Preserve request routing context when rendering previews

docs/CHANGELOG.md

@@ -10,6 +10,10 @@ nav_order: 6
 
 ## main
 
+* Restore request-dependent URL generation when using `render_preview` inside `with_request_url`.
+
+    *Joel Hawksley*
+
 * Speed up cold cache digests by skipping the `# Template Dependency:` scan for sources that declare none, and by not translating class names in synthetic templates, which only declare paths.
 
     *Erik Axel Nielsen*

docs/guide/testing.md

@@ -231,6 +231,15 @@ class ExampleComponentTest < ViewComponent::TestCase
 end
 ```
 
+`with_request_url` also applies to request-dependent URL generation inside `render_preview`:
+
+```ruby
+with_request_url "/products/42" do
+  render_preview(:default, from: ExampleComponentPreview)
+  assert_link "French", href: "/products/42?locale=fr"
+end
+```
+
 ## Setting `request.host`
 
 Since 3.3.0

lib/view_component/test_helpers.rb

@@ -89,14 +89,16 @@ def render_preview(name, from: __vc_test_helpers_preview_class, params: {})
       controller_class = Rails.application.config.view_component.previews.controller.constantize
       request = ActionDispatch::TestRequest.new(vc_test_request.env.dup)
       query_parameters = vc_test_request.query_parameters.deep_dup.merge(params.stringify_keys)
-      request.path_parameters = vc_test_request.path_parameters.except(*params.keys.map(&:to_sym)).merge(
-        controller: controller_class.controller_path,
-        action: "previews",
-        path: "#{from.preview_name}/#{name}"
-      )
+      request.path_parameters = vc_test_request.path_parameters.deep_dup
       request.set_header("action_dispatch.request.query_parameters", query_parameters)
       request.set_header(Rack::QUERY_STRING, query_parameters.to_query)
       previews_controller = __vc_test_helpers_build_controller(controller_class, request: request)
+      # Dispatch the preview without replacing the request's URL generation context.
+      previews_controller.params = request.parameters.merge(params.stringify_keys).merge(
+        "controller" => controller_class.controller_path,
+        "action" => "previews",
+        "path" => "#{from.preview_name}/#{name}"
+      )
       previews_controller.set_response!(ActionDispatch::Response.new)
       previews_controller.process(:previews)
       @rendered_content = previews_controller.response.body

test/sandbox/app/components/request_url_component.rb

@@ -2,6 +2,10 @@
 
 class RequestUrlComponent < ViewComponent::Base
   def call
-    content_tag(:span, request.path, class: "path") + content_tag(:span, request.fullpath, class: "fullpath")
+    content_tag(:span, request.path, class: "path") +
+      content_tag(:span, request.fullpath, class: "fullpath") +
+      content_tag(:span, content, class: "content") +
+      link_to("Request-dependent link", url_for(bar: "baz")) +
+      link_to("Absolute request-dependent link", url_for(bar: "baz", only_path: false))
   end
 end

test/sandbox/config/routes.rb

@@ -8,6 +8,7 @@
   get :content, to: "integration_examples#content"
   get :variants, to: "integration_examples#variants"
   get :products, to: "integration_examples#products"
+  get "products/:id", to: "integration_examples#products"
   get :inline_products, to: "integration_examples#inline_products"
   get :cached, to: "integration_examples#cached"
   get :render_check, to: "integration_examples#render_check"

test/sandbox/test/components/previews/request_url_component_preview.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class RequestUrlComponentPreview < ViewComponent::Preview
+  def default
+    render(RequestUrlComponent.new)
+  end
+
+  def with_id(id:)
+    render(RequestUrlComponent.new) { id }
+  end
+end

test/sandbox/test/components/render_preview_test.rb

@@ -63,6 +63,45 @@ def test_render_preview_preserves_the_original_request_parameters
     end
   end
 
+  def test_render_preview_uses_the_request_url_for_request_dependent_links
+    with_request_url("/products") do
+      fragment = render_preview(:default, from: RequestUrlComponentPreview)
+
+      assert_equal "/products", vc_test_request.path
+      assert_selector(".path", text: "/products")
+      assert_equal "/products?bar=baz", fragment.at_css("a")["href"]
+    end
+  end
+
+  def test_render_preview_preserves_route_parameters_when_preview_parameters_overlap
+    with_request_url("/products/42?id=query-id") do
+      render_preview(:with_id, from: RequestUrlComponentPreview, params: {id: "preview-id"})
+
+      assert_selector(".content", exact_text: "preview-id")
+      assert_link "Request-dependent link", href: "/products/42?bar=baz", exact: true
+      assert_equal "42", vc_test_request.path_parameters[:id]
+      assert_equal "query-id", vc_test_request.query_parameters["id"]
+    end
+  end
+
+  def test_render_preview_parameters_override_request_query_parameters
+    with_request_url("/products?title=Query+title") do
+      render_preview(:with_params, from: PreviewComponentPreview, params: {title: "Preview title"})
+
+      assert_text "Preview title"
+      assert_no_text "Query title"
+      assert_equal "Query title", vc_test_request.query_parameters["title"]
+    end
+  end
+
+  def test_render_preview_preserves_the_request_host_and_protocol_for_links
+    with_request_url("/products/42", host: "app.example.com:8443", protocol: :https) do
+      render_preview(:default, from: RequestUrlComponentPreview)
+
+      assert_link "Absolute request-dependent link", href: "https://app.example.com:8443/products/42?bar=baz"
+    end
+  end
+
   def test_render_preview_runs_locale_callbacks_and_restores_the_locale
     render_args = PreviewComponentPreview.method(:render_args)
     locales = []

test/sandbox/test/integration_test.rb

@@ -134,8 +134,8 @@ def test_inherited_component_with_call_method_does_not_recompile_superclass
       assert_select "div", "hello world"
       assert_response :success
     ensure
-      UncompilableComponent.singleton_class.silence_redefinition_of_method(:__vc_compile)
-      UncompilableComponent.define_singleton_method(:__vc_compile, original_method)
+      original_method.receiver.singleton_class.silence_redefinition_of_method(:__vc_compile)
+      original_method.receiver.define_singleton_method(:__vc_compile, original_method)
     end
   end