feat!: Allow for custom Coercers

lib/typed/coercion.rb

@@ -4,23 +4,18 @@ module Typed
   module Coercion
     extend T::Sig
 
-    # TODO: We can definitely improve how we select which coercer to use
-    #   Related issues:
-    #   * https://github.com/maxveldink/sorbet-schema/issues/9
-    #   * https://github.com/maxveldink/sorbet-schema/issues/10
+    sig { params(coercer: T.class_of(Coercer)).void }
+    def self.register_coercer(coercer)
+      CoercerRegistry.instance.register(coercer)
+    end
+
     sig { type_parameters(:U).params(field: Field, value: Value).returns(Result[Value, CoercionError]) }
     def self.coerce(field:, value:)
-      if field.type < T::Struct
-        StructCoercer.coerce(field: field, value: value)
-      elsif field.type == String
-        StringCoercer.coerce(field: field, value: value)
-      elsif field.type == Integer
-        IntegerCoercer.coerce(field: field, value: value)
-      elsif field.type == Float
-        FloatCoercer.coerce(field: field, value: value)
-      else
-        Failure.new(CoercionNotSupportedError.new)
-      end
+      coercer = CoercerRegistry.instance.select_coercer_by(type: field.type)
+
+      return Failure.new(CoercionNotSupportedError.new) unless coercer
+
+      coercer.new.coerce(field: field, value: value)
     end
   end
 end

lib/typed/coercion/coercer.rb

@@ -2,14 +2,18 @@
 
 module Typed
   module Coercion
-    module Coercer
+    class Coercer
       extend T::Sig
       extend T::Generic
 
       abstract!
 
       Target = type_member(:out)
 
+      sig { abstract.params(type: T::Class[T.anything]).returns(T::Boolean) }
+      def used_for_type?(type)
+      end
+
       sig { abstract.params(field: Field, value: Value).returns(Result[Target, CoercionError]) }
       def coerce(field:, value:)
       end

lib/typed/coercion/coercer_registry.rb

@@ -0,0 +1,37 @@
+# typed: strict
+
+require "singleton"
+
+module Typed
+  module Coercion
+    class CoercerRegistry
+      extend T::Sig
+
+      include Singleton
+
+      Registry = T.type_alias { T::Array[T.class_of(Coercer)] }
+
+      DEFAULT_COERCERS = T.let([StringCoercer, IntegerCoercer, FloatCoercer, StructCoercer], Registry)
+
+      sig { void }
+      def initialize
+        @available = T.let(DEFAULT_COERCERS.clone, Registry)
+      end
+
+      sig { params(coercer: T.class_of(Coercer)).void }
+      def register(coercer)
+        @available.prepend(coercer)
+      end
+
+      sig { void }
+      def reset!
+        @available = DEFAULT_COERCERS.clone
+      end
+
+      sig { params(type: T::Class[T.anything]).returns(T.nilable(T.class_of(Coercer))) }
+      def select_coercer_by(type:)
+        @available.find { |coercer| coercer.new.used_for_type?(type) }
+      end
+    end
+  end
+end

lib/typed/coercion/float_coercer.rb

@@ -2,16 +2,18 @@
 
 module Typed
   module Coercion
-    class FloatCoercer
-      extend T::Sig
+    class FloatCoercer < Coercer
       extend T::Generic
 
-      extend Coercer
+      Target = type_member { {fixed: Float} }
 
-      Target = type_template { {fixed: Float} }
+      sig { override.params(type: T::Class[T.anything]).returns(T::Boolean) }
+      def used_for_type?(type)
+        type == Float
+      end
 
       sig { override.params(field: Field, value: Value).returns(Result[Target, CoercionError]) }
-      def self.coerce(field:, value:)
+      def coerce(field:, value:)
         Success.new(Float(value))
       rescue ArgumentError, TypeError
         Failure.new(CoercionError.new("'#{value}' cannot be coerced into Float."))

lib/typed/coercion/integer_coercer.rb

@@ -2,16 +2,18 @@
 
 module Typed
   module Coercion
-    class IntegerCoercer
-      extend T::Sig
+    class IntegerCoercer < Coercer
       extend T::Generic
 
-      extend Coercer
+      Target = type_member { {fixed: Integer} }
 
-      Target = type_template { {fixed: Integer} }
+      sig { override.params(type: T::Class[T.anything]).returns(T::Boolean) }
+      def used_for_type?(type)
+        type == Integer
+      end
 
       sig { override.params(field: Field, value: Value).returns(Result[Target, CoercionError]) }
-      def self.coerce(field:, value:)
+      def coerce(field:, value:)
         Success.new(Integer(value))
       rescue ArgumentError, TypeError
         Failure.new(CoercionError.new("'#{value}' cannot be coerced into Integer."))

lib/typed/coercion/string_coercer.rb

@@ -2,16 +2,18 @@
 
 module Typed
   module Coercion
-    class StringCoercer
-      extend T::Sig
+    class StringCoercer < Coercer
       extend T::Generic
 
-      extend Coercer
+      Target = type_member { {fixed: String} }
 
-      Target = type_template { {fixed: String} }
+      sig { override.params(type: T::Class[T.anything]).returns(T::Boolean) }
+      def used_for_type?(type)
+        type == String
+      end
 
       sig { override.params(field: Field, value: Value).returns(Result[Target, CoercionError]) }
-      def self.coerce(field:, value:)
+      def coerce(field:, value:)
         Success.new(String(value))
       end
     end

lib/typed/coercion/struct_coercer.rb

@@ -2,16 +2,18 @@
 
 module Typed
   module Coercion
-    class StructCoercer
-      extend T::Sig
+    class StructCoercer < Coercer
       extend T::Generic
 
-      extend Coercer
+      Target = type_member { {fixed: T::Struct} }
 
-      Target = type_template { {fixed: T::Struct} }
+      sig { override.params(type: T::Class[T.anything]).returns(T::Boolean) }
+      def used_for_type?(type)
+        !!(type < T::Struct)
+      end
 
       sig { override.params(field: Field, value: Value).returns(Result[Target, CoercionError]) }
-      def self.coerce(field:, value:)
+      def coerce(field:, value:)
         type = field.type
 
         return Failure.new(CoercionError.new("Field type must inherit from T::Struct for Struct coercion.")) unless type < T::Struct

test/support/simple_string_coercer.rb

@@ -0,0 +1,17 @@
+# typed: true
+
+class SimpleStringCoercer < Typed::Coercion::Coercer
+  extend T::Generic
+
+  Target = type_member { {fixed: String} }
+
+  sig { override.params(type: T::Class[T.anything]).returns(T::Boolean) }
+  def used_for_type?(type)
+    type == String
+  end
+
+  sig { override.params(field: Typed::Field, value: Typed::Value).returns(Typed::Result[Target, Typed::Coercion::CoercionError]) }
+  def coerce(field:, value:)
+    Typed::Success.new("always this value")
+  end
+end

test/test_helper.rb

@@ -12,4 +12,4 @@
 require "sorbet-schema"
 require "sorbet-schema/struct_ext"
 
-Dir["test/support/structs/*.rb"].each { |file| require file }
+Dir["test/support/**/*.rb"].each { |file| require file }

test/typed/coercion/coercer_registry_test.rb

@@ -0,0 +1,17 @@
+# typed: true
+
+class CoercerRegistryTest < Minitest::Test
+  def teardown
+    Typed::Coercion::CoercerRegistry.instance.reset!
+  end
+
+  def test_register_prepends_coercer_so_it_overrides_built_in_ones
+    Typed::Coercion::CoercerRegistry.instance.register(SimpleStringCoercer)
+
+    assert_equal(SimpleStringCoercer, Typed::Coercion::CoercerRegistry.instance.select_coercer_by(type: String))
+  end
+
+  def test_when_type_doesnt_match_coercer_returns_nil
+    assert_nil(Typed::Coercion::CoercerRegistry.instance.select_coercer_by(type: Array))
+  end
+end

test/typed/coercion/float_coercer_test.rb

@@ -2,16 +2,22 @@
 
 class FloatCoercerTest < Minitest::Test
   def setup
+    @coercer = Typed::Coercion::FloatCoercer.new
     @field = Typed::Field.new(name: :testing, type: Float)
   end
 
+  def test_used_for_type_works
+    assert(@coercer.used_for_type?(Float))
+    refute(@coercer.used_for_type?(Integer))
+  end
+
   def test_when_coercable_returns_success
-    assert_payload(1.1, Typed::Coercion::FloatCoercer.coerce(field: @field, value: "1.1"))
-    assert_payload(1.0, Typed::Coercion::FloatCoercer.coerce(field: @field, value: 1))
+    assert_payload(1.1, @coercer.coerce(field: @field, value: "1.1"))
+    assert_payload(1.0, @coercer.coerce(field: @field, value: 1))
   end
 
   def test_when_not_coercable_returns_failure
-    assert_error(Typed::Coercion::CoercionError.new("'a' cannot be coerced into Float."), Typed::Coercion::FloatCoercer.coerce(field: @field, value: "a"))
-    assert_error(Typed::Coercion::CoercionError.new("'true' cannot be coerced into Float."), Typed::Coercion::FloatCoercer.coerce(field: @field, value: true))
+    assert_error(Typed::Coercion::CoercionError.new("'a' cannot be coerced into Float."), @coercer.coerce(field: @field, value: "a"))
+    assert_error(Typed::Coercion::CoercionError.new("'true' cannot be coerced into Float."), @coercer.coerce(field: @field, value: true))
   end
 end

test/typed/coercion/integer_coercer_test.rb

@@ -2,16 +2,22 @@
 
 class IntegerCoercerTest < Minitest::Test
   def setup
+    @coercer = Typed::Coercion::IntegerCoercer.new
     @field = Typed::Field.new(name: :testing, type: Integer)
   end
 
+  def test_used_for_type_works
+    assert(@coercer.used_for_type?(Integer))
+    refute(@coercer.used_for_type?(Float))
+  end
+
   def test_when_coercable_returns_success
-    assert_payload(1, Typed::Coercion::IntegerCoercer.coerce(field: @field, value: "1"))
-    assert_payload(1, Typed::Coercion::IntegerCoercer.coerce(field: @field, value: 1.1))
+    assert_payload(1, @coercer.coerce(field: @field, value: "1"))
+    assert_payload(1, @coercer.coerce(field: @field, value: 1.1))
   end
 
   def test_when_not_coercable_returns_failure
-    assert_error(Typed::Coercion::CoercionError.new("'a' cannot be coerced into Integer."), Typed::Coercion::IntegerCoercer.coerce(field: @field, value: "a"))
-    assert_error(Typed::Coercion::CoercionError.new("'true' cannot be coerced into Integer."), Typed::Coercion::IntegerCoercer.coerce(field: @field, value: true))
+    assert_error(Typed::Coercion::CoercionError.new("'a' cannot be coerced into Integer."), @coercer.coerce(field: @field, value: "a"))
+    assert_error(Typed::Coercion::CoercionError.new("'true' cannot be coerced into Integer."), @coercer.coerce(field: @field, value: true))
   end
 end

test/typed/coercion/string_coercer_test.rb

@@ -1,10 +1,18 @@
 # typed: true
 
 class StringCoercerTest < Minitest::Test
-  def test_returns_success
-    field = Typed::Field.new(name: :testing, type: String)
+  def setup
+    @coercer = Typed::Coercion::StringCoercer.new
+    @field = Typed::Field.new(name: :testing, type: String)
+  end
 
-    assert_payload("1", Typed::Coercion::StringCoercer.coerce(field: field, value: 1))
-    assert_payload("[1, 2]", Typed::Coercion::StringCoercer.coerce(field: field, value: [1, 2]))
+  def test_used_for_type_works
+    assert(@coercer.used_for_type?(String))
+    refute(@coercer.used_for_type?(Integer))
+  end
+
+  def test_returns_success
+    assert_payload("1", @coercer.coerce(field: @field, value: 1))
+    assert_payload("[1, 2]", @coercer.coerce(field: @field, value: [1, 2]))
   end
 end

test/typed/coercion/struct_coercer_test.rb

@@ -1,22 +1,32 @@
 # typed: true
 
 class StructCoercerTest < Minitest::Test
+  def setup
+    @coercer = Typed::Coercion::StructCoercer.new
+  end
+
+  def test_used_for_type_works
+    assert(@coercer.used_for_type?(Job))
+    refute(@coercer.used_for_type?(T::Struct))
+    refute(@coercer.used_for_type?(Integer))
+  end
+
   def test_when_non_struct_field_given_returns_failure
-    result = Typed::Coercion::StructCoercer.coerce(field: Typed::Field.new(name: :testing, type: Integer), value: "testing")
+    result = @coercer.coerce(field: Typed::Field.new(name: :testing, type: Integer), value: "testing")
 
     assert_failure(result)
     assert_error(Typed::Coercion::CoercionError.new("Field type must inherit from T::Struct for Struct coercion."), result)
   end
 
   def test_when_struct_can_be_coerced_returns_success
-    result = Typed::Coercion::StructCoercer.coerce(field: Typed::Field.new(name: :job, type: Job), value: {"title" => "Software Developer", "salary" => 90_000_00})
+    result = @coercer.coerce(field: Typed::Field.new(name: :job, type: Job), value: {"title" => "Software Developer", "salary" => 90_000_00})
 
     assert_success(result)
     assert_payload(Job.new(title: "Software Developer", salary: 90_000_00), result)
   end
 
   def test_when_struct_cannot_be_coerced_returns_failure
-    result = Typed::Coercion::StructCoercer.coerce(field: Typed::Field.new(name: :job, type: Job), value: "bad")
+    result = @coercer.coerce(field: Typed::Field.new(name: :job, type: Job), value: "bad")
 
     assert_failure(result)
     assert_error(Typed::Coercion::CoercionError.new("Value must be a Hash for Struct coercion."), result)

test/typed/coercion_test.rb

@@ -3,35 +3,24 @@
 require "date"
 
 class CoercionTest < Minitest::Test
-  def test_coercion_coerces_structs
-    result = Typed::Coercion.coerce(field: Typed::Field.new(name: :job, type: Job), value: {"title" => "Software Developer", "salary" => 90_000_00})
-
-    assert_success(result)
-    assert_payload(Job.new(title: "Software Developer", salary: 90_000_00), result)
+  def teardown
+    Typed::Coercion::CoercerRegistry.instance.reset!
   end
 
-  def test_coercion_coerces_strings
-    result = Typed::Coercion.coerce(field: Typed::Field.new(name: :name, type: String), value: 1)
+  def test_new_coercers_can_be_registered
+    Typed::Coercion.register_coercer(SimpleStringCoercer)
 
-    assert_success(result)
-    assert_payload("1", result)
+    assert_equal(SimpleStringCoercer, Typed::Coercion::CoercerRegistry.instance.select_coercer_by(type: String))
   end
 
-  def test_coercion_coerces_integers
-    result = Typed::Coercion.coerce(field: Typed::Field.new(name: :name, type: Integer), value: "1")
-
-    assert_success(result)
-    assert_payload(1, result)
-  end
-
-  def test_coercion_coerces_floats
-    result = Typed::Coercion.coerce(field: Typed::Field.new(name: :name, type: Float), value: "1.1")
+  def test_when_coercer_is_matched_coerce_coerces
+    result = Typed::Coercion.coerce(field: Typed::Field.new(name: :name, type: String), value: 1)
 
     assert_success(result)
-    assert_payload(1.1, result)
+    assert_payload("1", result)
   end
 
-  def test_when_coercer_isnt_matched_returns_failure
+  def test_when_coercer_isnt_matched_coerce_returns_failure
     result = Typed::Coercion.coerce(field: Typed::Field.new(name: :testing, type: Date), value: "testing")
 
     assert_failure(result)