Fix line numbers and empty output for ERB templates Rails doesn't annotate - #2716
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joelhawksley merged 1 commit intoSep 14, 2026
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Rails 8.1 added a newline to compiled ERB output (rails/rails#53731), and ViewComponent compensates with a lineno of -1 so backtraces point at the right line. That newline lives inside the `<!-- BEGIN ... -->` annotation, which Rails only prepends when `annotate_rendered_view_with_filenames` is enabled *and* the template's format is HTML. Compensating for every ERB template shifted backtraces by one line for non-HTML templates (`.text.erb`, `.css.erb`) and for every ERB template when annotations are disabled, such as in production. When coverage was running, the same mismatch made `strip_annotation_line?` drop everything up to the first `;` of a preamble that was never emitted, so non-HTML templates rendered empty. Move the annotation conditions into `erb_newline_compensation_needed?` on `Template` so every call site fires exactly when Rails emits the annotation. The negative lineno is still avoided under coverage (bugs.ruby-lang.org/issues/19363). `Template::Inline` had the same off-by-one, and decided the compensation when the component class was defined rather than when it compiled. It now shares the predicate and resolves it at compile time, matching `Template::File`. Also add the missing `ensure` to the `without_template_annotations` test helper, so an exception escaping the block no longer leaves annotations disabled for the rest of the process.
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Summary
Rails 8.1 added a newline to compiled ERB output (rails/rails#53731), and #2502 compensates for it on every ERB template. But Rails only adds that newline when it emits the
<!-- BEGIN ... -->annotation:Line numbers in backtraces are off by one for
.text.erband.css.erbtemplates, and for all ERB templates when annotations are off, which is the default in production.Under coverage, non-HTML templates render empty. The annotation stripping from #2541 / #2552 checks the annotation setting but not the format, so it cuts into the template body.
Fix
Move both conditions into
erb_newline_compensation_needed?onTemplate.linenois still never negative while coverage is running.Template::Inlinehad the same off-by-one. It also picked its lineno when the class was defined instead of when it compiled, so it now uses the shared predicate at compile time likeTemplate::File.Notes
without_template_annotationswas missing anensure, so an exception escaping the block left annotations off for the rest of the process.Tested on Rails 8.1.3.1 / Ruby 4.0.6. I haven't run the full appraisal matrix. Rails < 8.1 is unaffected.