Backport Sidekiq::JobUtil#verify_json error message to v6.x

[jai-x]

In this PR (#5786), a very useful change was made to the error message when a non-JSON serializable argument was passed to job. The error message includes the unsafe_item.inspect and unsafe_item.class in the error message, however this is only available in v7.

I'm in the middle of trying diagnose a mysterious occurance of this error message in a v6 install of Sidekiq.
I have raising enabled for non-JSON args, but finding it hard to pinpoint what is causing this in my app.

It would be great if this error message, including the inspect and class outputs for the unsafe item were backported to v6.
It would make upgrading to v7 a lot easier in my case.

[mperham]

I consider Sidekiq 6 frozen except for high-priority compatibility fixes or security issues. Can you monkeypatch the method in your initializer?

[jai-x]

Sure, I've ended up with a monkeypatch solution.

For reference it's this:

# in file: config/initializers/sidekiq.rb

Sidekiq.strict_args!

Sidekiq.configure_server do |config|
   # ...
end

class Sidekiq::Client
  def verify_json(item)
    job_class = item["wrapped"] || item["class"]
    args = item["args"]
    mode = Sidekiq[:on_complex_arguments]

    if mode == :raise || mode == :warn
      if (unsafe_item = json_unsafe?(args))
        msg = <<~EOM
          Job arguments to #{job_class} must be native JSON types.
          Argument #{unsafe_item.inspect} is a #{unsafe_item.class}.
          All arguments to job: #{args.inspect}
          See https://github.com/sidekiq/sidekiq/wiki/Best-Practices
          To disable this error, add `Sidekiq.strict_args!(false)` to your initializer.
        EOM

        if mode == :raise
          raise(ArgumentError, msg)
        else
          Sidekiq.logger.warn(msg)
        end
      end
    end
  end

  private

  RECURSIVE_JSON_UNSAFE = {
    Integer => ->(val) {},
    Float => ->(val) {},
    TrueClass => ->(val) {},
    FalseClass => ->(val) {},
    NilClass => ->(val) {},
    String => ->(val) {},
    Array => ->(val) {
      val.each do |e|
        unsafe_item = RECURSIVE_JSON_UNSAFE[e.class].call(e)
        return unsafe_item unless unsafe_item.nil?
      end
      nil
    },
    Hash => ->(val) {
      val.each do |k, v|
        return k unless String === k

        unsafe_item = RECURSIVE_JSON_UNSAFE[v.class].call(v)
        return unsafe_item unless unsafe_item.nil?
      end
      nil
    }
  }

  RECURSIVE_JSON_UNSAFE.default = ->(val) { val }
  RECURSIVE_JSON_UNSAFE.compare_by_identity
  private_constant :RECURSIVE_JSON_UNSAFE

  def json_unsafe?(item)
    RECURSIVE_JSON_UNSAFE[item.class].call(item)
  end
end

[mperham]

Exactly. I would move it to its own file and add a guard up top which raises an error if Sidekiq::VERSION > "7" since you don't want to patch v7 when you upgrade.