Address review feedback: strip annotation line instead of adjusting lineno

- Remove coverage_running? check from Inline class (inline templates start
  at line 2+, so subtracting 1 won't result in negative line numbers)
- For File templates, strip the first line of compiled source when coverage
  is running AND annotations are enabled, instead of using lineno=1
- Add regression tests for coverage segfault fix

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: george-bit

lib/view_component/template.rb

@@ -21,13 +21,21 @@ def initialize(component:, details:, lineno: nil, path: nil)
 
     class File < Template
       def initialize(component:, details:, path:)
+        @strip_annotation_line = false
+
         # Rails 8.1 added a newline to compiled ERB output (rails/rails#53731).
         # Use -1 to compensate for correct line numbers in stack traces.
         # However, negative line numbers cause segfaults when Ruby's coverage
-        # is enabled (bugs.ruby-lang.org/issues/19363), so use 1 in that case.
+        # is enabled (bugs.ruby-lang.org/issues/19363). In that case, strip the
+        # annotation line from compiled source instead.
         lineno =
           if Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0 && details.handler == :erb
-            coverage_running? ? 1 : -1
+            if coverage_running? && ActionView::Base.annotate_rendered_view_with_filenames
+              @strip_annotation_line = true
+              0
+            else
+              -1
+            end
           else
             0
           end
@@ -48,6 +56,16 @@ def type
       def source
         ::File.read(@path)
       end
+
+      private
+
+      def compiled_source
+        result = super
+        # Strip the annotation line to maintain correct line numbers when coverage
+        # is running (avoids segfault from negative lineno)
+        result = result.sub(/\A[^\n]*\n/, "") if @strip_annotation_line
+        result
+      end
     end
 
     class Inline < Template
@@ -58,11 +76,11 @@ def initialize(component:, inline_template:)
 
         # Rails 8.1 added a newline to compiled ERB output (rails/rails#53731).
         # Subtract 1 to compensate for correct line numbers in stack traces.
-        # However, negative line numbers cause segfaults when Ruby's coverage
-        # is enabled (bugs.ruby-lang.org/issues/19363), so skip the adjustment in that case.
+        # Inline templates start at line 2+ (defined inside a class), so this
+        # won't result in negative line numbers that cause segfaults with coverage.
         lineno =
           if Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0 && details.handler == :erb
-            coverage_running? ? inline_template.lineno : inline_template.lineno - 1
+            inline_template.lineno - 1
           else
             inline_template.lineno
           end

test/sandbox/test/inline_template_test.rb

@@ -189,4 +189,54 @@ class InlineComponentDerivedFromComponentSupportingVariants < Level2Component
 
     assert_selector(".greeting-container h1", text: "Hello, Fox Mulder!")
   end
+
+  # Regression test for https://github.com/ViewComponent/view_component/issues/2540
+  # Negative lineno values in class_eval cause segfaults when Ruby's Coverage module
+  # 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
+
+    with_new_cache do
+      with_coverage_running do
+        # Force recompilation with coverage "enabled"
+        ViewComponent::CompileCache.cache.delete(ErbComponent)
+
+        # This would segfault before the fix due to negative lineno
+        render_inline(ErbComponent.new(message: "Foo bar"))
+
+        assert_selector("div", text: "Foo bar")
+      end
+    end
+  end
+
+  test "inline templates compile without segfault when coverage is running" do
+    skip unless Rails::VERSION::MAJOR >= 8 && Rails::VERSION::MINOR > 0
+
+    with_new_cache do
+      with_coverage_running do
+        # Force recompilation with coverage "enabled"
+        ViewComponent::CompileCache.cache.delete(InlineRaiseErbComponent)
+
+        # Inline templates should still work (lineno is 2+, so -1 won't be negative)
+        error = assert_raises ArgumentError do
+          render_inline(InlineRaiseErbComponent.new("Fox Mulder"))
+        end
+
+        # Verify backtrace still points to correct line
+        assert_match %r{test/sandbox/test/inline_template_test.rb:22}, error.backtrace[0]
+      end
+    end
+  end
+
+  private
+
+  def with_coverage_running
+    require "coverage"
+    already_running = Coverage.running?
+    Coverage.start unless already_running
+    yield
+  ensure
+    Coverage.result unless already_running
+  end
 end