fix bug with Rails 8.1 ERB compilation

Author: joelhawksley

docs/CHANGELOG.md

@@ -10,6 +10,10 @@ nav_order: 6
 
 ## main
 
+* Fix bug where error line numbers were incorrect in Rails 8.1.
+
+    *Joel Hawksley*
+
 ## 4.1.1
 
 * Add Consultport to list of companies using ViewComponent.

lib/view_component/template.rb

@@ -21,11 +21,21 @@ def initialize(component:, details:, lineno: nil, path: nil)
 
     class File < Template
       def initialize(component:, details:, path:)
+        # Rails 8.1 added a newline to the compiled ERB output in
+        # https://github.com/rails/rails/pull/53731
+        lineno = Rails::VERSION::STRING > "8.0" ? -1 : 0
+        lineno =
+          if Rails::VERSION::MAJOR == 8 && Rails::VERSION::MINOR > 0 && details.handler == :erb
+            - 1
+          else
+            0
+          end
+
         super(
           component: component,
           details: details,
           path: path,
-          lineno: 0
+          lineno: lineno
         )
       end
 
@@ -45,11 +55,20 @@ class Inline < Template
       def initialize(component:, inline_template:)
         details = ActionView::TemplateDetails.new(nil, inline_template.language.to_sym, nil, nil)
 
+        # Rails 8.1 added a newline to the compiled ERB output in
+        # https://github.com/rails/rails/pull/53731
+        lineno =
+          if Rails::VERSION::MAJOR == 8 && Rails::VERSION::MINOR > 0 && details.handler == :erb
+            inline_template.lineno - 1
+          else
+            inline_template.lineno
+          end
+
         super(
           component: component,
           details: details,
           path: inline_template.path,
-          lineno: inline_template.lineno,
+          lineno: lineno,
         )
 
         @source = inline_template.source.dup

test/sandbox/app/components/exception_in_slim_template_component.html.slim

@@ -0,0 +1,2 @@
+p
+  = a_method_that_does_not_exist_i_hope

test/sandbox/app/components/exception_in_slim_template_component.rb

@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+
+class ExceptionInSlimTemplateComponent < ViewComponent::Base
+end

test/sandbox/test/inline_template_test.rb

@@ -27,6 +27,18 @@ def initialize(name)
     end
   end
 
+  class InlineRaiseSlimComponent < ViewComponent::Base
+    attr_reader :name
+
+    slim_template <<~SLIM
+      = raise ArgumentError, "oh no"
+    SLIM
+
+    def initialize(name)
+      @name = name
+    end
+  end
+
   class InlineErbSubclassComponent < InlineErbComponent
     erb_template <<~ERB
       <h1>Hey, <%= name %>!</h1>
@@ -107,6 +119,14 @@ class InlineComponentDerivedFromComponentSupportingVariants < Level2Component
     assert_match %r{test/sandbox/test/inline_template_test.rb:22}, error.backtrace[0]
   end
 
+  test "error backtrace locations work in slim" do
+    error = assert_raises ArgumentError do
+      render_inline(InlineRaiseSlimComponent.new("Fox Mulder"))
+    end
+
+    assert_match %r{test/sandbox/test/inline_template_test.rb:34}, error.backtrace[0]
+  end
+
   test "renders inline slim templates" do
     render_inline(InlineSlimComponent.new("Fox Mulder"))
 

test/sandbox/test/rendering_test.rb

@@ -645,6 +645,16 @@ def test_backtrace_returns_correct_file_and_line_number
     assert_match %r{app/components/exception_in_template_component\.html\.erb:2}, error.backtrace[component_error_index]
   end
 
+  def test_backtrace_returns_correct_file_and_line_number_in_slim
+    error =
+      assert_raises NameError do
+        render_inline(ExceptionInSlimTemplateComponent.new)
+      end
+
+    component_error_index = (Rails::VERSION::STRING < "8.0") ? 0 : 1
+    assert_match %r{app/components/exception_in_slim_template_component\.html\.slim:2}, error.backtrace[component_error_index]
+  end
+
   def test_render_collection
     products = [Product.new(name: "Radio clock"), Product.new(name: "Mints")]
     render_inline(ProductComponent.with_collection(products, notice: "On sale"))