first_attempt.rb

opts = {}
str = '{{ options.foo__required }}{{ options.bar__required }}{{ options.baz_9 }}'

# I'm still flattening right now... though just once in this case.
keys = str.scan(/\{\{ options.(\w+) \}\}/).flatten
=> ["foo__required", "bar__required", "baz_9"]

opts.merge!(Hash[keys.product([nil])])
=> {"foo__required"=>nil, "bar__required"=>nil, "baz_9"=>nil}

i_dont_even_know_anymore.rb

# if liquid tags are unlikely to change, maybe we quarantine their shittiness to one place?
# also includes uniq
# also uses match + named capture, but I don't know if that's an improvement. no more flattens!

def extract_opts(optstring)
  tag_bodies(optstring).map { |option| option_name(option) }.compact.uniq
end

def option_name(option)
  option.match(/options.(?<name>\w+)/)[:name]
end

def tag_bodies(str)
  str.scan(/\{[\{%] ([^%\}]*) [%\}]\}/).flatten
end

str = '{{ options.foo__required }}{{ options.bar__required | upcase }}{% options.baz_9 %}{{ options.quux__integer | downcase }}'
extract_opts(str)

real_final_v09-june-27.rb

# liquid expressions may contain multiple variables.
# tons of flattens now, but compaction is automatic!

def extract_opts(optstring)
  tag_bodies(optstring).inject([]) do |result, option|
    result + option_names(option)
  end.uniq
end

def option_names(option)
  option.scan(/options.(\w+)/).flatten || []
end

def tag_bodies(str)
  str.scan(/\{[\{%] ([^%\}]*) [%\}]\}/).flatten
end

str = '{{ options.foo__required }}
       {{ options.bar__required | upcase }}
       {% options.baz_9 %}
       {{ nuffin }}
       {{ options.quux__number | downcase }}
       {{ options.boop__number | times: options.donk__number }}'

extract_opts(str)
=> ["foo__required", "bar__required", "baz_9", "quux__number", "boop__number", "donk__number"]

with_some_naming_help.rb

def extract_opts(optstring)
  proper_flags(optstring) + classic_flags(optstring)
end

def proper_flags(str)
  str.scan(/\{\{ options.(\w+) \}\}/).flatten
end

# looks like this is an oldschool liquid thing? trying adding a name for it.
# also prevents some of the worst of the unnesting of scan results
def classic_flags(str)
  str.scan(/\{% options.(\w+) %\}/).flatten
end

str = '{{ options.foo__required }}{{ options.bar__required }}{% options.baz_9 %}'
extract_opts(str)
=> ["foo__required", "bar__required", "baz_9"]

with_transforms.rb

# properly disregards transforms, but I'd like to template the regexes to be a bit more readable...

def extract_opts(optstring)
  proper_flags(optstring) + classic_flags(optstring)
end

def proper_flags(str)
  str.scan(/\{\{ options.(\w+)[^}]*\}\}/).flatten
end

def classic_flags(str)
  str.scan(/\{% options.(\w+)[^%]*%\}/).flatten
end

str = '{{ options.foo__required }}{{ options.bar__required | upcase }}{% options.baz_9 %}{{ options.quux__integer | downcase }}'
extract_opts(str)
=> ["foo__required", "bar__required", "quux__integer", "baz_9"]