From c3dc6180fb933b6498c60ca810867ecff4b882bf Mon Sep 17 00:00:00 2001
From: MAEDA Go <maeda@farend.jp>
Date: Thu, 20 Aug 2026 20:12:12 +0900
Subject: [PATCH 2/3] Preview Adobe Illustrator files saved in the PDF
 compatible format

---
 app/controllers/attachments_controller.rb     |  6 ++++
 app/models/attachment.rb                      |  5 ++-
 .../functional/attachments_controller_test.rb | 35 +++++++++++++++++++
 test/unit/attachment_test.rb                  | 16 +++++----
 4 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/app/controllers/attachments_controller.rb b/app/controllers/attachments_controller.rb
index 168b344ed..699ba6670 100644
--- a/app/controllers/attachments_controller.rb
+++ b/app/controllers/attachments_controller.rb
@@ -296,6 +296,12 @@ class AttachmentsController < ApplicationController
   def detect_content_type(attachment, is_thumb = false)
     content_type = Redmine::MimeType.infer_type(attachment.content_type, attachment.filename)
 
+    if Marcel::Magic.child?(content_type, "application/pdf")
+      # Send PDF compatible files, such as Illustrator files, as PDF so that
+      # browsers display them inline
+      content_type = "application/pdf"
+    end
+
     if is_thumb && !content_type.start_with?("image/")
       # Thumbnails of non-image files are stored in PNG format
       content_type = "image/png"
diff --git a/app/models/attachment.rb b/app/models/attachment.rb
index 6ac97daf3..7c3825e8f 100644
--- a/app/models/attachment.rb
+++ b/app/models/attachment.rb
@@ -322,8 +322,11 @@ class Attachment < ApplicationRecord
     /\.(patch|diff)$/i.match?(filename)
   end
 
+  # Returns true for PDF files, including PDF compatible files such as Adobe
+  # Illustrator (application/illustrator)
   def is_pdf?
-    Redmine::MimeType.of(filename) == "application/pdf"
+    type = Redmine::MimeType.infer_type(content_type, filename)
+    !!Marcel::Magic.child?(type, 'application/pdf')
   end
 
   def is_video?
diff --git a/test/functional/attachments_controller_test.rb b/test/functional/attachments_controller_test.rb
index f2eefcb4a..4050dcaa9 100644
--- a/test/functional/attachments_controller_test.rb
+++ b/test/functional/attachments_controller_test.rb
@@ -406,6 +406,41 @@ class AttachmentsControllerTest < Redmine::ControllerTest
     assert_match %r{\Aattachment}, @response.headers['Content-Disposition']
   end
 
+  def test_show_pdf_compatible_illustrator_file_should_be_previewed
+    set_tmp_attachments_directory
+    attachment = Attachment.create!(
+      :file => mock_file_with_options(
+        :original_filename => 'logo.ai',
+        :content => File.binread("#{Rails.root}/test/fixtures/files/hello.pdf")
+      ),
+      :author_id => 2,
+      :container => Issue.find(1)
+    )
+    assert_equal 'application/illustrator', attachment.content_type
+
+    get(:show, :params => {:id => attachment.id})
+    assert_response :success
+    assert_select 'div.filecontent.pdf object[type=?]', 'application/pdf'
+  end
+
+  def test_download_pdf_compatible_illustrator_file_should_be_sent_inline_as_pdf
+    set_tmp_attachments_directory
+    attachment = Attachment.create!(
+      :file => mock_file_with_options(
+        :original_filename => 'logo.ai',
+        :content => File.binread("#{Rails.root}/test/fixtures/files/hello.pdf")
+      ),
+      :author_id => 2,
+      :container => Issue.find(1)
+    )
+
+    get(:download, :params => {:id => attachment.id})
+    assert_response :success
+    # Sent as PDF so that browsers display it inline
+    assert_equal 'application/pdf', @response.media_type
+    assert_match %r{\Ainline}, @response.headers['Content-Disposition']
+  end
+
   def test_download_version_file_with_issue_tracking_disabled
     Project.find(1).disable_module! :issue_tracking
     get(:download, :params => {:id => 9})
diff --git a/test/unit/attachment_test.rb b/test/unit/attachment_test.rb
index 820feafde..16a81d976 100644
--- a/test/unit/attachment_test.rb
+++ b/test/unit/attachment_test.rb
@@ -829,13 +829,17 @@ class AttachmentTest < ActiveSupport::TestCase
 
   def test_is_pdf
     to_test = {
-      'report.pdf' => true,
-      # Illustrator files are not PDF files, even though some of them are
-      # PDF compatible
-      'logo.ai' => false,
+      ['application/pdf', 'report.pdf'] => true,
+      # PDF compatible Illustrator files are detected as application/illustrator
+      ['application/illustrator', 'logo.ai'] => true,
+      # Illustrator files saved in the PostScript format are not PDF files
+      ['application/postscript', 'logo.ai'] => false,
+      # Attachments whose content type is undetermined fall back to the filename
+      ['application/octet-stream', 'report.pdf'] => true,
     }
-    to_test.each do |filename, expected|
-      assert_equal expected, Attachment.new(:filename => filename).is_pdf?, filename
+    to_test.each do |(content_type, filename), expected|
+      attachment = Attachment.new(:content_type => content_type, :filename => filename)
+      assert_equal expected, attachment.is_pdf?, "#{content_type} (#{filename})"
     end
   end
 end
-- 
2.55.0