Remove dead code from bun_bundler, the JS parser, the help command, and PackageJSONEditor - #44687

Removed, one group each

1. parse_task::ResultValue::Empty, bun_bundler::Error::EmptyAST and bun_bundler::Error::ModuleNotFound (33 lines). EmptyAST has no constructor: the only expression that names it is if e == crate::Error::EmptyAST in ParseTask.rs, and no From impl or name table produces it. That if held the one constructor of ResultValue::Empty. So the variant, its three match arms (source_index, drop_result_owned_fields, on_parse_task_complete) and the error variant go. ModuleNotFound of the same enum has no constructor either. The bundler reports a missing module through Error::Resolver(bun_resolver::Error::ModuleNotFound).
2. esbuild's "weird code" warnings in the JS parser (53 lines). Options.suppress_warnings_about_weird_code is true in Options::default(), Options::init, the literal in src/bundler/transpiler.rs, and the two assignments in function_identities.rs and pm_diff_normalize.rs. clone_for_lazy_export copies it. Its two readers are the ASI warning after a bare return (parse/mod.rs) and an !a instanceof b block whose body is a TODO comment (parse_suffix.rs). With them go P::latest_return_had_semicolon (its one reader was the ASI block), the local return_without_semicolon_start, and the option. The !a in b block of sfx_t_in is the same empty TODO block without the option check, so it goes too.
3. help_command::Reason::InvalidCommand (31 lines net, src/runtime/cli/mod.rs). Nothing constructs it. exec() and the two other callers pass Reason::Explicit. The enum, the reason parameter, the Uh-oh not sure what to do with that command arm and the exit(1) branch go. print_cli_helptext! loses its printer parameter, because pretty! is its one printer now.
4. impl Default for linker_graph::File (14 lines). Nothing calls it. LinkerGraph::load creates the rows zeroed, and MultiArrayList<File> has no File: Default bound.
5. keep_catalog_reference in PackageJSONEditor::edit (10 lines). The flag can be true only when manager.subcommand == Subcommand::Update. Its one reader is the last operand of a condition that has manager.subcommand != Subcommand::Update before it.

Open pull requests

• The head of each of the 5,483 open pull requests was compared with this branch on 2026-10-15. None deletes one of the five groups.
• 478 of them touch one of the 14 files. A trial merge (git merge-tree) of each with this branch, against the same merge with main: no pull request that merges cleanly with main gets a conflict from this branch.
• Six pull requests that conflict with main already get one more conflicted file. To resolve each: drop the hunk inside the removed block.
  • A Loc is always a byte offset: Option<Loc> for absence, no -1 sentinel #38825 changes the type of return_without_semicolon_start inside the removed ASI block (group 2).
  • Real lifetimes for Source, import records and resolver results #44493 deletes drop_result_owned_fields, which loses one arm here (group 1).
  • install: exit 1 from the shared add/link/update helper when a package fails to install #44989, install: record a failed bin link at every log level, so --silent exits 1 #44997, pm pkg get: print several values as one object through print_json #45061 and ini: reject a source of 2 GiB or more in Parser::parse instead of aborting on an int cast #45206 change lines next to the removed block in PackageJSONEditor.rs (group 5).
• Three more change a line inside a removed block and already conflict in that file: Replace boolean flag parameters with two-variant enums #37180 (the signature of print_with_reason), Make the allocation-only collection APIs infallible and drop the OOM wrappers around them #38888 (one line of impl Default for File), bundler: remove unsafe from bundle_v2, ParseTask, LinkerContext and the bundler thread pool #40438 (drop_result_owned_fields).

Verified and left out, because an open pull request deletes or changes the same lines

• The unused arena of Glob.scan and Glob.scanSync: One bindgen: replace bindgen v1 and v2, add classes, generate the Rust side #45104 rewrites glob.rs and removes it. An earlier version of this PR held the removal.
• HostProvider::from_shortcut(.., with_colon), whose one caller passes false: install: fix regressions and older bugs found after the package manager consolidation #45307 makes the function pub(crate) and keeps the parameter. An earlier version of this PR held the removal.
• bun_bundler::cache::DISABLED, the resolver's BundleOptions.{production, tree_shaking, allow_runtime} and resolver::Result.import_kind (all written, none read): Remove cross-crate layering workarounds #33152.
• The interface counting pass of os.networkInterfaces(): node:os, CompressionStream, TextEncoder/TextDecoder: remove unsafe #40244.
• H2FrameParser.used_window_size and Stream.used_window_size (always 0): node:http2: keep setLocalWindowSize() off SETTINGS_INITIAL_WINDOW_SIZE #40180.
• MatchedRoute.needs_deinit (always true): fs_router: make MatchedRoute non-self-referential #37535.
• Scanner.exclusion_names (always empty): bun test: do not follow a directory link back to a directory the scan is already inside #44487.
• The unused locals and TreeContext::clear_path_tracker of bun why: bun why: print a package's dependents once, mark repeats as *deduped #37922.
• StmtListWhich::AllStmts: Remove dead code from bun_core, bun_jsc, bun_css, react_compiler, and two C++ bindings #40367.
• Left out because an open pull request rewrites the same function: the None arms of set_buffers in node:zlib (node:zlib: avoid aliasing compression input/output buffers #31633), Error::FailedToCopyFile (Make the Windows hardlink install backend link serially #33113), PackageWorkspaceSearchPathFormatter.quoted (Add ForeignRef<T> and make FetchHeaders the owned handle #33820), the ack parameter of H2FrameParser::send_ping (Make unrooted JSValues, views across JS re-entry, and JSC buffer-ownership contracts compile errors #34230), the lockfile parameter of Scripts::create_list (install: fold the inline default node-gyp predicates into Scripts::wants_default_node_gyp #43912, install: derive the bun.lockb meta hash in the writer #44501).

Leads, not proved to the end or not removable without a conflict

• Options.keep_names and Options.transform_only of the parser (parse_entry.rs) are written and never read. The removal builds on 12 targets, but it conflicts with install: fix regressions and older bugs found after the package manager consolidation #45307 and js_parser: validate TypeScript class member modifiers like esbuild #40817, which both merge cleanly today, so it is not in this PR.
• LinkerOptions.mode is always LinkerOptionsMode::Bundle, so should_strip_exports in convertStmtsForChunk.rs is always true. The removal dedents about 100 lines in a file that 18 open pull requests touch.
• ServerComponentParseTask::Data::ClientEntryWrapper is constructed only as the placeholder of impl Default. The removal needs a constructor in place of that impl.
• NetworkTask.apply_patch_task is written and never read. PatchTask::new_apply_patch_hash, which builds the value, calls compute_cache_dir_and_subpath, so its side effects need a review first.
• The "merge adjacent @layer rules" block of findImportedFilesInCSSOrder.rs never runs, because wip_order is always empty there. esbuild's version of the block appends each entry to wip_order. This is a missing step of the port, not dead code.

Self-review

Four concerns survived the review, and the seven proofs of the first version held when they were derived again.

• The description listed three new conflicts, and a merge would have caused more. Addressed: the branch is rebased on main after bun check: fix more differences from tsc #44685 merged, two groups and two fields that collide with pull requests that merge cleanly are out, and the list above comes from trial merges with every open pull request.
• Dead code of the same kind stayed next to the hunks. Addressed: the !a in b block and Error::ModuleNotFound are in. Options.keep_names and Options.transform_only are named under Leads with the reason.
• The branch had to wait for bun check: fix more differences from tsc #44685, which moved a line that this PR deletes. Addressed by the rebase. That line's file no longer exists on main.
• A lint could find this class of code (a flag with one value, a variant without a constructor) and stop new cases. Not addressed here: it is a change to the mordant lint pack, not to this repository's sources.

How the candidates were found

• Readers went through 24 chunks of Rust (about 180,000 lines in src/install, src/runtime/cli, src/runtime/api, src/bundler and part of src/runtime/node) and listed about 140 places where a value has one possible state.
• A rustc driver recorded each field read and write, each variant construction and the constant arguments of each call in the workspace. It found the write-only fields and the variants without a constructor. Its output did not survive a reset of the work container, so each group above was proved again by hand on current main.
• Not covered in this run: src/runtime/webcore, src/runtime/server, the rest of src/js_parser, src/http, src/runtime/shell, src/sql, src/css, the C++ bindings and src/js.

Verification

The base is main at 5f5799e.

• bun bd passes (debug build with ASAN). bun run rust:check-all passes for 12 of 12 targets. cargo check --workspace passes with --all-targets, with --cfg bun_asan --cfg bun_debug --cfg socket_fault_injection, and with --release. cargo clippy --workspace and cargo fmt --all --check are clean.
• Tests with the debug build, 0 fail: test/bundler/bundler_edgecase.test.ts (182 pass), test/bundler/transpiler/transpiler.test.js (238 pass), test/cli/bun.test.ts (47 pass), test/cli/install/bun-update.test.ts (173 pass), test/cli/install/catalogs.test.ts (146 pass).
• Probes against the canary binary of the base commit (1.4.4-canary.1+5f5799ed1):
  • bun build of a module graph with an empty .js file, a comment-only file, an empty .ts file and an empty .json file, in eight modes (default, --no-bundle, --minify, --format=cjs, --target=node with inline and with linked source maps, --splitting, --target=bun --minify-syntax): byte-identical output, no warning in either.
  • Bun.Transpiler.transformSync of five inputs with a return before a line break, !a instanceof b and !a in b: identical output.
  • bun --help: the same lines, apart from the version, the random example package names, and one flag that only debug builds have.
• The first version of this branch (before the rebase) passed CI in build 123735.