Herb Demo

A minimal Rails app that shows the new Herb template engine catching broken HTML in ERB templates, and a bin/rails herb:check step in bin/ci.

It is the companion code for the Code With Rails post:

Catch Broken HTML Before Deploy with Rails' New Herb Template Engine

Herb support is on Rails main (slated for 8.2) but not yet in a released version, so this app's Gemfile points rails at the GitHub main branch (#58552, #58721, #58770). Swap that for a version once 8.2 ships.

Branches

• main has the fixed templates. bin/rails herb:check passes.
• broken has the three broken partials from the post. bin/rails herb:check fails, but bin/rails test still passes.

Run it

bundle install
bin/rails db:setup   # create, migrate, and seed
bin/rails server

Then open http://localhost:3000 to see the project list.

Try the check

bin/rails herb:check
# All HTML+ERB templates compile through Herb. All is good!

git checkout broken
bin/rails herb:check
# app/views/projects/_project.html.erb:
#   [source]:3:3: Opening tag `<div>` at (3:3) doesn't have a matching closing tag `</div>` in the same scope.
# ...
# 3 HTML+ERB templates failed to compile through Herb.

On the broken branch, visit http://localhost:3000 to see the ActionView::SyntaxErrorInTemplate error for the unclosed <div>.

To run the full CI, including the Herb step:

bin/ci

Files to look at

• app/views/projects/_project.html.erb (the unclosed <div>)
• app/views/shared/_status_badge.html.erb (closing tags in the wrong order)
• app/views/shared/_flash.html.erb (ERB output in attribute position, fixed with tag.attributes)
• config/ci.rb (the Templates: Herb step)
• test/integration/projects_test.rb (passes on both branches, because the test database has no projects and the partial is never rendered)