instructure/canvas-lms · error · GraphQL::ExecutionError

Anonymous assignments cannot be posted by section

Error message

Anonymous assignments cannot be posted by section

What it means

When sections are supplied, the mutation refuses to act on anonymously graded assignments (assignment.anonymous_grading? is true), because posting/hiding by section would deanonymize students by revealing which students belong to each section.

Solutions

1. Hide/post grades for the whole assignment without section_ids (omit section_ids).
2. Turn off anonymous grading if section-level operations are truly required (only possible before submissions, per policy), or re-create the assignment without anonymity.
3. Gate the UI: disable section selection when assignment.anonymousGrading is true.
4. If only certain students should be affected, use only_student_ids/skip_student_ids instead of sections — anonymity of the mapping is preserved differently, verify policy allows it.

Example fix

// before
await HideAssignmentGrades.mutate({ assignmentId, sectionIds });
// after
if (assignment.anonymousGrading) {
  await HideAssignmentGrades.mutate({ assignmentId }); // no sections
} else {
  await HideAssignmentGrades.mutate({ assignmentId, sectionIds });
}

if (assignment.anonymousGrading && sectionIds?.length) {
  sectionIds = undefined; // whole-assignment operation instead
}

const sectionScopingAllowed = (a) => Boolean(a && !a.anonymousGrading && !a.anonymizeStudents);

try { await hideGrades({ assignmentId, sectionIds }); }
catch (e) {
  if (String(e).includes('Anonymous assignments')) return hideGrades({ assignmentId });
  throw e;
}

When it happens

Trigger: Calling hideAssignmentGrades with a non-empty section_ids on an assignment created with anonymous grading (anonymous_grading enabled and assignment is anonymous).

Common situations: Teachers used to section-level posting trying it on an anonymized assignment; scripts that always pass section_ids copied from non-anonymous flows; UI not hiding section options for anonymous assignments.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Anonymous assignments cannot be hidden by section
• and cannot be used together
• A course with that id does not exist
• Anonymous assignments cannot be posted by graded only
• Anonymous assignments cannot be posted by section

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/a470bbbf40bb3329. Report an issue: GitHub.

Appendix: source

Thrown at app/graphql/mutations/hide_assignment_grades.rb:47

  field :assignment, Types::AssignmentType, null: true
  field :progress, Types::ProgressType, null: true
  field :sections, [Types::SectionType], null: true

  def resolve(input:)
    begin
      assignment = AbstractAssignment.find_assignment_or_peer_review(input[:assignment_id])
      course = assignment.context
      sections = input[:section_ids] ? course.course_sections.where(id: input[:section_ids]) : nil
    rescue ActiveRecord::RecordNotFound
      raise GraphQL::ExecutionError, "not found"
    end

    verify_authorized_action!(assignment, :grade)

    unless assignment.grades_published?
      raise GraphQL::ExecutionError, "Assignments under moderation cannot be hidden before grades are published"
    end
    raise GraphQL::ExecutionError, "Anonymous assignments cannot be posted by section" if sections && assignment.anonymous_grading?

    if input[:only_student_ids] && input[:skip_student_ids]
      raise GraphQL::ExecutionError, I18n.t("{a} and {b} cannot be used together", a: "only_student_ids", b: "skip_student_ids")
    end

    visible_enrollments = course.apply_enrollment_visibility(course.student_enrollments, current_user, sections)
    visible_enrollments = visible_enrollments.where(user_id: input[:only_student_ids]) if input[:only_student_ids]
    visible_enrollments = visible_enrollments.where.not(user_id: input[:skip_student_ids]) if input[:skip_student_ids]

    submissions_scope = assignment.submissions.active.joins(user: :enrollments)
    submissions_scope = course.apply_enrollment_visibility(submissions_scope, current_user).merge(visible_enrollments)
    progress = course.progresses.new(tag: "hide_assignment_grades")

    if progress.save
      progress.process_job(
        assignment,
        :hide_submissions,
        { preserve_method_args: true, priority: Delayed::HIGH_PRIORITY },

View on GitHub (pinned to 1c9f0bb801)