From 22f957b98ae1f083b32277b6a2a9495914e62fda Mon Sep 17 00:00:00 2001
From: "Garen J. Torikian" <gjtorikian@users.noreply.github.com>
Date: Sat, 14 Mar 2026 00:26:17 -0400
Subject: [PATCH] Add `insert` extension for rendering `++text++` as
 `<ins>text</ins>`

---
 README.md                       |  1 +
 ext/commonmarker/src/options.rs |  4 ++++
 lib/commonmarker/config.rb      |  1 +
 test/extensions_test.rb         | 14 ++++++++++++++
 4 files changed, 20 insertions(+)

diff --git a/README.md b/README.md
index ac9abcdc..9715c7ef 100644
--- a/README.md
+++ b/README.md
@@ -219,6 +219,7 @@ Commonmarker.to_html('"Hi *there*"', options: {
 | `alerts`                      | Enables the alerts extension.                                                                                       | `false` |
 | `cjk_friendly_emphasis`       | Enables the [CJK friendly emphasis](https://github.com/tats-u/markdown-cjk-friendly) extension.                     | `false` |
 | `highlight`                   | Enables highlighting via `==`                                                                                       | `false` |
+| `insert`                      | Enables the insert extension, rendering `++text++` as `<ins>text</ins>`.                                            | `false` |
 
 For more information on these options, see [the comrak documentation](https://github.com/kivikakk/comrak#usage).
 
diff --git a/ext/commonmarker/src/options.rs b/ext/commonmarker/src/options.rs
index ad03181d..3a0f4715 100644
--- a/ext/commonmarker/src/options.rs
+++ b/ext/commonmarker/src/options.rs
@@ -126,6 +126,7 @@ const EXTENSION_SUBTEXT: &str = "subtext";
 const EXTENSION_ALERTS: &str = "alerts";
 const EXTENSION_CJK_FRIENDLY_EMPHASIS: &str = "cjk_friendly_emphasis";
 const EXTENSION_HIGHLIGHT: &str = "highlight";
+const EXTENSION_INSERT: &str = "insert";
 
 pub fn iterate_extension_options(
     comrak_options: &mut comrak::options::Extension,
@@ -213,6 +214,9 @@ pub fn iterate_extension_options(
                 Cow::Borrowed(EXTENSION_HIGHLIGHT) => {
                     comrak_options.highlight = TryConvert::try_convert(value)?;
                 }
+                Cow::Borrowed(EXTENSION_INSERT) => {
+                    comrak_options.insert = TryConvert::try_convert(value)?;
+                }
                 _ => {}
             }
             Ok(ForEach::Continue)
diff --git a/lib/commonmarker/config.rb b/lib/commonmarker/config.rb
index 9b222d45..cd53832d 100644
--- a/lib/commonmarker/config.rb
+++ b/lib/commonmarker/config.rb
@@ -53,6 +53,7 @@ module Config
         alerts: false,
         cjk_friendly_emphasis: false,
         highlight: false,
+        insert: false,
       }.freeze,
       format: [:html].freeze,
     }.freeze
diff --git a/test/extensions_test.rb b/test/extensions_test.rb
index c00f9725..e78e2880 100644
--- a/test/extensions_test.rb
+++ b/test/extensions_test.rb
@@ -127,4 +127,18 @@ def test_highlight_extension
       Commonmarker.to_html("This is ==important!==.", options: options),
     )
   end
+
+  def test_insert_extension
+    assert_equal(
+      "<p>This is ++important!++.</p>\n",
+      Commonmarker.to_html("This is ++important!++."),
+    )
+
+    options = { extension: { insert: true } }
+
+    assert_equal(
+      "<p>This is <ins>important!</ins>.</p>\n",
+      Commonmarker.to_html("This is ++important!++.", options: options),
+    )
+  end
 end