SourceAttributionVisitor

Stamps every element with the template and the position it was written at, so a finding about the rendered page can be pointed back at the line that produced it.

require "herb/engine/visitors/source_attribution_visitor"

Herb::Engine.new(source, filename: path, visitors: [Herb::Engine::SourceAttributionVisitor.new])

<div class="card">
  <h1>Title</h1>
</div>

<div class="card" data-herb-source="app/views/posts/_card.html.erb:1:1">
  <h1 data-herb-source="app/views/posts/_card.html.erb:2:3">Title</h1>
</div>

The attribute is data-herb-source unless attribute: names another one.

Some things are only visible once a page is rendered. Two partials can each be valid on their own and still collide on an id, a heading order only exists once a layout and everything it renders are composed, and a <form> inside another <form> is usually two templates that never see each other. A linter reading the response answers those, and the positions it reports are offsets into the response, which is not a place anyone can go and fix anything. The stamp is what turns them back into a file and a line.

An element that renders many times carries the line it was written at, not the line it rendered at, so the answer to a duplicate id is the line that renders more than once:

<ul data-herb-source="app/views/posts/_card.html.erb:1:1">
  <li data-herb-source="app/views/posts/_card.html.erb:3:5">a</li>
  <li data-herb-source="app/views/posts/_card.html.erb:3:5">b</li>
</ul>

A partial that InlineRender::Visitor brought into the template is stamped with the file it was written in, not the file it was inlined into.

Tag helpers and the parser option

A tag helper is stamped too. The action_view_helpers parser option turns <%= link_to "Home", "/" %> into an <a> that the compiler writes out as markup, and that <a> is stamped at the position of the <%= that asked for it:

<nav data-herb-source="app/views/posts/_card.html.erb:1:1">
  <a href="/" data-herb-source="app/views/posts/_card.html.erb:2:3">Home</a>
</nav>

This visitor declares that option with recommended_parser_option, so a stack that says nothing about it gets it.

The stamp is markup Herb added, so strip it before reporting positions back, and leave the visitor out of anything but a development build.