Update Statsd tag serializer to allow falsy values

[joseph-hughes]

Problem

If we provide a tag which has a boolean value, we are unable to properly track the false case, since the "true" string appears with the tag name, but the "false" string does not show up. This is because of this logic, which checks for tag value presence:

dogstatsd-ruby/lib/datadog/statsd/serialization/tag_serializer.rb

Lines 58 to 66 in 517b830

	def to_tags_list(tags)
	case tags
	when Hash
	tags.map do |name, value|
	if value
	escape_tag_content("#{name}:#{value}")
	else
	escape_tag_content(name)
	end

true is evaluated to present, so we would add that tag name and value; however, false is evaluated to not present, so we would only add that tag name (not the value).

Solution

First, check for nil explicitly then also check for nil after converting to a string.

This does result in other values being deemed "present" now which were not previously though, such as [] and {}. Is this a problem though?

[marcotc]

This gem supports Ruby as low as 2.1, so we cannot use &., sorry :/

I suggest keeping the if/else as it was, and just change the check to a nil-check explicitly:

Suggested change

	if value&.to_s.nil?
	escape_tag_content(name)
	else
	escape_tag_content("#{name}:#{value}")
	if !value.nil?
	escape_tag_content("#{name}:#{value}")
	else
	escape_tag_content(name)

[joseph-hughes]

I wish to also ignore nil when casted to a string to be extra safe, so I went with this suggestion but updated it to:

if !value.nil? && !value.to_s.nil?

[ivoanjo]

(Unrelated to this PR but -- should we raise the minimum version for this gem? dd-trace-rb has moved on for a long time, so it's weird to still keep this one at 2.1)

[joseph-hughes]

Hi, @marcotc, @chouetz, @StephenWakely, and @rayz 👋🏼

Pinging to see if there's any feedback or blockers for this PR. Happy to make changes if needed. Thanks!

[marcotc]

Hey @joseph-hughes, so sorry for the delay. The issue totally makes sense!
I'll take a look at the PR as a whole today.