Add a global type registry, used to lookup and register types

As per previous discussions, we want to give users the ability to
reference their own types with symbols, instead of having to pass the
object manually. This adds the class that will be used to do so.

    ActiveRecord::Type.register(:money, MyMoneyType)

4 files changed, 336 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/type.rb b/activerecord/lib/active_record/type.rb
index f18b076d58..7ce0370d8b 100644
--- a/activerecord/lib/active_record/type.rb
+++ b/activerecord/lib/active_record/type.rb
@@ -16,5 +16,30 @@ require 'active_record/type/text'
 require 'active_record/type/time'
 require 'active_record/type/unsigned_integer'
 
+require 'active_record/type/adapter_specific_registry'
 require 'active_record/type/type_map'
 require 'active_record/type/hash_lookup_type_map'
+
+module ActiveRecord
+  module Type
+    @registry = AdapterSpecificRegistry.new
+
+    class << self
+      attr_accessor :registry # :nodoc:
+
+      def register(*args)
+        registry.register(*args)
+      end
+
+      def lookup(*args, adapter: current_adapter_name, **kwargs)
+        registry.lookup(*args, adapter: adapter, **kwargs)
+      end
+
+      private
+
+      def current_adapter_name
+        ActiveRecord::Base.connection.adapter_name.downcase.to_sym
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/type/adapter_specific_registry.rb b/activerecord/lib/active_record/type/adapter_specific_registry.rb
new file mode 100644
index 0000000000..ce9ff6a557
--- /dev/null
+++ b/activerecord/lib/active_record/type/adapter_specific_registry.rb
@@ -0,0 +1,139 @@
+module ActiveRecord
+  module Type
+    class AdapterSpecificRegistry # :nodoc:
+      def initialize
+        @registrations = []
+      end
+
+      def register(type_name, klass = nil, **options, &block)
+        block ||= proc { |_, *args| klass.new(*args) }
+        registrations << Registration.new(type_name, block, **options)
+      end
+
+      def lookup(symbol, *args)
+        registration = registrations
+          .select { |r| r.matches?(symbol, *args) }
+          .max
+
+        if registration
+          registration.call(self, symbol, *args)
+        else
+          raise ArgumentError, "Unknown type #{symbol.inspect}"
+        end
+      end
+
+      def add_modifier(options, klass, **args)
+        registrations << DecorationRegistration.new(options, klass, **args)
+      end
+
+      protected
+
+      attr_reader :registrations
+    end
+
+    class Registration
+      def initialize(name, block, adapter: nil, override: nil)
+        @name = name
+        @block = block
+        @adapter = adapter
+        @override = override
+      end
+
+      def call(_registry, *args, adapter: nil, **kwargs)
+        if kwargs.any? # https://bugs.ruby-lang.org/issues/10856
+          block.call(*args, **kwargs)
+        else
+          block.call(*args)
+        end
+      end
+
+      def matches?(type_name, *args, **kwargs)
+        type_name == name && matches_adapter?(**kwargs)
+      end
+
+      def <=>(other)
+        if conflicts_with?(other)
+          raise TypeConflictError.new("Type #{name} was registered for all
+                                      adapters, but shadows a native type with
+                                      the same name for #{other.adapter}".squish)
+        end
+        priority <=> other.priority
+      end
+
+      protected
+
+      attr_reader :name, :block, :adapter, :override
+
+      def priority
+        result = 0
+        if adapter
+          result |= 1
+        end
+        if override
+          result |= 2
+        end
+        result
+      end
+
+      def priority_except_adapter
+        priority & 0b111111100
+      end
+
+      private
+
+      def matches_adapter?(adapter: nil, **)
+        (self.adapter.nil? || adapter == self.adapter)
+      end
+
+      def conflicts_with?(other)
+        same_priority_except_adapter?(other) &&
+          has_adapter_conflict?(other)
+      end
+
+      def same_priority_except_adapter?(other)
+        priority_except_adapter == other.priority_except_adapter
+      end
+
+      def has_adapter_conflict?(other)
+        (override.nil? && other.adapter) ||
+          (adapter && other.override.nil?)
+      end
+    end
+
+    class DecorationRegistration < Registration
+      def initialize(options, klass, adapter: nil)
+        @options = options
+        @klass = klass
+        @adapter = adapter
+      end
+
+      def call(registry, *args, **kwargs)
+        subtype = registry.lookup(*args, **kwargs.except(*options.keys))
+        klass.new(subtype)
+      end
+
+      def matches?(*args, **kwargs)
+        matches_adapter?(**kwargs) && matches_options?(**kwargs)
+      end
+
+      def priority
+        super | 4
+      end
+
+      protected
+
+      attr_reader :options, :klass
+
+      private
+
+      def matches_options?(**kwargs)
+        options.all? do |key, value|
+          kwargs[key] == value
+        end
+      end
+    end
+  end
+
+  class TypeConflictError < StandardError
+  end
+end
diff --git a/activerecord/test/cases/type/adapter_specific_registry_test.rb b/activerecord/test/cases/type/adapter_specific_registry_test.rb
new file mode 100644
index 0000000000..8b836b4793
--- /dev/null
+++ b/activerecord/test/cases/type/adapter_specific_registry_test.rb
@@ -0,0 +1,133 @@
+require "cases/helper"
+
+module ActiveRecord
+  class AdapterSpecificRegistryTest < ActiveRecord::TestCase
+    test "a class can be registered for a symbol" do
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, ::String)
+      registry.register(:bar, ::Array)
+
+      assert_equal "", registry.lookup(:foo)
+      assert_equal [], registry.lookup(:bar)
+    end
+
+    test "a block can be registered" do
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo) do |*args|
+        [*args, "block for foo"]
+      end
+      registry.register(:bar) do |*args|
+        [*args, "block for bar"]
+      end
+
+      assert_equal [:foo, 1, "block for foo"], registry.lookup(:foo, 1)
+      assert_equal [:foo, 2, "block for foo"], registry.lookup(:foo, 2)
+      assert_equal [:bar, 1, 2, 3, "block for bar"], registry.lookup(:bar, 1, 2, 3)
+    end
+
+    test "filtering by adapter" do
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, String, adapter: :sqlite3)
+      registry.register(:foo, Array, adapter: :postgresql)
+
+      assert_equal "", registry.lookup(:foo, adapter: :sqlite3)
+      assert_equal [], registry.lookup(:foo, adapter: :postgresql)
+    end
+
+    test "an error is raised if both a generic and adapter specific type match" do
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, String)
+      registry.register(:foo, Array, adapter: :postgresql)
+
+      assert_raises TypeConflictError do
+        registry.lookup(:foo, adapter: :postgresql)
+      end
+      assert_equal "", registry.lookup(:foo, adapter: :sqlite3)
+    end
+
+    test "a generic type can explicitly override an adapter specific type" do
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, String, override: true)
+      registry.register(:foo, Array, adapter: :postgresql)
+
+      assert_equal "", registry.lookup(:foo, adapter: :postgresql)
+      assert_equal "", registry.lookup(:foo, adapter: :sqlite3)
+    end
+
+    test "a generic type can explicitly allow an adapter type to be used instead" do
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, String, override: false)
+      registry.register(:foo, Array, adapter: :postgresql)
+
+      assert_equal [], registry.lookup(:foo, adapter: :postgresql)
+      assert_equal "", registry.lookup(:foo, adapter: :sqlite3)
+    end
+
+    test "a reasonable error is given when no type is found" do
+      registry = Type::AdapterSpecificRegistry.new
+
+      e = assert_raises(ArgumentError) do
+        registry.lookup(:foo)
+      end
+
+      assert_equal "Unknown type :foo", e.message
+    end
+
+    test "construct args are passed to the type" do
+      type = Struct.new(:args)
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, type)
+
+      assert_equal type.new, registry.lookup(:foo)
+      assert_equal type.new(:ordered_arg), registry.lookup(:foo, :ordered_arg)
+      assert_equal type.new(keyword: :arg), registry.lookup(:foo, keyword: :arg)
+      assert_equal type.new(keyword: :arg), registry.lookup(:foo, keyword: :arg, adapter: :postgresql)
+    end
+
+    test "registering a modifier" do
+      decoration = Struct.new(:value)
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, String)
+      registry.register(:bar, Hash)
+      registry.add_modifier({ array: true }, decoration)
+
+      assert_equal decoration.new(""), registry.lookup(:foo, array: true)
+      assert_equal decoration.new({}), registry.lookup(:bar, array: true)
+      assert_equal "", registry.lookup(:foo)
+    end
+
+    test "registering multiple modifiers" do
+      decoration = Struct.new(:value)
+      other_decoration = Struct.new(:value)
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, String)
+      registry.add_modifier({ array: true }, decoration)
+      registry.add_modifier({ range: true }, other_decoration)
+
+      assert_equal "", registry.lookup(:foo)
+      assert_equal decoration.new(""), registry.lookup(:foo, array: true)
+      assert_equal other_decoration.new(""), registry.lookup(:foo, range: true)
+      assert_equal(
+        decoration.new(other_decoration.new("")),
+        registry.lookup(:foo, array: true, range: true)
+      )
+    end
+
+    test "registering adapter specific modifiers" do
+      decoration = Struct.new(:value)
+      type = Struct.new(:args)
+      registry = Type::AdapterSpecificRegistry.new
+      registry.register(:foo, type)
+      registry.add_modifier({ array: true }, decoration, adapter: :postgresql)
+
+      assert_equal(
+        decoration.new(type.new(keyword: :arg)),
+        registry.lookup(:foo, array: true, adapter: :postgresql, keyword: :arg)
+      )
+      assert_equal(
+        type.new(array: true),
+        registry.lookup(:foo, array: true, adapter: :sqlite3)
+      )
+    end
+  end
+end
diff --git a/activerecord/test/cases/type_test.rb b/activerecord/test/cases/type_test.rb
new file mode 100644
index 0000000000..d45a9b3141
--- /dev/null
+++ b/activerecord/test/cases/type_test.rb
@@ -0,0 +1,39 @@
+require "cases/helper"
+
+class TypeTest < ActiveRecord::TestCase
+  setup do
+    @old_registry = ActiveRecord::Type.registry
+    ActiveRecord::Type.registry = ActiveRecord::Type::AdapterSpecificRegistry.new
+  end
+
+  teardown do
+    ActiveRecord::Type.registry = @old_registry
+  end
+
+  test "registering a new type" do
+    type = Struct.new(:args)
+    ActiveRecord::Type.register(:foo, type)
+
+    assert_equal type.new(:arg), ActiveRecord::Type.lookup(:foo, :arg)
+  end
+
+  test "looking up a type for a specific adapter" do
+    type = Struct.new(:args)
+    pgtype = Struct.new(:args)
+    ActiveRecord::Type.register(:foo, type, override: false)
+    ActiveRecord::Type.register(:foo, pgtype, adapter: :postgresql)
+
+    assert_equal type.new, ActiveRecord::Type.lookup(:foo, adapter: :sqlite)
+    assert_equal pgtype.new, ActiveRecord::Type.lookup(:foo, adapter: :postgresql)
+  end
+
+  test "lookup defaults to the current adapter" do
+    current_adapter = ActiveRecord::Base.connection.adapter_name.downcase.to_sym
+    type = Struct.new(:args)
+    adapter_type = Struct.new(:args)
+    ActiveRecord::Type.register(:foo, type, override: false)
+    ActiveRecord::Type.register(:foo, adapter_type, adapter: current_adapter)
+
+    assert_equal adapter_type.new, ActiveRecord::Type.lookup(:foo)
+  end
+end