refactor: one hot.inject enum for what is added to the compilation

[alexander-akait]

hot.inject (boolean) and hot.client: false were two overlapping switches: inject: false dropped both the runtime and HotModuleReplacementPlugin, while client: false dropped only the runtime. This replaces both with one enum. Neither option has shipped yet, so nothing released breaks.

hot.inject	Runtime (client + overlay)	HotModuleReplacementPlugin	For
"all" (default)	✓	✓	nothing to add to the webpack configuration
"plugin"		✓	a page that wires a client of its own
"client"	✓		a configuration that applies the plugin itself
"none"			wiring both yourself, or using the endpoint only through subscribe

• hot.client now takes options only. hot.inject: true/false and hot.client: false fail validation with the valid values listed.
• "client" is new: the runtime is added without the plugin, and a plugin in the configuration is kept without the "redundant plugin" warning.
• The hot.token requirement is turned off whenever no client is added ("plugin" / "none"), as inject: false did before.
• hot.client.transport still names a wire ("sse"/"ws") or a module exporting a client class: the first commit split the module out into hot.client.module, and the second reverts that, so there stays a single option.

Tests

• Unit tests for every mode, a plugin of your own under "client", and validation cases for the enum and for the old shapes. Existing uses are mapped (inject: false → "none", client: false → "plugin").
• e2e: "client" with the configuration's own plugin applies updates in place; "client" with no plugin connects and leaves module.hot undefined.
• Locally: unit 7377 of 7379 (the other two expect a writeToDisk EACCES, which root never gets); e2e 233 of 233; lint, types and schema check clean.
• webpack-dev-server #5750 maps its client: false to "plugin" with hot and "none" without, on a build of this branch: its full suite shows the same sandbox-only failures as before.

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Summary by CodeRabbit

• New Features
  • hot.inject supports "all", "plugin", "client", and "none" modes to control whether the browser client, HMR plugin, both, or neither are added.
  • "client" mode can add the browser client while preserving an HMR plugin already configured in your project.
  • Token requirements depend on whether the selected mode adds a client.
• Documentation
  • Updated configuration guidance to explain the injection modes and their effects.

[changeset-bot]

⚠️ No Changeset found

Latest commit: ca03931

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes changesets to release 1 package

Name	Type
webpack-dev-middleware	Minor

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📒 Files selected for processing: 3

• README.md
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Walkthrough

hot.inject now accepts "all", "plugin", "client", or "none" to select whether the middleware adds the client runtime and the HMR plugin. hot.client: false is no longer accepted. Token resolution, option validation, and TypeScript declarations reflect these modes. Unit and end-to-end tests cover the mode behavior.

Priority: ➖ Normal

Merge Risk: ⚪ Minimal · up to ca039

The injection-mode change is mergeable after normal checks; no concrete outstanding behavior issue is established.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly summarizes the main change: replacing overlapping hot injection switches with one hot.inject enum that controls what is added to the compilation.
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 10 files. (1 skipped: 1…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 10 files. (1 skipped: 1 unsupported.)

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test/inject-client.test.js

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ESLint: 9.39.5

Error: Error while loading rule 'jest/no-deprecated-functions': Unable to detect Jest version - please ensure jest package is installed, or otherwise set version explicitly
Occurred while linting /test/inject-client.test.js
at detectJestVersion (/.eslint-tmp/node_modules/eslint-plugin-jest/lib/rules/utils/detectJestVersion.js:22:9)
at create (/.eslint-tmp/node_modules/eslint-plugin-jest/lib/rules/no-deprecated-functions.js:31:107)
at Object.create (/.eslint-tmp/node_modules/@typescript-eslint/utils/dist/eslint-utils/RuleCreator.js:39:20)
at createRuleListeners (/.eslint-tmp/node_modules/eslint/lib/linter/linter.js:1019:15)
at /.eslint-tmp/node_modules/eslint/lib/linter/linter.js:1151:7
at Array.forEach ()
at runRules (/.eslint-tmp/node_modules/eslint/lib/linter/linter.js:1085:31)
at #flatVerifyWithoutProcessors (/.eslint-tmp/node_modules/eslint/lib/linter/linter.js:2115:4)
at Linter._verifyWithFlatConfigArrayAndWithoutProcessors (/.eslint-tmp/node_modules/eslint/lib/linter/linter.js:2203:43)
at Linter._verifyWithFlatConfigArray (/.eslint-tmp/node_modules/eslint/lib/linter/linter.js:2306:15)

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Actionable comments posted: 3

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• src/utils.js
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• test/e2e/inject.test.js
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.59%. Comparing base (f9ad683) to head (ca03931).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2484   +/-   ##
=======================================
  Coverage   96.58%   96.59%           
=======================================
  Files          24       24           
  Lines        2637     2640    +3     
=======================================
+ Hits         2547     2550    +3     
  Misses         90       90           

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[alexander-akait]

codecov/project is red at 96.55% (−0.04%, one more missed line). That line isn't in this diff: codecov/patch reports 100% of the changed lines hit, and unit-test coverage of main and this branch, compared locally, misses exactly the same 777 lines. What's left is the browser-measured client coverage, which moves between runs without a code change: #2476's head measured 96.66% and main at f9ad683, with only dependency bumps since, measures 96.58%. Re-running the workflow once to confirm. codecov/project is not a required check.

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