feat: support server custom message handling by module.hot.on by SyMind · Pull Request #7003 · web-infra-dev/rsbuild

SyMind · 2026-01-20T10:19:27Z

Summary

This PR improves the client-side HMR custom message handling by extracting the module.hot.on interception logic into a dedicated helper setupCustomHMRListeners.

Checklist

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

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gemini-code-assist · 2026-01-20T10:19:47Z

Summary of Changes

Hello @SyMind, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the development server's capabilities by enabling it to send custom messages to the client-side HMR system. This feature allows for more flexible and powerful interactions between the server and client during development, facilitating custom HMR behaviors. The changes also include careful management of HMR event listeners to ensure they are correctly disposed of when modules are reloaded, preventing potential issues.

Highlights

Custom Server Messages: Implements a new mechanism for the development server to send custom messages to the client-side HMR runtime.
HMR Listener Management: Introduces a robust system to register and automatically dispose of custom HMR event listeners, preventing memory leaks on module reloads.
Rspack Runtime Integration: Adds a custom Rspack plugin to correctly inject HMR runtime globals (module.hot, RuntimeGlobals.interceptModuleExecution) into the bundled assets.
End-to-End Testing: Includes new e2e tests to validate the functionality of custom server messages and the proper disposal of HMR event callbacks.

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Code Review

This pull request introduces a great feature for sending custom messages from the dev server to the client using module.hot.on. The implementation is well-thought-out, especially the mechanism for disposing of HMR listeners to prevent leaks. The accompanying e2e tests cover the new functionality well. I've provided a few suggestions to improve the robustness and performance of the implementation, including a fix for a potential race condition in one of the new tests.

e2e/cases/javascript-api/server-custom-message/src/index.js

e2e/cases/javascript-api/server-custom-message/index.test.ts

packages/core/rslib.config.ts

packages/core/src/client/hmr.ts

Copilot

Pull request overview

This PR adds support for server-side custom message handling through the HMR system, enabling developers to send custom events from the server to the client via module.hot.on. The implementation extracts custom message handling logic into a dedicated helper function.

Changes:

Added ServerCustomMessage type to support custom WebSocket messages
Implemented setupCustomHMRListeners to intercept and manage module.hot.on listeners with proper cleanup on module disposal
Added RspackRuntimeReplacePlugin to replace build-time constants with runtime values
Created comprehensive E2E tests verifying custom message handling and listener disposal

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
packages/core/src/server/socketServer.ts	Adds `ServerCustomMessage` type definition to the message union
packages/core/src/client/hmr.ts	Implements custom HMR listener setup with disposal logic and message handling
packages/core/rslib.config.ts	Adds plugin for runtime constant replacement and reorganizes imports
e2e/cases/javascript-api/server-custom-message/src/index.js	Test source file demonstrating custom event listener usage
e2e/cases/javascript-api/server-custom-message/index.test.ts	E2E tests validating custom message delivery and listener cleanup

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e2e/cases/javascript-api/server-custom-message/index.test.ts

packages/core/src/client/hmr.ts

packages/core/rslib.config.ts

packages/core/src/client/hmr.ts

packages/core/rslib.config.ts

packages/core/src/client/hmr.ts

packages/core/src/server/socketServer.ts

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packages/core/src/client/hmr.ts

chenjiahan · 2026-01-22T10:08:34Z

e2e/cases/javascript-api/server-custom-message/index.test.ts

+  const rsbuild = await createRsbuild({
+    cwd: import.meta.dirname,
+  });
+
+  const server = await rsbuild.createDevServer();
+
+  await server.listen();


Can we just use the dev helper?

I cannot get dev server instance from dev() function.

Feel free to update the helper

…EXECUTION

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chenjiahan · 2026-01-23T13:09:30Z

👍

SyMind added 3 commits January 20, 2026 17:05

feat: support server custom message

a83dec9

chore: test case

97885cb

fix: fmt

0aa63e1

github-actions bot added the release: feature label Jan 20, 2026

SyMind changed the title ~~feat: support server custom message~~ feat: support server custom message by module.hot.on Jan 20, 2026

SyMind changed the title ~~feat: support server custom message by module.hot.on~~ feat: support server custom message handling by module.hot.on Jan 20, 2026

SyMind marked this pull request as ready for review January 20, 2026 10:21

Copilot AI review requested due to automatic review settings January 20, 2026 10:21

Copilot started reviewing on behalf of SyMind January 20, 2026 10:22 View session

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SyMind force-pushed the module.hot.on branch from affc8c5 to 4e80958 Compare January 20, 2026 10:32

refactor

537888d

SyMind force-pushed the module.hot.on branch from 4e80958 to 537888d Compare January 20, 2026 10:36

fix: ts type

8d4c3c8

chenjiahan reviewed Jan 21, 2026

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packages/core/rslib.config.ts Show resolved Hide resolved

chenjiahan reviewed Jan 21, 2026

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chenjiahan reviewed Jan 21, 2026

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packages/core/src/server/socketServer.ts Outdated Show resolved Hide resolved

refactor: ts type

7b93b23

SyMind force-pushed the module.hot.on branch from ca942c0 to 7b93b23 Compare January 22, 2026 01:34

SyMind added 2 commits January 22, 2026 09:38

add comments

c780b2b

fix: tsc error

2efad7e

SyMind force-pushed the module.hot.on branch from 0de6ff9 to 2efad7e Compare January 22, 2026 05:09

chenjiahan reviewed Jan 22, 2026

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chenjiahan reviewed Jan 22, 2026

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chenjiahan reviewed Jan 22, 2026

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chore: add ts type for RSPACK_MODULE_HOT and RSPACK_INTERCEPT_MODULE_…

d431722

…EXECUTION

chenjiahan approved these changes Jan 23, 2026

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chenjiahan merged commit 4c48709 into main Jan 23, 2026
6 checks passed

chenjiahan deleted the module.hot.on branch January 23, 2026 13:09

This was referenced Jan 24, 2026

test: streamline custom message tests #7027

Merged

chore(build): simplify rspack runtime replacement plugin #7026

Merged

fix(types): add public typing for import.meta.webpackHot.on #7028

Merged

docs: update sockWrite with custom message support #7029

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