test(aot): an `import()` of a module that a `require()` still evaluates settles by robobun · Pull Request #47538 · oven-sh/bun

robobun · 2026-10-31T12:08:11Z

Problem

In an executable built by bun build --compile --aot, an import() of an ES module that a require() is still evaluating never settled. No .then callback ran, and a top-level await of it never ended. bun run fulfils it.
The engine fix is on oven-sh/WebKit main: AOT: follow-up to #982: 48 fixes WebKit#983 (Modules::evaluateWithOwnStack, aot/runtime/AOTModuleEvaluation.cpp). main here does not pin an engine with it yet, and has no test for these cases.

Fix

Tests only: ten programs under test/aot/parallel/modules/ and one row of a-module-that-has-run-keeps-no-record.test.ts. Each must print and exit as plain Bun does.
The WEBKIT_VERSION commit is temporary. It pins a preview build with the same engine change on the commit that main pins, so that the programs pass today. It goes away when main pins oven-sh/WebKit b83d8a12ae or later.
Verified: nine programs and the row fail on an engine without the change. All pass on oven-sh/WebKit main at b83d8a12ae (Notes).

Background

--aot compiles the modules of a program to machine code. The engine half of that compiler and its run time are in oven-sh/WebKit.
WEBKIT_VERSION (scripts/build/deps/webkit.ts) names the oven-sh/WebKit release that the build links. autobuild-preview-pr-<n>-<sha> is the build of a pull request there.
[JSC] AOT: settle the import() of a module that a require() still evaluates WebKit#961 made the same engine change and is closed: AOT: follow-up to #982: 48 fixes WebKit#983 landed first.
Three more programs are marked // Todo: for imports that stay wrong in an executable, on that main too (Notes).

Downsides

None found. The diff that lands is tests: the pin commit goes away first (Fix).

Notes

The report

@sosukesuzuki, bun 1.4.4-canary.1+da867c60b, linux-x64, every run. a.mjs requires c.mjs. c.mjs imports d.mjs and requires x.mjs. x.mjs calls import("./c.mjs").then(..). bun a.mjs prints the line of the .then callback, the executable does not. Without the import of d.mjs the executable is right, which modules/import-of-module-require-running-settles already covers.

The programs

Each is a folder under test/aot/parallel/modules/. run-parallel.ts builds it with --compile --aot and compares what the executable prints with plain Bun. "Fails" is without the engine change.

Program	What it adds
`import-of-required-module-with-import-settles`	the report, with `.then`. It also counts one module with a start of its own (`// STATISTIC: ModulesWithState = 1`): without that start it passes on any engine	fails
`import-of-required-module-with-import-awaited`	an async function awaits the `import()`	fails
`import-of-required-module-with-import-rejects`	the module throws behind the `require`: the promise is rejected with the same error	passes
`import-of-required-module-with-import-job`	four chains of jobs around the end of the module: the fulfilment lands between the same jobs as under plain Bun	fails
`import-of-imported-module-with-import-job`	the same where an `import()` is the root, where no synchronous queue of a `require()` takes the jobs of the loader	fails
`import-of-required-module-with-import-again`	a later `import()` of the module inside another `require()`	fails
`import-of-imported-module-with-import-settles`	the module is the root of an `import()`, not of a `require`	fails
`import-of-required-module-without-code-settles`	the required module has no code of its own and gets no start	fails
`imports-of-nested-required-modules-settle`	two nested required modules	fails
`import-of-required-cycle-root-settles`	the module is the root of an import cycle	fails

The row of a-module-that-has-run-keeps-no-record.test.ts: while the promise of such an import() is pending, the run time retires no record. Without the engine change the executable holds 240 records behind 120 modules.

Programs marked `// Todo:`

They print something else than plain Bun before and after the engine change, also on oven-sh/WebKit main at b83d8a12ae. run-parallel.ts reports them as skipped, and fails them when they pass.

import-by-name-of-entry-point-require-runs-settles: no import() is compiled, so the build makes the require() a call of the start of the module. An import() of it from text that the build did not read stays pending. That needs a second engine change, in callModules.
import-again-of-cycle-member-imported-while-it-runs: a later import() of a member of a cycle gets the promise that an earlier one left pending.
import-of-member-of-cycle-that-fails-is-rejected: the executable fulfils an import() of a member whose body has ended when its cycle fails.

How it was run

oven-sh/WebKit main at b83d8a12ae (AOT: follow-up to #982: 48 fixes WebKit#983), release build with assertions. The Bun tree was AOT: hangs, wrong answers, failed builds; bun test --aot follows #44833's mocks #47605 (22621ef913), with three lines of src/aot/engine.rs stubbed locally for an option that this engine no longer has. run-parallel.ts passes the ten programs and skips the three // Todo: programs. The six rows of the test pass.
The other lines are about the change of [JSC] AOT: settle the import() of a module that a require() still evaluates WebKit#961. AOT: follow-up to #982: 48 fixes WebKit#983 makes the same change, and takes the status only where it fulfils the promise.
Ahead of the next pin: Bun at AOT: hangs, wrong answers, failed builds; bun test --aot follows #44833's mocks #47605 (64ddaea8aa) with the engine at oven-sh/WebKit main (115632d802) plus the change, release build with assertions. run-parallel.ts passes the ten programs and skips the three // Todo: programs. The six rows of the test pass.
This head, release build with assertions (1.4.4-canary.1+0ae6b714b), with the engine built from source at the commit of [JSC] AOT: settle the import() of a module that a require() still evaluates WebKit#961 (fedb2feecd): run-parallel.ts passes the ten programs and skips the three // Todo: programs. All six rows of a-module-that-has-run-keeps-no-record.test.ts pass. Of the 434 programs of test/aot/parallel/modules, 427 pass, 6 are skipped by their // Todo: line and 1 fails: plain Bun with assertions aborts on reassigned-functions-in-cycles, with and without the engine change.
This head, bun bd on this pin: run-parallel.ts skips every program on a debug build (only a canary build of Bun reads BUN_AOT_START_AT). So each program was built with bun-debug build --compile --aot, run, and compared with BUN_FEATURE_FLAG_DISABLE_ASYNC_TRANSPILER=1 bun-debug main.*. The ten programs print the same, and the three // Todo: programs do not. The six rows of the test pass.
Earlier trees, each with and without the engine change: Bun f7607a3d35 with the engine at 8c6c963e3c, and Bun at AOT: bun test --aot on large suites, module loading fixes, fuzzer fixes #47316 (8aea497349) with the engine at oven-sh/WebKit main (4d45755fed). 9 programs and the row fail without it, 10 programs and the row pass with it, and the three // Todo: programs are skipped in all four.
The release build on 8c6c963e3c also ran the other 4538 programs of test/aot/parallel: no program changed its result.

The pin

autobuild-preview-pr-961-fedb2fee is oven-sh/WebKit main at 4d45755fed, which main pins since #47316, plus the engine change as oven-sh/WebKit#961 had it. That pull request is closed, and the release stays. The pin is temporary: see Fix.

What does not change

An import() of a module that is a dependency of the running evaluation, not its root, stays pending in plain Bun and in an executable. Node.js v26.3.0 fulfils it. oven-sh/WebKit#871 is a draft for that.

no test proof · iteration 2 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/aot/a-module-that-has-run-keeps-no-record.test.ts

robobun · 2026-10-31T12:08:23Z

^{Updated 3:48 PM PT - Oct 31st, 2026}

✅ @robobun, your commit 0ae6b714b51df7bfb1cf27b061a0af7324e671f3 passed in Build #136195! 🎉

🧪 To try this PR locally:

bunx bun-pr 47538

That installs a local version of the PR into your bun-47538 executable, so you can run:

bun-47538 --bun

robobun · 2026-10-31T12:08:25Z

Status: reproduced on bun 1.4.4-canary.1+da867c60b (linux-x64) with the four files of the report. The executable built with --compile --aot prints five of the six lines that bun a.mjs prints. Nine of the ten new programs and the new row of a-module-that-has-run-keeps-no-record.test.ts fail on an engine without the fix.

The engine fix landed on oven-sh/WebKit main as oven-sh/WebKit#983 (b83d8a12ae). On that engine the ten programs and the row pass. oven-sh/WebKit#961, which made the same change, is closed.

This pull request is now tests only. Its WEBKIT_VERSION commit is temporary and goes away when main pins oven-sh/WebKit b83d8a12ae or later. It stays a draft until then.

…ettles Eight programs for `bun build --compile --aot`. A `require()` or an `import()` runs an ES module that imports another one, and a module that it requires calls `import()` on it while it runs. The promise settles when the first module has run, in the same job as under plain Bun. - import-of-required-module-with-import-settles: the `.then` form - import-of-required-module-with-import-awaited: the `await` form - import-of-required-module-with-import-rejects: the module throws - import-of-required-module-with-import-job: the job of the fulfilment - import-of-required-module-with-import-again: a later `import()` inside another `require()` - import-of-imported-module-with-import-settles: the root of an `import()` - imports-of-nested-required-modules-settle: two nested roots, CommonJS entry point - import-of-required-cycle-root-settles: the root of an import cycle

The AOT run time fulfils an `import()` of a module that a `require()` or an `import()` is still evaluating, where the module keeps its status in the table of status bytes.

… code, and the records - import-of-required-module-with-import-settles counts one module with a start of its own (`// STATISTIC: ModulesWithState = 1`): without that start the program passes on any engine. - import-of-required-module-with-import-job: the imported module queues jobs too, so its importer keeps the start. - import-of-imported-module-with-import-job: the job of the fulfilment where an `import()` is the root. No synchronous queue is open there. - import-of-required-module-without-code-settles: the required module has no code of its own and gets no start. - imports-of-nested-required-modules-settle starts from an ES module. - a-module-that-has-run-keeps-no-record.test.ts: a sixth shape. While the promise of such an `import()` is pending no record goes (240 records behind 120 modules).

…nge leaves as they are - import-again-of-cycle-member-imported-while-it-runs: a later `import()` of a member of a cycle gets the promise that an earlier one left pending. - import-of-member-of-cycle-that-fails-is-rejected: the executable fulfils an `import()` of a member whose body has ended when its cycle fails. - import-by-name-of-entry-point-require-runs-settles: with no `import()` in compiled code the `require()` is a call of the start of the module, and an `import()` from text that the build did not read stays pending.

robobun assigned sosukesuzuki Oct 31, 2026

github-actions Bot added the claude label Oct 31, 2026

This was referenced Oct 31, 2026

[JSC] AOT: settle the import() of a module that a require() still evaluates oven-sh/WebKit#961

Closed

[JSC] Settle an Evaluate() of an EVALUATING module when the walk pops its cycle oven-sh/WebKit#871

Draft

robobun added 4 commits October 31, 2026 20:09

Bump WebKit to the preview build of oven-sh/WebKit#961

0b43a8b

The AOT run time fulfils an `import()` of a module that a `require()` or an `import()` is still evaluating, where the module keeps its status in the table of status bytes.

robobun force-pushed the robobun/8fc1579a/aot-import-of-required-module-settles branch from 858d546 to 0ae6b71 Compare October 31, 2026 20:37

robobun mentioned this pull request Nov 2, 2026

[JSC] AOT: do not bind a require() of an ES module that uncompiled code can import oven-sh/WebKit#988

Draft

robobun changed the title ~~Bump WebKit (oven-sh/WebKit#961 preview): --aot settles an import() of a module that a require() still evaluates~~ test(aot): an import() of a module that a require() still evaluates settles Nov 2, 2026

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test(aot): an `import()` of a module that a `require()` still evaluates settles - #47538

test(aot): an `import()` of a module that a `require()` still evaluates settles#47538
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Problem

Fix

Background

Downsides

The report

The programs

Programs marked // Todo:

How it was run

The pin

What does not change

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