Ruby tool to update the "Content-Length" in VCR test fixture "cassettes" to match the body length (it skips HEAD requests)

README.md

VCR Cassette Cleaner

I made this tool to update the Content-Length header to match the bytesize of the body response in VCR cassettes. This is only necessary when the body has been manually edited (usually done to reduce the size of the YAML fixture). While VCR has an option to automatically update the Content-Length header on-the-fly (it doesn't update the cassette itself), the option also affects HEAD requests and sets their Content-Length to 0 (issue). This tool will skip HEAD requests to avoid that.

This tool has only been tested with Ruby 2.6 and VCR 5.0.0.

cassette_cleaner.rb

#!/usr/bin/env ruby -wKU
#
# A Ruby script for "cleaning" cassettes from the VCR library.
# 
# * Update `Content-Length` header to match body length for non-HEAD
#   requests
#
# USAGE: ruby cassette_cleaner.rb [-i] cassette.yml [-o output.yml]
# 
# * -i: update YAML file in-place (overwrite)
# * -o: output updated YAML in new file
# 
# These options are exclusive and cannot be used together.

require 'optparse'
require 'psych'

# Parse the command line options to adjust the output
options = {}
OptionParser.new do |opts|
  opts.banner = "Usage: cassette_cleaner.rb [-i] cassette.yml [-o output.yml]"

  opts.on("-i", "--inplace", "Update in-place") do
    options[:output] = nil
    options[:inplace] = true
  end

  opts.on("-o", "--output FILE", "Output to file") do |output|
    options[:inplace] = false
    options[:output] = output
  end

  opts.on("-h", "--help", "Prints this help") do
    puts opts
    exit
  end
end.parse!

input_file = ARGV[0]

if input_file.nil?
  puts "Input file required"
  exit 1
end

# Read in the input YAML cassette file
input_doc = Psych.load_file(input_file)

# Iterate over the HTTP interactions in the cassette, and filter out
# HEAD requests as we don't want to adjust the body size there.
input_doc["http_interactions"].select { |http|
  http["request"]["method"] != "head"
}.each { |http|
  # Get the *bytesize* of the body, and update the "Content-Length"
  # header to match. If there is no Content-Length header, skip.
  if http["response"]["headers"].keys.include?("Content-Length")
    body_size = http["response"]["body"]["string"].bytesize

    if http["response"]["headers"]["Content-Length"][0].to_i != body_size
      http["response"]["headers"]["Content-Length"] = [body_size.to_s]
      puts "Content-Length updated in cassette."
    else
      puts "Content-Length did not change."
    end
  end
}

if options[:output]
  outfile = File.new(options[:output], "w")
  Psych.dump(input_doc, outfile)
elsif options[:inplace]
  outfile = File.new(input_file, "w")
  Psych.dump(input_doc, outfile)
end