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Upgrade WebKit to d3720d515e14: module linking without sorting import names or resolving every import up front - #42823
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bundler_compile_prelinked.test.ts: - New cases where every module is a chunk of its own, so each import crosses a record boundary: namespace imports of builtin modules before, between and after named imports; named, default and namespace imports of builtin modules next to imports of other chunks; one record importing 96 bindings; imports that are never read, first read late, or first read once the reading function is hot; one variable reaching a record under several names and through re-exporting records; a record loaded by import() after the records it imports from. - bindingCase(): graphCase() plus the same program built without --bytecode (no embedded module graph; records are made from each chunk's source), with and without splitting. Used for the new cases and for the existing cycle, star-export, re-export, namespace, default, dynamic import, top-level await, CommonJS interop and TDZ cases.
…lots without sorting) Pins the preview release of oven-sh/WebKit#665 for CI; to be replaced by the merged main sha.
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Included review availability: Your plan provides up to 10 included reviews per hour; 7 remain after this review. WalkthroughThe change expands bundler and VM module-binding tests across execution modes and contexts. It adds live-binding scenarios and updates the selected WebKit autobuild identifier. ChangesBundler binding coverage
SourceTextModule coverage
WebKit autobuild pin
Suggested reviewers: Priority: ⬇️ Low Merge Risk: ⚪ Minimal · up to The added SourceTextModule coverage aligns with the stated binding-identity behavior, with no concrete merge-blocking issue identified. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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In `@test/bundler/bundler_compile_prelinked.test.ts`:
- Line 78: Replace the manual loop over the splitting variants with a
describe.each() parameterized test block, preserving both false and true cases
and the existing test behavior.
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scripts/build/deps/webkit.tstest/bundler/bundler_compile_prelinked.test.ts
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Updated 6:49 PM PT - Sep 15th, 2026
❌ @dylan-conway, your commit 7423794 has 1 failures in 🧪 To try this PR locally: bunx bun-pr 42823That installs a local version of the PR into your bun-42823 --bun |
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- bundler_compile_prelinked.test.ts: RegistryDeleteImporter and RegistryDeleteImporterAndExporter. Deleting a chunk's registry entry and importing the key again gives the loader a second record of the module while the first one's functions are hot; the module imports bindings of another chunk, a named binding of a builtin module and a builtin module's namespace. With the exporting chunk deleted too, the second record links to a second record of it (with its own state) while the first stays linked to the first. Built with and without --bytecode and --splitting, the bytecode builds run in the three loader modes. - vm.test.ts: SourceTextModules with one identifier and one source text linked to dependencies whose exports sit at different places each read their own bindings, in the main context and in a new one.
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scripts/build/deps/webkit.ts:6—Merging this pin as-is will break every fresh Bun build once oven-sh/WebKit#665 merges or closes, because GitHub delete…
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This review covers commit 16e5634, which is no longer the latest commit on this pull request; later commits are not covered by it.
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NodeVMSourceTextModule::createModuleRecord asserts that a module has no more import declarations than requested modules, which does not hold for two declarations that name the same specifier; builds with assertions enabled abort there. That is independent of what this case is about, so its importer now imports everything it reads in one declaration.
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…fier Runs where it works (one entry in moduleRequests, bindings read through each declaration); todo on builds with assertions enabled, where NodeVMSourceTextModule::createModuleRecord aborts on "More attributes nodes than requests". In a subprocess, so the abort cannot take the test runner with it.
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dylan-conway
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I reviewed the latest push and found no bugs; since the behavioral change lives entirely in the upstream JSC commit this pin now points at, a human should still confirm the pin and give the engine change a look before merge.
What was reviewed:
scripts/build/deps/webkit.ts: the pin is now a full 40-char SHA (the commit message says oven-sh/WebKit#665 merged asd3720d51), and no other file in the repo carries the old value. I could not independently confirm from this checkout that the SHA is on oven-sh/WebKitmainand that theautobuild-<sha>release has assets for every platform x flavor, so that check is the one worth a human doing.bundler_compile_prelinked.test.ts: traced the expected stdout of every new case by hand (RegistryDeleteImporter/AndExporter in bothexporterToostates, NamespaceOrders, BuiltinExporters, Many, FirstUse, AliasesAndReExports, DynamicImporter) and they match the programs.bindingCase()mirrorsgraphCase()minussplitRun, which onlyGeneratedGraph(stillgraphCase) uses, so nothing is dropped today.vm.test.ts: thetest.eachexpectations follow from the bump counts; thetodoIf(isDebug || isASAN)case names the observed assertion (NodeVMSourceTextModule.cpp:212), runs in a subprocess, drains pipes withPromise.all, and asserts stdout before the exit code; themoduleRequestsshape matchessrc/js/node/vm.ts:411-415.
Extended reasoning...
Overview
The diff touches three files: the prebuilt WebKit pin in scripts/build/deps/webkit.ts (moved from the autobuild-preview-pr-665-* tag flagged earlier to a full SHA that the latest commit message describes as the merged oven-sh/WebKit#665), a new bindingCase() helper and seven new import-binding programs in test/bundler/bundler_compile_prelinked.test.ts (plus ten existing graphCase registrations widened to also run without --bytecode), and two additions to test/js/node/vm/vm.test.ts covering several SourceTextModule records of one module keeping separate import bindings, and a todoIf(isDebug || isASAN) case documenting the existing createModuleRecord position-pairing assertion. There is no Rust or C++ change in this repo; the runtime behavior under test is the upstream JSC import-slot rework.
Security risks
None specific to this diff. The tests spawn only the locally built executable and use node: builtins; nothing contacts the network, no credentials or user input parsing is involved. The engine change itself (module linking) is not security-sensitive in the auth/crypto sense, though any JSC upgrade carries generic engine risk that the repo's normal CI on every platform is the right guard for.
Level of scrutiny
The in-repo parts warrant moderate scrutiny and I applied it: I traced every new expected-stdout string against its program (including the exporterToo split where the second b record links to a fresh state record, giving 1,true,string 2,true,string 1 2), confirmed bindingCase() only omits splitRun, which no converted case uses, and confirmed the moduleRequests JSON shape against src/js/node/vm.ts. The upstream WebKit change is the part that actually needs human judgment: it alters how import slots are numbered and when imports are resolved, and its correctness cannot be established from this checkout. I also could not run gh from this environment to verify the release assets for the new SHA, which is why the body asks a human to confirm the pin rather than treating the commit message as proof.
Other factors
The bug-hunting run exhausted its search without findings (dry_streak). My earlier inline finding on the ephemeral preview tag concerned exactly the line that changed in the last commit; the thread's resolution is left to the resolve phase and a human, since I could not verify the artifact independently. The todoIf case follows the repo's rule of naming the observed failure, and it is legitimately todo rather than skip because the abort is a real Bun bug (JSC dedupes requestedModules by specifier while the C++ pairs declarations by position) that remains unfixed in this PR. The new bundler cases each link an executable, but the file already serializes links via the freeSlots gate, so the added cases increase wall time rather than memory pressure. Approving was not appropriate because the substantive change is an engine upgrade whose code is outside the repo; staying silent was not appropriate because the pin change addresses the one blocking item from earlier reviews and a human now has something concrete to confirm.
What does this PR do?
Upgrades WebKit from
c775a5dc527dtod3720d515e14, which is that commit plus oven-sh/WebKit#665, and adds tests for import bindings between the module records of compiled executables and ofvm.SourceTextModules.The WebKit change. Since the WebKit upgrade in #42319 a module environment has an import slot per import binding. Three parts of that ran for every module record when it was linked: the record's import names were collected, atomized and sorted (and then binary-searched by string at every import access site when a function's code was linked), every import of the record was resolved to build a key used to compare executables, and every import was resolved again to fill the slots before the module ran. Before, an import was resolved when the code using it was first linked, so programs with many imports that are not all used while the program starts got slower to load.
oven-sh/WebKit#665 numbers import slots by position instead of by sorted name (the import's position in the embedded module graph for
--compile --bytecodeexecutables, the position among the record's import entries otherwise), resolves an import and finds its slot with one lookup per access site, resolves nothing to compare records until a second record for the same module turns up (and then, for a module of the embedded graph, only the imports the graph does not answer), and fills import slots on first use unless the code is shared.Measured with Bun built against WebKit
mainand against the WebKit change (medians, interleaved runs): a generated program of 400 modules with about 40 import bindings each, a sixth of which are read while it starts, went from 79.4 ms to 75.3 ms run from source, and from 22.6 ms to 19.6 ms built with--compile --bytecode --splitting(every module a chunk of its own).How did you verify your code works?
test/bundler/bundler_compile_prelinked.test.tsgrows from 39 to 79 cases:Six new programs in which every module is a chunk (module record) of its own, so each import crosses a record boundary: namespace imports of builtin modules before, between and after named imports (the only namespace imports that survive bundling); named, default and namespace imports of builtin modules next to imports of other chunks; one record importing 96 bindings that are all updated live; imports that are never read, first read long after evaluation, or first read on a path only taken once the function is hot; one variable reaching a record under several names and through renaming, star and chained re-exports; a record loaded by
import()long after the records it imports from.bindingCase():graphCase()(the executable run with the embedded graph, with the graph cross-checked, and with the graph disabled) plus the same program built without--bytecode, which embeds no graph, so its records are made from each chunk's source; with and without--splitting. Used for the new programs and for the existing cycle, star-export, re-export, namespace, default, dynamic import, top-level await, CommonJS interop and TDZ cases.RegistryDeleteImporterandRegistryDeleteImporterAndExporter(also throughbindingCase()): deleting a chunk's registry entry and importing the key again gives the loader a second record of the module while the first one's functions are hot. The module imports bindings of another chunk, a named binding of a builtin module and a builtin module's namespace; with the exporting chunk deleted too, the second record links to a second record of it, with its own state, while the first stays linked to the first.test/js/node/vm/vm.test.ts:SourceTextModules with one identifier and one source text, linked to dependencies whose exports sit at different places, each read their own bindings (from functions that were hot before the next record was made), in the main context and in a new one. A second case has several import declarations naming one specifier; it runs where that works and istodoIf(isDebug || isASAN), becauseNodeVMSourceTextModule::createModuleRecordasserts on it in builds with assertions enabled (independent of this change; fixed separately).All of these pass on a local build of this branch against WebKit
mainwith the WebKit change and on one without it.On the WebKit side the change comes with 26 new
JSTests/modules/import-slots-*.jsfiles and a JS↔wasm cycle test (every kind of import binding on the global object's own loader and across additional loaders, in six tier configurations), and every other test inJSTests/modulespasses.