Merge pull request #10673 from sgrif/master

Add ability to specify how a class is converted to Arel predicate when passed to where

activerecord/CHANGELOG.md

+*   Add ability to define how a class is converted to Arel predicates.
+    For example, adding a very vendor specific regex implementation:
+
+        regex_handler = proc do |column, value|
+          Arel::Nodes::InfixOperation.new('~', column, value.source)
+        end
+        ActiveRecord::PredicateBuilder.register_handler(Regexp, regex_handler)
+
+    *Sean Griffin & @joannecheng*
+
 *   Don't allow `quote_value` to be called without a column.
 
     Some adapters require column information to do their job properly.

activerecord/lib/active_record/relation/predicate_builder.rb

 module ActiveRecord
   class PredicateBuilder # :nodoc:
+    @handlers = []
+
+    autoload :RelationHandler, 'active_record/relation/predicate_builder/relation_handler'
+    autoload :ArrayHandler, 'active_record/relation/predicate_builder/array_handler'
+
     def self.resolve_column_aliases(klass, hash)
       hash = hash.dup
       hash.keys.grep(Symbol) do |key|
@@ -73,44 +78,36 @@ def self.references(attributes)
       end.compact
     end
 
+    # Define how a class is converted to Arel nodes when passed to +where+.
+    # The handler can be any object that responds to +call+, and will be used
+    # for any value that +===+ the class given. For example:
+    #
+    #     MyCustomDateRange = Struct.new(:start, :end)
+    #     handler = proc do |column, range|
+    #       Arel::Nodes::Between.new(column,
+    #         Arel::Nodes::And.new([range.start, range.end])
+    #       )
+    #     end
+    #     ActiveRecord::PredicateBuilder.register_handler(MyCustomDateRange, handler)
+    def self.register_handler(klass, handler)
+      @handlers.unshift([klass, handler])
+    end
+
+    register_handler(BasicObject, ->(attribute, value) { attribute.eq(value) })
+    # FIXME: I think we need to deprecate this behavior
+    register_handler(Class, ->(attribute, value) { attribute.eq(value.name) })
+    register_handler(Base, ->(attribute, value) { attribute.eq(value.id) })
+    register_handler(Range, ->(attribute, value) { attribute.in(value) })
+    register_handler(Relation, RelationHandler.new)
+    register_handler(Array, ArrayHandler.new)
+
     private
       def self.build(attribute, value)
-        case value
-        when Array
-          values = value.to_a.map {|x| x.is_a?(Base) ? x.id : x}
-          ranges, values = values.partition {|v| v.is_a?(Range)}
-
-          values_predicate = if values.include?(nil)
-            values = values.compact
-
-            case values.length
-            when 0
-              attribute.eq(nil)
-            when 1
-              attribute.eq(values.first).or(attribute.eq(nil))
-            else
-              attribute.in(values).or(attribute.eq(nil))
-            end
-          else
-            attribute.in(values)
-          end
+        handler_for(value).call(attribute, value)
+      end
 
-          array_predicates = ranges.map { |range| attribute.in(range) }
-          array_predicates << values_predicate
-          array_predicates.inject { |composite, predicate| composite.or(predicate) }
-        when ActiveRecord::Relation
-          value = value.select(value.klass.arel_table[value.klass.primary_key]) if value.select_values.empty?
-          attribute.in(value.arel.ast)
-        when Range
-          attribute.in(value)
-        when ActiveRecord::Base
-          attribute.eq(value.id)
-        when Class
-          # FIXME: I think we need to deprecate this behavior
-          attribute.eq(value.name)
-        else
-          attribute.eq(value)
-        end
+      def self.handler_for(object)
+        @handlers.detect { |klass, _| klass === object }.last
       end
   end
 end

activerecord/lib/active_record/relation/predicate_builder/array_handler.rb

+module ActiveRecord
+  class PredicateBuilder
+    class ArrayHandler # :nodoc:
+      def call(attribute, value)
+        values = value.map { |x| x.is_a?(Base) ? x.id : x }
+        ranges, values = values.partition { |v| v.is_a?(Range) }
+
+        values_predicate = if values.include?(nil)
+          values = values.compact
+
+          case values.length
+          when 0
+            attribute.eq(nil)
+          when 1
+            attribute.eq(values.first).or(attribute.eq(nil))
+          else
+            attribute.in(values).or(attribute.eq(nil))
+          end
+        else
+          attribute.in(values)
+        end
+
+        array_predicates = ranges.map { |range| attribute.in(range) }
+        array_predicates << values_predicate
+        array_predicates.inject { |composite, predicate| composite.or(predicate) }
+      end
+    end
+  end
+end

activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb

+module ActiveRecord
+  class PredicateBuilder
+    class RelationHandler # :nodoc:
+      def call(attribute, value)
+        if value.select_values.empty?
+          value = value.select(value.klass.arel_table[value.klass.primary_key])
+        end
+
+        attribute.in(value.arel.ast)
+      end
+    end
+  end
+end

activerecord/test/cases/relation/predicate_builder_test.rb

+require "cases/helper"
+require 'models/topic'
+
+module ActiveRecord
+  class PredicateBuilderTest < ActiveRecord::TestCase
+    def test_registering_new_handlers
+      PredicateBuilder.register_handler(Regexp, proc do |column, value|
+        Arel::Nodes::InfixOperation.new('~', column, value.source)
+      end)
+
+      assert_match %r{["`]topics["`].["`]title["`] ~ 'rails'}, Topic.where(title: /rails/).to_sql
+    end
+  end
+end