Set ttl for redis and memcache cache stores when using `expires_at`

activesupport/lib/active_support/cache.rb

@@ -678,6 +678,13 @@ module ActiveSupport
         def merged_options(call_options)
           if call_options
             call_options = normalize_options(call_options)
+            if call_options.key?(:expires_in) && call_options.key?(:expires_at)
+              raise ArgumentError, "Either :expires_in or :expires_at can be supplied, but not both"
+            end
+
+            expires_at = call_options.delete(:expires_at)
+            call_options[:expires_in] = (expires_at - Time.now) if expires_at
+
             if options.empty?
               call_options
             else

activesupport/test/cache/behaviors/cache_store_behavior.rb

@@ -536,6 +536,14 @@ module CacheStoreBehavior
     end
   end
 
+  def test_expires_in_and_expires_at
+    key = SecureRandom.uuid
+    error = assert_raises(ArgumentError) do
+      @cache.write(key, "bar", expire_in: 60, expires_at: 1.minute.from_now)
+    end
+    assert_equal "Either :expires_in or :expires_at can be supplied, but not both", error.message
+  end
+
   def test_race_condition_protection_skipped_if_not_defined
     key = SecureRandom.alphanumeric
     @cache.write(key, "bar")

activesupport/test/cache/stores/mem_cache_store_test.rb

@@ -127,6 +127,16 @@ class MemCacheStoreTest < ActiveSupport::TestCase
     end
   end
 
+  def test_write_expires_at
+    cache = lookup_store(raw: true, namespace: nil)
+
+    Time.stub(:now, Time.now) do
+      assert_called_with client(cache), :set, [ "key_with_expires_at", "bar", 30 * 60, Hash ] do
+        cache.write("key_with_expires_at", "bar", expires_at: 30.minutes.from_now)
+      end
+    end
+  end
+
   def test_increment_expires_in
     cache = lookup_store(raw: true, namespace: nil)
     assert_called_with client(cache), :incr, [ "foo", 1, 60 ] do

activesupport/test/cache/stores/redis_cache_store_test.rb

@@ -179,6 +179,11 @@ module ActiveSupport::Cache::RedisCacheStoreTests
       end
     end
 
+    def test_write_expires_at
+      @cache.write "key_with_expires_at", "bar", expires_at: 30.minutes.from_now
+      assert @cache.redis.ttl("#{@namespace}:key_with_expires_at") > 0
+    end
+
     def test_increment_expires_in
       assert_called_with @cache.redis, :incrby, [ "#{@namespace}:foo", 1 ] do
         assert_called_with @cache.redis, :expire, [ "#{@namespace}:foo", 60 ] do