From 9543c59f3df04b4d63c2d808d49c8352f78988f0 Mon Sep 17 00:00:00 2001
From: Nick Adams <nadams@oreilly.com>
Date: Wed, 11 Feb 2026 10:19:11 -0500
Subject: [PATCH] Add details/summary support for collapsible blocks

Add support for the HTML5 details tag via Asciidoctor collapsible
option on example blocks. The block title becomes the summary text.
---
 htmlbook-autogen/block_example.html.erb | 11 +++++--
 htmlbook/block_example.html.erb         | 11 +++++--
 spec/htmlbook_spec.rb                   | 39 +++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/htmlbook-autogen/block_example.html.erb b/htmlbook-autogen/block_example.html.erb
index b29b4f0..df4684c 100644
--- a/htmlbook-autogen/block_example.html.erb
+++ b/htmlbook-autogen/block_example.html.erb
@@ -1,4 +1,9 @@
-<%#encoding:UTF-8%><div<%= @id && %( id="#{@id}") %> data-type="example"<%= attr?('role') ? %( class="#{attr 'role'}") : nil %>>
+<%#encoding:UTF-8%><% if option? 'collapsible' %><details<%= @id && %( id="#{@id}") %><%= attr?('role') ? %( class="#{attr 'role'}") : nil %>>
+<summary class="title"><%= title %></summary>
+<div class="content">
+<%= content %>
+</div>
+</details><% else %><div<%= @id && %( id="#{@id}") %> data-type="example"<%= attr?('role') ? %( class="#{attr 'role'}") : nil %>>
 <h5><%= title %></h5>
-<%= content 
-%></div>
+<%= content
+%></div><% end %>
diff --git a/htmlbook/block_example.html.erb b/htmlbook/block_example.html.erb
index b29b4f0..df4684c 100644
--- a/htmlbook/block_example.html.erb
+++ b/htmlbook/block_example.html.erb
@@ -1,4 +1,9 @@
-<%#encoding:UTF-8%><div<%= @id && %( id="#{@id}") %> data-type="example"<%= attr?('role') ? %( class="#{attr 'role'}") : nil %>>
+<%#encoding:UTF-8%><% if option? 'collapsible' %><details<%= @id && %( id="#{@id}") %><%= attr?('role') ? %( class="#{attr 'role'}") : nil %>>
+<summary class="title"><%= title %></summary>
+<div class="content">
+<%= content %>
+</div>
+</details><% else %><div<%= @id && %( id="#{@id}") %> data-type="example"<%= attr?('role') ? %( class="#{attr 'role'}") : nil %>>
 <h5><%= title %></h5>
-<%= content 
-%></div>
+<%= content
+%></div><% end %>
diff --git a/spec/htmlbook_spec.rb b/spec/htmlbook_spec.rb
index c3a2327..5e1cdd1 100755
--- a/spec/htmlbook_spec.rb
+++ b/spec/htmlbook_spec.rb
@@ -203,6 +203,45 @@
 		expect(html.xpath("//div[@data-type='example'][1]/pre[@data-type='programlisting']/@data-code-language").text).to eq("php")
 	end
 
+	# Tests collapsible block (details tag) support
+	it "should convert collapsible blocks to details/summary elements" do
+		html = Nokogiri::HTML(convert("
+.Details
+[%collapsible]
+====
+This would be the show and hide!
+====
+"))
+		expect(html.xpath("//details/summary[@class='title']").text).to eq("Details")
+		expect(html.xpath("//details/div[@class='content']/p").text).to eq("This would be the show and hide!")
+	end
+
+	it "should convert collapsible blocks with an id" do
+		html = Nokogiri::HTML(convert("
+[[my-details]]
+.Click to expand
+[%collapsible]
+====
+Hidden content here.
+====
+"))
+		expect(html.xpath("//details/@id").text).to eq("my-details")
+		expect(html.xpath("//details/summary[@class='title']").text).to eq("Click to expand")
+		expect(html.xpath("//details/div[@class='content']/p").text).to eq("Hidden content here.")
+	end
+
+	it "should convert collapsible blocks with a role attribute" do
+		html = Nokogiri::HTML(convert("
+.Summary text
+[%collapsible,role='special']
+====
+Content with a role.
+====
+"))
+		expect(html.xpath("//details/@class").text).to eq("special")
+		expect(html.xpath("//details/summary[@class='title']").text).to eq("Summary text")
+	end
+
 	it "should convert line numbering attribute in informal code listing" do
 		html = Nokogiri::HTML(convert("
 [source, php, linenums]