Deprecate automatic type casting within Arel

Rails now performs all casting eagerly, before passing the value into
Arel. Once we remove this, the code on both sides will be simplified
greatly. Ideally, we can provide the appropriate public APIs on the
Rails side to ease this transition for library authors who depend on
this behavior.

2 files changed, 13 insertions, 0 deletions

diff --git a/lib/arel/nodes.rb b/lib/arel/nodes.rb
index 7d900fe710..8432106719 100644
--- a/lib/arel/nodes.rb
+++ b/lib/arel/nodes.rb
@@ -87,6 +87,17 @@ module Arel
       else
         case attribute
         when Arel::Attributes::Attribute
+          unless $arel_silence_type_casting_deprecation
+            warn <<-eowarn
+Arel performing automatic type casting is deprecated, and will be removed in Arel 8.0. If you are seeing this, it is because you are manually passing a value to an Arel predicate.
+
+If you're certain the value is already of the right type, change `attribute.eq(value)` to `attribute.eq(Arel::Nodes::Quoted.new(value))` (you will be able to remove that in Arel 8.0, it is only required to silence this deprecation warning).
+
+You can also silence this warning globally by setting `$arel_silence_type_casting_deprecation` to `true`. (Do NOT do this if you are a library author)
+
+If you are passing user input to a predicate, you are responsible for type casting appropriately before passing the value to Arel.
+            eowarn
+          end
           Casted.new other, attribute
         else
           Quoted.new other
diff --git a/test/helper.rb b/test/helper.rb
index 6e8ac836fc..87f5756d24 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -6,6 +6,8 @@ require 'arel'
 require 'support/fake_record'
 Arel::Table.engine = FakeRecord::Base.new
 
+$arel_silence_type_casting_deprecation = true
+
 class Object
   def must_be_like other
     gsub(/\s+/, ' ').strip.must_equal other.gsub(/\s+/, ' ').strip