1 files changed, 79 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/table_metadata.rb b/activerecord/lib/active_record/table_metadata.rb
new file mode 100644
index 0000000000..b67479fb6a
--- /dev/null
+++ b/activerecord/lib/active_record/table_metadata.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  class TableMetadata # :nodoc:
+    delegate :foreign_type, :foreign_key, :join_primary_key, :join_foreign_key, to: :association, prefix: true
+
+    def initialize(klass, arel_table, association = nil)
+      @klass = klass
+      @arel_table = arel_table
+      @association = association
+    end
+
+    def resolve_column_aliases(hash)
+      new_hash = hash.dup
+      hash.each do |key, _|
+        if (key.is_a?(Symbol)) && klass.attribute_alias?(key)
+          new_hash[klass.attribute_alias(key)] = new_hash.delete(key)
+        end
+      end
+      new_hash
+    end
+
+    def arel_attribute(column_name)
+      if klass
+        klass.arel_attribute(column_name, arel_table)
+      else
+        arel_table[column_name]
+      end
+    end
+
+    def type(column_name)
+      if klass
+        klass.type_for_attribute(column_name)
+      else
+        Type.default_value
+      end
+    end
+
+    def has_column?(column_name)
+      klass && klass.columns_hash.key?(column_name.to_s)
+    end
+
+    def associated_with?(association_name)
+      klass && klass._reflect_on_association(association_name)
+    end
+
+    def associated_table(table_name)
+      association = klass._reflect_on_association(table_name) || klass._reflect_on_association(table_name.to_s.singularize)
+
+      if !association && table_name == arel_table.name
+        return self
+      elsif association && !association.polymorphic?
+        association_klass = association.klass
+        arel_table = association_klass.arel_table.alias(table_name)
+      else
+        type_caster = TypeCaster::Connection.new(klass, table_name)
+        association_klass = nil
+        arel_table = Arel::Table.new(table_name, type_caster: type_caster)
+      end
+
+      TableMetadata.new(association_klass, arel_table, association)
+    end
+
+    def polymorphic_association?
+      association && association.polymorphic?
+    end
+
+    def aggregated_with?(aggregation_name)
+      klass && reflect_on_aggregation(aggregation_name)
+    end
+
+    def reflect_on_aggregation(aggregation_name)
+      klass.reflect_on_aggregation(aggregation_name)
+    end
+
+    private
+      attr_reader :klass, :arel_table, :association
+  end
+end