Reviewers: Using git diff -w is highly recommended, otherwise this change looks a lot larger than it actually is.

CodSpeed Performance Report

Merging #5593 will not alter performance

_{Comparing felix/112625-stw-refactor (077d68e) with main (2aeb641)}

Summary

✅ 57 untouched
⏩ 30 skipped¹

Added another commit here needed just for downstream lint checks to pass – with this change trace-stream.c++ is covered by the mutable globals check, so the static kj::StringPtr [] instances and corresponding js.obj() calls needed to be converted.

Overall LGTM but will leave the actual sign off to Mar. I would say that I'm not sure the [nfc] label (non-functional change) is quite accurate given the extent of the updates here.

Overall LGTM but will leave the actual sign off to Mar. I would say that I'm not sure the [nfc] label (non-functional change) is quite accurate given the extent of the updates here.

It's not obvious based on the size of the diff, but this is mostly just moving code around. We are getting rid of the lambda by replacing it with a regular function and merge the functionality of TailStreamWriterState into TailStreamWriter, but the actual behavior should be the same as before.