Merge pull request #2410 from ViewComponent/shared_view_context_in_test_helpers

Share the view context in tests

Author: camertron

docs/CHANGELOG.md

@@ -10,6 +10,7 @@ nav_order: 6
 
 ## main
 
+* Share the view context in tests to prevent out-of-order rendering issues for certain advanced use-cases, eg. testing instances of Rails' `FormBuilder`.
 * Fix double rendering issue for partials that yield.
 
     *Cameron Dutro*

lib/view_component/test_helpers.rb

@@ -38,9 +38,19 @@ def assert_component_rendered
     # @return [Nokogiri::HTML5]
     def render_inline(component, **args, &block)
       @page = nil
-      @rendered_content = vc_test_controller.view_context.render(component, args, &block)
+      @rendered_content = vc_test_view_context.render(component, args, &block)
 
-      Nokogiri::HTML5.fragment(@rendered_content)
+      fragment = Nokogiri::HTML5.fragment(@rendered_content)
+      @vc_test_view_context = nil
+      fragment
+    end
+
+    # Returns the view context used to render components in tests. Note that the view context
+    # is reset after each call to `render_inline`.
+    #
+    # @return [ActionView::Base]
+    def vc_test_view_context
+      @vc_test_view_context ||= vc_test_controller.view_context
     end
 
     # `JSON.parse`-d component output.
@@ -103,7 +113,7 @@ def render_preview(name, from: __vc_test_helpers_preview_class, params: {})
     # ```
     def render_in_view_context(...)
       @page = nil
-      @rendered_content = vc_test_controller.view_context.instance_exec(...)
+      @rendered_content = vc_test_view_context.instance_exec(...)
       Nokogiri::HTML5.fragment(@rendered_content)
     end
 

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

@@ -0,0 +1,3 @@
+<%= @builder.label :foo do %>
+  <%= content %>
+<% end %>

test/sandbox/app/components/custom_form_builder_component.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class CustomFormBuilderComponent < ViewComponent::Base
+  def initialize(builder:)
+    @builder = builder
+  end
+end

test/sandbox/test/rendering_test.rb

@@ -34,7 +34,7 @@ def test_render_collection_inline_allocations
     ViewComponent::CompileCache.cache.delete(ProductComponent)
     ProductComponent.__vc_ensure_compiled
 
-    allocations = {"3.5" => 76, "3.4" => 82, "3.3" => 86, "3.2" => 89..90}
+    allocations = {"3.5" => 66, "3.4" => 82, "3.3" => 86, "3.2" => 89..90}
 
     products = [Product.new(name: "Radio clock"), Product.new(name: "Mints")]
     notice = "On sale"

test/sandbox/test/test_helper_test.rb

@@ -43,4 +43,10 @@ def test_with_request_url_under_constraint
   def test_vc_test_controller_exists
     assert vc_test_controller.is_a?(ActionController::Base)
   end
+
+  def test_vc_test_view_context_is_shared_reference
+    builder = ActionView::Helpers::FormBuilder.new(nil, Object.new, vc_test_view_context, {})
+    render_inline(CustomFormBuilderComponent.new(builder: builder)) { "Label content" }
+    assert_selector("label[for=foo]", text: "Label content")
+  end
 end