Figuring out where objects are coming from

finding_where_objs_come_from.rb

# followup for https://twitter.com/kirill_shevch/status/1577930057728856064
require 'objspace'
require 'json'
def some_code
  [ 10_000.times.map { "hi" },
    5_000.times.map { "there" },
    JSON.load('{ "omg": 123, "wtf": true, "bbq": 23.45 }'),
  ]
end

ObjectSpace.trace_object_allocations do
  _ = some_code # saving to a variable so they don't get gc'd
  ObjectSpace
    .each_object(String)
    .to_a # eager load them so it doesn't consider strings created during iteration
    .filter_map {
      file = ObjectSpace.allocation_sourcefile _1
      line = ObjectSpace.allocation_sourceline _1
      file && line && "#{file}##{line}"
    }
    .tally
    .sort_by { -_2 }
    # => [["program.rb#4", 10000],
    #     ["program.rb#5", 5000],
    #     ["/Users/josh/.gem/ruby/3.0.2/gems/json-2.6.1/lib/json/common.rb#216",
    #      3],
    #     ["program.rb#6", 1]]
end