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Pin lol-html to oven-sh/lol-html@77a9728 (oven-sh/lol-html#5). Each captured end tag walked every registered end-tag handler, and every still-open element that called onEndTag() has one, so n nested elements cost n^2/2 visits: 100k nested <a> (700 KB) took 5.3 s. The walk now stops once the handlers that end tag activated have run. The new pin sits on the fork bun head ea6125b, so it also carries the selector VM change from oven-sh/lol-html#2. Adds a nested/multi-pop ordering test and a 400k-deep onEndTag test that the released bun cannot finish inside the spawn timeout.
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Included review availability: Your plan provides up to 10 included reviews per hour; 2 remain after this review. WalkthroughThe PR updates the pinned lol-html commit and adds HTML rewriter tests for end-tag handler ordering, multi-element closure, output preservation, and large nested inputs. ChangesHTML rewriter end-tag dispatch
Suggested reviewers: Priority: ➖ Normal Severity of issue fixed: Medium Merge Risk: 🔵 Low · up to The change improves deeply nested HTMLRewriter end-tag performance while preserving output and handler behavior. Mergeability is low risk, with a remaining possibility that benign diagnostic stderr could make the subprocess regression test fail. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Inline comments:
In `@test/js/workerd/html-rewriter.test.js`:
- Line 3368: Remove the empty-string assertion for stderr in the relevant HTML
rewriter test while continuing to drain or consume stderr. Keep assertions for
transformed output, exit code, and signal unchanged.
- Line 3372: Reduce the debug workload in the affected test while preserving the
release workload at 400,000 elements, then remove the explicit 60-second timeout
override so the test uses the default timeout.
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scripts/build/deps/lolhtml.tstest/js/workerd/html-rewriter.test.js
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I reviewed this PR and didn't find any bugs. Because the actual algorithm change lives in the oven-sh/lol-html fork (the pin bump also carries the selector-VM commit from #41479, not just the onEndTag fix), a human look at the fork's 725ce499..77a97289 range would still be worthwhile.
What was reviewed
- The two new tests follow harness conventions:
bunExe/bunEnv,Buffer.alloc(...).toString(), concurrent stdout/stderr/exited drain, combined-object assert withsignal: nullhang-guard, andisDebug-branched workload. - The correctness test covers the invariant the optimization must preserve (innermost-first, including one end tag popping several implicitly-closed elements).
- The perf test's failure mode on the old build (SIGKILL at 30s →
signal !== null) is distinguishable from the pass condition, so it fails for the right reason underUSE_SYSTEM_BUN=1. isDebugis already imported at the top ofhtml-rewriter.test.js.
Extended reasoning...
Overview
This PR bumps the LOLHTML_COMMIT pin in scripts/build/deps/lolhtml.ts from 725ce499… to 77a97289…, pulling in a change to the vendored oven-sh/lol-html fork that makes HandlerVec::do_for_each_active_and_remove stop scanning once no active handlers remain — turning element.onEndTag() on n nested elements from O(n²) to O(n). It adds two tests to test/js/workerd/html-rewriter.test.js: a correctness test for nested end-tag handler ordering (including implicit multi-element close), and a spawned-subprocess regression test that times out under the old quadratic scan.
Security risks
None identified. HTMLRewriter processes untrusted HTML, but the change described is a scan-early-exit in handler dispatch, not parsing or bounds logic. The tests are hermetic (no network, no external hosts) and the pin points at Bun's own fork.
Level of scrutiny
Moderate. The in-repo diff is small and mechanical (a commit hash + tests), but the load-bearing change is in the fork repo and not visible in this diff. Per the PR description, the new pin sits on top of ea6125b and therefore also carries the selector-VM change that #41479 pins — so more than one behavioral commit rides in on this bump. REVIEW.md's dependencies-and-vendoring guidance and the fact that the actual Rust change to handlers_dispatcher.rs cannot be reviewed from this diff alone argue for a human confirming the fork's 725ce499..77a97289 range contains exactly what's claimed and that the early-stop is sound for the fork's suspend/resume path.
Other factors
The tests are well-constructed against the repo's stated conventions: Buffer.alloc over .repeat, concurrent pipe drain, combined {stdout, stderr, exitCode, signal} assertion, signal: null proving self-exit, and isDebug-scaled workload. The 60s per-test timeout technically conflicts with test/CLAUDE.md's "no timeouts" rule, though root CLAUDE.md permits it for rare outliers and this test's subprocess has a 30s SIGKILL ceiling that justifies the outer bound. The correctness test directly guards the invariant the optimization relies on (activated handlers are a suffix of the pushed order), which gives reasonable confidence the early-exit doesn't skip handlers. No CODEOWNERS entry covers the changed files. No prior review activity on the timeline.
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Updated 3:08 PM PT - Sep 10th, 2026
✅ @robobun, your commit 41fe1d24b03e64ab96607bbe39cecaae6da678ee passed in 🧪 To try this PR locally: bunx bun-pr 42234That installs a local version of the PR into your bun-42234 --bun |
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Status: ready for review. Waiting on CI. Reproduced on a release build of main (5f55496) and on 1.4.2 with the fuzz-ledger script: nested Fail-before: The pin range 725ce49..77a9728 in oven-sh/lol-html is exactly two commits: ea6125b (oven-sh/lol-html#2, already on the fork Review: the two bot comments on the test (stderr assertion, explicit per-test timeout) are addressed in a8bb8d8. |
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The This fix is still needed on v3.0.1. On a debug build of #43266, nested |
Problem
element.onEndTag()on n nested elements is quadratic. n nested<a>that each calle.onEndTag(() => {})take 2.4 s at n = 65536 and 5.3 s at 100000 (700 KB) on 1.4.3. WithoutonEndTag: 91 ms.HandlerVec::do_for_each_active_and_remove(vendor/lolhtml/src/rewriter/handlers_dispatcher.rs:155). Each captured end tag walks every registered end-tag handler, and every still-open element that calledonEndTaghas one: n^2/2 visits.Fix
LOLHTML_COMMITto 77a9728, on top of the forkbunhead ea6125b. So it also carries the selector-VM change that Bump lol-html so descendant selector matching is linear in nesting depth #41479 pins.test/js/workerd/html-rewriter.test.js, two new cases. 1.4.3 is killed at the 30 s spawn timeout on the 400k one. The fix takes 0.42 s. All HTMLRewriter test files pass.Background
HTMLRewriteris the vendored oven-sh/lol-html fork, fetched by commit. A fix there lands in bun by moving the pin.HandlerVecper handler kind. An item is active whileuser_count > 0.onEndTagpushes an inactive item.Notes
"<a>".repeat(n) + "</a>".repeat(n)throughnew HTMLRewriter().on("a", { element(e) { e.onEndTag(() => {}); } }).transform(doc)."<a></a>".repeat(n)) were already linear: 131 ms at 100000.resumestill finds the remaining active items at the tail. The fork'scargo testpasses (172 lib + 34 other). All 9 HTMLRewriter test files in bun pass on debug and release builds (217 tests).do_for_each_active_and_remove_tail(05ff4b0, "Drain end handlers"). It finds the first active item with a frontposition()scan, so it is still O(open handlers) per end tag for this shape, and itsdraindrops the remaining handlers when one returns early, which does not fit the fork's suspend and resume. The fork keeps the reverse walk and adds the early stop.src/andpackages/for its fail-before run. This fix lives in the pin and the vendored crate, so that run already has the fix. The released binary is the fail-before proof:USE_SYSTEM_BUN=1 bun test test/js/workerd/html-rewriter.test.js -t "stays linear"is killed at 30 s with exit code 137.bun.no test proof · iteration 0 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/workerd/html-rewriter.test.js