can I attach functions to the coffee console before it starts? - coffeescript

Question

Let's say I want to have a pp function:
coffee> pp = (obj) -> JSON.stringify(obj)
[Function]
coffee> pp({cat: "fancy"})
'{"cat":"fancy"}'
coffee>
Is there a way that I can have that function be available immediately when the console loads? I'm looking at coffee -r "utils.coffee", but don't see any way to put that required library into an object that's available at the command line. It looks like I might be able to alter repl.js, but that seems like a bad idea.

Answer 1

You can put those functions into the global variable (which is kinda Node's version of window) and then use the -r option.
# utils.coffee
global.pp = (obj) -> JSON.stringify(obj)
And then run, on the same directly utils.coffee of:
coffee -r ./utils
It should start a CoffeeScript REPL and have the pp function available as a global variable:
coffee> pp ohmy: 'neat'
'{"ohmy":"neat"}'
Update: it seems the -r command-line option was removed in CoffeeScript's master. It probably wasn't meant to be used this way :(
Update 2: There's another way to do this! And it doesn't rely on any command-specific parameter:
{ echo "require './utils'"; cat; } | coffee
It will, however, not work 100% like the Coffee REPL. The arrow keys for example don't seem to work.
Edit (jc): Using this method allows you to make an unload for node, which is handy:
# utils.coffee
global.unload = (moduleName) ->
cacheName = require.resolve(moduleName)
delete require.cache[cacheName]
$ coffee -r ~/Dev/utils.coffee
coffee> unload
[Function]
Update 3: Another possibility is to "create your own REPL". Not really reimplementing anything. Based on this hacky solution, you could do something like:
#! /usr/bin/env coffee
# REPL functions.
global.pp = (obj) -> JSON.stringify(obj)
# Start the REPL.
require 'coffee-script/lib/coffee-script/repl'
And then use that script as your new REPL. It will work exactly like the normal Coffee REPL plus the new functions (no problems with arrow keys nor TAB completion :)
BTW, i think you'll need to have CoffeeScript installed without the -g option on npm for that to work.
It is a very hacky solution though. It relies on the internal CoffeeScript implementation file structure and its functionality, and that could change at any moment (in fact, i'm aware that there has been some work done in a new revamped Coffee REPL based on Node's one... i hope that functionality gets exposed to be used programmatically, so these kind of hacks are not hacks any more).

Answer 2

Have a look at #Daniel's (Daniel Taylor's) excellent nesh, an enhanced node shell that also speaks CoffeeScript: http://danielgtaylor.github.io/nesh/
Here's how you would load your pp function into a CoffeeScript REPL:
nesh -c -e 'pp = (obj) -> JSON.stringify(obj)'
Similarly, if you wanted to load a file, say ~/.nesh_profile.coffee (analogous to loading a shell profile), on startup, use:
nesh -c -e ~/.nesh_profile.coffee
Small caveat: The REPL language - JavaScript v. CoffeeScript - and the language of the code you're loading must be the same. Edit: The only exception is that you can always load JavaScript via a file with extension .js, even when starting a CoffeeScript REPL. (By contrast, you can't specify a JS string when starting a CoffeeScript REPL).
To automate loading of your 'nesh profile' into a CoffeeScript REPL you could define an alias in your shell profile; e.g.:
alias neshc='nesh -c -e ~/.nesh_profile.coffee'
Update: Here's how you can use the very same 'nesh profile' with a JavaScript REPL; compilation to JavaScript is performed on the fly using process substitution:
alias neshj='nesh -e <(coffee -bp ~/.nesh_profile.coffee)'
nesh is available as an npm package, so you can easily install it as follows:
sudo npm install nesh -g