feat(jest,rstest): add prefer-snapshot-hint rule

[elecmonkey]

Motivation

Descriptive hints make external snapshots easier to identify during review, especially when one test produces several snapshots.

Changes

Add rstest/prefer-snapshot-hint and jest/prefer-snapshot-hint.

The default multi mode requires hints in groups containing multiple external snapshot assertions; always requires a hint on every external snapshot assertion. Inline and file snapshots are excluded.

Share hint detection, lexical grouping, options and diagnostics between both plugins, while each adapter retains its framework's call parsing and binding resolution. No fixes are offered because the hint describes what the user intends to capture.

Register the rules without adding them to either recommended preset, because snapshot naming is a style choice.

Credits

Port from eslint-plugin-jest@29.16.6's and @vitest/eslint-plugin@1.6.27's prefer-snapshot-hint.

Intentional differences from upstream

• Rstest recognizes matchSnapshot and checks every snapshot matcher in a Chai chain. The alias uses the same snapshot implementation as toMatchSnapshot.

• Rstest accepts interpolated template literals as hints. They always produce strings, and their text becomes part of the snapshot name.

• Rstest excludes negated snapshots, expect.poll and expect.element chains, and static calls without an assertion factory. These forms do not provide a valid Rstest snapshot assertion.

• Rstest uses its own binding analysis. This covers test-context assertions, rstack/test, import.meta.rstest and ordinary Rstest assertions exposed by @rstest/playwright.

Related Links

Related #935.

Checklist

• Tests updated.
• Documentation updated.

[github-actions]

🦀📦 Binary size

Commit d6ec397 merged into base 4812542 — feat(unicorn): add consistent-template-literal-escape rule (#2315).

Binary	Base	This PR	Change
rslint (linux-x64-gnu)	39.40 MiB	39.42 MiB	+24.00 KiB (+0.06%)

_{Stripped go build -ldflags="-s -w" ./cmd/rslint, Go 1.27.0, linux/amd64 · run · 2026-09-28 06:40 UTC}

[fansenze]

Found two reproducible false positives in jest/prefer-snapshot-hint. The existing tests for 14 affected Go packages pass; the additional examples below reproduce the issues on this commit. The equivalent Rstest cases pass.

[fansenze]

@elecmonkey Could you please resolve the merge conflicts?