Jest Preset Default: Support self-referencing via exports

[manzoorwanijk]

What?

Follow up to #80767.

Adds an exports field to @wordpress/jest-preset-default so the package can be resolved by its own name from within itself, and simplifies how test/unit/jest.config.js points at the preset.

Why?

The test added in #80767 does require( '@wordpress/jest-preset-default' ) from inside the package. That only resolves because npm hoists every workspace into the root node_modules. Under an isolated/linked install strategy there is no root link, and the test fails with Cannot find module '@wordpress/jest-preset-default' — see the failing run on #75814.

Node's self-referencing is the supported way to import a package from within itself, and it requires an exports field.

How?

Adds a minimal exports map exposing only the package root, jest-preset, and package.json.

The ./jest-preset entry is load-bearing. jest-config resolves a preset given as a bare package name by looking up the extensionless <pkg>/jest-preset subpath, and extensions are not appended to exports subpaths. A map without that entry breaks every consumer using preset: "@wordpress/jest-preset-default", and ./jest-preset.js does not work as a substitute.

Since the package root resolves to jest-preset.js (main, as of #80767), test/unit/jest.config.js can now pass the resolved path straight to preset instead of deriving the containing directory from a subpath import.

This narrows the published surface: scripts/ and index.js still ship via files but are no longer resolvable as deep imports. Nothing in the repo relies on them — jest-preset.js reaches scripts/ through relative require.resolve — but it is a breaking change for anyone deep-importing them, so it is noted in the changelog.

Testing Instructions

1. npm run test:unit -- packages/jest-preset-default/test/index.js passes.
2. npm run test:unit passes.
3. Confirm downstream preset usage still works — in a scratch package with @wordpress/jest-preset-default linked and a config of { preset: "@wordpress/jest-preset-default" }, Jest resolves the preset and runs. Use a fresh --cacheDirectory; a warm Jest cache will mask preset resolution changes.

Use of AI Tools

Investigated and drafted with Claude Code (Opus). The exports shapes were verified empirically against jest-resolve and Node, and end to end with a standalone consumer package. Please adjust this disclosure to match your own review.

[github-actions]

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Co-authored-by: manzoorwanijk <manzoorwanijk@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[github-actions]

Size Change: -82 B (0%)

Total Size: 7.76 MB

📦 View Changed

Filename	Size	Change
build/scripts/upload-media/index.min.js	15.5 kB	-82 B (-0.53%)

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[Mamaduka]

Followed testing instructions and everything looks to be in order ✅