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With `splitting`, a chunk that several entrypoints load runs its modules in one order: the import order of one of those entrypoints. The bundler docs now say so, say which entrypoint the chunk follows since v1.4.3, and show how to make one module run before another one under every entrypoint. The `splitting` JSDoc and the esbuild comparison page point to the new section. The tests pin each statement of the section: an entrypoint of the build ahead of an `import()` target (both CLI orders, `[hash]` entry naming, the browser target, an executable with a Worker), the first of two entrypoints, the first of two HTML pages, the first of two `import()` calls, and the example of the section with its remedy.
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Updated 11:47 PM PT - Oct 18th, 2026
✅ @robobun, your commit bd641ba13637db6a2105d90bec3ee7fc7b9df408 passed in 🧪 To try this PR locally: bunx bun-pr 45998That installs a local version of the PR into your bun-45998 --bun |
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Status: docs and tests only, ready for review. The build warning for this case is not part of this PR. Reproduction: five files:
The new tests in |
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No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info
WalkthroughThe documentation describes how entrypoints determine module order in shared chunks, including dynamic imports and ordering caveats. Bundler tests cover entrypoint ordering and compare source and bundled results for the documented examples. ChangesShared-chunk evaluation order
Suggested reviewers: Priority: ⬇️ Low Merge Risk: ⚪ Minimal · up to
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| Title check |  |
The title clearly and concisely describes the main documentation change: documenting shared-chunk evaluation order under splitting. |
| Description check | |
The description explains the problem, documents the fix, identifies the affected files, and provides verification commands and test coverage. It does not use the template headings exactly, but it incl… |
| Linked Issues check | |
Check skipped because no linked issues were found for this pull request. |
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Check skipped because no linked issues were found for this pull request. |
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The description explains the problem, documents the fix, identifies the affected files, and provides verification commands and test coverage. It does not use the template headings exactly, but it includes the required content and is sufficiently complete.
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Actionable comments posted: 2
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Inline comments:
Review comments at @docs/bundler/index.mdx:
- Line 601: Update the example involving index.ts and worker.ts to state that
APP_MODE must be unset before each run, or make its initial state explicit, so
the printed values are unambiguous.
Review comments at @test/bundler/bundler_splitting.test.ts:
- Line 2667: Update the Bun.spawn call to pass an environment based on bunEnv
with APP_MODE removed, preserving the other environment variables so the example
process sees APP_MODE as undefined regardless of the test runner environment.
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docs/bundler/esbuild.mdxdocs/bundler/index.mdxpackages/bun-types/bun.d.tstest/bundler/bundler_splitting.test.ts
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Beyond the inline findings, I also checked the new links: the three bun lint rule pages named in docs/bundler/index.mdx exist under docs/lint/rules/, and the #evaluation-order-in-a-shared-chunk anchor used by docs/bundler/esbuild.mdx and the splitting JSDoc matches the new heading. The "since v1.4.3" claim and the numbered entrypoint-priority list are behavior statements about the linker that this checkout cannot confirm, and the description itself asks a maintainer whether the docs may commit to that list, so that decision still needs a human.
Extended reasoning...
The change is docs-only plus JSDoc and tests: a new section in docs/bundler/index.mdx on shared-chunk evaluation order under splitting, two table rows in docs/bundler/esbuild.mdx, a JSDoc addition on BuildConfig.splitting, and about 200 lines of itBundled and Bun.build subprocess tests pinning the documented behavior. No bundler or runtime code changes and no security-sensitive surface. The inline findings are test-quality nits; the deciding fact against approval is that the section commits the public docs to a specific chunk-ownership rule and version boundary that the author explicitly flags as needing maintainer sign-off.
The tests of the docs example no longer take `APP_MODE` from the environment of the test run. They use the `run` helper of the file, so a failure shows the stderr of the program, and they check how many output files hold `p.ts` and `q.ts`: one, or two with the third entrypoint.
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2 participants
Problem
--splitting, a chunk that several entrypoints load runs its modules in the import order of one of them. Another entrypoint that loads the chunk first gets that order too. No doc says so.index.jscallsimport("./a.js").a.jshasimport "./p.js"ahead ofq.js.worker.jsimportsq.jsfirst. From source,index.jsprintsok aqP. The build printsok aq-noPsince v1.4.3. A v1.4.2 build printedok aqP.Fix
docs/bundler/index.mdxgets the section "Evaluation order in a shared chunk": the rule, which entrypoint a chunk follows, an example, and a remedy that also holds when the two modules are in different chunks.splittingJSDoc and the twosplittingrows ofdocs/bundler/esbuild.mdxpoint to it.test/bundler/bundler_splitting.test.tspins each statement of the section (13 tests). They pass on main, because this PR changes no code.bun bd test test/bundler/bundler_splitting.test.tsandtest/integration/bun-types/bun-types.test.ts. Each claim of the section was run.Background
robobun/1c4e3771/warn-shared-chunk-order. It is not in this PR. It needs a decision first (Notes).Notes
Claims that were run (release build of main,
bun build --splitting --target=bun):index.ts,worker.ts)production,undefinedundefined,undefinedproduction,productionq.tsusesmodefromp.ts)production,productionproduction,productionadmin.tsas a third entrypointproduction,productionproduction,productionimport "./p.ts"inq.tsandadmin.tsproduction,productionundefined,productionok aqPandworker qP aqPfor the graph of the Problem section, as v1.4.2 did. The chunk there follows theimport()target. No bundler of the three gets both programs right.bun lintwith the three rules that the section names reports 8 places in the example, and nothing with its defaults.splitting/SharedChunkOwnerLoadTimeRead*pin it.Tests.
SharedChunkFollowsEntryPointBeforeImportCall(both CLI orders,target: "browser",[hash]entry naming, theimport()in the second entrypoint, an executable with a Worker),SharedChunkFollowsFirstEntryPoint(both orders),SharedChunkFollowsFirstHTMLEntryPoint,SharedChunkFollowsFirstImportCall,SharedChunkOrderOfDocsExample,SharedChunkOrderOfDocsRemedy,SharedChunkOrderOfDocsRemedyInTwoChunks.Open questions for a maintainer.
import()targets it is not exact: it can warn about a target that never loads first (for example one behind a second lazy module), and the graph of the Problem section has such a target as the losing side. The choices are a default-level warning for entrypoints of the build only, a default-level warning that includesimport()targets after more analysis, the debug log level only, or no report.Not covered by the section. An entrypoint's own side-effect import that runs after a shared chunk (#44028, #44495), modules in different chunks, CommonJS modules.