Allow I18n in render lifecycle

docs/CHANGELOG.md

@@ -10,6 +10,12 @@ nav_order: 6
 
 ## main
 
+* Allow I18n calls in `render?`.
+* Split render lifecycle into separate methods, to be able to test component methods that rely on `t(...)` directly.
+* Added `setup_render` test helper to allow testing of component methods that rely on `t(...)` without rendering the component.
+
+    *23tux*
+
 * Resolve deprecation warning for `ActiveSupport::Configurable`.
 
     *Simon Fish*

docs/api.md

@@ -301,6 +301,23 @@ render_inline(MyComponent.new)
 assert_text("Hello, World!")
 ```
 
+### `#setup_render(component)` → [ViewComponent::Base]
+
+Triggers the render setup of a component without actually rendering it.
+The method is also called internally by `#render_in` when a component is rendered.
+Useful for testing methods of components that need access to the view context or the `@virtual_path` variable like I18n's `t(...)` helper.
+
+```ruby
+class MyComponent < ViewComponent::Base
+  def message
+    t("hello.world")
+  end
+end
+
+component = setup_render(MyComponent.new)
+assert_equal(component.message, "Hello, World!")
+```
+
 ### `#render_preview(name, from: __vc_test_helpers_preview_class, params: {})` → [Nokogiri::HTML5]
 
 Render a preview inline. Internally sets `page` to be a `Capybara::Node::Simple`,

lib/view_component/base.rb

@@ -102,6 +102,14 @@ def initialize
     #
     # @return [String]
     def render_in(view_context, &block)
+      setup_render(view_context, &block)
+      before_render
+      perform_render
+    ensure
+      teardown_render(view_context)
+    end
+
+    def setup_render(view_context, &block)
       self.class.__vc_compile(raise_errors: true)
 
       @view_context = view_context
@@ -123,7 +131,7 @@ def render_in(view_context, &block)
 
       # For caching, such as #cache_if
       @current_template = nil unless defined?(@current_template)
-      old_current_template = @current_template
+      @old_current_template = @current_template
 
       if block && defined?(@__vc_content_set_by_with_content)
         raise DuplicateContentError.new(self.class.name)
@@ -132,13 +140,15 @@ def render_in(view_context, &block)
       @__vc_content_evaluated = false
       @__vc_render_in_block = block
 
-      before_render
+      @view_context.instance_variable_set(:@virtual_path, virtual_path)
+      self
+    end
 
+    def perform_render
       if render?
         value = nil
 
         @output_buffer.with_buffer do
-          @view_context.instance_variable_set(:@virtual_path, virtual_path)
 
           rendered_template =
             around_render do
@@ -162,8 +172,11 @@ def render_in(view_context, &block)
       else
         ""
       end
-    ensure
+    end
+
+    def teardown_render(view_context)
       view_context.instance_variable_set(:@virtual_path, @old_virtual_path)
+      old_current_template = remove_instance_variable(:@current_template) if defined?(@current_template)
       @current_template = old_current_template
     end
 

lib/view_component/test_helpers.rb

@@ -45,6 +45,10 @@ def render_inline(component, **args, &block)
       fragment
     end
 
+    def setup_render(component)
+      component.setup_render(vc_test_view_context)
+    end
+
     # Returns the view context used to render components in tests. Note that the view context
     # is reset after each call to `render_inline`.
     #

test/sandbox/config/locales/en.yml

@@ -24,3 +24,7 @@ en:
 
   my_component:
     message: "OH NO! (you shouldn't see me)"
+
+  rendering_test:
+    i18n_test_component:
+      message: "I can be called in render?"

test/sandbox/test/rendering_test.rb

@@ -20,7 +20,7 @@ def test_render_inline_allocations
     MyComponent.__vc_ensure_compiled
 
     with_instrumentation_enabled_option(false) do
-      assert_allocations({"3.5" => 67, "3.4" => 72..74, "3.3" => 72, "3.2" => 75..76}) do
+      assert_allocations({"3.5" => 67, "3.4" => 72..74, "3.3" => 72..75, "3.2" => 71..76}) do
         render_inline(MyComponent.new)
       end
     end
@@ -34,7 +34,7 @@ def test_render_collection_inline_allocations
     ViewComponent::CompileCache.cache.delete(ProductComponent)
     ProductComponent.__vc_ensure_compiled
 
-    allocations = {"3.5" => 66, "3.4" => 70..82, "3.3" => 86, "3.2" => 89..90}
+    allocations = {"3.5" => 66, "3.4" => 70..82, "3.3" => 86, "3.2" => 70..90}
 
     products = [Product.new(name: "Radio clock"), Product.new(name: "Mints")]
     notice = "On sale"
@@ -1322,4 +1322,30 @@ def test_render_partial_with_yield
     render_inline(PartialWithYieldComponent.new)
     assert_text "hello world", exact: true, normalize_ws: true
   end
+
+  class I18nTestComponent < ViewComponent::Base
+    def message
+      t(".message")
+    end
+
+    def render?
+      message
+    end
+
+    def call
+      content_tag :div, t(".message")
+    end
+  end
+
+  def test_i18n_in_render_hook
+    vc_test_request.params[:hello] = "world"
+    render_inline(I18nTestComponent.new)
+
+    assert_selector("div", text: I18n.t("rendering_test.i18n_test_component.message"))
+  end
+
+  def test_render_lifecycle_hooks
+    component = setup_render(I18nTestComponent.new)
+    assert_equal(component.message, I18n.t("rendering_test.i18n_test_component.message"))
+  end
 end