Attribute name parsing converts double underscores to double hyphens, breaking some frontend frameworks

[watzon]

Problem

The AttributesRenderer#parse_name method converts all underscores to hyphens:

private def parse_name(name) : String
  name.to_s.gsub("_", "-")
end

This works well for standard HTML attributes (e.g., data_foo_bar → data-foo-bar), but breaks frameworks that use double underscores as meaningful syntax.

For example, https://data-star.dev uses double underscores for action modifiers:
- `data-on:click__prevent` - prevents default behavior
- `data-on:click__debounce_500ms` - debounces the action

With the current implementation, "data-on:click__prevent" becomes data-on:click--prevent, which is invalid.

## Current Workaround

I'm monkey-patching parse_name in my adapter to preserve double underscores:

```crystal
module Blueprint::HTML::AttributesRenderer
  private def parse_name(name) : String
    result = name.to_s.gsub("__", "\x00\x01\x00")
    result = result.gsub("_", "-")
    result.gsub("\x00\x01\x00", "__")
  end
end

Suggested Solutions

1. Preserve double underscores by default - Change parse_name to only convert single underscores, leaving __ intact.
2. Make the conversion configurable - Allow users to customize or disable the underscore-to-hyphen conversion.

Would either of these approaches be acceptable? Happy to submit a PR if so.

[stephannv]

Thanks for the report @watzon, it makes sense allow users to not convert _ to -.

What do you think about this solution? (It needs to be implemented)

# using NamedTuple, converts _ to -
input("data-on:mycustomevent__window": "$result = evt.detail.value")
# <input data-on:mycustomevent--window="$result = evt.detail.value")

# using Hash keeps the original attribute name
input({ "data-on:mycustomevent__window" => "$result = evt.detail.value" })
# <input data-on:mycustomevent__window="$result = evt.detail.value")

It allows, for example, using Hash inside NameTuple:

# Using only Hash
input({ "name" => "y", "data-on:mycustomevent__window" => "$result = evt.detail.value" })
# or using NamedTuple with Hash
input(name: "y", data: { "on:mycustomevent__window" => "$result = evt.detail.value" })

# result:
# <input name="y" data-on:mycustomevent__window="$result = evt.detail.value")

[watzon]

Sure I think that's an acceptable solution

[stephannv]

I've just released the 1.1.0 version with Hash support, and you can easily override the attributes-processing method if you need:

class Example
  include Blueprint::HTML

  private def blueprint
    input x: {y: 2}
  end

  private def render_attributes(attributes : Hash | NamedTuple) : Nil
    buffer << " my-own-logic"
  end
end

Example.new.to_s # <input my-own-logic>