Merge pull request #24523 from BlakeMesdag/as-max_time-fix-edges

Handle max_time edge cases for epoch times and add test

2 files changed, 28 insertions, 7 deletions

diff --git a/activesupport/lib/active_support/file_update_checker.rb b/activesupport/lib/active_support/file_update_checker.rb
index 4f0a2dedc5..fa0b1a4bcf 100644
--- a/activesupport/lib/active_support/file_update_checker.rb
+++ b/activesupport/lib/active_support/file_update_checker.rb
@@ -112,23 +112,27 @@ module ActiveSupport
     # reloading is not triggered.
     def max_mtime(paths)
       time_now = Time.now
-      time_at_zero = Time.at(0)
-      max_time = time_at_zero
+      max_mtime = nil
 
       paths.each do |path|
-        time = File.mtime(path)
+        mtime = File.mtime(path)
+
+        # Prevent dates in the future being considered
+        # Equivalent ruby:
+        # time.now < mtime
+        next if time_now.compare_without_coercion(mtime) < 0
 
         # 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
+        # max_mtime.nil? || max_mtime < mtime
+        if max_mtime.nil? || max_mtime.compare_without_coercion(mtime) < 0
+          max_mtime = mtime
         end
       end
 
-      max_time.object_id == time_at_zero.object_id ? nil : max_time
+      max_mtime
     end
 
     def compile_glob(hash)
diff --git a/activesupport/test/file_update_checker_shared_tests.rb b/activesupport/test/file_update_checker_shared_tests.rb
index 5207860a0e..a78c3a67b6 100644
--- a/activesupport/test/file_update_checker_shared_tests.rb
+++ b/activesupport/test/file_update_checker_shared_tests.rb
@@ -134,6 +134,23 @@ module FileUpdateCheckerSharedTests
     assert_equal 1, i
   end
 
+  test 'should return max_time for files with mtime = Time.at(0)' do
+    i = 0
+
+    FileUtils.touch(tmpfiles)
+
+    now  = Time.now
+    time = Time.at(0) # wrong mtime from the future
+    File.utime(time, time, tmpfiles[0])
+
+    checker = new_checker(tmpfiles) { i += 1 }
+
+    touch(tmpfiles[1..-1])
+
+    assert checker.execute_if_updated
+    assert_equal 1, i
+  end
+
   test 'should cache updated result until execute' do
     i = 0