HoneyFormat

Makes working with CSVs as smooth as honey.

Proper objects for CSV headers and rows, convert column values, filter columns and rows, small(-ish) perfomance overhead, no dependencies other than Ruby stdlib.

Features

• Proper objects for CSV header and rows
• Convert row and header column values
• Pass your own custom row builder
• Filter what columns and rows are included in CSV output
• Gracefully handle missing and duplicated header columns
• CLI - Simple command line interface
• Only ~5-10% overhead from using Ruby CSV, see benchmarks
• Has no dependencies other than Ruby stdlib
• Supports Ruby >= 2.3

Read the usage section, RubyDoc or examples/ directory for how to use this gem.

Quick use

csv_string = <<-CSV
Id,Username,Email
1,buren,buren@example.com
2,jacob,jacob@example.com
CSV
csv = HoneyFormat::CSV.new(csv_string, type_map: { id: :integer })
csv.columns     # => [:id, :username, :email]
csv.rows        # => [#<Row id=1, username="buren", email="buren@example.com">, #<Row id=2, username="jacob", email="jacob@example.com">]
user = csv.rows.first
user.id         # => 1
user.username   # => "buren"

csv.to_csv(columns: [:id, :username]) { |row| row.id < 2 }
# => "id,username\n1,buren\n"

Installation

Add this line to your application's Gemfile:

gem 'honey_format'

And then execute:

$ bundle

Or install it yourself as:

$ gem install honey_format

Usage

By default assumes a header in the CSV file

csv_string = "Id,Username\n1,buren"
csv = HoneyFormat::CSV.new(csv_string)

# Header
header = csv.header
header.original # => ["Id", "Username"]
header.columns  # => [:id, :username]


# Rows
rows = csv.rows # => [#<Row id="1", username="buren">]
user = rows.first
user.id         # => "1"
user.username   # => "buren"

Set delimiter & quote character

csv_string = "name;id|'John Doe';42"
csv = HoneyFormat::CSV.new(
  csv_string,
  delimiter: ';',
  row_delimiter: '|',
  quote_character: "'",
)

Type converters

Type converters are great if you want to convert column values, like numbers and dates.

There are a bunch of default type converters

csv_string = "Id,Username\n1,buren"
type_map = { id: :integer }
csv = HoneyFormat::CSV.new(csv_string, type_map: type_map)
csv.rows.first.id # => 1

Pass your own

csv_string = "Id,Username\n1,buren"
type_map = { username: proc { |v| v.upcase } }
csv = HoneyFormat::CSV.new(csv_string, type_map: type_map)
csv.rows.first.username # => "BUREN"

Combine multiple converters

csv_string = "Id,Username\n1,  BuRen  "
type_map = { username: [:strip, :downcase] }
csv = HoneyFormat::CSV.new(csv_string, type_map: type_map)
csv.rows.first.username # => "buren"

Register your own converter

HoneyFormat.configure do |config|
  config.converter_registry.register :upcased, proc { |v| v.upcase }
end

csv_string = "Id,Username\n1,buren"
type_map = { username: :upcased }
csv = HoneyFormat::CSV.new(csv_string, type_map: type_map)
csv.rows.first.username # => "BUREN"

Remove registered converter

HoneyFormat.configure do |config|
  config.converter_registry.unregister :upcase
  # now you're free to register your own
  config.converter_registry.register :upcase, proc { |v| v.upcase if v }
end

Access registered converters

decimal_converter = HoneyFormat.converter_registry[:decimal]
decimal_converter.call('1.1') # => 1.1

Default converter names

HoneyFormat.config.default_converters.keys

See Converters::DEFAULT for a complete list of the default converter names.

Row builder

Pass your own row builder if you want more control of the entire row or if you want to return your own row object.

Custom row builder

csv_string = "Id,Username\n1,buren"
upcaser = ->(row) { row.tap { |r| r.username.upcase! } }
csv = HoneyFormat::CSV.new(csv_string, row_builder: upcaser)
csv.rows # => [#<Row id="1", username="BUREN">]

As long as the row builder responds to #call you can pass anything you like

class Anonymizer
  def call(row)
    @cache ||= {}
    # Return an object you want to represent the row
    row.tap do |r|
      # given the same value make sure to return the same anonymized value every time
      @cache[r.email] ||= "#{SecureRandom.hex(6)}@example.com"
      r.email = @cache[r.email]
      r.payment_id = '<scrubbed>'
    end
  end
end

csv_string = <<~CSV
Email,Payment ID
buren@example.com,123
buren@example.com,998
CSV
csv = HoneyFormat::CSV.new(csv_string, row_builder: Anonymizer.new)
csv.rows.to_csv(columns: [:email])
# => 8f6ed70a7f98@example.com
#    8f6ed70a7f98@example.com
#    0db96f350cea@example.com

Output CSV

Makes it super easy to output a subset of columns/rows.

Manipulate the rows before output

csv_string = "Id,Username\n1,buren"
csv = HoneyFormat::CSV.new(csv_string)
csv.rows.each { |row| row.id = nil }
csv.to_csv # => "id,username\n,buren\n"

Output a subset of columns

csv_string = "Id, Username, Country\n1,buren,Sweden"
csv = HoneyFormat::CSV.new(csv_string)
csv.to_csv(columns: [:id, :country]) # => "id,country\nburen,Sweden\n"

Output a subset of rows

csv_string = "Name, Country\nburen,Sweden\njacob,Denmark"
csv = HoneyFormat::CSV.new(csv_string)
csv.to_csv { |row| row.country == 'Sweden' } # => "name,country\nburen,Sweden\n"

Headers

By default generates method-like names for each header column, but also gives you full control: define them or convert them.

By default assumes a header in the CSV file.

csv_string = "Id,Username\n1,buren"
csv = HoneyFormat::CSV.new(csv_string)

# Header
header = csv.header
header.original # => ["Id", "Username"]
header.columns  # => [:id, :username]

Define header

csv_string = "1,buren"
csv = HoneyFormat::CSV.new(csv_string, header: ['Id', 'Username'])
csv.rows.first.username # => "buren"

Set default header converter

HoneyFormat.configure do |config|
  config.header_converter = proc { |v| v.downcase }
end

# you can get the default one with
header_converter = HoneyFormat.converter_registry[:header_column]
header_converter.call('First name') # => "first_name"

Use any converter registry as the header converter

csv_string = "Id,Username\n1,buren"
csv = HoneyFormat::CSV.new(csv_string, header_converter: :upcase)
csv.columns # => [:ID, :USERNAME]

Pass your own header converter

# unmapped keys use the default header converter,
# mix simple key => value mapping with key => proc
converter = {
  'First^Name' => :first_name,
  'Username' => -> { :handle }
}

csv_string = "ID,Username,First^Name\n1,buren,Jacob"
user = HoneyFormat::CSV.new(csv_string, header_converter: converter).rows.first
user.first_name # => "Jacob"
user.handle     # => "buren"
user.id         # => "1"

# you can also pass a proc or any callable object
converter = Class.new do
  define_singleton_method(:call) { |value, index| "#{value}#{index}" }
end
# or
converter = ->(value, index) { "#{value}#{index}"  }
user = HoneyFormat::CSV.new(csv_string, header_converter: converter)

Missing header values are automatically set and deduplicated

csv_string = "first,,third,third\nval0,val1,val2,val3"
csv = HoneyFormat::CSV.new(csv_string)
user = csv.rows.first
user.column1 # => "val1"
user.third   # => "val2"
user.third1  # => "val3"

Duplicated header values

csv_string = <<~CSV
  email,email,name
  john@example.com,jane@example.com,John
CSV
# :deduplicate is the default value
csv = HoneyFormat::CSV.new(csv_string, header_deduplicator: :deduplicate)
user = csv.rows.first
user.email  # => john@example.com
user.email1 # => jane@example.com

# you can also choose to raise an error instead
HoneyFormat::CSV.new(csv_string, header_deduplicator: :raise)
# => HoneyFormat::DuplicateHeaderColumnError

If your header contains special chars and/or chars that can't be part of Ruby method names, things can get a little awkward..

csv_string = "ÅÄÖ\nSwedish characters"
user = HoneyFormat::CSV.new(csv_string).rows.first
# Note that these chars aren't "downcased" in Ruby 2.3 and older versions of Ruby,
# "ÅÄÖ".downcase # => "ÅÄÖ"
user.ÅÄÖ # => "Swedish characters"
# while on Ruby > 2.3
user.åäö

csv_string = "First^Name\nJacob"
user = HoneyFormat::CSV.new(csv_string).rows.first
user.public_send(:"first^name") # => "Jacob"
# or
user['first^name'] # => "Jacob"

Emoji characters

csv_string = "😎⛷\nEmoji characters"
csv = HoneyFormat::CSV.new(csv_string)
csv.rows.first.😎⛷ # => Emoji characters

Errors

When you need to be extra safe.

If you want to there are some errors you can rescue

begin
  HoneyFormat::CSV.new(csv_string)
rescue HoneyFormat::HeaderError => e
  puts 'there was a problem with the header'
  raise(e)
rescue HoneyFormat::RowError => e
  puts 'there was a problem with a row'
  raise(e)
end

You can see all available errors here.

Skip lines

Skip comments and/or other unwanted lines from being parsed.

csv_string = <<~CSV
Id,Username
1,buren
# comment
2,jacob
CSV
regexp = %r{\A#} # Match all lines that start with "#"
csv = HoneyFormat::CSV.new(csv_string, skip_lines: regexp)
csv.rows.length # => 2

Matrix

Use whats under the hood.

Actually HoneyFormat::CSV is a very thin wrapper around HoneyFormat::Matrix. You can use Matrix directly it support all options that aren't specifically tied to parsing a CSV.

Example

data = [
  %w[name id],
  %w[jacob 1]
]
type_map = {
  id: :integer,
  name: :upcase
}

matrix = HoneyFormat::Matrix.new(data, type_map: { id: :integer, name: :upcase })
matrix.columns   # => [:name, :id]
matrix.rows.to_a # => [#<Row name="JACOB", id=1>]
matrix.to_csv    # => "name,id\nJACOB,1\n"

If you want to see more usage examples check out the examples/ and spec/ directories and of course on RubyDoc.

SQL example

When you want the result as an object, with certain columns converted to objects.

require 'mysql2'

class DBClient
  def initialize(host:, username:, password:, port: 3306)
    @client = Mysql2::Client.new(
      host: host,
      username: username,
      password: password,
      port: port
    )
  end

  def query(sql, type_map: {})
    result = @client.query(sql)
    return if result.first.nil?

    matrix = HoneyFormat::Matrix.new(
      result.map(&:values),
      header: result.first.keys,
      type_map: type_map
    )
    matrix.rows
  end
end

Usage example with a fictional "users" database table (schema: name, created_at)

client = DbClient.new(host: '127.0.0.1', username: 'root', password: nil)
users = client.query(
  'SELECT * FROM users',
  type_map: { created_at: :datetime! }
)
user = users.first
user.name # => buren
user.created_at.class # => Time

Configuration

Configuration is optional

HoneyFormat.configure do |config|
  config.header_converter = proc { |column| column.downcase }
  config.delimiter = ";"
  config.row_delimiter = "|"
  config.quote_character = "'"
  config.skip_lines = %r{\A#} # Match all lines that start with "#"
end

Default configuration values

HoneyFormat.configure do |config|
  config.header_converter = HoneyFormat::Registry.new(Converters::DEFAULT)[:header_column]
  config.delimiter = ","
  config.row_delimiter = :auto
  config.quote_character = "\""
  config.skip_lines = nil
end

CLI

Perfect when you want to get something simple done quickly.

Usage: honey_format [options] <file.csv>
        --csv=input.csv              CSV file
        --columns=id,name            Select columns
        --output=output.csv          CSV output (STDOUT otherwise)
        --delimiter=,                CSV delimiter (default: ,)
        --skip-lines=,               Skip lines that match this pattern
        --[no-]header-only           Print only the header
        --[no-]rows-only             Print only the rows
    -h, --help                       How to use
        --version                    Show version

Output a subset of columns to a new file

# input.csv
id,name,username
1,jacob,buren

$ honey_format input.csv --columns=id,username > output.csv

Benchmark

Note: This gem, adds some overhead to parsing a CSV string, typically ~5-10%. I've included some benchmarks below, your mileage may vary.. The benchmarks have been run with Ruby 2.5.

204KB (1k lines)

 CSV no options:       51.0 i/s
 CSV with header:      36.1 i/s - 1.41x  slower
HoneyFormat::CSV:      48.7 i/s - 1.05x  slower

2MB (10k lines)

  CSV no options:        5.1 i/s
 CSV with header:        3.6 i/s - 1.42x  slower
HoneyFormat::CSV:        4.9 i/s - 1.05x  slower

You can run the benchmarks yourself

Usage: bin/benchmark [file.csv] [options]
        --csv=[file1.csv]            CSV file(s)
        --[no-]verbose               Verbose output
        --lines-multipliers=[1,2,10] Multiply the rows in the CSV file (default: 1)
        --time=[30]                  Benchmark time (default: 30)
        --warmup=[5]                 Benchmark warmup (default: 5)
    -h, --help                       How to use

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/buren/honey_format. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.