Fix coverage(eval) segfault when annotations are disabled

[joshsadam]

What are you trying to accomplish?

Prevent a segfault when running with Ruby coverage of eval'd code enabled (for example SimpleCov.enable_coverage_for_eval) on Rails 8.1 ERB templates with ActionView::Base.annotate_rendered_view_with_filenames = false.

The current logic can still pass lineno = -1 to class_eval in this case, which triggers a Ruby crash in branch coverage instrumentation.

What approach did you choose and why?

Two targeted changes:

1. In Template::File, when coverage_running? is true, always avoid negative line numbers by using lineno = 0.
2. Keep annotation stripping conditional on ActionView::Base.annotate_rendered_view_with_filenames so stack trace behavior remains unchanged where annotations are enabled.

This preserves existing behavior outside of coverage mode while removing the crash path.

I also updated the regression helper to start coverage with eval: true:

Coverage.start(lines: true, branches: true, eval: true)

Without eval: true, the test does not exercise the crashing path.

Anything you want to highlight for special attention from reviewers?

Context:

• Ruby bug: https://bugs.ruby-lang.org/issues/19363
• Related ViewComponent issue: Segmentation fault with Ruby 3.4 + Rails 8.1 when coverage is enabled (negative lineno in class_eval) #2536
• Previous fix PR: Fix segfault when Ruby coverage is enabled with Rails 8.1 ERB templates #2541

Minimal reproducer (outside ViewComponent):

require "coverage"
Coverage.start(lines: true, branches: true, eval: true)
klass = Class.new
klass.class_eval("def x(v); v ? 1 : 2; end", "fake_template.erb", -1)

On Ruby 3.4 this segfaults with a backtrace through add_trace_branch_coverage.

[joshsadam]

This is not working the way I thought. I will get back to you on this fix.

[joelhawksley]

@joshsadam thanks for digging into it. I just landed #2552 to main, can you rebase this branch and see if that fix worked for you?

[joshsadam]

That's great, thanks @joelhawksley I pinned your main branch in our gemfile, and running the CI tests now. I will let you know how it goes.

[joshsadam]

@joelhawksley our tests pass on CI now after pinning your main version. Can you do a minor release with this update?

[joelhawksley]

@joshsadam yes, I'll be getting a release out today. Thank you for your help validating!