Kojo Configuration Ninja

• Installation
• Usage
  • Variables
  • Import
  • Transform an Entire Folder
  • Transform One to Many using Config
  • Transform One to Many using Front Matter
  • Convert YAML to JSON
  • Interactive Form Templates
  • Conditions and Loops with ERB
• Interactive Fallback
• Using from Ruby Code
• Contributing / Support

$ gem install kojo

Or with Homebrew:

$ brew install brew-gem    # once only, to enable the brew gem command
$ brew gem install kojo

Or with Docker:

$ alias kojo='docker run --rm -it --user $(id -u):$(id -g) --volume "$PWD:/app" dannyben/kojo'

If you prefer to learn by example, see the examples folder for several use cases. Each example subfolder contains the command to run, the relevant files, and the expected output.

Include variables in your configuration templates by using this syntax: %{varname}

• Variables can be provided through the command line, or when using @import.
• When one or more variables are not provided, you will be prompted to provide a value.
• Variables from the top level will be forwarded downstream, and aggregated with any additional variables that are defined in subsequent @imports.

Note that since the % sign is used for variable replacement, if you want your generated file to include a literal percent sign, you need to escape it as %% in your template.

Use the @import filename directive anywhere to include another file in the resulting configuration file.

• The @import directive should be the only thing in the line.
• The indentation will be respected when importing.
• The filename parameter does not have to include an extension - Kojo will use the same extension as the parent file.
• The included file will be searched for relative to the file it is included in.
• Arguments can be passed down to the included template by using this syntax:

@import filename (arg: "value", arg2: "value")

The space after filename is optional, and the arguments list can be split to multiple lines:

@import filename (
  arg: "value",
  arg2: "value"
)

Process a folder containing templates and @imports, and generate a mirror output folder, with all the variables and @imports evaluated.

You may use %{variables} in filenames.

Using the kojo config command together with a simple definitions file, you can:

1. Generate multiple output files based on a single template file
2. Generate multiple output directories, based on a single source directory.

To achieve this, you need to:

1. Create the configuration template or directory of templates.
2. Create a configuration YAML file using this syntax:

input: base-template.yml

output:
  outfile1.yml:
    argument1: value
    argument2: value

  outfile2.yml:
    argument1: value
    argument2: value

When using a folder as input, simply provide the folder name in the input property, and instead of providing desired output filenames in the output property, provide desired output directories:

input: base

output:
  app1:
    argument1: value
    argument2: value

  app2:
    argument1: value
    argument2: value

Define a template that contains the instructions on how to transform it as a YAML front matter.

The YAML front matter should be structured like this:

filename1:
  arg: value
  another_arg: value

filename2:
  arg: value
  another_arg: value
---
Your template that uses %{arg} goes here
...

Additional arguments provided to the command line, will also be transferred to the template.

Convert one or more YAML files to JSON.

This can be useful when you require JSON files as output, but wish to edit (or generate using Kojo) using the less error-prone and more aesthetically pleasing YAML format.

Note that this Kojo command does not provide any additional preprocessing - the input files should be valid YAML.

Using the kojo form command lets you define an ERB or ERBX template, and include interactive prompts to enter the input.

1. Use either ERB tags (<%= %>, <%- -%>) or ERBX tags ({{ }}, (( ))).
2. Use the built in prompt object, which is a TTY::Prompt instance, to prompt for input when running the command (for example: {{ prompt.ask? "Your Name?" }})
3. Any unidentified ruby command will be forwarded to the prompt object, so prompt.ask is the same as just using ask.
4. If there is a file with the same name as the template, and with an .rb extension (for example form.md and form.md.rb), then the ruby file will be loaded into the ERB template as if it was written inside it.
5. If you prefer using a single template file (without the ruby appendix), you can simply use regular ERB/ERBX tags, like demonstrated below.

Template files are evaluated using ERB, so you can use any Ruby code for more advanced templates (for conditions, loops etc.).

Use this syntax for ruby code:

<%- ruby code here -%>     # for code that should not be printed
<%= ruby code here -%>     # for code that should be printed

When Kojo encounters a variable that was not supplied (either through the command line or through a configuration file), it will prompt for a value.

You can enable or disable interactive mode by setting the environment variable KOJO_INTERACTIVE to yes or no.

By default, interactivity is enabled when running the CLI, and disabled when running from within Ruby code.

When running from within Ruby code, you can also use Kojo.interactive = true and Kojo.interactive? to get the current state.

Although Kojo was primarily designed as a command line utility, you can also use it as a library from your Ruby code.

These are the primary classes:

# Template
template = Kojo::Template.new 'examples/variables/main.yml'
result = template.render domain: 'example.com', scale: 2
puts result

# Collection
collection = Kojo::Collection.new 'examples/dir'
collection.import_base = 'examples/dir/imports'

params = { env: 'env', app: 'app' }
result = collection.render params do |path, content|
  # code to handle results here
end

# Config
config = Kojo::Config.new 'examples/config-from-file/config.yml'
config.import_base = "examples/config-from-file/imports"

config.generate do |path, content|
  # code to handle results here
end

# FrontMatterTemplate
template = Kojo::FrontMatterTemplate.new 'examples/single/Dockerfile'
params = { version: '0.1.1' }

template.render params do |path, content|
  # code to handle results here
end

# Form
template = Kojo::Form.new 'examples/form/movie.md'
puts template.render

In addition, Kojo extends Ruby's File class with the File.deep_write method, which lets you write the file and create the directory structure as needed. You may use it in your code like this:

# Config
config = Kojo::Config.new 'examples/config-from-file/config.yml'
config.import_base = "examples/config-from-file/imports"

config.generate do |path, content|
  File.deep_write path, content
end

If you experience any issue, have a question or a suggestion, or if you wish to contribute, feel free to open an issue.