From c093eb5a383aa9ab10a4a84c83856a28fe5fef4f Mon Sep 17 00:00:00 2001
From: ishikawa999 <14245262+ishikawa999@users.noreply.github.com>
Date: Tue, 9 Jun 2026 08:28:59 +0900
Subject: [PATCH 3/3] Fix Tab/Shift+Tab indenting the line after a trailing
 newline in selection

---
 .../controllers/selection_indent_controller.js   |  3 ++-
 test/system/selection_indent_test.rb             | 16 ++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/app/javascript/controllers/selection_indent_controller.js b/app/javascript/controllers/selection_indent_controller.js
index e6555e7fe..007e94c0c 100644
--- a/app/javascript/controllers/selection_indent_controller.js
+++ b/app/javascript/controllers/selection_indent_controller.js
@@ -12,7 +12,8 @@ export default class extends Controller {
     const hasSelection = selectionStart !== selectionEnd
     if (!hasSelection) return
     const start = value.lastIndexOf("\n", selectionStart - 1) + 1
-    const end = value.indexOf("\n", selectionEnd)
+    const adjustedSelectionEnd = value[selectionEnd - 1] === "\n" ? selectionEnd - 1 : selectionEnd
+    const end = value.indexOf("\n", adjustedSelectionEnd)
     const endPos = end === -1 ? value.length : end
     const selectedText = value.slice(start, endPos)
     const lines = selectedText.split("\n")
diff --git a/test/system/selection_indent_test.rb b/test/system/selection_indent_test.rb
index 62dc9269c..9e8fcfe21 100644
--- a/test/system/selection_indent_test.rb
+++ b/test/system/selection_indent_test.rb
@@ -68,6 +68,22 @@ class SelectionIndentSystemTest < ApplicationSystemTestCase
     end
   end
 
+  def test_tab_does_not_indent_line_after_trailing_newline_in_selection
+    with_settings :text_formatting => 'common_mark' do
+      visit '/projects/ecookbook/issues/new'
+
+      within('form#issue-form') do
+        text = "line1\nline2\nline3"
+        el = find('#issue_description')
+        el.click
+        # Select "line1\n" — selection ends at the start of line2
+        set_textarea_value 'issue_description', text, selection: [0, "line1\n".length]
+        el.send_keys(:tab)
+        assert_equal "  line1\nline2\nline3", el.value
+      end
+    end
+  end
+
   def test_shift_tab_unindents_selected_text
     with_settings :text_formatting => 'common_mark' do
       visit '/projects/ecookbook/issues/new'
-- 
2.54.0