Merge pull request #24520 from BlakeMesdag/activesupport-fileupdate-checker-mtime-optimization

Use a single loop in ActiveSupport:FileUpdateChecker#max_mtime 

1 files changed, 17 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/file_update_checker.rb b/activesupport/lib/active_support/file_update_checker.rb
index 8708a502e6..4f0a2dedc5 100644
--- a/activesupport/lib/active_support/file_update_checker.rb
+++ b/activesupport/lib/active_support/file_update_checker.rb
@@ -112,7 +112,23 @@ module ActiveSupport
     # reloading is not triggered.
     def max_mtime(paths)
       time_now = Time.now
-      paths.map {|path| File.mtime(path)}.reject {|mtime| time_now < mtime}.max
+      time_at_zero = Time.at(0)
+      max_time = time_at_zero
+
+      paths.each do |path|
+        time = File.mtime(path)
+
+        # This avoids ActiveSupport::CoreExt::Time#time_with_coercion
+        # which is super slow when comparing two Time objects
+        #
+        # Equivalent Ruby:
+        # time < time_now && time > max_time
+        if time.compare_without_coercion(time_now) < 0 && time.compare_without_coercion(max_time) > 0
+          max_time = time
+        end
+      end
+
+      max_time.object_id == time_at_zero.object_id ? nil : max_time
     end
 
     def compile_glob(hash)