Toys-Core

Toys is a configurable command line tool. Write commands in Ruby using a simple DSL, and Toys will provide the command line executable and take care of all the details such as argument parsing, online help, and error reporting.

Toys-Core is the command line tool framework underlying Toys. It can be used to write command line executables using the Toys DSL and the power of the Toys classes.

For more detailed information about Toys-Core, see the Toys-Core User's Guide. For background information about Toys itself, see the Toys README and the Toys User Guide.

Introductory tutorial

Here's a tutorial to help you get a feel for how to write a basic command line executable using Toys-Core.

It assumes basic familiarity with Toys, so, if you have not done so, I recommend first walking through the tutorial in the Toys README. It also assumes you are running a unix-like system such as Linux or macOS. Some commands might need to be modified if you're running on Windows.

Install Toys

Install the toys-core gem using:

$ gem install toys-core

You may also install the toys gem, which brings in toys-core as a dependency.

Toys-Core requires Ruby 2.4 or later.

Most parts of Toys-Core work on JRuby. However, JRuby is not recommended because of JVM boot latency, lack of support for Kernel#fork, and other issues.

Most parts of Toys-Core work on TruffleRuby. However, TruffleRuby is not recommended because it has a few known bugs that affect Toys.

Create a new executable

We'll start by creating an executable Ruby script. Using your favorite text editor, create new a file called mycmd with the following contents:

#!/usr/bin/env ruby

require "toys-core"

cli = Toys::CLI.new

exit(cli.run(*ARGV))

Make sure the file's executable bit is set:

$ chmod a+x mycmd

That's it! This is a fully-functional Toys-based executable! Let's see what happens when you run it:

$ ./mycmd

Just as with Toys itself, you get a help screen by default (since we haven't yet actually implemented any behavior.) As you can see, some of the same features from Toys are present already: online help, and --verbose and --quiet flags. These features can of course all be customized or disabled, but they're often useful to have to start off.

Add some functionality

You implement the functionality of your executable using the same DSL that you use to write Toys files. You could point your executable at a directory containing actual Toys files, but the simplest option is to provide the information to the Toys CLI object in a block.

Let's add some functionality.

#!/usr/bin/env ruby

require "toys-core"

cli = Toys::CLI.new

#### Insert the following block ...
cli.add_config_block do
  desc "My first executable!"
  flag :whom, default: "world"
  def run
    puts "Hello, #{whom}!"
  end
end

exit(cli.run(*ARGV))

If you went through the tutorial in the README for the Toys gem, this should look familiar. Let's run it now, and experiment with passing flags to it.

$ ./mycmd
$ ./mycmd --whom=ruby
$ ./mycmd --bye
$ ./mycmd --help

Notice that we did not create a tool block, but instead set up description, flags, and functionality directly in the configuration block. This configures the "root tool", i.e. what happens when you run the executable without passing a tool name to it. (Note, it's legal to do this in Toys as well, by setting functionality at the "top level" of a .toys.rb file without including any tool block.)

Tool-based executables

But perhaps you want your executable to have multiple "tools", similar to other familiar executables like git or kubectl. You can define tools, including nested tools, by writing tool blocks in your config. Here's an example:

#!/usr/bin/env ruby

require "toys-core"

cli = Toys::CLI.new

#### Change the config block as follows ...
cli.add_config_block do
  # Things outside any tool block still apply to the root
  desc "My first executable with several tools"

  # We'll put the greet function here
  tool "greet" do
    desc "My first tool!"
    flag :whom, default: "world"
    def run
      puts "Hello, #{whom}!"
    end
  end

  # Try writing a second tool here. You could use the "new-repo"
  # example from the Toys tutorial.
end

exit(cli.run(*ARGV))

Now you can run greet as a tool:

$ ./mycmd greet

The "root" functionality once again shows global help, including a list of the available tools.

$ ./mycmd

Notice that the description set at the "root" of the config block (outside the tool blocks) shows up here.

Configuring the CLI

So far, our executable behaves very similarly to Toys itself. Help screens are shown by default, flags for help and verbosity are provided automatically, and any exceptions are displayed to the terminal.

These and many more aspects of the behavior of our executable can be customized by passing options to the Toys::CLI constructor. Here's an example that modifies error handling and delimiter parsing.

#!/usr/bin/env ruby

require "toys-core"

#### Pass some additional options to the CLI constructor ...
cli = Toys::CLI.new(
  extra_delimiters: ":",
  error_handler: ->(_err) {
    puts "Dude, an error happened..."
    return 1
  }
)

#### Change the config block as follows ...
cli.add_config_block do
  tool "example" do
    tool "greet" do
      def run
        puts "Hello, world!"
      end
    end
    tool "error" do
      def run
        raise "Whoops!"
      end
    end
  end
end

exit(cli.run(*ARGV))

Try these runs. Do they behave as you expected?

$ ./mycmd example greet
$ ./mycmd example:greet
$ ./mycmd example.greet
$ ./mycmd example error

Configuring middleware

Toys middleware are objects that provide common functionality for all the tools in your executable. For example, a middleware adds the --help flag to your tools by default.

The next example modifies the middleware stack to alter this common tool functionality.

#!/usr/bin/env ruby

require "toys-core"

#### Change the CLI construction again ...
middlewares = [
  [:set_default_descriptions, default_tool_desc: "Hey look, a tool!"],
  [:show_help, help_flags: true]
]
cli = Toys::CLI.new middleware_stack: middlewares

#### Use this config block ...
cli.add_config_block do
  tool "greet" do
    def run
      puts "Hello, world!"
    end
  end
end

exit(cli.run(*ARGV))

We've now modified the default description applied to tools that don't provide their own description. See the effect with:

$ ./mycmd greet --help

We've also omitted some of the default middleware, including the one that adds the --verbose and --quiet flags to all your tools. Notice those flags are no longer present.

We've also omitted the middleware that provides default execution behavior (i.e. displaying the help screen) when there is no run method. Now, since we haven't defined a toplevel run method in this last example, invoking the root tool will cause an error:

$ ./mycmd

It is even possible to write your own middleware. In general, while the Toys::CLI constructor provides defaults that should work for many use cases, you can also customize it heavily to suit the needs of your executable.

Packaging as a gem

So far we've created simple one-file executables that you could distribute by itself. However, the toys-core gem is a dependency, and your users will need to have it installed. You could alleviate this by wrapping your executable in a gem that can declare toys-core as a dependency explicitly.

The examples directory includes a few simple examples that you can use as a starting point.

To experiment with the examples, clone the Toys repo from GitHub:

$ git clone https://github.com/dazuma/toys.git
$ cd toys

Navigate to the simple-gem example:

$ cd toys-core/examples/simple-gem

This example wraps the simple "greet" executable that we covered earlier in a gem. You can see the executable file in the bin directory.

Try it out by building and installing the gem. From the examples/simple-gem directory, run:

$ toys install

Once the gem has successfully installed, you can run the executable, which Rubygems should have added to your path. (Note: if you are using a ruby installation manager, you may need to "rehash" or "reshim" to gain access to the executable.)

$ toys-core-simple-example --whom=Toys

Clean up by uninstalling the gem:

$ gem uninstall toys-core-simple-example

If the implementation of your executable is more complex, you might want to break it up into multiple files. The multi-file gem example demonstrates this.

$ cd ../multi-file-gem

This executable's implementation resides in its lib directory, a technique that may be familiar to writers of command line executables. More interestingly, the tools themselves are no longer defined in a block passed to the CLI object, but have been moved into a separate "tools" directory. This directory has the same structure and supports the same features that are available when writing complex sets of tools in a .toys directory. You then configure the CLI object to look in this directory for its tools definitions, as you can see in the code.

Try it out now. From the examples/multi-file-gem directory, run:

$ toys install

$ toys-core-multi-file-example greet

Clean up by uninstalling the gem:

$ gem uninstall toys-core-multi-file-example

Learning more

This introduction should be enough to get you started. However, Toys-Core is a deep framework with many more features. Learn about how to write tools using the Toys DSL, including validating and interpreting command line arguments, using templates and mixins, controlling subprocesses, and producing nice styled output, in the Toys User Guide. Learn more about how to customize and package your own executable, including handling errors, controlling log output, and providing your own mixins, templates, and middleware, in the Toys-Core User Guide.

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.