ref(inject): Keep sourceMappingURL comment at end

[loewenheim]

This keeps the sourceMappingURL comment at the end of a source file when injecting debug ids. It does this by reading the file to memory and writing it back line by line, but saving the comment line to the very end. It works fine in my limited tests, but it doesn't feel elegant to me. Suggestions for how to improve this would be very welcome.

[kamilogorek]

Maybe we can shortcircuit the iteration for the non-sourcemapurl path?

(pseudocode)

let sourcemap_ref = sourcemap::locate_sourcemap_reference_slice(content).unwrap_or(None);

let lines = if sourcemap_ref.is_some() {
  lines.into_iter().filter(|line| line.starts_with("//# sourceMappingURL=") || line.starts_with("//@ sourceMappingURL=")
} else {
  content.lines()
};

let mut file = File::options().write(true).open(js_path)?;

file.append(lines);
if sourcemap_ref.is_some() {
  file.append(format!("//# sourceMappingURL={sourcemap_ref}"));
}
file.append(snippet);
file.append(debug_id);

[loewenheim]

We don't call the function fixup_js_file unless the file contains a sourceMappingURL comment.

[kamilogorek]

Oh, my bad. It shooould be fine then. Probably not the most optimal way to write such transformations, but it's a CLI, we can prefer being obvious over being overly performant.