Intercepting template content with ActionView - ruby-on-rails

Question

I have a Haml template with a bunch of “custom tags” scattered around, e.g. {{REPLACE_ME}}. Before rendering this template, I am going through the template and replacing all occurrences using Ruby’s String#gsub.
That has not been a problem—I have simply created a custom template handler, which essentially acts as a middleman by first modifying the template source and then passing it on to the Haml template handler.
For each occurrence of one of these “custom tags” in the view, it adds to a numerator that is stored in the background. The problem that I am facing, however, is that the numerator is being bumped up for content that will never be displayed to the user, e.g. <% if false %>{{SECTION_NO}}<% end %>.
Such content as above should be filtered out before I replace the content. I seem, however, to have hit a wall, as the Haml (and ERB) handlers return a content buffer and not the “end/finished” content.
Is there a straight-forward solution to this issue?
Here is an example of a view:
- if true
%h1 {{SECTION_NO}}
- if false
%h1 {{SECTION_NO}}
- if true
%h1 {{SECTION_NO}}
So basically, I need a way to filter out the middle (false-statement) of the view source before replacing and numerating occurrences of “{{SECTION_NO}}”.
For reference, here is the gist of the template handler I created for this purpose:
class ActionView::Template::Handlers::Caml
def initialize
#section = 0
#paragraph = 0
#references = {}
end
def call(template)
rendered_haml = ActionView::Template.registered_template_handler(:haml).call(template)
updated_source = render_sections(rendered_haml)
updated_source = render_paragraphs(updated_source)
updated_source = render_references(updated_source)
return ActionView::Template.new(
updated_source,
template.identifier,
template.handler,
{
locals: template.locals,
virtual_path: template.virtual_path,
updated_at: template.updated_at
}
)
end
private
def render_sections(source)
source.gsub(/{{section:([a-zA-Z0-9-_]+)}}/).each do |match|
fail 'Key already exists.' if #references.key?($1)
#section += 1
#references[$1] = "#{#section}"
"#{#section}"
end
end
def render_paragraphs(source)
# ...
end
def render_references(source)
source.gsub(/{{([a-zA-Z0-9-_]+)}}/).each do |match|
#references.fetch($1)
end
end
end
ActionView::Template.register_template_handler(
:caml,
ActionView::Template::Handlers::Caml.new
)