[ruby-core:112591] [Ruby master Feature#19458] Expose HEREDOC identifier

25 Feb 2023

      Issue #19458 has been updated by sawa (Tsuyoshi Sawada).

If you want to keep the string and the markup language information together, then perhaps something like the following is the way to go.

Preparation:
```ruby
class String
  def lang_set(lang); tap{@lang = lang} end
  def lang; @lang end
end
```

Using it to write a template:
```ruby
class Component
  template <<~ERB.lang_set(:erb)
    <h1>Hello, <%= @name %>!</h1>
  ERB
end
```

And then in your `template` code:
```ruby
def template(string)
  lang = string.lang
  raise "Markup language is not set" unless lang
  case lang
    when :erb then erb_template(lang)
    ...
  end
end
```

----------------------------------------
Feature #19458: Expose HEREDOC identifier
https://bugs.ruby-lang.org/issues/19458#change-102039

* Author: joelhawksley (Joel Hawksley)
* Status: Open
* Priority: Normal
----------------------------------------
I’d like to have access to the HEREDOC identifier.

In the ViewComponent framework I help maintain, we added a method to declare a template as such:

```ruby
class Component
  erb_template <<~ERB
    <h1>Hello, <%= @name %>!</h1>
  ERB
end
```

I'd prefer to be able to write:

```ruby
class Component
  template <<~ERB
    <h1>Hello, <%= @name %>!</h1>
  ERB
end
```

And be able to see that the argument passed to `.template` was from a HEREDOC with an `ERB` identifier, which would allow me to use the correct template handler to compile the template.

I could see this being implemented:

1) As a new property of String, such as `identifier` or `heredoc_identifier`.
2) By having HEREDOCs return a subclass of String that includes an `identifier` property.

I'd be happy to work on implementing this change.

-- 
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