Strip trailing whitespace in templates

docs/CHANGELOG.md

@@ -9,6 +9,10 @@ title: Changelog
 
 ## main
 
+* Add per-component config option for stripping newlines from templates before compilation.
+
+    *Cameron Dutro*
+
 * Add link to article by Matouš Borák.
 
     *Joel Hawksley*

docs/api.md

@@ -10,17 +10,35 @@ nav_order: 3
 
 ## Class methods
 
+### .strip_trailing_whitespace(value = true)
+
+Strips trailing whitespace from templates before compiling them.
+
+```ruby
+class MyComponent < ViewComponent::Base
+  strip_trailing_whitespace
+end
+```
+
+### .strip_trailing_whitespace? → [Boolean]
+
+Whether trailing whitespace will be stripped before compilation.
+
 ### .with_collection(collection, **args)
 
 Render a component for each element in a collection ([documentation](/guide/collections)):
 
-    render(ProductsComponent.with_collection(@products, foo: :bar))
+```ruby
+render(ProductsComponent.with_collection(@products, foo: :bar))
+```
 
 ### .with_collection_parameter(parameter)
 
 Set the parameter name used when rendering elements of a collection ([documentation](/guide/collections)):
 
-    with_collection_parameter :item
+```ruby
+with_collection_parameter :item
+```
 
 ## Instance methods
 
@@ -79,8 +97,10 @@ Returns HTML that has been escaped by the respective template handler.
 Subclass components that call `super` inside their template code will cause a
 double render if they emit the result:
 
-    <%= super %> # double-renders
-    <% super %> # does not double-render
+```erb
+<%= super %> # double-renders
+<% super %> # does not double-render
+```
 
 Calls `super`, returning `nil` to avoid rendering the result twice.
 
@@ -110,7 +130,9 @@ _Will be removed in v3.0.0._
 
 Parent class for generated components
 
-    config.view_component.component_parent_class = "MyBaseComponent"
+```ruby
+config.view_component.component_parent_class = "MyBaseComponent"
+```
 
 Defaults to nil. If this is falsy, generators will use
 "ApplicationComponent" if defined, "ViewComponent::Base" otherwise.
@@ -132,25 +154,33 @@ stated.
 
 Always generate a component with a sidecar directory:
 
-    config.view_component.generate.sidecar = true
+```ruby
+config.view_component.generate.sidecar = true
+```
 
 #### #stimulus_controller
 
 Always generate a Stimulus controller alongside the component:
 
-    config.view_component.generate.stimulus_controller = true
+```ruby
+config.view_component.generate.stimulus_controller = true
+```
 
 #### #locale
 
 Always generate translations file alongside the component:
 
-    config.view_component.generate.locale = true
+```ruby
+config.view_component.generate.locale = true
+```
 
 #### #distinct_locale_files
 
 Always generate as many translations files as available locales:
 
-    config.view_component.generate.distinct_locale_files = true
+```ruby
+config.view_component.generate.distinct_locale_files = true
+```
 
 One file will be generated for each configured `I18n.available_locales`,
 falling back to `[:en]` when no `available_locales` is defined.
@@ -159,7 +189,9 @@ falling back to `[:en]` when no `available_locales` is defined.
 
 Always generate preview alongside the component:
 
-     config.view_component.generate.preview = true
+```ruby
+config.view_component.generate.preview = true
+```
 
  Defaults to `false`.
 
@@ -193,7 +225,9 @@ Defaults to `/rails/view_components` when `show_previews` is enabled.
 
 Set if render monkey patches should be included or not in Rails <6.1:
 
-    config.view_component.render_monkey_patch_enabled = false
+```ruby
+config.view_component.render_monkey_patch_enabled = false
+```
 
 ### #show_previews
 
@@ -215,7 +249,9 @@ Defaults to `false`.
 
 Set the controller used for testing components:
 
-    config.view_component.test_controller = "MyTestController"
+```ruby
+config.view_component.test_controller = "MyTestController"
+```
 
 Defaults to ApplicationController. Can also be configured on a per-test
 basis using `with_controller_class`.
@@ -224,7 +260,9 @@ basis using `with_controller_class`.
 
 Path for component files
 
-    config.view_component.view_component_path = "app/my_components"
+```ruby
+config.view_component.view_component_path = "app/my_components"
+```
 
 Defaults to `app/components`.
 
@@ -253,6 +291,10 @@ render_inline(MyComponent.new)
 assert_text("Hello, World!")
 ```
 
+### #rendered_component → [String]
+
+Returns the result of a render_inline call.
+
 ### #with_controller_class(klass)
 
 Set the controller to be used while executing the given block,

docs/guide/templates.md

@@ -103,3 +103,19 @@ To render a parent component's template from a subclass, call `render_parent`:
   <% render_parent %>
 </div>
 ```
+
+## Trailing whitespace
+
+Code editors commonly add a trailing newline character to source files in keeping with the Unix standard. Including trailing whitespace in component templates can result in unwanted whitespace in the HTML, eg. if the component is rendered before the period at the end of a sentence.
+
+To strip trailing whitespace from component templates, use the `strip_trailing_whitespace` class method.
+
+```ruby
+class MyComponent < ViewComponent::Base
+  # do strip whitespace
+  strip_trailing_whitespace
+
+  # don't strip whitespace
+  strip_trailing_whitespace(false)
+end
+```

lib/view_component/base.rb

@@ -31,6 +31,10 @@ class Base < ActionView::Base
     class_attribute :content_areas
     self.content_areas = [] # class_attribute:default doesn't work until Rails 5.2
 
+    # Config option that strips trailing whitespace in templates before compiling them.
+    class_attribute :__vc_strip_trailing_whitespace, instance_accessor: false, instance_predicate: false
+    self.__vc_strip_trailing_whitespace = false # class_attribute:default doesn't work until Rails 5.2
+
     attr_accessor :__vc_original_view_context
 
     # Components render in their own view context. Helpers and other functionality
@@ -135,8 +139,10 @@ def perform_render
     # Subclass components that call `super` inside their template code will cause a
     # double render if they emit the result:
     #
-    #     <%= super %> # double-renders
-    #     <% super %> # does not double-render
+    # ```erb
+    # <%= super %> # double-renders
+    # <% super %> # does not double-render
+    # ```
     #
     # Calls `super`, returning `nil` to avoid rendering the result twice.
     def render_parent
@@ -315,7 +321,9 @@ def content_evaluated?
 
     # Set the controller used for testing components:
     #
-    #     config.view_component.test_controller = "MyTestController"
+    # ```ruby
+    # config.view_component.test_controller = "MyTestController"
+    # ```
     #
     # Defaults to ApplicationController. Can also be configured on a per-test
     # basis using `with_controller_class`.
@@ -325,21 +333,27 @@ def content_evaluated?
 
     # Set if render monkey patches should be included or not in Rails <6.1:
     #
-    #     config.view_component.render_monkey_patch_enabled = false
+    # ```ruby
+    # config.view_component.render_monkey_patch_enabled = false
+    # ```
     #
     mattr_accessor :render_monkey_patch_enabled, instance_writer: false, default: true
 
     # Path for component files
     #
-    #     config.view_component.view_component_path = "app/my_components"
+    # ```ruby
+    # config.view_component.view_component_path = "app/my_components"
+    # ```
     #
     # Defaults to `app/components`.
     #
     mattr_accessor :view_component_path, instance_writer: false, default: "app/components"
 
     # Parent class for generated components
     #
-    #     config.view_component.component_parent_class = "MyBaseComponent"
+    # ```ruby
+    # config.view_component.component_parent_class = "MyBaseComponent"
+    # ```
     #
     # Defaults to nil. If this is falsy, generators will use
     # "ApplicationComponent" if defined, "ViewComponent::Base" otherwise.
@@ -355,25 +369,33 @@ def content_evaluated?
     #
     # Always generate a component with a sidecar directory:
     #
-    #     config.view_component.generate.sidecar = true
+    # ```ruby
+    # config.view_component.generate.sidecar = true
+    # ```
     #
     # #### #stimulus_controller
     #
     # Always generate a Stimulus controller alongside the component:
     #
-    #     config.view_component.generate.stimulus_controller = true
+    # ```ruby
+    # config.view_component.generate.stimulus_controller = true
+    # ```
     #
     # #### #locale
     #
     # Always generate translations file alongside the component:
     #
-    #     config.view_component.generate.locale = true
+    # ```ruby
+    # config.view_component.generate.locale = true
+    # ```
     #
     # #### #distinct_locale_files
     #
     # Always generate as many translations files as available locales:
     #
-    #     config.view_component.generate.distinct_locale_files = true
+    # ```ruby
+    # config.view_component.generate.distinct_locale_files = true
+    # ```
     #
     # One file will be generated for each configured `I18n.available_locales`,
     # falling back to `[:en]` when no `available_locales` is defined.
@@ -382,7 +404,9 @@ def content_evaluated?
     #
     # Always generate preview alongside the component:
     #
-    #      config.view_component.generate.preview = true
+    # ```ruby
+    # config.view_component.generate.preview = true
+    # ```
     #
     #  Defaults to `false`.
     mattr_accessor :generate, instance_writer: false, default: ActiveSupport::OrderedOptions.new(false)
@@ -436,7 +460,9 @@ def _sidecar_files(extensions)
 
       # Render a component for each element in a collection ([documentation](/guide/collections)):
       #
-      #     render(ProductsComponent.with_collection(@products, foo: :bar))
+      # ```ruby
+      # render(ProductsComponent.with_collection(@products, foo: :bar))
+      # ```
       #
       # @param collection [Enumerable] A list of items to pass the ViewComponent one at a time.
       # @param args [Arguments] Arguments to pass to the ViewComponent every time.
@@ -532,13 +558,35 @@ def identifier
 
       # Set the parameter name used when rendering elements of a collection ([documentation](/guide/collections)):
       #
-      #     with_collection_parameter :item
+      # ```ruby
+      # with_collection_parameter :item
+      # ```
       #
       # @param parameter [Symbol] The parameter name used when rendering elements of a collection.
       def with_collection_parameter(parameter)
         @provided_collection_parameter = parameter
       end
 
+      # Strips trailing whitespace from templates before compiling them.
+      #
+      # ```ruby
+      # class MyComponent < ViewComponent::Base
+      #   strip_trailing_whitespace
+      # end
+      # ```
+      #
+      # @param value [Boolean] Whether or not to strip newlines.
+      def strip_trailing_whitespace(value = true)
+        self.__vc_strip_trailing_whitespace = value
+      end
+
+      # Whether trailing whitespace will be stripped before compilation.
+      #
+      # @return [Boolean]
+      def strip_trailing_whitespace?
+        self.__vc_strip_trailing_whitespace
+      end
+
       # Ensure the component initializer accepts the
       # collection parameter. By default, we don't
       # validate that the default parameter name

lib/view_component/compiler.rb

@@ -238,6 +238,7 @@ def variants_from_inline_calls(calls)
     def compiled_template(file_path)
       handler = ActionView::Template.handler_for_extension(File.extname(file_path).gsub(".", ""))
       template = File.read(file_path)
+      template.rstrip! if component_class.strip_trailing_whitespace?
 
       if handler.method(:call).parameters.length > 1
         handler.call(component_class, template)

lib/view_component/test_helpers.rb

@@ -32,6 +32,9 @@ def refute_component_rendered
     # @private
     attr_reader :rendered_content
 
+    # Returns the result of a render_inline call.
+    #
+    # @return [String]
     def rendered_component
       ViewComponent::Deprecation.warn(
         "`rendered_component` is deprecated and will be removed in v3.0.0. " \

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

@@ -0,0 +1 @@
+Hello, world!

test/sandbox/app/components/trailing_whitespace_component.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class TrailingWhitespaceComponent < ViewComponent::Base
+  strip_trailing_whitespace
+end