Merge pull request #36340 from jhawthorn/evented_file_checker_symlink

Fix EventedFileUpdateChecker through a symlink 

2 files changed, 43 insertions, 20 deletions

diff --git a/activesupport/lib/active_support/evented_file_update_checker.rb b/activesupport/lib/active_support/evented_file_update_checker.rb
index 3f6fd58f5e..84caa00b58 100644
--- a/activesupport/lib/active_support/evented_file_update_checker.rb
+++ b/activesupport/lib/active_support/evented_file_update_checker.rb
@@ -107,6 +107,7 @@ module ActiveSupport
 
     private
       def boot!
+        normalize_dirs!
         Listen.to(*@dtw, &method(:changed)).start
       end
 
@@ -114,6 +115,12 @@ module ActiveSupport
         Listen.stop
       end
 
+      def normalize_dirs!
+        @dirs.transform_keys! do |dir|
+          dir.exist? ? dir.realpath : dir
+        end
+      end
+
       def changed(modified, added, removed)
         unless updated?
           @updated.make_true if (modified + added + removed).any? { |f| watching?(f) }
diff --git a/activesupport/test/evented_file_update_checker_test.rb b/activesupport/test/evented_file_update_checker_test.rb
index a6bd2ade31..4d5a9bed7a 100644
--- a/activesupport/test/evented_file_update_checker_test.rb
+++ b/activesupport/test/evented_file_update_checker_test.rb
@@ -77,32 +77,48 @@ class EventedFileUpdateCheckerTest < ActiveSupport::TestCase
     Process.wait(pid)
   end
 
+  test "should detect changes through symlink" do
+    actual_dir = File.join(tmpdir, "actual")
+    linked_dir = File.join(tmpdir, "linked")
+
+    Dir.mkdir(actual_dir)
+    FileUtils.ln_s(actual_dir, linked_dir)
+
+    checker = new_checker([], linked_dir => ".rb") { }
+
+    assert_not_predicate checker, :updated?
+
+    FileUtils.touch(File.join(actual_dir, "a.rb"))
+    wait
+
+    assert_predicate checker, :updated?
+    assert checker.execute_if_updated
+  end
+
   test "updated should become true when nonexistent directory is added later" do
-    Dir.mktmpdir do |dir|
-      watched_dir = File.join(dir, "app")
-      unwatched_dir = File.join(dir, "node_modules")
-      not_exist_watched_dir = File.join(dir, "test")
+    watched_dir = File.join(tmpdir, "app")
+    unwatched_dir = File.join(tmpdir, "node_modules")
+    not_exist_watched_dir = File.join(tmpdir, "test")
 
-      Dir.mkdir(watched_dir)
-      Dir.mkdir(unwatched_dir)
+    Dir.mkdir(watched_dir)
+    Dir.mkdir(unwatched_dir)
 
-      checker = new_checker([], watched_dir => ".rb", not_exist_watched_dir => ".rb") { }
+    checker = new_checker([], watched_dir => ".rb", not_exist_watched_dir => ".rb") { }
 
-      FileUtils.touch(File.join(watched_dir, "a.rb"))
-      wait
-      assert_predicate checker, :updated?
-      assert checker.execute_if_updated
+    FileUtils.touch(File.join(watched_dir, "a.rb"))
+    wait
+    assert_predicate checker, :updated?
+    assert checker.execute_if_updated
 
-      Dir.mkdir(not_exist_watched_dir)
-      wait
-      assert_predicate checker, :updated?
-      assert checker.execute_if_updated
+    Dir.mkdir(not_exist_watched_dir)
+    wait
+    assert_predicate checker, :updated?
+    assert checker.execute_if_updated
 
-      FileUtils.touch(File.join(unwatched_dir, "a.rb"))
-      wait
-      assert_not_predicate checker, :updated?
-      assert_not checker.execute_if_updated
-    end
+    FileUtils.touch(File.join(unwatched_dir, "a.rb"))
+    wait
+    assert_not_predicate checker, :updated?
+    assert_not checker.execute_if_updated
   end
 end