:user_id, :course_section_id)
+                                            .each { |user_id, section_id| (sections_per_user[user_id] ||= Set.new) << section_id }
+
+                                  # build hash of section_ids to array of visible topic ids
+                                  all_section_ids = sections_per_user.values.reduce([]) { |all_ids, section_ids| all_ids.concat(section_ids.to_a) }
+                                  topic_ids_per_section = {}
+                                  DiscussionTopicSectionVisibility.active.where(course_section_id: all_section_ids)
+                                                                  .pluck(:course_section_id, :discussion_topic_id)
+                                                                  .each { |section_id, topic_id| (topic_ids_per_section[section_id] ||= Set.new) << topic_id }
+                                  topic_ids_per_section.each { |section_id, topic_ids| topic_ids_per_section[section_id] = topic_ids.to_a }
+
+                                  # finally, build hash of user_ids to array of visible topic ids
+                                  topic_ids_per_user = {}
+                                  opts[:user_id].each { |user_id| topic_ids_per_user[user_id] = sections_per_user[user_id]&.map { |section_id| topic_ids_per_section[section_id] }&.flatten&.uniq&.compact }
+                                  topic_ids_per_user
                                 else
                                   []
                                 end
 
       # build map of user_ids to array of item ids {1 => [2,3,4], 2 => [2,4]}
       opts[:user_id].index_with do |student_id|
-        ids_from_pluck = (plucked_visibilities[student_id] || []).map { |id, _, _| id }
-        ids_from_pluck.concat(ids_visible_to_all).concat(ids_visible_to_sections)
+        assignment_item_ids = (plucked_visibilities[student_id] || []).map { |id, _, _| id }
+        section_specific_ids = ids_visible_to_sections[student_id] || []
+        assignment_item_ids.concat(ids_visible_to_all).concat(section_specific_ids)
       end
     end
 

spec/lib/submittable_spec.rb

@@ -162,6 +162,28 @@ def add_section_to_topic(topic, section)
     expect(vis_hash[student.id].first).to eq(section_specific_topic1.id)
   end
 
+  it "filters section specific topics properly for multiple users" do
+    course = course_factory(active_all: true)
+    section1 = course.course_sections.create!(name: "section 1")
+    section2 = course.course_sections.create!(name: "section 2")
+    topic1 = course.discussion_topics.create!(title: "topic 1 (for section 1)")
+    topic2 = course.discussion_topics.create!(title: "topic 2 (for section 2)")
+    topic3 = course.discussion_topics.create!(title: "topic 3 (for all sections)")
+    topic4 = course.discussion_topics.create!(title: "topic 4 (for section 2)")
+    add_section_to_topic(topic1, section1)
+    add_section_to_topic(topic2, section2)
+    add_section_to_topic(topic4, section2)
+    student = user_factory(active_all: true)
+    teacher = user_factory(active_all: true)
+    course.enroll_student(student, section: section2)
+    course.enroll_teacher(teacher, section: section1)
+    course.reload
+
+    vis_hash = DiscussionTopic.visible_ids_by_user(course_id: course.id, user_id: [student.id, teacher.id], item_type: :discussion)
+    expect(vis_hash[student.id]).to contain_exactly(topic2.id, topic3.id, topic4.id)
+    expect(vis_hash[teacher.id]).to contain_exactly(topic1.id, topic3.id)
+  end
+
   it "properly filters section specific topics for deleted section visibilities" do
     course = course_factory(active_course: true)
     section1 = course.course_sections.create!(name: "section for student")
@@ -174,4 +196,30 @@ def add_section_to_topic(topic, section)
     vis_hash = DiscussionTopic.visible_ids_by_user(course_id: course.id, user_id: [student.id], item_type: :discussion)
     expect(vis_hash[student.id].length).to eq(0)
   end
+
+  it "handles sections that don't have any discussion topics" do
+    course = course_factory(active_all: true)
+    section1 = course.course_sections.create!(name: "section 1")
+    section2 = course.course_sections.create!(name: "section 2")
+    topic1 = course.discussion_topics.create!(title: "topic 1 (for section 1)")
+    add_section_to_topic(topic1, section1)
+    student = user_factory(active_all: true)
+    course.enroll_student(student, section: section2)
+    course.reload
+
+    vis_hash = DiscussionTopic.visible_ids_by_user(course_id: course.id, user_id: [student.id], item_type: :discussion)
+    expect(vis_hash[student.id].length).to be(0)
+  end
+
+  it "handles user not enrolled in any sections" do
+    course = course_factory(active_all: true)
+    section1 = course.course_sections.create!(name: "section 1")
+    topic1 = course.discussion_topics.create!(title: "topic 1 (for section 1)")
+    add_section_to_topic(topic1, section1)
+    student = user_factory(active_all: true)
+    course.reload
+
+    vis_hash = DiscussionTopic.visible_ids_by_user(course_id: course.id, user_id: [student.id], item_type: :discussion)
+    expect(vis_hash[student.id].length).to be(0)
+  end
 end