Fix: Avoid union with EmptyObject for ctx

[RobinTail]

Related to #3166

This fix prevents ctx from having unions with Record<string, never>, but it does not change the type of ctx in defaultEndpointsFactory that remains Record<string, never>.

The scope of the change are only the factories having at least one Middleware attached (that makes a union for ctx)

Summary by CodeRabbit

• Refactor

  • Improved type inference for endpoints when no context is provided, simplifying type composition to avoid empty-object intersections.

• Tests

  • Updated type expectations to reflect the simplified type shape.

• Documentation

  • Added a changelog entry describing the type fix.
  • Added a contributor entry to the README.

• Chores

  • Bumped package version to a pre-release.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR refines EndpointsFactory's internal #extend generic: the CTX parameter now collapses to RET when CTX is EmptyObject via (CTX extends EmptyObject ? RET : CTX) & RET, updating type inference for empty contexts and adjusting corresponding tests and changelog/README entries.

Changes

Cohort / File(s)	Summary
Type parameter refinement express-zod-api/src/endpoints-factory.ts	Changed #extend instantiation second generic from CTX & RET to (CTX extends EmptyObject ? RET : CTX) & RET, preventing EmptyObject from leaking into inferred ctx types.
Test type expectations express-zod-api/tests/endpoints-factory.spec.ts	Updated test type assertions: replaced EmptyObject & { ... } with { ... } in EndpointsFactory<..., ...> expectations to match new inference.
Changelog & contributors CHANGELOG.md, README.md	Added v26.3.1 changelog entry describing the ctx type fix and credited contributor pycanis; README updated contributors list.
Package metadata express-zod-api/package.json	Bumped version to 26.3.1-beta.1.

Sequence Diagram(s)

(Skipped — changes are type-level/type-inference adjustments without new runtime control flow.)

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• feat(v25): undefined input schema for factories and middlewares by default #2777: Modifies EndpointsFactory #extend generic/context type inference in a closely related way.

Suggested labels

documentation

Poem

🐰 I nibble types with careful paws,
Empty crumbs tucked out of laws,
Contexts snug where they belong,
Middleware hums a clearer song,
Hooray — a hop, a tidy cause! 🥕

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Fix: Avoid union with EmptyObject for ctx' accurately describes the main technical change—preventing union types with EmptyObject for the ctx parameter in factories with middleware.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

---

📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between d8f8c27 and 1ebf969.

📒 Files selected for processing (2)

• express-zod-api/package.json
• express-zod-api/src/endpoints-factory.ts

✅ Files skipped from review due to trivial changes (1)

• express-zod-api/package.json

🧰 Additional context used

🧠 Learnings (2)

📚 Learning: 2025-05-28T18:58:10.064Z

Learnt from: RobinTail
Repo: RobinTail/express-zod-api PR: 2428
File: express-zod-api/src/index.ts:44-44
Timestamp: 2025-05-28T18:58:10.064Z
Learning: The type-only import `import type {} from "qs";` in express-zod-api/src/index.ts is necessary to avoid TS2742 errors for exported functions like attachRouting, makeRequestMock, testEndpoint, and testMiddleware that have types depending on types/qs. This import provides the reference TypeScript needs to infer portable type names.

Applied to files:

• express-zod-api/src/endpoints-factory.ts

📚 Learning: 2025-08-08T11:59:04.814Z

Learnt from: RobinTail
Repo: RobinTail/express-zod-api PR: 2878
File: zod-plugin/runtime.ts:39-42
Timestamp: 2025-08-08T11:59:04.814Z
Learning: express-zod-api/zod-plugin/runtime.ts (TypeScript): Do not memoize the ZodType.prototype.brand getter. The current design returning setBrand.bind(this) on each access is intentional/preferred; avoid redefining "brand" as a data property per instance.

Applied to files:

• express-zod-api/src/endpoints-factory.ts

🧬 Code graph analysis (1)

express-zod-api/src/endpoints-factory.ts (1)

express-zod-api/src/common-helpers.ts (1)

• EmptyObject (19-19)

🔇 Additional comments (1)

express-zod-api/src/endpoints-factory.ts (1)

82-95: LGTM! Clean type-level improvement.

The conditional type logic correctly collapses EmptyObject & RET to just RET, eliminating redundant intersections in the type signature. When CTX is not empty, the behavior remains identical (CTX & RET). This achieves the stated goal of preventing ctx from having unions with Record<string, never> while preserving type safety.

The implementation is sound:

• When starting with an empty context: (RET) & RET simplifies to RET
• When context is already populated: (CTX) & RET maintains the original behavior

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[coveralls-official]

coverage: 100.0%. remained the same
when pulling 7775172 on fix-ctx-empty-object-union
into 2749eca on master.