Add new helper API

docs/CHANGELOG.md

@@ -18,6 +18,9 @@ nav_order: 5
 
     *Alexandre Ignjatovic*
 
+* Add `use_helper` api
+
+    *Reegan Viljoen*
 * Reduce UnboundMethod objects by memoizing initialize_parameters
 
     *Rainer Borene*

lib/view_component/base.rb

@@ -12,6 +12,7 @@
 require "view_component/slotable"
 require "view_component/translatable"
 require "view_component/with_content_helper"
+require "view_component/use_helpers"
 
 module ViewComponent
   class Base < ActionView::Base

lib/view_component/test_helpers.rb

@@ -190,6 +190,29 @@ def with_request_url(path, host: nil)
       @vc_test_controller = old_controller
     end
 
+    # Set the controller helpers to be used while executing the given block,
+    #
+    # ```ruby
+    # with_helpers(UsersHelper) do
+    #   render_inline(MyComponent.new)
+    # end
+    # ```
+    #
+    # @param *args [Array<Module>] The helpers to be used.
+    def with_helpers(*args)
+      args.each do |helper_mthd|
+        vc_test_controller.class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+          def #{helper_mthd}
+            return #{return send(helper_mthd)}
+          end
+
+          ruby2_keywords(:'#{helper_mthd}')
+        RUBY
+        vc_test_controller.class.helper_method helper_mthd
+      end
+      yield
+    end
+
     # Access the controller used by `render_inline`:
     #
     # ```ruby

lib/view_component/use_helpers.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module ViewComponent::UseHelpers
+  extend ActiveSupport::Concern
+
+  class_methods do
+    def use_helpers(*args)
+      args.each do |helper_mtd|
+        class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+          def #{helper_mtd}(*args, &block)
+            raise HelpersCalledBeforeRenderError if view_context.nil?
+            __vc_original_view_context&.send(#{helper_mtd.inspect}, *args, &block) || view_context.send(#{helper_mtd.inspect}, *args, &block)
+          end
+        RUBY
+
+        ruby2_keywords(helper_mtd) if respond_to?(:ruby2_keywords, true)
+      end
+    end
+  end
+end

test/sandbox/app/components/use_helpers_component.html.erb

@@ -0,0 +1,3 @@
+<div class="helper__message">
+  <%= test_helper %>
+</div>

test/sandbox/app/components/use_helpers_component.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class UseHelpersComponent < ViewComponent::Base
+  include ViewComponent::UseHelpers
+
+  use_helpers :test_helper
+end

test/sandbox/test/rendering_test.rb

@@ -1094,4 +1094,17 @@ def test_content_security_policy_nonce
 
     assert_selector("script", text: "\n//<![CDATA[\n  \"alert('hello')\"\n\n//]]>\n", visible: :hidden)
   end
+
+  def test_use_helper
+    with_helpers(:test_helper) do
+      render_inline(UseHelpersComponent.new)
+      assert_selector ".helper__message", text: "Hello helper method"
+    end
+  end
+
+  private
+
+  def test_helper
+    "Hello helper method"
+  end
 end