[turbopack] Use an arena for `JSValue`s by sampoder · Pull Request #94297 · vercel/next.js

sampoder · 2026-06-01T10:29:26Z

This PR takes the arena introduced in #94296 and uses it! It's large but shouldn't change functionality beyond the use of the arena. Some syntax related to pattern-matching had to change because bumpalo's Box doesn't support the same pattern matching that the standard library's Box does but the code should be equivalent.

github-actions · 2026-06-01T10:29:47Z

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github-actions · 2026-06-01T10:29:50Z

Failing test suites

Commit: d72a407 | About building and testing Next.js

pnpm test-start test/production/app-dir/metadata-static-route-cache/metadata-static-route-cache.test.ts (job)

app dir - metadata static routes cache > should generate different content after replace the static metadata file (DD)

Expand output

● app dir - metadata static routes cache › should generate different content after replace the static metadata file

next already started

  65 |   ) {
  66 |     if (this.childProcess) {
> 67 |       throw new Error('next already started')
     |             ^
  68 |     }
  69 |
  70 |     this._cliOutput = ''

  at NextStartInstance.start (lib/next-modes/next-start.ts:67:13)
  at Object.start (production/app-dir/metadata-static-route-cache/metadata-static-route-cache.test.ts:17:16)

pnpm test-start test/production/create-next-app/package-manager/pnpm.test.ts (job)

create-next-app with package manager pnpm > should use pnpm for --use-pnpm flag with example (DD)
create-next-app with package manager pnpm > should use pnpm when user-agent is pnpm with example (DD)

Expand output

● create-next-app with package manager pnpm › should use pnpm for --use-pnpm flag with example

Command failed with exit code 1 (EPERM): node /__w/next.js/next.js/packages/create-next-app/dist/index.js use-pnpm-with-example --use-pnpm --example https://github.com/vercel/next.js/tree/canary/examples/basic-css

  159 |     await useTempDir(async (cwd) => {
  160 |       const projectName = 'use-pnpm-with-example'
> 161 |       const res = await run(
      |                   ^
  162 |         [projectName, '--use-pnpm', '--example', FULL_EXAMPLE_PATH],
  163 |         nextTgzFilename,
  164 |         { cwd }

  at makeError (../node_modules/.pnpm/execa@2.0.3/node_modules/execa/lib/error.js:58:11)
  at handlePromise (../node_modules/.pnpm/execa@2.0.3/node_modules/execa/index.js:112:26)
  at production/create-next-app/package-manager/pnpm.test.ts:161:19
  at useTempDir (lib/use-temp-dir.ts:24:5)
  at Object.<anonymous> (production/create-next-app/package-manager/pnpm.test.ts:159:5)

● create-next-app with package manager pnpm › should use pnpm when user-agent is pnpm with example

Command failed with exit code 1 (EPERM): node /__w/next.js/next.js/packages/create-next-app/dist/index.js user-agent-pnpm-with-example --example https://github.com/vercel/next.js/tree/canary/examples/basic-css

  177 |     await useTempDir(async (cwd) => {
  178 |       const projectName = 'user-agent-pnpm-with-example'
> 179 |       const res = await run(
      |                   ^
  180 |         [projectName, '--example', FULL_EXAMPLE_PATH],
  181 |         nextTgzFilename,
  182 |         {

  at makeError (../node_modules/.pnpm/execa@2.0.3/node_modules/execa/lib/error.js:58:11)
  at handlePromise (../node_modules/.pnpm/execa@2.0.3/node_modules/execa/index.js:112:26)
  at production/create-next-app/package-manager/pnpm.test.ts:179:19
  at useTempDir (lib/use-temp-dir.ts:24:5)
  at Object.<anonymous> (production/create-next-app/package-manager/pnpm.test.ts:177:5)

pnpm test-start-turbo test/e2e/app-dir/navigation/navigation.test.ts (turbopack) (job)

app dir - navigation > hash > should scroll to the specified hash (DD)

Expand output

● app dir - navigation › hash › should scroll to the specified hash

expect(received).toBe(expected) // Object.is equality

Expected: false
Received: true

  197 |           url.includes('with-query-param')
  198 |         )
> 199 |         expect(hasQueryParamRscRequest).toBe(false)
      |                                         ^
  200 |       }
  201 |
  202 |       await checkLink('query-param', 2284)

  at Object.toBe (e2e/app-dir/navigation/navigation.test.ts:199:41)

bgw · 2026-06-03T19:14:30Z

 #[derive(Debug)]
-pub enum Effect {
+pub enum Effect<'a> {


Follow up: Maybe also make Effect use the arena for everything? Right now it has some global-heap-allocated types.

bgw · 2026-06-03T19:17:35Z

 };

-enum EarlyReturn {
+enum EarlyReturn<'a> {


Possible future PR: Also use an arena here

…#94296) This PR implements `BumpVec` this is a custom vector implementation that takes in a `Bump` as a type (from bumpalo) so that we get `Send`/`Sync` on our `JSValue` vectors when we make that switch in: #94297.

Bump-allocates the analyzer's `JsValue` tree into a per-thread arena (`ThreadLocal<Bump>`) that lives for the duration of `analyze_ecmascript_module_internal` and is freed in one shot when it returns, replacing the previous `Arc`/`Box`/`Vec` heap allocations. `JsValue` becomes `JsValue<'a>`, with its list children stored in `BumpVec` (growable) or `bumpalo::boxed::Box<[_]>` (fixed) and scalar children in `bumpalo::boxed::Box`. Sync functions take `&Bump` and allocate directly; the async (`Send`-bound) analysis pipeline holds a `&ThreadLocal<Bump>` and obtains a `&Bump` via `get_or_default()`, so no `!Send` `&Bump` is ever held across an `.await`. Builds on the `BumpVec` introduced in the previous commit.

lukesandberg

it would be useful to describe the thread_local! design in the PR description, how this is solving a problem with async and the associated risks

sampoder mentioned this pull request Jun 1, 2026

[turbopack] Add BumpVec (vector implementation that takes a Bump) #94296

Merged

sampoder requested review from bgw and lukesandberg June 1, 2026 18:31

sampoder marked this pull request as ready for review June 1, 2026 18:31

sampoder force-pushed the sp/turbopack/analyzer-arena-infra branch from a98d014 to e21492c Compare June 1, 2026 23:29

sampoder force-pushed the sp/turbopack/analyzer-arena-jsvalue branch from 4b5a6ea to 9c87cd9 Compare June 1, 2026 23:29

bgw reviewed Jun 3, 2026

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Base automatically changed from sp/turbopack/analyzer-arena-infra to canary June 3, 2026 21:43

sampoder force-pushed the sp/turbopack/analyzer-arena-jsvalue branch 2 times, most recently from 9b57fe5 to b83e7c6 Compare June 3, 2026 22:06

sampoder force-pushed the sp/turbopack/analyzer-arena-jsvalue branch from b83e7c6 to 4cc4b5b Compare June 3, 2026 22:09

sampoder requested a review from bgw June 3, 2026 22:10

bgw reviewed Jun 4, 2026

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PR reviews to normalize.rs

916162c

sampoder force-pushed the sp/turbopack/analyzer-arena-jsvalue branch from 5610ae9 to 916162c Compare June 4, 2026 08:32

Respond to PR review

d72a407

sampoder requested a review from bgw June 4, 2026 16:30

lukesandberg requested changes Jun 4, 2026

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sampoder commented Jun 1, 2026 •

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