YAMLColumn: use `YAML.safe_dump` if available

One particularly annoying thing with YAMLColumn type restriction
is that it is only checked on load.

Which means if your code insert data with unsupported types, the
insert will work, but now you'll be unable to read the record, which
makes it hard to fix etc.

That's the reason why I implemented `YAML.safe_dump` (https://github.com/ruby/psych/pull/495).

It applies exactly the same restrictions than `safe_load`, which means
if you attempt to store non-permitted fields, it will fail on insertion
and not on further reads, so you won't create an invalid record in your
database.

Gemfile.lock

@@ -333,7 +333,7 @@ GEM
       activesupport (>= 7.0.0)
       rack
       railties (>= 7.0.0)
-    psych (5.0.1)
+    psych (5.1.0)
       stringio
     public_suffix (5.0.1)
     puma (6.0.2)

activerecord/CHANGELOG.md

@@ -1,3 +1,14 @@
+*   YAML columns use `YAML.safe_dump` is available.
+
+    As of `psych 5.1.0`, `YAML.safe_dump` can now apply the same permitted
+    types restrictions than `YAML.safe_load`.
+
+    It's preferable to ensure the payload only use allowed types when we first
+    try to serialize it, otherwise you may end up with invalid records in the
+    database.
+
+    *Jean Boussier*
+
 *   `ActiveRecord::QueryLogs` better handle broken encoding.
 
     It's not uncommon when building queries with BLOB fields to contain

activerecord/lib/active_record/coders/yaml_column.rb

@@ -26,11 +26,24 @@ module ActiveRecord
         @unsafe_load = coder["unsafe_load"]
       end
 
-      def dump(obj)
-        return if obj.nil?
+      if Gem::Version.new(Psych::VERSION) >= "5.1"
+        def dump(obj)
+          return if obj.nil?
 
-        assert_valid_value(obj, action: "dump")
-        YAML.dump obj
+          assert_valid_value(obj, action: "dump")
+          if unsafe_load?
+            YAML.dump(obj)
+          else
+            YAML.safe_dump(obj, permitted_classes: permitted_classes, aliases: true)
+          end
+        end
+      else
+        def dump(obj)
+          return if obj.nil?
+
+          assert_valid_value(obj, action: "dump")
+          YAML.dump obj
+        end
       end
 
       def load(yaml)

activerecord/test/cases/coders/yaml_column_test.rb

@@ -97,6 +97,17 @@ module ActiveRecord
         end
       end
 
+      def test_yaml_column_permitted_classes_are_consumed_by_safe_dump
+        if Gem::Version.new(Psych::VERSION) < "5.1"
+          skip "YAML.safe_dump is either missing on unavailable on #{Psych::VERSION}"
+        end
+
+        coder = YAMLColumn.new("attr_name")
+        assert_raises(Psych::DisallowedClass) do
+          coder.dump([Time.new])
+        end
+      end
+
       def test_yaml_column_permitted_classes_option
         ActiveRecord.yaml_column_permitted_classes = [Symbol]