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Add ERB lexer #1228

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Merged
alecthomas merged 1 commit into from
Mar 13, 2026
+1,413 −0
Merged

Add ERB lexer #1228

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37 changes: 37 additions & 0 deletions lexers/embedded/erb.xml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,37 @@
<lexer>
<config>
<name>ERB</name>
<dot_all>true</dot_all>
</config>
<rules>
<state name="root">
<rule pattern="(&lt;%#)(.*?)(-?%&gt;)">
<bygroups>
<token type="CommentPreproc"/>
<token type="Comment"/>
<token type="CommentPreproc"/>
</bygroups>
</rule>
<rule pattern="(&lt;%-?=)(.*?)(-?%&gt;)">
<bygroups>
<token type="CommentPreproc"/>
<using lexer="Ruby"/>
<token type="CommentPreproc"/>
</bygroups>
</rule>
<rule pattern="(&lt;%-?)(.*?)(-?%&gt;)">
<bygroups>
<token type="CommentPreproc"/>
<using lexer="Ruby"/>
<token type="CommentPreproc"/>
</bygroups>
</rule>
<rule pattern="[^&lt;]+">
<token type="Other"/>
</rule>
<rule pattern="&lt;">
<token type="Other"/>
</rule>
</state>
</rules>
</lexer>
29 changes: 29 additions & 0 deletions lexers/erb.go
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package lexers

import (
"strings"

. "github.com/alecthomas/chroma/v2" // nolint
)

// ERB lexer is Ruby embedded in HTML.
var ERB = Register(DelegatingLexer(HTML, MustNewXMLLexer(
embedded,
"embedded/erb.xml",
).SetConfig(
&Config{
Name: "ERB",
Aliases: []string{"erb", "html+erb", "html+ruby", "rhtml"},
Filenames: []string{"*.erb", "*.html.erb", "*.xml.erb", "*.rhtml"},
MimeTypes: []string{"application/x-ruby-templating"},
DotAll: true,
},
).SetAnalyser(func(text string) float32 {
if strings.Contains(text, "<%=") && strings.Contains(text, "%>") {
return 0.4
}
if strings.Contains(text, "<%") {
return 0.1
}
return 0.0
})))
113 changes: 113 additions & 0 deletions lexers/testdata/erb.actual
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<!DOCTYPE html>
<html lang="<%= I18n.locale %>">
<head>
<title><%= content_for?(:title) ? yield(:title) : "Default Title" %></title>
<%= csrf_meta_tags %>
<%= csp_meta_tag %>
<%= stylesheet_link_tag "application", "data-turbo-track": "reload" %>
</head>
<body class="<%= controller_name %> <%= action_name %>">

<%# Navigation partial %>
<%= render "shared/navbar", user: current_user %>

<%# ERB comment spanning
multiple lines %>

<% if current_user.admin? %>
<div class="admin-banner">
<p>Welcome, <%= current_user.name %>! You have <%= current_user.roles.count %> roles.</p>
</div>
<% end %>

<% @posts.each_with_index do |post, index| %>
<article id="post-<%= post.id %>" class="<%= cycle('odd', 'even') %>" data-tags="<%= post.tags.pluck(:name).join(',') %>">
<h2><%= link_to post.title, post_path(post), class: "post-link" %></h2>

<div class="meta">
<span><%= l(post.created_at, format: :long) %></span>
<span><%= pluralize(post.comments.count, "comment") %></span>
<%= "Featured" if post.featured? %>
</div>

<div class="body">
<%= sanitize post.body, tags: %w[p br strong em a ul ol li code pre], attributes: %w[href class id] %>
</div>

<% if post.tags.any? %>
<ul class="tags">
<% post.tags.each do |tag| %>
<li><%= link_to tag.name, tag_path(tag) %></li>
<% end %>
</ul>
<% end %>

<%# Render comments if they exist %>
<% unless post.comments.empty? %>
<section class="comments">
<%= render partial: "comments/comment", collection: post.comments, as: :comment, locals: { editable: current_user&.admin? } %>
</section>
<% end %>
</article>
<% end %>

<%= form_with(model: @post, local: true, data: { turbo: false, controller: "form" }) do |f| %>
<% if @post.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(@post.errors.count, "error") %> prohibited this post from being saved:</h2>
<ul>
<% @post.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>

<div class="field">
<%= f.label :title %>
<%= f.text_field :title, placeholder: "Enter title...", required: true, maxlength: 255 %>
</div>

<div class="field">
<%= f.label :body %>
<%= f.text_area :body, rows: 10, data: { action: "input->form#validate" } %>
</div>

<div class="field">
<%= f.label :category_id %>
<%= f.collection_select :category_id, Category.order(:name), :id, :name, { prompt: "Select a category" }, { class: "form-control" } %>
</div>

<div class="actions">
<%= f.submit @post.persisted? ? "Update Post" : "Create Post", class: "btn btn-primary" %>
<%= link_to "Cancel", posts_path, class: "btn btn-secondary" %>
</div>
<% end %>

<%- trimmed = @items.select { |i| i.active? && i.visible_to?(current_user) } -%>
<%= render partial: "items/grid", locals: { items: trimmed, columns: 3 } %>

<% content_for :sidebar do %>
<div class="sidebar">
<h3>Recent Posts</h3>
<ul>
<% Post.published.order(created_at: :desc).limit(5).each do |post| %>
<li><%= link_to post.title, post %></li>
<% end %>
</ul>

<h3>Archives</h3>
<% Post.published.group_by { |p| p.created_at.strftime("%B %Y") }.each do |month, posts| %>
<p><%= link_to "#{month} (#{posts.size})", archive_path(month: month) %></p>
<% end %>
</div>
<% end %>

<script>
var postCount = <%= @posts.count %>;
var config = <%= raw({ api_key: ENV["API_KEY"], debug: Rails.env.development? }.to_json) %>;
</script>

<%= javascript_include_tag "application", "data-turbo-track": "reload", defer: true %>
</body>
</html>
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