BREAKING: Allow slots to be redefined, removing RedefinedSlotError

Author: joelhawksley

docs/CHANGELOG.md

@@ -10,6 +10,24 @@ nav_order: 6
 
 ## main
 
+* BREAKING: Allow slots to be redefined, removing `RedefinedSlotError`. The following is now possible:
+
+    ```ruby
+    class ButtonComponent < ViewComponent::Base
+      renders_many :leading_items, types: {
+        icon: IconComponent,
+        svg: SvgComponent
+      }
+    end
+
+    class SpecialButtonComponent < ButtonComponent
+      renders_many :leading_items, types: {
+        svg: SvgComponent,
+        checkbox: CheckboxComponent
+      }
+    end
+    ```
+
 ## 4.0.0.rc1
 
 Almost six years after releasing [v1.0.0](https://github.com/ViewComponent/view_component/releases/tag/v1.0.0), we're proud to ship the first release candidate of ViewComponent 4. This release marks a shift towards a Long Term Support model for the project, having reached significant feature maturity. While contributions are always welcome, we're unlikely to accept further breaking changes or major feature additions.

lib/view_component/errors.rb

@@ -125,16 +125,6 @@ def initialize(klass_name, slot_name)
     end
   end
 
-  class RedefinedSlotError < StandardError
-    MESSAGE =
-      "COMPONENT declares the SLOT_NAME slot multiple times.\n\n" \
-      "To fix this issue, choose a different slot name."
-
-    def initialize(klass_name, slot_name)
-      super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("SLOT_NAME", slot_name.to_s))
-    end
-  end
-
   class ReservedSingularSlotNameError < InvalidSlotNameError
     MESSAGE =
       "COMPONENT declares a slot named SLOT_NAME, which is a reserved word in the ViewComponent framework.\n\n" \

lib/view_component/slotable.rb

@@ -311,7 +311,6 @@ def __vc_validate_plural_slot_name(slot_name)
         __vc_raise_if_slot_name_uncountable(slot_name)
         __vc_raise_if_slot_conflicts_with_call(slot_name)
         __vc_raise_if_slot_ends_with_question_mark(slot_name)
-        __vc_raise_if_slot_registered(slot_name)
       end
 
       def __vc_validate_singular_slot_name(slot_name)
@@ -325,13 +324,6 @@ def __vc_validate_singular_slot_name(slot_name)
 
         __vc_raise_if_slot_conflicts_with_call(slot_name)
         __vc_raise_if_slot_ends_with_question_mark(slot_name)
-        __vc_raise_if_slot_registered(slot_name)
-      end
-
-      def __vc_raise_if_slot_registered(slot_name)
-        if registered_slots.key?(slot_name)
-          raise RedefinedSlotError.new(name, slot_name)
-        end
       end
 
       def __vc_raise_if_slot_ends_with_question_mark(slot_name)

test/sandbox/app/components/slots_subclass_component.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class SlotsSubclassComponent < SlotsComponent
+  renders_one :title, ->(&block) do
+    content_tag :h1 do
+      block.call
+    end
+  end
+end

test/sandbox/test/slotable_test.rb

@@ -38,8 +38,6 @@ def test_renders_slots
 
     assert_selector(".title", text: "This is my title!")
 
-    assert_selector(".subtitle", text: "This is my subtitle!")
-
     assert_selector(".tab", text: "Tab A")
     assert_selector(".tab", text: "Tab B")
 
@@ -137,15 +135,6 @@ def test_renders_slots_template_raise_with_unknown_slot
     end
   end
 
-  def test_sub_component_raise_with_duplicate_slot_name
-    exception =
-      assert_raises ViewComponent::RedefinedSlotError do
-        SlotsComponent.renders_one :title
-      end
-
-    assert_includes exception.message, "declares the title slot multiple times"
-  end
-
   def test_sub_component_with_positional_args
     render_inline(SlotsWithPosArgComponent.new) do |component|
       component.with_item("my item", classes: "hello") { "My rad item" }
@@ -647,36 +636,28 @@ def test_component_delegation_slots_work_with_helpers
     assert_equal 1, PartialHelper::State.calls
   end
 
-  def test_lambda_slot_content_can_be_provided_via_a_block
-    render_inline LambdaSlotComponent.new do |component|
-      component.with_header(classes: "some-class") do
-        "This is a header!"
+  def test_subclass_can_redefine_slot
+    render_inline(SlotsSubclassComponent.new(classes: "mt-4")) do |component|
+      component.with_title do
+        "This is my title!"
       end
-    end
-
-    assert_selector("h1.some-class", text: "This is a header!")
-  end
-
-  def test_raises_error_on_conflicting_slot_names
-    error = assert_raises ViewComponent::RedefinedSlotError do
-      Class.new(ViewComponent::Base) do
-        renders_one :conflicting_item
-        renders_many :conflicting_items
+      component.with_subtitle do
+        "This is my subtitle!"
       end
     end
 
-    assert_includes error.message, "conflicting_item slot multiple times"
+    assert_selector("h1", text: "This is my title!")
+    assert_selector(".subtitle", text: "This is my subtitle!")
   end
 
-  def test_raises_error_on_conflicting_slot_names_in_reverse_order
-    error = assert_raises ViewComponent::RedefinedSlotError do
-      Class.new(ViewComponent::Base) do
-        renders_many :conflicting_items
-        renders_one :conflicting_item
+  def test_lambda_slot_content_can_be_provided_via_a_block
+    render_inline LambdaSlotComponent.new do |component|
+      component.with_header(classes: "some-class") do
+        "This is a header!"
       end
     end
 
-    assert_includes error.message, "conflicting_items slot multiple times"
+    assert_selector("h1.some-class", text: "This is a header!")
   end
 
   def test_slots_dont_interfere_with_content