BishBosh - A domain specific language for writing command line interfaces

Thanks to Chris Ross for the illustration!

Disclaimer - (This is at Proposal-Stage) - At the moment this is nothing other than an opionated braindump. If you read something here which aligns with you or otherwise, please make a pr or an issue.

Update: - I've implemented a lexer with moo so far, as well and am using nearley to generate a parser. So far so good.

By all means, tell me your opinion, whether it'd be a rant, encouragement, or an idea for improvement - I welcome feedback and am reaching out to you for it!

🔥 🔥 Warning - opinions ahead 🔥 🔥

Problem - Writing cli's is hard

• Writing cli's is harder than it should be
• Bash scripting sucks
• Using languages for writing cli's kinda sucks too.

😱 😱 😱 😱 😱 😱

Idea: A small language for scripting command line interfaces:

What if you had a dsl for cli's that:

• is very restricted and easy to learn for the sole purpose of writing clis
• limits you to conform to best practices
• encourages good UX
• is language agnostic (run scripts in any language)
• makes it so easy to write cli's that you could write one for small usecases (Like onboarding developers, setting up projects, scaffolding, deployment, ci etc)

In an ideal world, when I write CLIs, I want focus on content. Rather than reinventing the wheel everytime and implementing a cli with language X, I'd like to write down a script with as little syntax as possible, that describes:

• a user flow for prompts
• commands & documentation for commands

Eyo - Welcome to this {{green}}super amazing{{/green}} cli whoop whoop!

? So what do you want to do
  c > create a new app
    -> ./create-new-app.sh
    Yippie!
    Your app is now created!
    You can run it by typing {{yellow}}npm start{{/yellow}}

  a > add a module to your app

    ?:component Where do you want your component?
      ? Which one?
        # Copies around files
        m > a middleware -> cp ./templates/middleware {{component}}
        r > a reducer -> cp ./templates/middleware {{component}}

  d > deploy the app -> ./deploy.sh

Possible applications:

• Scaffolding
• Text adventures
• Clis for environments - How often I wished there was a cli that just walked me through setting up a dev environment

Here's a slightly contrived example for a cli tool that helps setting up a vm

Welcome to Project X, to cancel just press ctrl[c]
# To keep it simple, we could do if/else statements that rely on whether a process exits with 0 or 1

if -> sudo service elasticsearch status
  {green}Elasticsearch running{/green}
else
  Looks like elasticsearch isn't running, wanna restart it?
    - Yes -> sudo service elasticsearch restart
    - No

if -> sudo service dynamo status
  - {green}Dynamo DB is running{/green}
else
  Looks like dynamo isn't running, wanna restart it?
    > Yes
      if -> sudo service dynamo restart
        {green}Dynamo DB is running{/green}
      else
        I can't get dynamo db running sry dude, ask your sysadmin for help -> exit 0

    > No

Right, that's all, see you later aligator!

Syntax

Whitespace

Bishbosh is whitespace sensitive. Indentations create new scope. So writing something like this:

build > Builds the ci
  # the below line will be executed only if the build command is run
  -> ./build.sh

Comments

# Yo I am a comment

Prompts

? Some prompt that asks you a question or not If no options are specified, any key can be pressed to continue

Prompt with Options

? What do you want to do?
  > run the app
  > build the app
  > deploy the app

Options can be chosen with arrow keys

Prompt with Options with key commands

? What do you want to do?
  r > run the app
  b > build the app
  d > deploy the app

Options can be chosen with arrow keys or key commands

Prompt with Input

?:input What do you want to say?

The input will be used as env variable for the process, which you can reference in other places.

Execution statements

Execution statements are in essence shell scripts. They spin up processes.

• If the process fails the app will exit.

-> cp ./template ./src/something
-> ./run-a-shell-thing.sh
-> ./run-a-js-thing.js
-> ./run-a-ruby-thing.js

Conditionals

You can use conditionals. Conditional expressions use C-style operators, like ==, !=, &&.

You can also use execution statements. If you do, a failed execution statement (one that exits with 1) will be interpreted false, a successfull execution statement (exit 0) will be evaluated as true.

?:input Hello there what can I do for you?
if input == "build"
  Ok, I'll build the app for you, hold on a sec -> ./build.sh
elseif input == "deploy"
  Ok, I'll deploy the app for you, hold on a sec -> ./deploy.sh
else
  Sorry, that's not a valid command, by then -> exit

Color output

You can color your output like so:

{red}Hello there{/red}

Commands

Commands can be in two different contexts. When they are defined in root, they act as cli commands, when they are nested in a prompt, they act as prompt options.

b, build > Build the app and stuff
  -> execute something

Todo:

• Commands Syntax
• Documentation Syntax
• Build a parser and play around with the syntax more
• Get to a simple mvp asap so I can validate the idea