refactor(factory.ts): improve typing

[chimurai]

Summary by CodeRabbit

• TypeScript Improvements
  • Proxy middleware now supports custom types for the callback passed to continue request handling or report an error.
  • Callback types are preserved when creating and using middleware, improving compatibility with applications that provide their own compatible callback signatures. The default callback type remains unchanged for callers that do not specify a custom type.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 38c123f9-6772-4a95-8763-5deed77d367d

📥 Commits

Reviewing files that changed from the base of the PR and between 4ed80ab and 1bb6fb2.

📒 Files selected for processing (2)

• src/factory.ts
• src/http-proxy-middleware.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

The middleware factory and HttpProxyMiddleware now propagate a configurable TNext callback type. The factory returns the middleware without a type assertion.

Changes

Middleware callback types

Layer / File(s)	Summary
Callback type propagation src/http-proxy-middleware.ts, src/factory.ts	HttpProxyMiddleware adds a TNext generic and uses it for its public middleware property. createProxyMiddleware constrains and passes TNext, then returns the middleware without a type assertion.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Refactor

Merge Risk: ⚪ Minimal · up to 1bb6f

Consumers retain the default callback type or can specify a custom one through the factory. No concrete compatibility or runtime regression is established, so the change is mergeable subject to normal checks.

Security Architecture Review

Security architecture risk: ⚪ Minimal · up to 1bb6f

The change constrains and propagates callback types without changing executable request handling, proxy routing, or callback invocation. No introduced or worsened security risk was identified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The demonstrated impact is on callers compiling against the public handler types. Because the construction and handler execution paths are unchanged, this delta does not expand attacker-controlled runtime reachability or downstream authority.

Trust Boundaries and Controls

• observed — The callback constraint is a compile-time contract, not a security enforcement boundary. Existing proxy-routing and target-validation behavior is preserved; its broader security adequacy is not established by this review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: improved typing in the factory and middleware API.
Docstring Coverage	✅ Passed	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 1 functions across 2 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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[pkg-pr-new]

npm i https://pkg.pr.new/http-proxy-middleware@1300

commit: 1bb6fb2

[coveralls]

coverage: 96.364%. remained the same — type-factory.ts into master