Fix compensation of ERB line numbers on the next major Rails version

docs/CHANGELOG.md

@@ -10,6 +10,10 @@ nav_order: 6
 
 ## main
 
+* Keep compensating ERB line numbers for the annotation newline on future major Rails versions. The version check required a minor version above 0, so it would have stopped compensating on the next major's `.0` release.
+
+    *Clément Joubert*
+
 ## 4.23.0
 
 * Restore request-dependent URL generation when using `render_preview` inside `with_request_url`.

lib/view_component/template.rb

@@ -5,6 +5,10 @@ class Template
     DEFAULT_FORMAT = :html
     private_constant :DEFAULT_FORMAT
 
+    # Rails 8.1 added a newline to compiled ERB output (rails/rails#53731).
+    ERB_NEWLINE_RAILS_VERSION = Gem::Version.new("8.1.0.alpha")
+    private_constant :ERB_NEWLINE_RAILS_VERSION
+
     DataWithSource = Struct.new(:format, :identifier, :short_identifier, :type)
 
     attr_reader :details, :path
@@ -209,7 +213,7 @@ def normalized_variant_name
     attr_reader :lineno
 
     def erb_newline_compensation_needed?
-      Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0 &&
+      Rails.gem_version >= ERB_NEWLINE_RAILS_VERSION &&
         details.handler == :erb &&
         annotated?
     end

test/sandbox/test/inline_template_test.rb

@@ -249,7 +249,7 @@ def call
   # is enabled. This test verifies that components can be compiled and rendered when
   # coverage is running.
   test "file-based templates compile without segfault when coverage is running" do
-    skip unless Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0
+    skip unless Rails.gem_version >= Gem::Version.new("8.1.0.alpha")
 
     with_new_cache do
       with_coverage_running do
@@ -267,7 +267,7 @@ def call
   # Regression test for segfault when coverage is running but annotations are DISABLED.
   # This is the common case in CI environments.
   test "file-based templates compile without segfault when coverage is running and annotations disabled" do
-    skip unless Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0
+    skip unless Rails.gem_version >= Gem::Version.new("8.1.0.alpha")
 
     without_template_annotations do
       with_coverage_running do
@@ -284,7 +284,7 @@ def call
   end
 
   test "inline templates compile without segfault when coverage is running" do
-    skip unless Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0
+    skip unless Rails.gem_version >= Gem::Version.new("8.1.0.alpha")
 
     with_new_cache do
       with_coverage_running do

test/sandbox/test/rendering_test.rb

@@ -642,7 +642,7 @@ def test_backtrace_returns_correct_file_and_line_number
         render_inline(ExceptionInTemplateComponent.new)
       end
 
-    component_error_index = (Rails::VERSION::STRING < "8.0") ? 0 : 1
+    component_error_index = (Rails::VERSION::MAJOR < 8) ? 0 : 1
     assert_match %r{app/components/exception_in_template_component\.html\.erb:2}, error.backtrace[component_error_index]
   end
 
@@ -652,7 +652,7 @@ def test_backtrace_returns_correct_file_and_line_number_in_slim
         render_inline(ExceptionInSlimTemplateComponent.new)
       end
 
-    component_error_index = (Rails::VERSION::STRING < "8.0") ? 0 : 1
+    component_error_index = (Rails::VERSION::MAJOR < 8) ? 0 : 1
     assert_match %r{app/components/exception_in_slim_template_component\.html\.slim:2}, error.backtrace[component_error_index]
   end
 

test/sandbox/test/template_annotation_test.rb

@@ -9,7 +9,7 @@ class TemplateAnnotationTest < ViewComponent::TestCase
   # conditions, otherwise backtraces point at the wrong line and, when coverage
   # is running, template source is stripped away.
   def setup
-    skip unless Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0
+    skip unless Rails.gem_version >= Gem::Version.new("8.1.0.alpha")
   end
 
   def teardown
@@ -72,3 +72,37 @@ def with_coverage_running
     Coverage.result unless already_running
   end
 end
+
+# The version check doesn't depend on the installed Rails, so it runs on every
+# version, unlike the tests above.
+class TemplateAnnotationRailsVersionTest < ActiveSupport::TestCase
+  def test_line_numbers_are_compensated_on_later_major_versions
+    template = ViewComponent::Template::File.new(
+      component: RaisingFormatsComponent,
+      details: ActionView::TemplateDetails.new(nil, :erb, :html, nil),
+      path: "#{Rails.root}/app/components/raising_formats_component.html.erb"
+    )
+
+    with_rails_version("9.0.0") { assert template.send(:erb_newline_compensation_needed?) }
+    with_rails_version("8.0.3") { refute template.send(:erb_newline_compensation_needed?) }
+  end
+
+  private
+
+  def with_rails_version(version)
+    major, minor = version.split(".").map(&:to_i)
+    original = {MAJOR: Rails::VERSION::MAJOR, MINOR: Rails::VERSION::MINOR, STRING: Rails::VERSION::STRING}
+
+    replace_version_constants(MAJOR: major, MINOR: minor, STRING: version)
+    yield
+  ensure
+    replace_version_constants(**original)
+  end
+
+  def replace_version_constants(**constants)
+    constants.each do |name, value|
+      Rails::VERSION.send(:remove_const, name)
+      Rails::VERSION.const_set(name, value)
+    end
+  end
+end