Included model scopes break on includes and joins

[chrisdpeters]

Example query:

@content_template = current_site.content_templates.live
                                                  .includes(:draft, blocks: :draft, displays: :draft)
                                                  .where(blocks: { trashed_at: nil }, displays: { trashed_at: nil })
                                                  .find(params[:id])

Throws such an exception (in PostgreSQL):

PG::AmbiguousColumn: ERROR: column reference "trashed_at" is ambiguous LINE 1: ...id" WHERE "content_templates"."site_id" = $1 AND (trashed_at... ^ : SELECT DISTINCT "content_templates"."id" FROM "content_templates" LEFT OUTER JOIN "drafts" ON "drafts"."id" = "content_templates"."draft_id" LEFT OUTER JOIN "blocks" ON "blocks"."content_template_id" = "content_templates"."id" LEFT OUTER JOIN "drafts" "drafts_blocks" ON "drafts_blocks"."id" = "blocks"."draft_id" LEFT OUTER JOIN "displays" ON "displays"."content_template_id" = "content_templates"."id" LEFT OUTER JOIN "drafts" "drafts_displays" ON "drafts_displays"."id" = "displays"."draft_id" WHERE "content_templates"."site_id" = $1 AND (trashed_at IS NULL) AND "blocks"."trashed_at" IS NULL AND "displays"."trashed_at" IS NULL AND "content_templates"."id" = $2 LIMIT 1