Bun preload transforms for legacy Slate JSX lanes must target the imported fixture files

Problem

Legacy Slate TSX fixture lanes do not compile through the Slate hyperscript path under raw bun test in this repo.

Without help, Bun turns fixture JSX like <element>word</element> into React-style element objects instead of Slate hyperscript output.

That shows up in the current dynamic-import lanes:

• packages/slate-hyperscript/test/index.spec.ts importing packages/slate-hyperscript/test/fixtures/*.tsx
• packages/slate/test/index.spec.ts importing the full packages/slate/test/** fixture corpus
• packages/slate-history/test/index.spec.ts importing the full packages/slate-history/test/** fixture corpus

What Didn't Work

1. Trusting plain Bun runtime imports for the fixture modules

The official Bun docs say per-file JSX pragmas are supported, and Bun.Transpiler does honor them. The problem was the plain runtime import path used by the dynamic fixture imports, not the pragma contract itself.

2. Targeting the spec entrypoint instead of the imported fixtures

The current slate-hyperscript Bun lane imports test/fixtures/*.tsx from index.spec.ts. A preload regex that targets a dead or non-imported spec path does nothing for the actual failing modules.

3. Reaching for package-local bunfig.toml

That is still the wrong fix. It papers over the import path and breaks the single-root Bun setup.

Solution

Keep the legacy fixture syntax and fix the import path that Bun actually uses.

Use one scoped preload transform in config/bun-test-setup.ts that targets the legacy fixture directories directly:

• packages/slate-hyperscript/test/**/*.tsx
• packages/slate/test/**/*.tsx excluding the Bun spec entrypoints

For plain legacy fixtures, keep the files as bare TSX and let the preload inject import { jsx } from 'slate-hyperscript' before running the classic JSX transform. Only keep a local const jsx = createHyperscript(...) inside files that truly need a custom factory.

For the current slate and slate-history Bun lanes, keep the shared editor helpers and let the fixtures import a side-effect-free package-local index.js helper for jsx:

• keep the legacy custom JSX factory only inside packages/slate/test/index.js and packages/slate-history/test/index.js as pure helper exports for legacy fixture imports
• move the editor helper into packages/slate/test/support/with-test.js
• keep one Bun suite entry at packages/slate/test/index.spec.ts and packages/slate-history/test/index.spec.ts for the full package fixture corpora
• keep those package-local index.js files side-effect free so fixtures can import jsx from them without re-entering an old suite bootstrap
• when Bun reveals type-only imports as runtime imports, convert them to import type instead of papering over the error

That keeps all legacy Slate fixture packages on the single root Bun config while letting Bun own the migrated fixture lanes.

Why This Works

The real contract was not "Bun cannot run Slate JSX tests."

It was "raw Bun runtime imports are not reproducing the hyperscript pragma path for the imported fixture modules."

Using Bun.Transpiler inside a scoped preload gives Bun the transform path it actually needs while keeping the single root config. The important detail is scope: the preload has to intercept the TSX files that Bun is dynamically importing, not some neighboring spec filename. A broad test-directory rule also avoids turning filename suffixes into tooling metadata, and the injected stock import removes the per-file pragma and import { jsx } boilerplate for ordinary fixtures.

Prevention

• For legacy Slate fixture lanes, do not assume plain runtime imports tell the truth about Bun pragma support.
• If a Bun spec dynamically imports legacy TSX fixtures, scope the preload regex to the legacy fixture directories, not a hand-maintained bucket list.
• If a Bun slice lives under a legacy Mocha test/**/*.ts tree, keep the Bun entrypoint off that glob so Mocha does not accidentally execute it.
• Use package-local bunfig.toml only if there is a real runtime reason, not to emulate old Babel behavior.

Verification

pnpm install
pnpm turbo build --filter=./packages/slate-hyperscript
pnpm turbo typecheck --filter=./packages/slate-hyperscript
pnpm turbo build --filter=./packages/slate
pnpm turbo typecheck --filter=./packages/slate
pnpm exec tsc --project config/tsconfig.test.json --noEmit
bun test ./packages/slate-hyperscript/test/index.spec.ts
bun test ./packages/slate/test/bun/editor-above.spec.tsx
pnpm test:bun
pnpm test:mocha
pnpm lint