What causes "Checkpoints not found" in instructure/canvas-lms?

Check assignment.has_sub_assignments? (and sub_assignments.any?) before calling the deleter and treat no-op as success.

instructure/canvas-lms · error · Checkpoints::NoCheckpointsFoundError

Checkpoints not found

Error message

Checkpoints not found

What it means

DiscussionCheckpointDeleterService#find_checkpoints loads @assignment.sub_assignments and raises NoCheckpointsFoundError if there are none. The deleter is meant to tear down checkpoint sub-assignments for a discussion with has_sub_assignments; if the assignment has no sub-assignments there is nothing to delete, indicating the assignment isn't checkpointed (anymore).

Solutions

Check assignment.has_sub_assignments? (and sub_assignments.any?) before calling the deleter and treat no-op as success.
Make the caller idempotent: rescue NoCheckpointsFoundError and skip.
If data is inconsistent (has_sub_assignments true but no sub_assignments), repair by setting has_sub_assignments: false instead of deleting.

Example fix

// before
Checkpoints::DiscussionCheckpointDeleterService.call(assignment: a)
// after
if a.has_sub_assignments? && a.sub_assignments.any?
  Checkpoints::DiscussionCheckpointDeleterService.call(assignment: a)
end

Defensive patterns

Strategy: try-catch

Validate before calling

return :noop unless assignment.has_sub_assignments? && assignment.sub_assignments.any?

Try / catch

begin
  Checkpoints::DiscussionCheckpointDeleterService.call(assignment:)
rescue Checkpoints::NoCheckpointsFoundError
  # already deleted or never checkpointed; treat as idempotent success
end

Prevention

Make delete operations idempotent by checking sub_assignments.any? first
Keep has_sub_assignments in sync when sub_assignments change
Guard UI delete buttons on the assignment actually having checkpoints

When it happens

Trigger: Calling the deleter on an assignment whose has_sub_assignments is false or whose sub_assignments were already removed (double delete), e.g. duplicate delete requests or deleting checkpoints on a regular (non-checkpoint) discussion.

Common situations: Idempotency issues where the UI fires delete twice and the second call fails; calling the deleter for a plain discussion topic; data migrations/fixups that cleared sub_assignments without updating has_sub_assignments.

Understand the failure class

Background: EmptyResultError / "no results found": when an API or scraper succeeds but returns zero rows — this error's family across 9 libraries.

Related errors

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/5addb42720af706e. Report an issue: GitHub.

Appendix: source

Thrown at app/services/checkpoints/discussion_checkpoint_deleter_service.rb:48

    checkpoints.each do |checkpoint|
      checkpoint.active_assignment_overrides.destroy_all
    end

    @assignment.active_assignment_overrides.destroy_all

    checkpoints.destroy_all

    update_assignment_and_discussion

    true
  end

  private

  def find_checkpoints
    checkpoints = @assignment.sub_assignments

    raise Checkpoints::NoCheckpointsFoundError, "Checkpoints not found" unless checkpoints.any?

    checkpoints
  end

  def update_assignment_and_discussion
    @assignment.update!(has_sub_assignments: false)
    @discussion_topic.update!(reply_to_entry_required_count: 0)
  end
end

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