[ruby-core:113402] [Ruby master Feature#19015] Language extension by a heredoc

Issue #19015 has been updated by duerst (Martin D=FCrst).





@pyromaniac I think the main problem would be how to handle namespacing. Wi=
th single letters, the chance of collision is very high. How does Elixir ha=
ndle this?



----------------------------------------

Feature #19015: Language extension by a heredoc

https://bugs.ruby-lang.org/issues/19015#change-102973



* Author: ko1 (Koichi Sasada)

* Status: Open

* Priority: Normal

----------------------------------------

This propose new heredoc extension with `<<!LANG` like



```ruby

doc =3D <<!LANG

  # description written in lang LANG

  foo bar

LANG

```



and it is translated to:



```ruby

doc =3D heredoc_extension_LANG(heredoc_text, binding)

```



## Example



```ruby

require 'erb'



def heredoc_extension_erb str, b

  ERB.new(str).run(b)

end



name =3D 'ko1'



html =3D <<!erb

<div>Hello <%=3D name %></div>

erb



puts html #=3D> <div>Hello ko1</div>

```



## Background / considerations



* Sometimes we write Ruby syntax string with `<<RUBY` and this proposal ins=
pired by it.

* it is similar to shebang (`#!LANG` in shell)

* [Elixir's custom sigil](https://elixir-lang.org/getting-started/sigils.ht=
ml) translates `~u(...)` translates to `sigil_u(...)`. This is why it trans=
lated to `heredoc_extension_LANG(...)` private method call.

* JavaScript has JSX but I don't think it is fit to the Ruby language.

* Heredoc is Ruby's chaos part and already confusing a lot. Additional chao=
s doesn't matter.

* `<<!foo` is valid syntax but now I don't think it is not used. gem codese=
arch doesn't find the usage.

* Sorry I couldn't wait 1st/Apr.



## Implementation



I attached the experimental implementation which only supports `erb` (becau=
se I couldn't find how to get delimiter to determine a method name :p).





---Files--------------------------------

heredoc_extension.patch (2.7 KB)





--=20

https://bugs.ruby-lang.org/

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