How to include a YAML file inside a YAML file in Ruby

Question

Is there a custom tag in YAML for ruby to include a YAML file inside a YAML file?

#E.g.:  
--- !include
filename: another.yml

A similar question was asked some time ago and there was no relevant answer.

I am wondering if there is some custom tag for Ruby similar to this one for Python.

Answer 1

If you are in Rails, YAML can include ERB.

Combine that together, and here is how you can use <%= %> to include one file from another:

database.yml

<% if File.exists?('/tmp/mysql.sock') %>
<%= IO.read('config/database.mysql.yml') %>
<% else %>
<%= IO.read('config/database.sqlite.yml') %>
<% end %>

database.sqlite.yml

sqlite: &defaults
  adapter: sqlite3
  pool: 5
  timeout: 5000

development:
  <<: *defaults
  database: db/development.sqlite3

test:
  <<: *defaults
  database: db/test.sqlite3

production:
  <<: *defaults
  database: db/production.sqlite3

database.mysql.yml

development:
  adapter: mysql2
  # ... the rest of your mysql configuration ...

Answer 2

I found a way to address my scenario using ERB.

I monkey patched YAML module to add two new methods

module YAML
    def YAML.include file_name
      require 'erb'
      ERB.new(IO.read(file_name)).result
    end

    def YAML.load_erb file_name
      YAML::load(YAML::include(file_name))
    end  
end

I have three YAML files.

mod1_config.yml

mod1:
    age: 30
    city: San Francisco

mod2_config.yml

mod2:
    menu: menu1
    window: window1

all_config.yml

<%= YAML::include("mod1_config.yml") %>
<%= YAML::include("mod2_config.yml") %>

Parse the yaml file using the method YAML::load_erb instead of the method YAML::load.

  config = YAML::load_erb('all_config.yml') 
  config['mod1']['age'] # 30
  config['mod2']['menu'] # menu1

Caveats:

1. Does not support document merge
2. Last include overwrites same named keys

Answer 3

If your aim is avoiding duplication in your YAML file, not necessarily including external file, I recommend doing something like this:

development: &default
  adapter: mysql
  encoding: utf8
  reconnect: false
  database: db_dev
  pool: 5
  username: usr
  password: psw
  host: localhost
  port: 3306

dev_cache:
  <<: *default

new:
  <<: *default
  database: db_new

test:
  <<: *default
  database: db_test

Answer 4

If you just want to inherit from another YAML file, there is a gem providing this functionality you are asking for by extending the ruby YAML library:

https://github.com/entwanderer/yaml_extend

https://rubygems.org/gems/yaml_extend

Usage

yaml_extend adds the method YAML#ext_load_file to YAML.

This method works like the original YAML#load_file, by extending it with file inheritance.

Examples

# start.yml
extends: 'super.yml'
data:
    name: 'Mr. Superman'
    age: 134    
    favorites:
        - 'Raspberrys'

-

# super.yml
data:
    name: 'Unknown'
    power: 2000
    favorites:
        - 'Bananas'
        - 'Apples'

Basic Inheritance

YAML.ext_load_file('start.yml')

results in

data:
    name: 'Mr. Superman'
    age: 134
    power: 2000
    favorites:
        - 'Bananas'
        - 'Apples'
        - 'Raspberrys'

Answer 5

I'm using this:

load_config.rb (initializer)

cf_1 = YAML::load(File.read("/etc/my_app/config.yml"))
cf_2 = YAML::load(File.read(File.join(Rails.root, "config", "config.yml")))
CONFIG = cf_1.merge(cf_2)

Later, you can access config values by doing:

CONFIG['value']

Answer 6

1. !include is not a directive but a tag.

2. it is not a feature of Python (or PyYAML) but a feature of the "poze" library:

   poze.configuration exposes a default directive named include.

3. YAML specification does not define such a standard tag.

Answer 7

Depends what you need it for. If you need to transport file, you can base64 encode internal yaml file.