refactor(lazy-compilation): use POST request to transfer ids of active modules #12678

stormslowly · 2026-01-08T10:23:44Z

Summary

The original method of passing module IDs to the active state via URL query strings may encounter limitations related to browser/server constraints or URL length. Therefore, we are refactoring this process to pass those IDs through the POST body instead.

To handle potential bursts of requests when activating modules, we will implement a request queue during the activation process. The steps are as follows:

During the activation request for lazy modules, all active requests will be buffered in a compiling set.
After the Hot Module Replacement (HMR) for the previous request is completed, we will proceed to make the next active request, including all buffered module IDs. Then, we will return to step 1 to manage further requests.

Checklist

Tests updated (or not required).
Documentation updated (or not required).

netlify · 2026-01-08T10:23:51Z

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github-actions · 2026-01-08T10:32:38Z

Rsdoctor Bundle Diff Analysis

Found 5 projects in monorepo, 0 projects with changes.

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Project	Total Size	Change
react-10k	5.7 MB	0
react-5k	2.7 MB	0
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react-1k	825.4 KB	0
ui-components	2.1 MB	0

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github-actions · 2026-01-08T10:35:47Z

📦 Binary Size-limit

Comparing c0078ad to chore(deps): update patch crates (#12716) by renovate[bot]

🙈 Size remains the same at 47.90MB

codspeed-hq · 2026-01-08T11:21:14Z

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing refactor/lazy_active_module_id_goes_to_post_body (c0078ad) with main (36866ea)}

Summary

✅ 16 untouched benchmarks
⏩ 1 skipped benchmark¹

1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

…module_id_goes_to_post_body

github-actions · 2026-01-09T09:29:40Z

📝 Ecosystem CI detail: Open

suite	result
rsdoctor	✅ success
modernjs	✅ success
rspress	✅ success
rsbuild	✅ success
nuxt	✅ success
plugin	✅ success
rstest	❌ failure
lynx-stack	❌ failure
devserver	❌ failure
rslib	❌ failure
examples	✅ success

…module_id_goes_to_post_body

1. 如果其他中间件一个解析好了body，并挂载在req.body 上的花就直直接使用 req.body 2. packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts body 解析的时候不能简单的使用 string 的拼接，需要考虑多字节符号的截断的问题。

packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts 当req.body 非空时，直接假body中时一组 module ids，如果没有 body 自行拼接完，之后也 parse json string，返回 module ids 数组

…body

chenjiahan

PR title: refactor -> refactor(lazy-compilation)

packages/rspack/hot/lazy-compilation-web.js

Co-authored-by: neverland <chenjiahan.jait@bytedance.com>

packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts

Copilot

Pull request overview

This pull request refactors the lazy compilation mechanism to transmit active module IDs via POST request body instead of URL query parameters, addressing URL length limitations in browsers and servers. The change replaces EventSource-based communication with XMLHttpRequest using simple CORS requests (Content-Type: text/plain) to avoid preflight checks in cross-origin scenarios.

Changes:

Migrated from EventSource to XMLHttpRequest with POST requests for activating lazy-compiled modules
Implemented request queuing to batch module activations and avoid overwhelming the server
Added backward compatibility by maintaining GET request support in the middleware
Added comprehensive tests for cross-origin scenarios and handling many modules with long filenames

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
packages/rspack/hot/lazy-compilation-web.js	Complete rewrite from EventSource to XMLHttpRequest with request queuing logic
packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts	Added POST body parsing with backward-compatible GET support
tests/e2e/cases/lazy-compilation/cross-origin/*	New test suite verifying cross-origin POST requests work correctly
tests/e2e/cases/lazy-compilation/active-lots-modules/*	New test for URL length limitation scenario with many long-named modules
tests/e2e/cases/lazy-compilation/custom-prefix/index.test.ts	Updated test to not check request method (now supports both GET and POST)
packages/rspack-test-tools/src/runner/web/index.ts	Added POST request proxying for lazy compilation in test environment
packages/rspack/etc/core.api.md	Marked lazyCompilationMiddleware as undocumented

Comments suppressed due to low confidence (1)

packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts:231

The middleware always sets Server-Sent Events (SSE) headers even for POST requests. For POST requests, the response should end immediately (which it does on line 247), but setting SSE headers like 'content-type: text/event-stream' is misleading and inappropriate for a simple POST response. These headers should only be set for GET requests that maintain a persistent connection.

    req.socket.setNoDelay(true);

    res.setHeader('content-type', 'text/event-stream');
    res.writeHead(200);
    res.write('\n');

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packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts

tests/e2e/cases/lazy-compilation/active-lots-modules/rspack.config.js

tests/e2e/cases/lazy-compilation/cross-origin/README.md

tests/e2e/cases/lazy-compilation/active-lots-modules/index.test.ts

packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts

packages/rspack/hot/lazy-compilation-web.js

packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts

…thub.com:web-infra-dev/rspack into refactor/lazy_active_module_id_goes_to_post_body

…e modules (#12678) * refactor: use post transfer module ids * test: skip lazy active method * test: add lazy post request help * test: add large module id container * test: add case introduction * refactor: remove about controller * test: we are using post method now * refactor: rename * fix body parser (vibe-kanban 09797829) 1. 如果其他中间件一个解析好了body，并挂载在req.body 上的花就直直接使用 req.body 2. packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts body 解析的时候不能简单的使用 string 的拼接，需要考虑多字节符号的截断的问题。 * refactor read module ids from body (vibe-kanban a7874ac1) packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts 当req.body 非空时，直接假body中时一组 module ids，如果没有 body 自行拼接完，之后也 parse json string，返回 module ids 数组 * refactor: downgrading to lower web api * test: ✅ add lazy compilation active cors cases * chore: update test case doc * fix: we all need cors header no matter is simple request or not * refactor:delete cors header setting * refactor: set cors header should set by user * Update packages/rspack/hot/lazy-compilation-web.js Co-authored-by: neverland <chenjiahan.jait@bytedance.com> * test: fix case name * chore: api-extract update * fix: memory leak of requst listeners * refactor: remove event source handle logic * fix: jsdom XMLHTTPRequets need strict cors header * refactor: node lazy compilation client use post too --------- Co-authored-by: neverland <chenjiahan.jait@bytedance.com>

stormslowly added 2 commits January 8, 2026 15:53

refactor: use post transfer module ids

a66dd0a

test: skip lazy active method

8149c31

github-actions bot added release: refactor team The issue/pr is created by the member of Rspack. labels Jan 8, 2026

stormslowly added 8 commits January 8, 2026 20:40

Merge remote-tracking branch 'origin/main' into refactor/lazy_active_…

f8e3322

…module_id_goes_to_post_body

test: add lazy post request help

cef1dc7

test: add large module id container

093bf25

test: add case introduction

cf5349f

refactor: remove about controller

b253637

Merge remote-tracking branch 'origin/main' into refactor/lazy_active_…

78d904c

…module_id_goes_to_post_body

test: we are using post method now

0c136db

refactor: rename

890aede

stormslowly added 7 commits January 12, 2026 11:26

Merge remote-tracking branch 'origin/main' into refactor/lazy_active_…

5ace8c0

…module_id_goes_to_post_body

refactor read module ids from body (vibe-kanban a7874ac1)

332146a

packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts 当req.body 非空时，直接假body中时一组 module ids，如果没有 body 自行拼接完，之后也 parse json string，返回 module ids 数组

refactor: downgrading to lower web api

a0619ae

test: ✅ add lazy compilation active cors cases

f4f10d6

chore: update test case doc

2ba3cd6

fix: we all need cors header no matter is simple request or not

5d8eeb5

stormslowly force-pushed the refactor/lazy_active_module_id_goes_to_post_body branch from 7362078 to 5d8eeb5 Compare January 13, 2026 07:33

stormslowly and others added 3 commits January 14, 2026 11:39

refactor:delete cors header setting

401d886

refactor: set cors header should set by user

363dfa5

Merge branch 'main' into refactor/lazy_active_module_id_goes_to_post_…

3be7a91

…body

stormslowly marked this pull request as ready for review January 14, 2026 03:59

stormslowly requested a review from LingyuCoder as a code owner January 14, 2026 03:59

stormslowly requested a review from hardfist as a code owner January 14, 2026 03:59

Copilot AI review requested due to automatic review settings January 14, 2026 03:59

Copilot started reviewing on behalf of stormslowly January 14, 2026 03:59 View session

stormslowly requested a review from chenjiahan January 14, 2026 04:01

chenjiahan reviewed Jan 14, 2026

View reviewed changes

packages/rspack/hot/lazy-compilation-web.js Outdated Show resolved Hide resolved

Update packages/rspack/hot/lazy-compilation-web.js

bd739dd

Co-authored-by: neverland <chenjiahan.jait@bytedance.com>

chenjiahan reviewed Jan 14, 2026

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packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts Show resolved Hide resolved

Copilot AI reviewed Jan 14, 2026

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chenjiahan reviewed Jan 14, 2026

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packages/rspack/src/builtin-plugin/lazy-compilation/middleware.ts Outdated Show resolved Hide resolved

stormslowly added 2 commits January 14, 2026 12:16

test: fix case name

bfd543e

Merge branch 'refactor/lazy_active_module_id_goes_to_post_body' of gi…

0487659

…thub.com:web-infra-dev/rspack into refactor/lazy_active_module_id_goes_to_post_body

stormslowly changed the title ~~refactor: use post transfer ids of active modules~~ refactor(lazy-compilation): use post transfer ids of active modules Jan 14, 2026

stormslowly added 2 commits January 14, 2026 14:10

chore: api-extract update

2064a1b

fix: memory leak of requst listeners

0c66e27

stormslowly requested a review from chenjiahan January 14, 2026 06:16

stormslowly added 2 commits January 14, 2026 14:28

refactor: remove event source handle logic

5b2ff93

fix: jsdom XMLHTTPRequets need strict cors header

bf0fc1f

stormslowly force-pushed the refactor/lazy_active_module_id_goes_to_post_body branch from 1d54eb6 to bf0fc1f Compare January 14, 2026 07:08

refactor: node lazy compilation client use post too

c0078ad

stormslowly changed the title ~~refactor(lazy-compilation): use post transfer ids of active modules~~ refactor(lazy-compilation): use POST request to transfer ids of active modules Jan 14, 2026

chenjiahan approved these changes Jan 15, 2026

View reviewed changes

chenjiahan merged commit ad662bc into main Jan 15, 2026
54 checks passed

chenjiahan deleted the refactor/lazy_active_module_id_goes_to_post_body branch January 15, 2026 05:42

This was referenced Jan 15, 2026

feat!: remove deprecated draft option from LightningCSS minimizer #12740

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feat!: Rspack off modules and assets in normal stats #12701

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refactor(lazy-compilation): use POST request to transfer ids of active modules #12678

refactor(lazy-compilation): use POST request to transfer ids of active modules #12678

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