New escape javascript (`) token

[matthewmueller]

I'm building an asset bundler that can merge both coffeescript and javascript together. It works fine placing coffeescript inside javascript -- compile it and stick it in the js file.

The problem I'm running into is when I try to include javascript into coffeescript. My approach was to bring in the javascript, escape with `, and then compile the coffeescript.

The problem is many libraries use ` in comments -- including backbone. One thought is to use ``` to escape javascript like comment blocks in coffeescript.

Please let me know your thoughts on this.

After some discussion: The whole point of this issue is to point out that the single backtick does not always work the way it's intended. Use cases and outside discussion should be irrelevant here. Currently, the backtick does not work if you try to escape a file like backbone or jquery or even a two line javascript file that has a comment that includes a backtick.

Thanks,
Matt

[michaelficarra]

God, that sounds disgusting.

edit: So, what's the use case here? Large chunks of javascript embedded in coffeescript? Who is doing that?

[matthewmueller]

No one is writing large chunks of javascript embedded in coffeescript, but people are writing/using tools like Sprockets that need to be able to add javascript to coffeescript files and have it compile correctly.

[michaelficarra]

Can you give some example code that would use these backtick heredocs?

for prop of obj
  ```
  } while(1) {
  ```

I can only assume these would be used for something like that. As in, a horrible abuse of a feature that's already highly discouraged as it is.

edit: Hopefully this doesn't derail the conversion, but I don't understand a tool like Sprockets. It "turns your messy javascript into clean modules", but I already write clean (for some definitions of clean) modules, what are these "messy javascript" files with paperclips and thumbtacks? And then, amazingly, it produces a single file. The same tool has been around for 40 years now: cat. So what can't be done by just compiling the CS files and concatenating that output with the JS files?

[matthewmueller]

I think you're missing the point.. Yes, the example you posted is an awful abuse of the feature. That example should not be used even if there is only one backtick for escaping javascript. Hopefully this will clear it up:

You start with something like this in your coffeescript file:

#= require "../lib/backbone.js"

# Backbone will now be available
console.log Backbone

Something like Sprockets reads the require goes in and bundles the assets into a build.js that looks like this:

//     Backbone.js 0.3.3
//     (c) 2010 Jeremy Ashkenas, DocumentCloud Inc.
// ..... The entire backbone library ....

// Backbone will now be available
console.log(Backbone);

Make sense?

Edit: Okay. This is not a discussion of Sprockets. The whole point of this issue is to point out that the single backtick does not always work the way it's intended. Use cases and outside discussion should be irrelevant here. Currently, the backtick does not work if you try to escape a file like backbone or jquery or even a two line javascript file that has a comment that includes a backtick.

[michaelficarra]

So what you're saying is coffee and cat are good enough to do what you're looking for:

• build.sh:

  coffee -o js/ -c coffee/
  cat vendor/backbone/backbone.js js/myfile.js
  

• coffee/myfile.coffee:

  console.log Backbone # hey look, it's available!
  

edit: By the way, I'm purposely simplifying your proposal to better understand the most basic reason for its necessity. Don't take it personally. At this point, it looks like this is yet another macro proposal.

edit 2: It looks like we don't properly support backslash-escaping backticks:

$ coffee -bpe '`// \`abc`'
// \`abc;

[jashkenas]

Usefulness aside, I think it would be great to support "here-embedded-js" with triple backticks. It makes them just a bit more consistent with all the other quoting operators in the language.

[satyr]

Note that ``` can only appear in literals in JS, and ``` works fine in both string and regex:

$ node -e '/\`/.test("\`")'
true

Comments do suffer, but aren't essential.

[matthewmueller]

@satyr

I guess the whole point is that it breaks when there are any backticks in the javascript. You can have perfectly valid javascript that contains a backtick in a literal string or in regex and, as you said, it will break. No this isn't a huge deal, but as @jashkenas mentioned, it makes it more consistent with the language and it fixes these minor issues with a less conflicting operator.

[satyr]

it breaks when there are any backticks in the javascript

Yes, therefore you need to escape them with backslash when embedding. This is true for whatever escape method we use. With the proposed triple backtick literal, you'd still have to take care of `````s in your embedded JS.

[matthewmueller]

Yah true, why not just have Coffeescript escape the backticks? Maybe that's what you were thinking. Then one backtick would work just fine. Then it just becomes a debate over the style of the syntax, which I don't know if that would be worth our time for an issue like this :-)

[michaelficarra]

@satyr and @matthewmueller: see my edit #2 above from a few hours ago. Yes, you can use backslashes to escape backticks, and yes, they're broken.

[bdkjones]

Hi there. Can we get the triple backtick delimiter added?

I write CodeKit and I cannot tell you how many people have asked me to let them combine Javascript and CoffeeScript files together. The most common case is that they want to stick jQuery at the beginning and then write some CoffeeScript against that library.

If you add the ``` delimiter, as suggested here, providing this capability in build tools would become trivial. Thank you.

[rstacruz]

Just chiming in to bump this for 2 reasons:

1. ES6 will have template strings made using backticks, ie, a = Hello, ${name}``.

2. We've been working on a new js2coffee that uses ``` extensively when "compatibility mode" is on to preserve JS behavior in things it can't translate (eg, ==). It would be nice to make backticks escapable in case they're converting ES6.