feat(jest): port no-unnecessary-assertion rule

[elecmonkey]

Motivation

TypeScript types can prove that some Jest assertions cannot produce the asserted result, so these assertions either add no coverage or point at inaccurate types.

Changes

Add the type-aware jest/no-unnecessary-assertion rule. It reports toBeNull(), toBeUndefined(), toBeDefined() and toBeNaN(), with or without .not, when the subject's type cannot be null, undefined or a number, and warns when strictNullChecks is disabled.

Move the rule shell shared with rstest/no-unnecessary-assertion (the strictNullChecks check, the checked matchers and the messages) into internal/utils/test_framework/rules/no_unnecessary_assertion, and move the Rstest rule onto it without changing its behavior. Each plugin keeps its own expect parsing and subject type analysis, because the Rstest rule deliberately skips unresolved generics, void and intersection types that eslint-plugin-jest reports.

The rule is not added to the recommended preset.

Credits

Port from eslint-plugin-jest@29.16.0's no-unnecessary-assertion.

Related Links

Related #935.

Checklist

• Tests updated.
• Documentation updated.

[github-actions]

🦀📦 Binary size

Commit 026ac67 merged into base 3c4a05e — feat(react): add state-in-constructor rule (#2307).

Binary	Base	This PR	Change
rslint (linux-x64-gnu)	39.47 MiB	39.48 MiB	+4.00 KiB (+0.01%)

_{Stripped go build -ldflags="-s -w" ./cmd/rslint, Go 1.27.0, linux/amd64 · run · 2026-09-28 09:24 UTC}