Remove dead code from the bake HMR runtime

[robobun]

Problem

• hasExportStar in src/runtime/bake/hmr-module.ts has no caller. Its only call site is a block that fix dev server regressions from 1.2.5's hmr rewrite #18109 commented out on 2025-03-14. The availableExportKeys local above that block is read only by the commented-out code.
• firstConnection in src/runtime/bake/client/websocket.ts is assigned once and never read.
• No lint reports them. Earlier sweeps ran tsc --noUnusedLocals over src/js and scripts only, not over src/runtime/bake.

Fix

• Delete hasExportStar, the commented-out check, availableExportKeys, and firstConnection. 2 files, 40 lines removed.
• Correct because the bundler already drops hasExportStar. The generated bake.client.js, bake.server.js and bake.error.js differ from main only by the two removed local declarations.
• Verified: tsc -p src/runtime/bake/tsconfig.json --noUnusedLocals no longer reports either file. test/bake/dev/esm.test.ts (17 pass), hot.test.ts (11 pass) and bundle.test.ts (23 pass) with the debug build.

Behaviour change: none

Background

• hmr-module.ts is the module loader that the dev server sends to the browser and to the SSR realm. parseEsmDependencies walks the dependency list of an ES module. Each entry carries the export names that the importer uses.
• The removed check compared those names with the exports of the dependency and threw a SyntaxError for a missing one. It has been off for 18 months. A missing export fails at the use site.
• A deletion has one possible place, so no other design was weighed.

Downsides

• The commented-out check was the only sketch of export verification in the HMR runtime. A person who wants to build it starts from the history of fix dev server regressions from 1.2.5's hmr rewrite #18109.

Notes

Why this run is small

Every other hit of this run is live, is platform code with a user on another target, or is a line that one of the 34 open dead-code pull requests already deletes. Each removed line here was checked against those diffs. #40492 and #43378 touch websocket.ts in other hunks.

Scans of this run, all clean or already claimed

• Debug objects linked again with --gc-sections --print-gc-sections, then llvm-symbolizer for file:line. 20,668 discarded functions in bun's objects. The Rust ones outside macros and trait impls are Windows or macOS helpers, or claimed (Remove dead code from bun_jsc, bun_runtime, bun_core, and the JSC bindings #40824, Remove dead code from the inspector protocol package, bun_jsc, bun_install, and the Windows named pipe modules #40557, Remove dead code from the JSC bindings, headers.h, the console builtin, and bun_jsc #40232). The C++ ones are claimed, are template instantiations, or have a Rust caller on another target (bsd_socket_export, posix_spawnattr_reset_signals).
• Rust functions that never get a symbol (generic or #[inline], never instantiated), found by comparing every fn line with the DWARF declaration lines of all emitted functions. 86 hits outside cfg, trait impls and #[inline(always)]. All are Windows-only, test-only (the outbound half of api/bun/h2/connection.rs), or claimed.
• clang -fsyntax-only -Wunused-function -Wunused-macros -Wunused-template -Wunused-member-function over 588 translation units and the 69 unified ones (the build passes -Wno-unused-function). 3 functions and 6 macros. formatStackTraceToJSValueWithoutPrepareStackTrace, hostName, G_TRUE, G_FALSE, MAX_LABELS and us_ioctl are claimed (Remove dead code from bun_core, bun_jsc, bun_css, react_compiler, and two C++ bindings #40367, Remove dead code from the class and sink generators, JSBuffer, the bake client, bun-error, and the build scripts #43378, Remove dead code from the JSC bindings, the codegen scripts, the CI scripts, bun_core, and bun_jsc #40492, Remove dead code from bun-uws, bun-usockets, the require.extensions FFI, and unused Cargo dependencies #40294). us_quic_send_one is used under the non-Linux #if branch.
• A whole-program C++ reference index (c-index-test -index-file, 657 translation units, 32,018 symbols declared in bun's tree). 8,711 have no recorded reference. After filters for template-dependent uses, extern "C", virtual methods and names that WebKit headers use, 78 remain. All are index artifacts (typedef struct tags, primary templates with used specializations, requires clauses) or one-line getters in files that open pull requests rewrite.
• tsc --noUnusedLocals over src/js, scripts, src/codegen, src/runtime/bake, src/node-fallbacks and the sources of each package. The hits outside this change are claimed (Remove dead code from the build scripts, the vscode and debug-adapter packages, the bake overlay, and two WebCore files #40122, Remove dead code from bun_url, bun_react_compiler, the class codegen, and bun-error #41169, Remove dead code from bun_core, the JSC bindings, the debugger, and 24 other crates #41385, Remove dead code from the JSC bindings, the codegen scripts, the CI scripts, bun_core, and bun_jsc #40492, Remove dead code from the WebCore bindings, the WebView backends, and the build scripts #43778) or are loop variables.
• Regex scans for struct fields with no read and for bool or Option fields that only ever get one constant. Nothing new after Remove dead code: write-only fields and never-set options in 11 crates #43745.
• Exports of src/js modules and builtin functions with no mention in another file: none.
• Files that nothing includes, imports or names: none outside .idl copies (Remove dead code from the inspector agent, the WebKit IDL copies, and an orphaned package #41064). src/symbols.txt, symbols.def and the package.json scripts name nothing that is gone. No #if 0.

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no test proof · iteration 1 · the description declares no behaviour change, so there is no failing test to prove; the existing suite in CI is the check

[robobun]

^{Updated 10:57 PM PT - Sep 22nd, 2026}

❌ @robobun, your commit b3276f7 has 1 failures in Build #119941 (All Failures):

• test/js/bun/spawn/spawn.test.ts - code 1: stdout reader of an unref'd child and process lifetime > an idle reader stopped at the highwater … on 🐧 13 x64-asan

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🧪   To try this PR locally:

bunx bun-pr 43828

That installs a local version of the PR into your bun-43828 executable, so you can run:

bun-43828 --bun

[robobun]

Status: ready for review. The diff is green. The one red CI job does not come from this change.

How this was verified:

• tsc -p src/runtime/bake/tsconfig.json --noUnusedLocals reported hasExportStar, availableExportKeys and firstConnection on main. It reports none of them on this branch.
• The generated bake.client.js, bake.server.js and bake.error.js differ from main only by the two removed local declarations.
• bun bd test test/bake/dev/esm.test.ts (17 pass), hot.test.ts (11 pass), bundle.test.ts (23 pass).

CI on b3276f7 (build 119941): the build is finished, 180 of 181 jobs passed. No bake test failed or needed a retry on any lane.

• One job is red: debian 13 x64-asan - test-bun. test/js/bun/spawn/spawn.test.ts ("an idle reader stopped at the highwater mark does not keep the process alive") fails on all 4 attempts. The child's stderr holds the LeakSanitizer line WARNING: ptrace appears to be blocked (is seccomp enabled?), and the test expects an empty stderr. The same failure is on main in build 119887.
• This PR changes only src/runtime/bake/hmr-module.ts and src/runtime/bake/client/websocket.ts. The spawn test loads neither file.
• The other annotations (hoist, bun-audit, filesink, bun-install-registry, serve-http2-lifecycle, fs.watch.rewrite, css/color) passed on retry.

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📥 Commits

Reviewing files that changed from the base of the PR and between 6d504dd and 25cdd1c.

📒 Files selected for processing (2)

• src/runtime/bake/client/websocket.ts
• src/runtime/bake/hmr-module.ts

💤 Files with no reviewable changes (2)

• src/runtime/bake/hmr-module.ts
• src/runtime/bake/client/websocket.ts

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Walkthrough

The changes remove an unused local from WebSocket initialization and remove imported-key validation and its export-star search helper from ESM dependency parsing.

Changes

WebSocket cleanup

Layer / File(s)	Summary
Remove unused WebSocket local src/runtime/bake/client/websocket.ts	initWebSocket no longer declares the unused firstConnection local. The WebSocket connection behavior is otherwise unchanged.

ESM dependency parsing

Layer / File(s)	Summary
Remove imported-key validation src/runtime/bake/hmr-module.ts	parseEsmDependencies no longer checks imported keys against direct exports or export-star graphs. The hasExportStar helper is removed.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to b3276

The inspected removals leave WebSocket connection handling and ESM dependency parsing unchanged. No merge-blocking risk was identified.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the main change: removing dead code from the bake HMR runtime.
Description check	✅ Passed	The description explains the problem, fix, verification steps, behavior impact, and downsides. It does not use the exact template headings, but it provides the required change summary and verification…

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[claude]

Code review found no issues

No high-confidence issues detected in this change.